Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: HommeMarrBuckley on August 06, 2016, 02:43:30 pm
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Im trying to put together the Plexi6v6 done by Steve and Mark Huss and I am using Hammond A0-43 transformers.
http://sluckeyamps.com/6v6plexi/6v6plexi.htm
http://mhuss.com/Plexi6V6/
I hate posting these noob questions but it's best way to get moving.
I figure it is easy to describe better with pictures. I am trying to see if I am on the right track here and I am trying to configure what tag strips and points I will need.
The speaker jack
Yellow/orangish is NFB wire. Green and black are from OT. Confused because on steve's site with picture, black looks like connected to tip but thought sleeve was ground. I know it's something I don't understand or know. I modeled my picture after what I thought I saw in his picture.
Lamp
Mark's had a diode, Should it be 220k in series here, is that correct in pic?
Lamp has positive sign on one lug, it shouldn't matter which green from PT connects, right? They go off to heaters, then.
Bias pot
This bias pot is so tiny, supposed to use tiny flathead screwdriver to adjust it, maybe cut a chopstick head flat. I believe the bottom lug is ground but not sure if set correct. There's another pic of the biaspot with lugs up.
Lastly, presence pot is part of phase inverter section, Is master volume part of PI or Tone Stack?
Many Thanks in Advance
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black looks like connected to tip but thought sleeve was ground
Black is connected to the tip and the sleeve is ground. Your NFB wire needs to connect to the tip lug, not the switch lug. I normally would connect the black lead to ground but I had to swap the green and black OT wires to fix NFB squeal. This was easier than swapping the plate leads on this amp.
Mark's had a diode, Should it be 220k in series here, is that correct in pic?
Lamp has positive sign on one lug, it shouldn't matter which green from PT connects, right? They go off to heaters, then.
Quit thinking about what Mark has. Per our pms last month you will be using a NE2 neon bulb connected to 120VAC. That's why you bought that lamp holder and NE2, remember. None of this will connect to the PT green wires. The idea was to not put a #47 lamp on the filament string. Connect one side of the lamp holder to one of the PT primary leads. Connect a 220K resistor to the other side of the lamp holder. Connect the free end of the 220K resistor to the other PT primary lead. (I would mount that resistor on a terminal strip rather than solder a wire to the dangling end.)
If you just must use a #47 lamp, then forget the 220K resistor and just connect the two sides of the lamp holder to the two green filament leads. That lamp holder can use either lamp bulb.
I would get a small screwdriver to fit that small bias pot. You can never have too many tools.
The MV goes between the TS and the PI. I would call it part of the preamp. Some people call it a pre-PI MV.
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Ok
Speaker
Green OT and NFB connect to tip
Ring and Sleeve lugs are connected
and Black OT connected at sleeve.
I am clear on Lamp.
Bias pot correct?
Quit thinking about what Mark has.
:smiley:
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Pot looks right. How will you mount it?
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Pot looks right. How will you mount it?
:laugh: my typical unrefined way, eyelets are pretty close.
Pretty bummed now because lamp clearance is a no go with the PT. Tried spacers and nuts to lower PT height but just not enough to keep keps on. My own fault for not thinking about clearance beforehand. Have a #47 and NE2 and neither will clear without touching the PT. Anyone point to me specific LED/lamp, I'd appreciate it. I have a 11/16" chassis hole and about 5/8" space before contact with PT.
Also need to get a 4 1/2" x 1 7/8" piece of sheet metal/aluminum to cover holes in back so I can mount the fuse.
Really thought I was going to like getting to re-use this Hammond chassis but clearly I am without the proper design abilities to make this easy. Needless to say the chassis will have a lot of air flow.
Not going to show much else but here's the head cab. Waiting for the right time to rout and round off the edges. Stormy outside all day and want to take my time with a bunch of practice strokes on scrap.
The cab shell is glued up/needs cleats and baffles. Eminence Legend 15" came yesterday. But all that is meaningless right now.
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Here's one solution. Get four 1/2" x 3/4" x 3/4" L-brackets from Lowes and mount them on the PT so you can stand it up, rather than laid down like you have it now. Then it won't be in the way of anything. Like this...
(http://el34world.com/Forum/index.php?action=dlattach;topic=19557.0;attach=55559;image)
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Standing up, doesn't clear hole, like in the pic, I would have to lay another sheet down. Lowes/HD have sheet metal/alum? Perhaps but they probably don't cut it. (tried several times and pic is right side up--dunno why it reverts to being upside down-but you get idea)
In 2nd, this is about the only way on it's side but I dunno for this configuration with orientation to choke and PT and just normal operation.
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There's nothing awkward about what I suggested. But if you can't make it work then you could always just not use a pilot light. Plenty of amps don't have one. Or you could get another chassis and this time measure twice, cut once. A blank chassis would look so much better than that chassis. Or, you could buy Doug's precut chassis. Or, I could sell you another AO-43 chassis. Lot's of options. I would stand the PT up.
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Is this just too close? Lug and bulb shaft are pretty much touching. I dunno doesn't seem that bad. I added keps on the other side to give a few more mm of clearance.
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Use your needle nose pliers to rotate that rear lug so it is not pointing downward toward the PT. An/or bend it 90°. Then use your ohm meter to measure resistance between each lug and chassis. Should be infinity.
With it being that close, I'd not use the ne-2 connected to 120V, but I would not hesitate to using the #47 connected to the 6.3v filament winding. Just be sure neither lug is actually shorted to chassis.
EDIT... Another simple solution is to replace the four PT bolts with longer bolts. You can get longer bolts from a shop that repairs small electric motors.
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With ohm meter, got 0.L (does bulb need to be in?)
EDIT... Another simple solution is to replace the four PT bolts with longer bolts. You can get longer bolts from a shop that repairs small electric motors.
I thought of that but just didn't think you do it because those bolts are like super tight in there.
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Another idea to raise the PT that is in laying down position , is to find some threaded stand-offs of the same thread pitch as the pt bolts and thread them on each pt bolt and then using 4 small bolts thread them into the stand-offs from inside the chassis. For instance, https://www.grainger.com/category/round-standoffs/spacers-and-standoffs/fasteners/ecatalog/N-8nm (https://www.grainger.com/category/round-standoffs/spacers-and-standoffs/fasteners/ecatalog/N-8nm) and there are many more places that sell these and the octagonal variety.
some others https://www.zoro.com/value-brand-round-standoff-6-32-12-l-pk10-183519/i/G3691107/?gclid=CKqwvYPqr84CFUUdaQodygcJmQ&gclsrc=aw.ds (https://www.zoro.com/value-brand-round-standoff-6-32-12-l-pk10-183519/i/G3691107/?gclid=CKqwvYPqr84CFUUdaQodygcJmQ&gclsrc=aw.ds)
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Couldn't you just saw off the whole rear part of that lamp holder thing and figure out a way to use an LED as the light source?
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Appreciate everyone's help and ideas here. Thank you.
Another idea to raise the PT that is in laying down position , is to find some threaded stand-offs of the same thread pitch as .......
There's a mom and pop hardware store that I frequent that's close to me but closed today. I might look into this idea. I will just have to see about possible strain on the bolts (seems 8-32, because that size keps fits snug on it) but this sounds possible. To be cont.
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> Lowes/HD have sheet metal/alum? Perhaps but they probably don't cut it.
They do, but that's not it.
Hardware aisle, across from nails/screws, is hundreds of small drawers. Odd size nuts, washers, spacers, and also little pre-made L-brackets.
Sadly they usually have 3 when you need 4.....
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So, if I would use L brackets and stand it this way, the orientation with the choke and OT is ok?
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yes
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3/4 x 1/2 x 1/2 L Bracket.
Mount holes not exact but close. I had to watch how much I tightened everything but it is snug and secure. Excellent fit that suits this build.
Thanks Steve :grin:
I think the spacer idea would have worked too. :thumbsup:
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More snags—learning.
With PT now up, the filter cap is awfully close, I might move it to the right. Good idea or not worth it? (will probably have to drill another hole—note the power and standby switch* in the pic)
The choke is pretty close to the power tube socket but I think it should be ok.
With hardly any experience, I didn’t think of the opposite nature of this chassis compared to last one I did. Not too big a deal but now have to be careful with not having any lugs or connections touching the bottom of the chassis.
Bums me out that my power/standby switch will be upside down. I tried to turn it rightsize up and I bent the lugs to see but one was extremely close to the PT bolt and I could just see in time it getting loose and touching. Will just have to accept that flipping down is “On” position. Annoys me that little groove/channel* in them because really obvious to see.
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Just rotate the PT 180° to provide more clearance for the cap can.
And put the screw head on the inside of the chassis to provide more clearance for the switch.
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The bell cover end of the PT is the cooler side of the PT. The lams will be warmer.
And that amp sits right side up, tubes up? Heat will rise up and away from the cap can.
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Bare with me Steve, but did you mean 180° like in your pic in post#5?
If so, it can't stand that way because the hole is too big.
Why did you delete the part about the screwhead? That might work.
The switch lugs are really close to the chassis,
I was thinking of adhering some of the fiberboard onto the chassis there just in case the lugs might move or touch.
Wouldn't that help insulate from shorting?
I have been purposely procrastinating from the electronics because of the obstacles.
Plus, it has been nice outside after days of rain so I worked some more on the cabs (put in the cab section).
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Just do it. All 4 bolt holes will line up. Who cares about the big hole under the PT. It's supported by the L-brackets. If this doesn't work for you please take a pic with it rotated so I can understand why.
BTW, I recommend you cut a plate to go under the PT as shown in post #5.
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Who cares about the big hole under the PT. It's supported by the L-brackets............
BTW, I recommend you cut a plate to go under the PT as shown in post #5.
:icon_biggrin:
Like this? I thought the orientation with OT and choke should be opposite this but I am probably wrong.
Here's how close the switch lugs are--yikes--my own fault.
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Like this? I thought the orientation with OT and choke should be opposite this but I am probably wrong.
NO! I said rotate 180°. You only rotated 90°. Give it another quarter turn.
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There's an easy solution to your switch dilemma. Put those Carling switches aside for another project and buy some switches with solder lugs on the back, rather than the end. Like this...
http://sluckeyamps.com/PeeWee/A_big_bottom.jpg (http://sluckeyamps.com/PeeWee/A_big_bottom.jpg)
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This?
Ill work those L brackets.
Thanks--didn't even think of other different SPST switches.
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This?
Ill work those L brackets.
Arrgh! Put the L-brackets back on exactly like they were in reply #18. Then rotate the transformer 180° keeping the L-brackets on the chassis.
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Thanks for putting up with my ignorance. :BangHead:
Ill get the Ls on tomorrow and look for those switches.
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Now you're cooking! That should give you additional clearance for the cap and your L-bracket holes should line up just as before.
BTW, I struck the statement about screw head earlier because of a brain fart. I momentarily forgot you were using L-brackets and was thinking the screw was actually one of the long PT bolts. Since you are using short screws with the L-brackets, reversing the screw head would be easy and would provide more clearance for the switch.
There is some thin paper insulating material (usually gray colored) that is used in transformers, motors, and switch enclosures that is used for insulating purposes. It would work fine to insulate your switches. May have to drop by a motor repair shop. They would probably give you enough for your purpose. I would drill a 1/2" hole in it and put it between the switch body and front panel of the chassis. Then bend it to fit flat against the bottom of the chassis. The switch will hold it in place.
Here's a pic of what I'm talking about. I just used some hanging folder paper for illustration only because I don't have the correct electrical insulating paper. Please use the correct paper if you decide to do this.
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After a couple engine shops and boat motor places with nothing, it looks like internet yields possible solution but of where to buy.
DuPont trademarked Nomex flame retardant insulation paper. Wonder if there's a generic. Made progress on the circuit board, will have questions with PT wiring later.
Learning on this one. Pots are upside down too and backwards too, it's fine, I'm either going to check clearance to turn them upside down or just leave it the way it is (0 at 1o'clock, max at 11).
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> couple engine shops and boat motor places....
> DuPont trademarked Nomex flame retardant insulation paper.
?? Ah- Sluckey's "drop by a motor repair shop" means Electric Motor shop. Around here the sign says "starter and alternator rebuilding", because nobody repairs vacuum cleaners and we don't have big industrial motors (and the few who do know to go there).
Heck, it is electrical fishpaper. If you still had a local Radio/TV Repair shop they would whack off a foot for you.
Newark.com GC fish paper (http://www.newark.com/gc-electronics/560/fibroid-fish-paper-electrical/dp/94F4073?CMP=KNC-GUSA-GEN-SHOPPING-NEW-GC-ELECTRONICS) $4 for lifetime supply
Castech fish paper (http://castech.us/product-category/fish-paper-sheets/), $4 sheets to $90 rolls
ESPE Fishpaper & Vulcanized Fibre (http://www.electricalinsulationguys.com/fishpaper_and_vulcanized_fibre.html), mass quantities slit to your spec
You could also go to auto-parts store and ask for a sheet of "gasket material". "Grey cardboard, not cork". The "grey cardboard gasket sheet" is nearly the same (maybe THE same) stuff as electric fishpaper, except instead of electrical test it is checked for heat and oil resistance. It is very unlikely to conduct electricity, and you only got 130V there. This will be $7 to $9 but local avoids shipping.
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Thanks for the fish paper tip.
Without a scientific brain, I am prone to copy/paste until I learn actually what I am doing. This should be really easy for everyone here.
Here's my PT.
The black hot of my power cord connects to power switch lug then to 220k resistor then to Ne-51 lamp lug
The white of power cord connects to other NE-51 lug
The top three right are my fliaments--dark green to ground and other two go to heaters
Using solid state, so my red HiVoltage secondary (in middle) each one goes to each set of diodes on rec. board, striped to ground
The two left over (top left) they get twisted with the red secondary and goto rec board, as well?
One Black primary goes to remaining power switch lug, where does other go?-to fuse
Missing with what goes to fuse tip and side of fuse?
Do I need a .47uf cap and 220k resistor after A cap and between standby? Will I need that?
Steve, you recommended a sheet under the PT, does it need to be heavy gauge, could it be 22ga Aluminum. Is this sheet for structure or for better operation/noise/wave cutoff
I need to add a piece, as well, to the back to hold the fuse but I will go with a stronger gauge there.
Pardon my ignorance everyone and sorry If I am way off with what I wrote above.
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Just follow my schematic to wire the PT.
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What if I am not using a GZ34, no diff?
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What if I am not using a GZ34, no diff?
Then tape the ends of the two yellow wires and connect the two red wires to your rectifier board.
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Ok, so tape off and tuck away the yellows.
Power cord, fuse, lamp and 2 primary?
Im Lost
guessing---power cord (white/neutral and one primary meet at one end of 220k resistor and on to lamp
power cord (black/line to end of fuse) side of fuse onto power switch lug.
Leaves one lamp lug and one power switch lug.
Initially, I planned on using the GZ34 but my 6v6s were too close together so I used the far rectifier socket for the 2nd 6v6. That's why Im looking at his schematic as well. I have a standby and I think I need to add that .47cap and 220k resistor because I can't trace that or find it on yours.
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Let's put a pin in the mains and transformer wiring until you are actually ready to do the wiring. Right now you still have mechanical issues to deal with that will prevent you from actually doing any wiring. Get your fuse holder mounted. Put that plate under your PT if you like (I don't think it's necessary if the PT seems sturdy to you). Do what you intend to do with those switches. They are not safe as they are. Either rotate, get different style switch, or do the fish paper insulation. BTW, that fish paper electrical insulation is readily and cheaply available on eBay. Click on this link...
http://www.ebay.com/itm/2-Pcs-Fish-Paper-Adhesive-0-010-x-4-5-x-10-Battery-Electric-Fishpaper-Buy-USA-/121728054331?hash=item1c578eb43b:g:bpoAAOSwBLlVTXLs (http://www.ebay.com/itm/2-Pcs-Fish-Paper-Adhesive-0-010-x-4-5-x-10-Battery-Electric-Fishpaper-Buy-USA-/121728054331?hash=item1c578eb43b:g:bpoAAOSwBLlVTXLs)
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:smiley:
Yeah, that's the direction I needed. A lot of compulsion today, dunno.
Will look at a decent sheet of 16-18 ga aluminum to cut for fuse and that insulation paper or other switch. Thanks for the link.
Back when they're mounted.
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As a sidebar, let's check out your lamp holder. Some of this style bayonet lamp holder have a built in resistor and are made specifically for use with an NE-51 bayonet style neon lamp. They can not be used with any other lamp bulb. A simple resistance test will tell if you have this type holder. And if you do, you will not need an external resistor and that will really simplify your wiring.
Here's the test...
You need your lamp holder, an ohm meter, and a gator clip test lead. Set your meter to measure actual ohms, not just a continuity check. Connect one end of the gator clip lead to one of your meter probes. Connect the other end of that gator clip lead to one of the lugs on the lamp holder. Unscrew the bezel lens from the lamp holder. Use your other meter probe to measure resistance to the center post inside the lamp holder. If you measure infinity (open circuit) swap the gator clip to the other lamp holder lug and repeat. Now you will measure either zero ohms or some resistance value that's probably in the range of 47K to 220K. Write it down.
Now put the gator clip lead on the other lamp holder lug and measure resistance to the SIDE shell contact. You should measure either zero ohms or some resistance value that's probably in the range of 47K to 220K. Write it down.
If both numbers that you wrote down are zero, then you will need the external resistor. BUT, if either of those two numbers is an ohm value between approx. 47K and 220K, you are lucky and will not need the external resistor.
Let me know the outcome. Also, if I'm being overly simplistic with the test instructions, please let me know and I'll take it up a couple notches.
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Fail!
Didn't get anything above 1ohm if that. It's ok. I put one (of the zillion holes) for a tag strip up in that area.
Looks like fish paper route, too. Couldn't find where you got the toggle with lugs in the middle. Checked mouser and ebay.
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AES has some. eBay has thousands...
http://www.ebay.com/sch/i.html?_odkw=spst+toggle&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xcarling+spst+toggle.TRS0&_nkw=carling+spst+toggle&_sacat=0
(http://www.ebay.com/sch/i.html?_odkw=spst+toggle&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xcarling+spst+toggle.TRS0&_nkw=carling+spst+toggle&_sacat=0)
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=spst%20toggle%20-%28mini%29&rt=nc&LH_PrefLoc=1&_trksid=p2045573.m1684 (http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=spst%20toggle%20-%28mini%29&rt=nc&LH_PrefLoc=1&_trksid=p2045573.m1684)
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Are those ebay carling switches the real McCoy or copied in China?
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Not very pretty but should work. The Fuse is in snug and tight. The fish paper adhesive didn't stick as well as I thought it would, I might redo the bottom layer (where lugs are) and put a drop or 2 of loctite or crazy glue underneath. The screwhead creates the bump. The mounting hole piece is fine.
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If you were to make the fish paper 1 piece with an L shape 90 deg. bend, then the bottom part of the fish paper that's under the switches, if it did lift up off the chassis it would still stay in place under the switch connects.
You might have to make a cut in the bottom short L section in between the 2 switches because of that screw/bolt and then put a full length patch piece over the cut that will stick the patch to the cut bottom section and hold the bottom together and in place better.
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Yes, it should be fine. Just needing the assistance here with the wiring. I plan to keep the wiring on these two long, in case I don't like it, I will just reverse them.
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Sorry for crudeness. Is this accurate??
Had to do blend of Huss and Sluckey's schematic because I am not using tube rectifier.
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This is the correct way to wire your mains. I didn't include the secondary wiring because it was correct.
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Much Appreciated,Thank you Steve.
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Just finished with last point on bus bar, lots of thoughts but pretty late now, one that comes to mind is if 820Ω, 100k resistor and .68uf cap are they part of tone stack or pre-amp?---I have it wired as part of pre-amp section (with that section ground).
Just hoping that this thing won't be a firestarter :blob8:
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More
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Ready to fire up
Here is the speaker jack and bias pot.
Speaker jack has green OT with NFB and Black OT to ground lug (I hope no squealing)
Bias Pot
White goes to 47k resistor and green goes to .022uf cap
Should I turn the bias pot all the way to the left or leave as is?
Alright,
So with speaker connected and hooked up to lamp limiter
should I power on with tubes or without?
If all goes well with no shorts
Plug in to wall, power on and check voltages
Again, recommend with or without tubes?
Just need to remember with voltages to switch over to milliamps/volts for pins 8 on power tubes, correct?
I don't mind checking voltages-it's just that when look at MM my probe hand is sometimes prone to move slightly
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Bias Pot
White goes to 47k resistor and green goes to .022uf cap
Should I turn the bias pot all the way to the left or leave as is?
You do have a jumper between the wiper and one of the outside legs right? If not, put one there now.
***DO NOT PROCEED TO THE NEXT PARAGRAPH UNTIL YOU HAVE SATISFACTORY RESULTS***
No tubes. Plug into lamp limiter. Be sure standby switch is in standby position. Turn on. If lamp glows brightly, turn off and find problem in AC mains circuit or PT wiring, filament string, or rectifier diodes. If lamp only glows dimly or not at all proceed...
Adjust bias pot for maximum negative DC volts on pin 5 of each power tube socket. Turn standby switch to operate position. Lamp may briefly glow brighter as the caps charge but should settle down to a dim glow. Check dc voltages at each of the filter caps. Check for dc voltage on pins 3 and 4 of each power tube. Voltages will be kinda low because of the lamp limiter. We just want to know that there is dc at each filter cap and on the power tubes. If all is OK so far, you no longer need the lamp limiter. Proceed...
Now turn off and plug straight into the wall. Standby switch to standby. Still no tubes. Turn amp on and recheck negative dc voltage on pin 5 of each power tube socket. You should have approx. -35vdc or more. Standby switch to operate. Recheck dc voltage at each filter cap and on pins 3 and 4 of each power tube. Voltages should be higher than expected because no tubes are plugged in. Also check for dc voltage on pins 1 and 6 of all little tubes. These should be high also. If all is OK so far, proceed...
Standby switch to standby. Check the ac filament voltage at each tube socket. BE CAREFUL AND DON'T SHORT BETWEEN PINS! For 6V6s measure across pins 2 and 7. For little tubes measure across pins 4/5 and 9. You should have 6.3VAC for each of these sockets. If all is correct, proceed...
Turn amp off and plug in all tubes. Connect a speaker. Set all knobs to ZERO! Turn on and look/smell for smoke, and listen for strange sounds and/or hum. Verify that all filaments are glowing. If you hear a loud squeal of howl, shut down and swap the OT primary plate leads between power tubes. Turn amp back on an verify that squeal/howl is gone. If all is OK so far, proceed...
Plug in a guitar and see it the amp makes music.
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That was a very clear and excellent reply Steve, unfortunately, I gave it a go and didn't make it past the limiter.
The limiter glowed bright. I looked over everything and felt quite confident about my wiring but realize something is wrong.
I am hoping this PT isn't dead--I was told that all transformers were working.
My initial gut feeling is that it's the lamp because it didn't light up.
This is probably really dummy move.
I remember now the lamp had a (+) lug and the other didn't. I think I got caught up with something and when I came back I forgot about it.
Im guessing the white (power cord) and black primary need to be soldered to that positive lug. Mine isn't that way.
I have a second one (not going to use it) that I can show what I mean--(the other lug has two holes)
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If you wire it the way I showed you it will work.
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It is.
Looked at it repeatedly, has to be lamp lugs or PT is DOA.
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Disconnect the PT wire from the power switch. What happens?
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Disconnect the PT wire from the power switch.
Should I disconnect the resistor from it (same connection), as well?
PS. I did change lamp lugs and nothing happened. (white)power with black PT to +lug and resistor to other.
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Disconnect the PT wire from the power switch. What happens?
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Here's a current pic now with PT disconnected from Power.
I believe all connections can be seen.
Going to put through lamp limiter.
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Turned on Power--nothing
No Glow on lamp limiter.
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With the PT wire still disconnected from the power switch, plug the amp straight into the wall and turn it on. The NE-51 indicator lamp should illuminate. Does it?
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No
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Measure the voltage across the lugs of the lamp socket.
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20-21 mv or
.003 V
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Is your meter set to measure AC Volts?
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now, yes
clips on secure,
right now about 26.1mV
did you want it powered on? because that's with it turned off
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Arrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrgggggggggggggggggggggggggggghhhhhhhhhhhhhhhhhhhhhhhhh!
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does that mean it should be turned on?
with or w/out limiter?
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Measure the voltage across the lugs of the lamp socket.
To measure a voltage the power has to be on.
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Powered on straight to wall about 50V AC
measured the resistor too and its close to 220k
so isn't that about half the voltage it should be receiving?-should the other free pt wire then be connecting to the other lamp lug?
Can I switch out and use a Fender style lamp?
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OK, I'm back and all rested. Sorry about losing my patience last night. Since we got nowhere last night let's just start over.
Forget about using that NE-2 lamp. Totally remove the lamp holder and resistor. Connect the power cord white wire to a PT black wire. Reconnect the other PT black wire to the power switch.
Now, install your Fender style lamp holder with a #47 bulb. Connect the two PT yellow wires to the lamp holder. These yellow wires only have 5VAC on them but that will operate a 6V bulb just fine. In fact, the bulb should last longer.
Now you are ready to begin testing with the lamp limiter again.
Let me ask about your PT. It came from a Hammond AO-43 amp, right? Did you ever apply 120 VAC to it and check for proper secondary voltages? If you did check it, was it OK. If you didn't check it, why do you think it is good?
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AWWWWWWWWWWWWWWWWWW YEAAAAHHHHHHHHH!!!!!!!!!!!!
First of all, Many Many Thanks Steve
I switched out the lamps and hooked up and lamp fired up-nice--you can see lamp glowing hooked up to lamp limiter---there was like no glow at all from the limiter when I switched it on.
Then I went and played Operation (the board game) for real. Man, takes my breath away--I joke now but I do take it serious, found myself wiping my brow several times. Found myself at one point staring in to triple check the pin number before I probe, forgetting it was live right under my face, so quiet.
Here's the numbers
I did all steps (great tutorial-well written) Steve
but just will list values when it was fully operational
Filter Caps
preamp 443
tone 443
phase 443
plate 449
screen 449
Pins Valve 4 Valve 5
3 449 448
4 449 448
5 -54 -55
Pins Valve 1 Valve 2 Valve 3
1 440 441 438
6 439 444 439
Now, the only part that has me nervous a bit
My heaters all measured 7.36
Hopefully, this isn't a big deal.
I so bad want to put the tubes in and hook the speaker up
but I will wait to see if all is ok. That might have to wait until tomorrow when I get home from work--won't put the soldering iron away just yet--fingers crossed about the OT wires.
By the way, I noticed with the solid state rectifier schematic there is a 5k 5 watt resistor between the choke and plate cap that I don't have--dunno if that could be playing a factor in anything.
Anyway, Im really happy, can't wait to see how it plays out.
Thanks again Steve!!
Im going to go drink a beer--Here's to you!!
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Great news!
The high filament voltage will come down when you put tubes in it. The high B+ voltages will come down with tubes installed as well.
I'm drinking a beer with you right now! Congrats...
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Ok, Plugged in and I got sound--no squealing---Great!
However, its like the sound/volume is holding back--I have an 8 ohm speaker hooked up correctly.
When I play a chord--its full but dies and fades oddly--almost like rolling volume down
I am hoping this sound/issue is related with biasing power tubes because bias pot is still all the way counter clockwise--(please let it be this)
Quick tutorial on biasing these 6v6 tubes properly?
(I have bias points and tiny flathead screwdriver)
I am not in a hurry--got home from work late but couldn't resist putting tubes in and giving it a go but willing to take time to do it properly.
This one sounds like it got some bite :m11
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Read, understand, and do...
http://www.duncanamps.com/technical/lvbias.html (http://www.duncanamps.com/technical/lvbias.html)
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LOL
I am actually on that very site and reading it. But do you think this might be related to how sound dies when I play it?
For Pin 3 I need to set dmm to max dc voltage-understood.
When I measure pin 8 (bias point) I need to turn dmm to measure mV, correct?
But, should I remove red probe from dmm connection (VΩ) and re-connect red probe to dmm in mA connector (on dmm) when I do this measurement?
It seems I should take pin 3 voltage and turn bias to mA reading (that when multiplied) doesn't exceed 12 watts (because of 6v6 rating)
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Read the instructions for your meter. If you don't have any instructions, search for them with google.
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Alright, dejected.
measured 438 on pin 3
set dmm to mV and turned bias pot slightly to 2.8 mV which is low, correct
I dunno, something seemed amiss--left it at that, plugged guitar in and now no sound.
First thought is that I blew a fuse despite no smoke or sound, checked it and seems fine.
measured dc voltage at filter caps and points mentioned and it seems like I am getting accurate readings/voltages
Any help with why there is no sound?
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Upon further inspection, is this fuse toast? the strands look alittle off.
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Test it with your meter.
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Beeps for continuity.
Had to be when I checked the bias pot--I dunno set the meter to mV and put probes into bias points but remember some crackling (wasn't very loud) through speaker when slowly turned pot--reached 2.8 and stopped.
Lamp glows and tubes glow (read that doesn't necessarily mean they're good)
measured a couple points and a few filter caps and seemed like correct dc voltage.
Speaker has continuity and speaker and guitar cable.
Tomorrow, think I will remove tubes and redo Steve's reply 52
If readings are similar, I will swap 1st preamp tube with another and move on down the line if no sound continues, I dunno.
In terms of the speaker, it is a one 8ohm speaker. I wired speaker (-) lug to ground of speaker jack and (+) lug of speaker to tip of speaker jack.
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^ You don't by any chance still have the amp plugged into the light bulb limiter, do you?
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No.
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Maybe double check your OT drawing If it is a multi-tap OT with windings for 4-8-16ohm speakers make sure that you have the correct wire on your speaker jack tip. Iv'e plugged an 8 ohm speaker in the 4 ohm jack by mistake and had very low volume.
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No multitap.
I am going to pull tubes and check voltages--figure if they're like before, then the circuit and hardware involved should be ok, I assume. I was using JJ ECC83 S pre and JJ 6V6 S out tubes. After that, I was reading that I should maybe and try to put a new 1st pre tube and sub on down the line. But guess it could be a jack(s), speaker, cable, but they seem to be fine.
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Pulled tubes and inspected--no whitish stuff on inside--left them out.
Checked voltages and numbers are very similar to those in what I posted in #72 above.
When I checked the voltage in Pin 5 of the 1st output--it was tricky to get a reading on it but I did--5 on 2nd output was easier but they weren't as quick as other readings. I am going to re-solder both of these lugs. I dunno to tell how if a pin is too loose--it hasn't fallen out but it doesn't seem that sturdy either.
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Before I started with tubes,
This is my bias supply.
I dunno but with bias points--should those 1 ohm resistors just be connecting with pin 8 And Then from pin 8 connect to cap?
I have that the bias point connects to pin 8 And to Cap
Ran out of space on my board but tried to mimic Steve's layout using bias points
Here's the mm
When I am measuring the bias resistors--black probe connects to com,
What should my red probe connect to VΩ or mA,
and then what setting mV or mA/A
From what I read milliamps is nearly identical to millivolts
Dont mean to annoy anyone
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When I am measuring the bias resistors--black probe connects to com,
What should my red probe connect to VΩ or mA,
and then what setting mV or mA/A
From what I read milliamps is nearly identical to millivolts
With a 1 ohm bias R between the power tubes K (cathode) and ground the DCmV will convert directly to DCmA's. So to make the test measurement easy we test for DCmV's.
So set your meter for mV and plug the red meter probe into VΩ.
(Your not annoying anyone. :icon_biggrin: )
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Brad
You're my technical tool guy, probably wouldn't have built my limiter if you wouldn't have stressed it
I'll blast "Shadow Play" just for you later!
Thanks
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:laugh: RORY!!!!!!!! :blob8:
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B---You sure bring some good luck.
I won't be posting any more troubles----cuuzzzzzzzzzzzzz....
This baby is pumping!!!!!!!!!
You could probably tell but, for whatever reason, I was nervous to put the tubes in, well after Brad helping me understand my dmm, I thought I would put the tubes in and try it out, and wouldn't you know--put 'em in---and no sound--dejected yet again. Felt miserable.
So, I decided to just measure across the bias resistors with my guitar plugged in. The reading was less than 1mV so I decided to adjust the bias pot a little. Then I strummed my guitar which was lying by the floor--nothing. Turned it a little bit more probably till 2mV or so, leaned down and strummed---what? I could hear something--at first I thought is was the strings echoing off the wall but it was above me and the speaker was on the table---adjusted the pot more and the volume started to rise and I started smiling. The tubes just weren't getting any current. I immediately realized you need to be hella slow with adjusting the pot too because it jumped to 24 mA fast and I quickly backed it down. Here's my breakdown.
Pin 3
450V 20.5mA (.0205) = static dissipation wattage of 9.225, then
Pin 3
430V 20.5mA (.0205) = static dissipation idling wattage of 8.815 which I was cool with (no pun intended)
I may try to bump it a little but still will keep it well under 12
The funniest thing (now it is) is I shut it off and removed the dmm and turned it back on to give it a go with my guitar.
Well, I powered on and set normal to about 2 and cranked master----No Sound Again!!!! :BangHead:
What the $*%&!!!!!!!!!!!!!!! Started sweating like a maniac and realized I was looking at the controls backwards. HA!
SO, I only turned the presence and bright pots---Such a relief! Backward controls and reverse pots---Ill get it eventually.
But yeah it can get loud---I went through some riffs but it was getting late. I will have fun with it this weekend. There is no hum at all. (I know everyone has their system but I am a firm believer in grounding each section with their respected filter cap and then grounded at one point at input. Im a believer because it works for me.) Anyway, I am pretty exhausted and beat mentally--but nothing like solving a dilemma--such a great feeling! I will be able to sleep good tonight without all those questions running through my head like last night.
Thanks to Brad and other members for their help/support when I hit a wall, but most importantly supreme thanks to Steve for bearing with me through all of it--I would have never made this thing without you--you're a good man. Lastly, thanks to Matt for offering this forum--it has given me the opportunity to enjoy something I really love.
Cheers All! :smiley:
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Sluckey did all the heavy lifting.
Very glad you got her figured out and up and singing! :icon_biggrin:
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I see a big problem with your bias test point wiring! You have two red wires on each red test point. One red wire goes to pin 8 of a power tube. That's good. The other red wire appears to go to the positive side of the bias caps. THAT'S BAD!
Remove the red wire that goes to the bias cap. Do that for each red test point. There should now be ONLY ONE wire on each test point and it should connect directly to pin 8 of a 6V6. The black test point should connect to chassis ground, preferably at the same point the PT center tap connects to chassis ground.
Now, connect a wire from the positive lead of the bias cap to chassis ground. Look at my layout. This is clearly shown.
When you have made this correction recheck your bias adjustment.
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Yes, I wasn't sure and didnt know.
My grounds are ground.
I ran out of space for my board but tried to copy yours.
On your layout, the 1 ohm resistors are connected between the bias caps and pin 8 of power tubes.
Since my 1 ohm resistors aren't on the board, I thought I should mimic that on bias point by having a wire to the cap and wire to pin 8. My reasoning might not make sense, but i was trying to copy how it looked physically to the eye not realising that the bias pot enables the connection to the output tubes and I was probably providing it twice in a sense.
So I should just keep the 1ohm resistors only connection to pin 8. Gotcha.
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On your layout, the 1 ohm resistors are connected between the bias caps and pin 8 of power tubes.
You are overlooking the fact that the turrets where the top of the 1Ω resistors are connected to the bottom of the bias caps are all connected to ground. IOW, the positive side of the caps are connected to ground. And the top side of my 1Ω resistors are also connected to ground.
So, you need to think of it in terms that one end of the 1Ω resistors connect to pin 8 of the tubes and the other end of those 1Ω resistors connect to ground. That's not the case with the way you have yours wired. When you fix that, the bias pot should be much easier to adjust correctly.
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Alright, disconnected the extra wires on the red bias points. Actually, wasn't as bad as I thought it would be.
I disconnected one and had to be careful because it involved underboard wire connection with resistor. I don't mind working with this fiberboard but once you get it set and screwed in, it's difficult to take back out and examine, if your connections are tight and really need to look, you're going to have to desolder some wires to free the board up which opens the potential for wiring issues when you go back to re-solder. Fortunately, I didn't have to do all that. With the second bias point removal, I just disconnected it from the red bias point and then used that as a ground (it was originally connected underboard to the (+) bias caps but I only had one ground for bias--I realized that upon inspection-the black bias point was the only ground)
Might be hard to follow but now there is a ground from black bias point and ground from (+) bias caps that meet up with other output grounds (striped red 2ndary, striped green filament and plate and screen ground) and they are the last point (opposite input) on ground bus.
So, now out with it man!
Pin 3 Valve 4
438V
MA .0212 which equals 9.28 static dissipation wattage
Pin 3 Valve 4
418V
MA .0212 which equals 8.86 static dissipation idling wattage
Any other voltages you think I should check, Steve? (if so, if you could, just let me know if it's ac, dc etc so I don't short with my mm)
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Um yeah, this thing rocks.
I don't even know if I would use my Muff Pi or Soul Food pedal with this. Definitely giving me rock tones that I like--haven't even tried cleans.
First thing that always comes to me is that from day after day playing electric unplugged, messing around with garageband or little practice amp and then I plug into a quality amp like this, is the clarity and range---it's awesome but you need to be on point. You hit a chord or note wrong and it's there--nowhere to hide.
I really pushed it and gave the neighbors something to think about.
Will check out the different settings. Right off the bat, noticed that the Presence is way different than that on my Bassman. It has like a bellowy, almost like reverbish effect when you jack it. But definitely significant.
Really enjoying myself.
For sure, a cool, amp.
I have a second Hammond AO43 chassis w/transformers (scored both on ebay for $100) so beyond happy with little amount of money needed to fulfill this.
Unless Steve or someone has technical question, this is pretty much it. Ill post when I finished the cab, just have to tung oil it and put on the hardware (handle, feet, etc.)
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Good job. Glad it all worked out.
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Here's the finished product.
Considering filming how it sounds with my phone. Have played it more and more and still figuring out tones--I have a strat with 7 setting pup selection that I installed but overwhelms my brain because I am always checking it out how things sound with it--neck or bridge or neck middle or bridge middle or all three :think1: I even haven't had an urge to put any pedals with it which to me is a good sign. Good earthy grit and can pack a punch.
I goofed alittle on the back of head with finishing washers but the thing has got it's little quirks all over the place.
The tung oil will probably take on a darker tone with time. Curious to run it through different speaker combos.
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Looks very nice! :icon_biggrin:
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nice good job!
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Perhaps, I celebrated too early but I was able to really play it this weekend and noticed something.
The amp is dead silent, however, when I push Normal volume past 6 or 7 a buzz/hum starts.
I maxed master volume and no problems. With all pots to 0, and I turn normal the buzz will start as mentioned so looking at that area.
I'm thinking perhaps my cap there between normal and bright pot (470pf) is suspect. One might be I misread the cap value (I hope I can read value on side but something tells me it was just labeled on the bag) or two, its polystyrene type and very fragile.
I dunno but going to open it up.
Any thoughts for troubleshooting?
TIA
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Any thoughts for troubleshooting
swap out V1, check for DC on the grids of V1 n V2. Is the buzz hum, like if you left the cable plugged into the amp, but no guitar, or more like filament 60-120hum?