TOS issues (5879 heater hook up)

[nateflanigan]

I fired up my TOS for the first time last night.  Nothing smoked, and I had some sound so, ya know, it's a start.  I have to really dime the volume to get any sound, which is really distorted.  The channel switching seems to be working though.

Before I get too deep into trouble shooting, it's not completely clear to me how to hook up the 5879 heaters.  I just noticed on the layout pins 4 and 5 are connected like they would be on a triode.  I have a twisted pair like on most amps, coming off the pilot light, I wired one of those to pin 4 and one to pin 5 (not connecting the pins).  I'm thinking this is incorrect. 

THANKS!

[Geezer]

http://tdsl.duncanamps.com/show.php?des=5879

The way you describe that have the heaters is correct.....the 4-5 pins are NOT connected together, one heater supply wire goes to pin 4, the other wire to pin 5.

There is something else wrong in your circuit wiring....double & triple check all connections & component values against the schematic & layout.

G

I corrected the layouts to reflect the correct heater connections.

http://www.el34world.com/Forum/index.php?topic=9636.0

[nateflanigan]

Thanks for clearing that up. 

I found a few significant errors that I've fixed, but I don't think I've got it right yet.  The overdrive channel sounds pretty much how I thought it would but the clean channel can't be right, mostly because it sounds crappy and I can't get a clean sound out of it.  A few resistors despite having the correct color code have very odd values, I'll desolder one leg.  In the mean time while I'm searching I wanted to make sure I understand the relay wiring correctly.  In the layout, I was assuming that the two middle dots represented the poles, on the pinout for the actual relay the poles are the bottom set of pins.  I don't know if I phrased that clearly...

[Geezer]

In the layout, I was assuming that the two middle dots represented the poles, on the pinout for the actual relay the poles are the bottom set of pins.  I don't know if I phrased that clearly...

Set you meter for continuity & see where the switched poles actually are on you relay.......some are set up like a normal DPDT switch & others have the common @ one end & the switched poles together/beside each other at the opposite end.

[nateflanigan]

I'm using Doug's relay, so it was easy figure out where the poles were on the actual object.  What I was taking for granted was that in the layout drawing these were the poles. 



I know it's sort of a dumb question, but I also know that a lot of my mistakes come from thinking something is obvious.

[Geezer]

Yeah, the relays are drawn as simple DPDT switches, as we don't know what relays or other switching methods the builder may be using.
We tend to simplify the drawings & take for granted that folks know how to implement them using their own methods....sorry that you are learning that "on the fly", but I suspect you are learning things that you probably wouldn't if you did a "kit/paint by the numbers" build.

So, how's it coming along? Maybe post some voltages & we could spot something obvious in those that could point to where your problem is(?).

Geezer

[nateflanigan]

Right, I figured as much but didn't want to assume anything.  

Here's a link to my voltages...
For the most part everything looks OK to me, except the PI that seems pretty out of whack.  Pin 1 of V1 is a little high as well.  


http://www.el34world.com/charts/valve/ValveData.php?e=view&f=10618

I wanted to include my power rail node voltages as well.  They're on the high side as well.
A)  457
B)  456
C)  376
D)  323
E)  236
F)  233

FWIW all the resistors around the C node are measuring at the correct values.  I can't think of what else to check for regarding those high PI voltages.

[nateflanigan]

It dawned on me that I should try using the fx loop out to test out the preamp.  I have one of those Laney 100w Tony Iommi heads sitting around that has a poweramp input.  Long story short, it worked and sounds really cool. 

I'll continue to comb over the poweramp section for errors.  So far aside from changing out the plate resistors to get the B+ down I' don't really know how to proceed.

[sluckey]

Closely check the wiring and component values for V4 grids and cathodes circuit. You listed the grid voltages as zero, but they should be pretty high positive. It's hard to get an accurate grid voltage check on that circuit, but zero is definitely wrong. High plates and low cathode voltages indicate the tube is not conducting very well. Also insure the coupling cap between the FX jack and V4-2 is in place and good.

A common mistake I've seen several times is using a 470K rather than a 470Ω on V4 pins 3/8 cathodes.

[Geezer]

This has nothing to do with your high voltage problem, but something to check as part of the whole picture.......

Do you have the NFB (neg feedback) hooked up yet?
If yes, then try disconnecting it & giving the PA section a try.....any better?

Attach a clip lead to the NFB connection.
With the amp on, when you (carefully) re-connect the NFB, does the amp have less volume (softer) or more volume (louder)?
If less volume, the nfb phasing is correct.
If louder, the phasing is incorrect (you have POSITIVE feedback) and you need to reverse the OT primary leads.

That's one place on a new build that is good to eliminate as a problem before chasing other potential problems.

G

[nateflanigan]

Messed around some more tonight... now I'm really not sure what to think.  

measuring about 20v on the grids now, all other voltages are the same.  Maybe I was just being hasty.

The problem I guess is that I can't get any kind of usable clean sound.  If I have the master and the clean all the way up I can get the input gain up to maybe "two".  Even that I wouldn't call clean, it sounds pretty anemic and definitely isn't loud enough to play with other people .  If I bring up the input volume it's a pretty rich awesome distortion sound, but that makes the amp into an overdrive and super overdrive kind of thing.

What kind of settings are you guys using for clean tones?  Perception of volume is so relative, but I would say anything less than the master all the way up is bedroom levels.

The NFB test didn't change much either way.

[tubenit]

The problem I guess is that I can't get any kind of usable clean sound.  If I have the master and the clean all the way up I can get the input gain up to maybe "two".  Even that I wouldn't call clean, it sounds pretty anemic and definitely isn't loud enough to play with other people .

I think you have something wired incorrectly.  

Here are the original pot settings that I used the most and current ones (after recent tweaks).

The footswitchable relay goes between very nice clean and very overdriven tones.  These would be settings I use to actually play with the band which has a loud keyboard and drummer. I have waaayyy more volume still on tap. I had the VVR maybe set on 4-5 last time I used the amp with the band.

with respect, Tubenit

[nateflanigan]

Thank you, it's a little late to fire up the amp now, but that will be a big help.  I'll keep looking over the wiring.

[Geezer]

Does your amp have a VVR like Tubenit's, or did you not wire the VVR in?

If you DO have the VVR, that could be a problem right there (it could be installed incorrectly & limiting your headroom & overall volume).

Use a highlighter & go back over every connection & component value to be sure all is correct. Maybe take some hi-res pics & post them?

G

[nateflanigan]

No VVR, I wanted to get it working correctly before I messed with that.

[tubenit]

If you aren't using a VVR and have a pre LTPI master volume (as opposed to a PPIMV) then the amp should be capable of being quite loud.

Be sure to measure every resistor & potentiotmeter in the amp. Check grounds for continuity.

Do as Geezer suggested and use a highlighter pen to highlight each portion of the schematic and/or layout after you've checked it.

With respect, Tubenit

[Geezer]

No VVR, I wanted to get it working correctly before I messed with that.

Well, that's one less thing to worry about right now..........

[nateflanigan]

Insert Quote
If you aren't using a VVR and have a pre LTPI master volume (as opposed to a PPIMV) then the amp should be capable of being quite loud.

I wired everything up (well attempted) just like the layouts.  So that would be a PPIMV.

I set up the TOS with the laney head again using the settings tubenit posted.  Sounds great.  I feel confident that the issue is not in the pre amp. 

So far I haven't found any problems with the PI section, all components tested correctly.  I did find something odd though when I was checking to see if anything was shorting to ground.  I noticed pin 6 of the power tubes had continuity to ground, then I realized that the master volume (dual 250k) was all the way down.  When I turned it up pin 6 of v6 still had continuity to ground (pin 6 of v5 did not).  The wiper of the, we'll say, front half of the pot shorts to ground also.  I pulled the pot off of the chassis, no change, nor could I see anything touching anything it shouldn't be touching.  I'm wondering if the pot is bad, or if maybe I damaged it trying to solder the bus to the back (it was uncooperative).
 

[Geezer]

I'm wondering if the pot is bad, or if maybe I damaged it trying to solder the bus to the back (it was uncooperative).

I would say it is suspect.......disconnect it & (temp) put a couple of 220k (or something close) to ground in it's place....any change?

[sluckey]

Can you post some hi rez pics?

[nateflanigan]

I found some more problems.  The issue with PPIMV and the power tube pin shorting to ground was a kink in the shielded cable I used.  The shield had cut through and was touching the lead.  Fixed that, it helped with the overall volume but not the gaininess.  Then I noticed on the schematic there's a 1 ohm resistors of pin 8 of each tube that is not on the layout.  That helped as well, but sort of hard to say how.  I messed around with the NFB some more, I felt like maybe it was a little less edgy with the NFB disconnected, barely perceptible though.  So I switched the leads coming off of the PPIMV, meaning the lead that went to V5 now goes to V6 and vice versa.  Really not much difference that I can hear either way.

Set up that way I can get some sounds I like, some really nice cleanish picking, but if I strum a big chord it's a little dirty for my tastes. 

Then I switched V1 and V2, for me a 12ay7 sounds great in V1.  It took just enough of the edge off.  Using the 12ax7 in V2 is a little questionable. 

I'll try and post some pics today, I need to finish up a pre amp, and it probably wouldn't hurt to do some laundry...

[nateflanigan]

Some more observations and what not...

I think I've got the amp built correctly.  It behaves really differently with different guitars.  I had been testing it with an es-335 type guitar.  With humbuckers it's just too hot for me, I can barely squeeze out a clean tone, but the overdrives just wail.  With my jag it's the opposite, epic cleans, with a kind of crunchy boost on the od channel but definitely not searing lead sounds.  My Ric is pretty much in the middle, and sounds fantastic.

Has anyone else experienced anything like this?  I don't really know what to think about it.  I'll try it out with my band this week.

[tubenit]

Sure the TOS sounds different with different guitars.

If you can't get the TOS clean enough to suit yourself with the 5E3 type tone stack, you can consider this one and losing the fat control by going back to a single unparalleled triode.  That should get you a cleaner tone on the clean channel. However, with the mid-boost and PAB....... you can still get a great  overdriven tone.

With respect, Tubenit

[nateflanigan]

Thanks, tubenit I'll give that a try  What does PAB mean?  I'm really looking forward to tweaking around with this amp.  I moded the normal channel of my ab763 with freshstarts help but really felt no need to tinker beyond that.  But the TOS is so different, I guess it's kind of liberating that there's no real right or wrong with it.

I noticed that on the schematic there's a .001 cap bypassing the 100k resistor off of node D going to the plate of v2b that is not on the layout.

Thank you for all your help

[tubenit]

PAB is preamp boost. The PAB is that center off spdt that is shown.

I'd place the .001 across the 100k on V2b and see if you like it.  The TOS is a great amp. The favorite of all I've owned,played or built BUT you have to tweak it to match the tone you want.

With respect, Tubenit

[Tone Junkie]

With the TOS what I noticed the most was the volume knob on the guitar really has a lot of play in your tone with the hot pickups back off on the volume and it settles right down I like It in that if you need good cleans its right at your volume knob probably more so that any amp Ive had a chance to play around with, Thats part of the beauty of this design. Bill

[nateflanigan]

Tubenit, I get the PAB switch but whats the switch with the 390p cap?

Tone Junkie, I don't know if I'm crazy, or if my hearing is garbage or what but every time on every guitar with every amp I've ever rolled back the volume it just sounds terrible to me.  I don't know what I'm doing wrong there.

[tubenit]

whats the switch with the 390p cap?

However, with the mid-boost and PAB....... you can still get a great  overdriven tone.

With respect, Tubenit

[Tone Junkie]

For me the volume knob thing probably works better with my strat . I have emg,s on my SG and it doesnt work so well with that one.
Bill

[Geezer]

These amps are VERY sensitive to input signal from the guitar. You must to be able to roll back the guitar volume pot to get them to clean up, then roll it up to get the OD tones.
If your guitar becomes muddy/dull sounding when the pot is rolled back, then you need to install a "treble bleed" mod to get the brightness to stay as you roll it down.

Without that ability, all you are going to get is overdrive.
I use the volume pot all the time, constantly rolling to up & down slightly to get slightly cleaner & dirtier tones. When you learn to do that trick, you have almost endless tone variations at your command simply by moving the pot one way or another (along with the tone pot).

I used to just leave my volume all the way up & only recently (the last 10 years or so) found the "secret". It opened up a whole new world! Now I rarely have the pot all the way up, but adjust the amp to a good tone with the pot ~~ 1/2 to 2/3 up, then tweak on-the-fly from there.

See these threads, and there is a ton of info on the web, such as a Duncan, Kinman, Dimarzio & such.

http://www.el34world.com/Forum/index.php?topic=4963.0

http://www.el34world.com/Forum/index.php?topic=6388.0

http://www.kinman.com/guitar-pickups/technical-support/perfect-guitar/#volumePots

G

[nateflanigan]

Thank you Geezer.  I really look forward to reading up on that stuff, I've always wanted to do the volume pot thing.

Tubenit, I was just studying the differences between your schematic and the "standard" schematic.  The differences don't seem subtle, hopefully I'll have time to put together a parts list this weekend for a few variations.  I think it's great that this amp is all about tweaking, I don't want to say I'm over clones but it's refreshing to do something different.

I had a 2x10 cab set aside for this that I finally loaded with eminence ramrods, that was another step in the right direction.

[nateflanigan]

It's been a little while but I finally got around to installing the treble bleed mod, in addition I wired up a bunch of switching stuff.  My main guitar (a parts tele deluxe) now has 2 humbuckers, one volume, series/parallel, "spin-a-split" and phase reversal.  The switching is kind of fun and most effective on the bridge pick-up.  The Treble Bleed is great though, really fantastic.  Thanks for turning me on to it. 

I haven't tried it with the TOS yet, I need to reconnect a few things, plus my VVR just arrived in the mail.  Can't wait till the weekend.