New build based on Webster/Allan organ amp

[1blueheron]

I am starting this as a new thread as it appears the thread we had going on it became corrupted and it had moved past discussion of separate preamp/power amp PT's anyway.

So so for any one new to this discussion, a little background first. I am a newbie in tube amps.  A couple weeks ago I found a 1956 Allen s-12s organ at a local thrift store in semi-working condition.  The amp worked great but a few keys did not work and the pedal board was MIA.  Since my son is becoming a guitar nut, I thought hey, the thing is cheap enough let's buy it and use the amp as the base for a guitar amp.

And so this project was born.

It is a Webster Electric Co. Model 88-24 amplifier.  To this point I have been working with some great folks on this forum to get a working schematic of the amp and then figure out where to go from there.

We pretty much have the schematic complete but when I tried to post it in the thread last night something went haywire so we will start fresh and hopefully this will work better.

[1blueheron]

Here are a few photos for those who were not following in the other thread.
Current  tube layout is:

V1=6J5
V2= 6SL7
V3, V4 = 6L6
V5= 5U4

[1blueheron]

And a couple more

[1blueheron]

Special thanks to those who have been so helpful to this point, some really nice and helpful folks here.  I am learning a lot and appreciate their patience and mentoring.

BTW,   It has been brought to my attention by Bccowan that the amp apparently was made under several model numbers as he has one identical to it labelled as a  "Type 212-23648"   

[sluckey]

Take some voltage readings. I really need the voltages for points A, B, and C on the attached pic. Voltage readings for all tube pins would be helpful too. Be careful with your probe and be sure the meter switch is in the proper position.

[1blueheron]

Will do.  Hoping to borrow a better meter from work today.

[sluckey]

Here's what I've got for now. The schematic should agree with your wiring diagram at this point. If you have any questions or see anything that doesn't look right just ask.

[bmccowan]

Hi,
This is great of Sluckey to put in this level of effort helping with the project! Bravo - it's in excellent hands. And, does this qualify as yet another Sluckey "one last amp?"
I am the one with the identical Webster with a different model #. When I get a chance I will carefully compare mine with the schematic, but so far I am seeing no differences. I may also take some voltage readings to compare.
I plan to jump this amp in front of others as I think it'll be fun to work on it at the same time. I am likely to use a Valco, or Gibson type preamp, tweaking values trial and error, and may go pentode 6SJ7.
BlueHeron, you asked me about the transformer mfg. I don't know, and the code stamped on the PT does not coincide with any EIA mfg code that I know of. But, they sure look robust, and I have no concerns, as the Allen organs had a good reputation.

[1blueheron]

In the process of creating the schematic, I noticed that one of the black and yellow striped caps had a split in the side.  Should this be replaced?  What about the other caps?  There aren't that many so I could recap but I don't want to ruin any of the old mojo either so I am open to suggestions.  As I said in my first post on this, the amp sounded pretty good clean with very little hum or hiss detectable in the organ and was much the same when we hooked it up to a guitar, although it needed more pre-amp gain.

Bmccowan,  It will be interesting to see the two of these develop in the same general period of time and see what they sound like.  What are you thinking in terms of a speaker for it?  Will you build it as a head or combo?  I have the speaker from the organ I could use or I have some other speakers in my stash I might try.  If nothing suits our taste from the stockpile, I might spring for a new one but I'm getting ahead of myself...

 I am going to make a second attempt at pulling the voltage reading tonite.  Will post back when I have them.

[sluckey]

Don't replace anything until we see some voltage readings.

[bmccowan]

You will get way more gain with either preamp Sluckey offered up.
My amp - since I am always experimenting I will keep it as a head, and likely will just mount it on a board, until I decide to give it away to someone. I rarely (well never) sell these projects as I have an unrelated business to protect and do not want to risk a lawsuit if somebody decides to explore the guts and gets zapped! I've been know to trade an amp for a rhubarb pie.
I have vintage 12" and 15" Jensens I typically plug into. I would not hesitate to use any of the vintage series 12" Webers with this amp. But there are many other speakers that people rave about. I want to try the 12" Eminence Legend 1258 at some point. 

[1blueheron]

Take some voltage readings. I really need the voltages for points A, B, and C on the attached pic. Voltage readings for all tube pins would be helpful too. Be careful with your probe and be sure the meter switch is in the proper position.

I have some readings for you:

Wall voltage at time of testing was 124.0V AC

Voltage at Point"A" 341VDC
Voltage at point "B" 284VDC
Voltage at point "C" 260VDC

I will be adding them to the drawing.  Will take filament  and tube pin readings as well and post.

[sluckey]

OK. Now I want you to disconnect that orange wire from the top side of that big ole brown Ohmite 10K resistor. Tape the end of the wire. Now measure the voltages at A, B, and C again. They should be greater. Post those voltages. Then resolder the orange wire to the 10K resistor.

[1blueheron]

OK, will do shortly.  I just unplugged it a minute ago.  Detected a slight sizzling sound coming from the 30MFD 500 can capacitor.  It was very hot to the touch.  Does this mean it is bad, or just "reforming"? 
 

[1blueheron]

Disconnected orange wire from r16


Voltage at Point"A" 326VDC
Voltage at point "B" 310VDC
Voltage at point "C" 283VDC

[sluckey]

OK, will do shortly.  I just unplugged it a minute ago.  Detected a slight sizzling sound coming from the 30MFD 500 can capacitor.  It was very hot to the touch.  Does this mean it is bad, or just "reforming"? 

Filter caps should never be warm and definitely not hot. It's bad. Put the voltage checks on hold and replace that cap. It will cause the voltage readings to be invalid.

I suggest you get that 40x20x20x20/500v JJ can cap (and clamp) that Hoffman sells. It will replace that 30, the 16, and the 2x8s. All those filter caps are 60 years old and need to be replaced. That JJ can will save you some space and prevent some headaches later on.

[sluckey]

The voltage at point A is decreasing because that 30µF can is burning up. Don't turn the amp back on until you replace those caps.

[1blueheron]

Got it.  Amp is unplugged and will stay that way until I can get the caps replaced I resoldered the orange wire.

[PRR]

> Detected a slight sizzling sound coming from the 30MFD 500 can capacitor.  It was very hot to the touch.

You are not a Real Tech until you have blown-up a large cap and cleaned the wadding off the ceiling.

[sluckey]

When you order that JJ 40/20/20/20 cap can (with clamp) get two Mallory 150 series .1µF @ 630V to replace those two bumble bee caps. And get one 47µF @ 100V Nichion cap to replace the 50µF/100V can. Hoffman has all of these. Don't let the small size of that Nichion cap fool you. Electrolytic caps have come a long way since the '50s. Put the Nichion cap in parallel with R15 (big brown 225Ω resistor). The positive end must connect to V3 pin 8.

[1blueheron]

Ok, I plan to get those ordered today.  All the resistors should be good to go right other than possibly needing some differrent values depending on which preamp option we go with?

[sluckey]

Resistors are probably fine. You should be able to get a good reading on all those resistors except R7 and R17. Those are basically in parallel and the resistance reading for either will be about 1.8K. If you want to know the value of each individual resistor just disconnect one end of R17 and measure across each resistor. In fact, this may be a good exercise while you're waiting on parts. You don't have much time though if you order from Doug. 

I wouldn't worry about the preamp mod until the basic amp is up and running again.

Something else that will be a worthwhile learning experience... Study your wiring diagram and my schematic. Learn how they relate to each other. Especially the grounds. Schematics use a ground symbol rather than running confusing wires all over the place. Much easier to understand once you realize that all the ground symbols are electrically connected together, either by a wire or the metal chassis. Also, be able to locate a part on either drawing. Those reference designators for the components make that easy. This is all gonna be important when you begin building your new preamp because there aint no wiring diagram for that.

[1blueheron]

Parts are ordered.  I will check all resistor values in the meantime and replace if necessary.  I will also spend some time familiarizing myself with the schematics you have drawn and how they match up with the one I drew.

I found an additional piece of the puzzle today.  I figured I would go ahead and pull the speaker out of the organ.   It is connected to some type of transformer.  In the process of tracing the wires back it led me to the treble and bass controls and the tremolo/vibrato control.  I am not sure what produced the tremolo effect and how it all worked other than the gyro speaker.  I intend to draw a schematic of the wiring.  Perhaps the tone control portion will prove useful.  I will post some pictures of the affair tomorrow.  There are two wires that were cut off at the speaker and black taped.  Perhaps someone removed something?

[1blueheron]

Took resistor reading last night.

Here is what I came up with first number is the specified, second number in parenthesis is actual measured:

R1 =2.4k (2.74k)
R2 =100k (110k)
R3 =5.6k (5.7k)
R4 =1k (1.18k)
R5 =22k (20.3k)
R6 =300k (310k)
R7 =2k (1.9k) Did not un-solder so parallel reading with R7 will un-solder and check again.
R8 =2k (2k)
R9 =6.2k (6.6k)
R10 = 240k (246k)
R11 =100k (110k)
R12 =240k (244k)
R13 = 1000Ω (1028Ω)
R14 = 100k (108k)
R15 = 225k (236k)
R16 = 10,000Ω   Could not get a good reading on this one.
R17 = 16k (1.91K) Did not un-solder so parallel reading with R7 will un-solder and check again.

A quick google says values tend to drift upward with time and it looks like that is what mine have done.  Any reason to not just go ahead and replace with 1% metal film resistors?  Other than the ohmites, these are 1/2W resistors correct?

[sluckey]

R15 = 225k (236k)

That should be R15 = 225Ω (236Ω). Probably just an operator error but recheck.

R16 = 10,000Ω   Could not get a good reading on this one.

Look at the schematic (not your wiring diagram) and see if you can figure out why.

Any reason to not just go ahead and replace with 1% metal film resistors?  Other than the ohmites, these are 1/2W resistors correct?

Yes. DON'T FIX IT IF IT AIN'T BROKE! Nothing wrong with those resistors. There's a chance that something may go wrong during the process and then you'll have to figure out what. Leave 'em be.

[1blueheron]

Responses in Red

R15 = 225k (236k)

That should be R15 = 225Ω (236Ω). Probably just an operator error but recheck.  Correct.  Typo when I entered this AM.  Have it correct in my notebook and drawing.  I will edit table.

R16 = 10,000Ω   Could not get a good reading on this one.

Look at the schematic (not your wiring diagram) and see if you can figure out why.  I have a pretty good hunch based on your hint.  I will try again tonite and report back 

Any reason to not just go ahead and replace with 1% metal film resistors?  Other than the ohmites, these are 1/2W resistors correct?

Yes. DON'T FIX IT IF IT AIN'T BROKE! Nothing wrong with those resistors. There's a chance that something may go wrong during the process and then you'll have to figure out what. Leave 'em be.    OK.  Will do.

[1blueheron]

Here is some documentation of the speaker and the bass and treble controls.  Not sure if it is of any value in figuring this all out or re-use.

As you can see, someone hacked off the red and black wires here.  I assume this took the inductor offline as only one wire is connected to anything.  Not sure what its function was.

[1blueheron]

[quote R16 = 10,000Ω   Could not get a good reading on this one.

Look at the schematic (not your wiring diagram) and see if you can figure out why. 

R16 is good.  Lifted wire from one end to get the reading.  So before I was trying to read a loop correct?  Broke the loop by lifting one end?

[sluckey]

There's a big ole filter cap parallel to R16. That's messing up the meter reading.

[1blueheron]

Arrived home this eve to find my new parts in the Mailbox.  WooHoo!.  That was quick,  2 days turnaround on a USOS delivery,  Thanks Doug!

OK, so I have the old Caps removed.  They did not have removable leads.  They had threaded bases and wires extend up inside them.  So I will need to find some wire to install the new 40/20/20/20 Cap.  Is there a minimum gauge wire I need to use?  Wire on the old ones was pretty heavy.

Second question.  Can I delete the remote volume control at this point?  It is in the way of installing the caps and since I won't need it at least in that position, I thought it might be best to go ahead and delete it now.

I hope to get the new caps in tonite.

[sluckey]

I've been waiting for you. I have a plan that will remove the remote stuff and also free up some lugs on that terminal strip for the upcoming mod. Take some time to study this partial pic and be sure you understand what's happening. Please let me know if these instructions are too simplistic. Be careful when removing wires and components from the tube sockets and terminal strips. Don't want to break anything. 

1. Remove the three cans and their wire leads. Remove C3  (16µF) from the terminal strip. Discard caps.

2. Remove R3 and R4 and the remote connector. Discard resistors.

3. Disconnect the end of R2 (100K) from the small terminal strip. Just clip the lead very close to the small terminal strip. Leave the end dangling for now. The resistor will still be connected to V1-3.

4. Remove the small terminal strip and ground lug. Put the nut back on the choke.

5.Carefully remove R5 (22K) from the big terminal strip. Save it for use later.

6. Now carefully enlarge the hole where C6 (30µF) can was mounted and neatly install the new multi can and clamp. Orient the can as shown in the attached pic. You will probably need to temporarily move the shielded cable (and any other wires) out of the way while enlarging the hole. A hole punch makes this job very easy. You need one that's slightly smaller than the diameter of the new cap can. Hope you have one! Otherwise, roll your sleeves up and get sweaty.

7. Refer to the pic and wire the cap can EXACTLY as shown. Use fresh wires. AWG 20 is fine. Don't reuse any old wires you remove from this amp. Install the 22K resistor directly on the can as shown. If resistor leads are buggered then use a new 22K 1/2W.

8. Trim and connect the dangling end of R2 (100K) to the big terminal strip as shown.

9. Install the 47µF cap as shown. Positive end to the tube.

10. Install the two .1µF exactly as shown. Notice that I repositioned C4 away from the side of the chassis. This is to provide room for the tone pots later on.

Post a hi-rez pic when you are done. Be thinking about which preamp you want to use.

[sluckey]

BTW, I used that same cap can on my last project. Take a look at the pics. May give you ideas. Try to install your can as neatly as my can.

     http://sluckeyamps.com/smoky/smoky.htm

If you have any questions just ask. When you finish the above steps, your amp should be back operational just as before, but without the remote clutter. Don't turn on power until I see your next hi rez pic.
 

[1blueheron]

Instructions are perfect.  Working on it now.

[1blueheron]

I've been waiting for you. I have a plan that will remove the remote stuff and also free up some lugs on that terminal strip for the upcoming mod. Take some time to study this partial pic and be sure you understand what's happening. Please let me know if these instructions are too simplistic. Be careful when removing wires and components from the tube sockets and terminal strips. Don't want to break anything. 

1. Remove the three cans and their wire leads. Remove C3  (16µF) from the terminal strip. Discard caps.  Done.

2. Remove R3 and R4 and the remote connector. Discard resistors. Done

3. Disconnect the end of R2 (100K) from the small terminal strip. Just clip the lead very close to the small terminal strip. Leave the end dangling for now. The resistor will still be connected to V1-3. Done

4. Remove the small terminal strip and ground lug. Put the nut back on the choke.  Done

5.Carefully remove R5 (22K) from the big terminal strip. Save it for use later.  Done

6. Now carefully enlarge the hole where C6 (30µF) can was mounted and neatly install the new multi can and clamp. Orient the can as shown in the attached pic. You will probably need to temporarily move the shielded cable (and any other wires) out of the way while enlarging the hole. A hole punch makes this job very easy. You need one that's slightly smaller than the diameter of the new cap can. Hope you have one! Otherwise, roll your sleeves up and get sweaty.  I have a Greenlee slug buster at work.  I will bring it home tomorrow to neatly enlarge the hole.

7. Refer to the pic and wire the cap can EXACTLY as shown. Use fresh wires. AWG 20 is fine. Don't reuse any old wires you remove from this amp. Install the 22K resistor directly on the can as shown. If resistor leads are buggered then use a new 22K 1/2W. Tomorrow

8. Trim and connect the dangling end of R2 (100K) to the big terminal strip as shown. Done

9. Install the 47µF cap as shown. Positive end to the tube. Done

10. Install the two .1µF exactly as shown. Notice that I repositioned C4 away from the side of the chassis. This is to provide room for the tone pots later on.  Done

/quote ]

Will post a couple pics in the AM.

[sluckey]

I have a Greenlee slug buster at work.  I will bring it home tomorrow to neatly enlarge the hole.

My JJ can is 1-19/32" diameter. I used a radio chassis punch that cuts a 1-1/2" hole. This was perfect. The 1" conduit punch (1-3/16" actual size) is too small but may work. The 1-1/4" conduit punch (1-11/16" actual size) is too big but may also work if you have enough chassis left to drill the mounting screw holes for the clamp. Might be a good idea to punch a 1" and a 1-1/4" hole in a scrap piece of sheet metal and see which works best. Or you could just use the 1" punch and a little round file or Dremel work.

Also, a 1-3/8" step bit is an option.

EDIT... Here's another option that avoids making the big hole. If doing this, put the can in the same general location as my plan.

     https://el34world.com/projects/images/Img_9085.jpg

[1blueheron]

Ok, First, thank you for your kind help and clear instructions.  I was very tired last night and signed of without thanking you.  I apologize.

So here we go with some photos and questions.

1.  After installing the (2 ) .1uf Caps, and looking at the work,  particularly C4,  it occurred to me it might be best to put some insulating sleeves on the leads.  Are they fine as is or is shorting or is arcing an issue. If so I can go back and install sleeves.  Please advise.

2.  The old input leads and volume switch with grounding lug etc.  Should it be deleted at this time and (b) do I need to order a 1/4" shorting input jack?  If so, does input need to be insulated (isolated from chassis like marshal style input jack)

3.  What about Caps C1&C2?  Should I replace them?


As to the mounting location of the can cap.  I have space under the chassis  ( tired it last night and it just fits) if we are not going to re-use the holes where the remote volume connector and the input jack were at.  This would be cleaner and leave the chassis in more original condition than making a bigger hole in the top and also require less work.  It may also be easier for accessing and soldering the cap.   I can also do a little more work and mount it topside as I have it layed out in the pictures and as you originally advised, which would give more working space underneath.  Is there a preferred method?  I see pros and cons to both so I will seek your wisdom.

There was insufficient space in the hole of V4 pin 4 to make all the connections so I wrapped  the orange wire that will run from V4 pin 4 to X on the can, around the leg of R13 and soldered it.  Is there an issue with this? 

I still need to run the red wire for the cap can.  I was unclear on this.  I assume this is going to connect to the junction point of the red wire from V5 pin 5, the red wire from the output transformer and the red wire from the choke? In the drawing it does not show the red OT wire and the other two lines morph together without a clear junction point.  I am assuming the solder point on terminal strip is just left out?

[1blueheron]

And the Cap positioning

[1blueheron]

Obviously the can is upside down and just there to simulate size and location.

With any of the new connection points I tried as much as possible to remove old solder, clean,  install a mechanical connection of the wire and then re-solder.  It is tight space to work in. But I believe I have good joints on everything I touched.

Please feel free to criticize so that I can correct bad habits, learn, and improve my craft.

[sluckey]

1.  After installing the (2 ) .1uf Caps, and looking at the work,  particularly C4,  it occurred to me it might be best to put some insulating sleeves on the leads.  Are they fine as is or is shorting or is arcing an issue. If so I can go back and install sleeves.  Please advise.

Yes. Put sleeves on the leads of both caps.

2.  The old input leads and volume switch with grounding lug etc.  Should it be deleted at this time and (b) do I need to order a 1/4" shorting input jack?  If so, does input need to be insulated (isolated from chassis like marshal style input jack)

No. Don't delete those yet. They will be eliminated eventually, but not now.

3.  What about Caps C1&C2?  Should I replace them?

Leave them. They will eventually be eliminated, but not now.

As to the mounting location of the can cap.

My preferred method is to enlarge the hole so the body of the can will sit on the outside of the chassis and only the solder lugs will be inside the chassis. This will be the neatest and easiest to wire/work on solution. Next choice would be to mount the cap inside the chassis with the clamp attached to the end wall of the chassis.

There was insufficient space in the hole of V4 pin 4 to make all the connections so I wrapped  the orange wire that will run from V4 pin 4 to X on the can, around the leg of R13 and soldered it.  Is there an issue with this?

That's fine for now, as long as there is a good connection and no possibility of shorting to anything. Keep in mind that we will probably be removing R16 (10K/10W) and the orange wire that connects it to V4-4. If so, you can redo the soldering on V4-4 at that time.

I still need to run the red wire for the cap can.  I was unclear on this.  I assume this is going to connect to the junction point of the red wire from V5 pin 5, the red wire from the output transformer and the red wire from the choke?

That's correct. Let's call that lug 2. In future drawings I will label the lugs 1, 2, 3, etc., from left to right. There will be a wire from V5-5, another from the OT, another from the choke, and another from the cap can. There is another red wire that jumps to lug 6 on the terminal strip. Remove that wire. That will leave lugs 6 and 7 empty. We'll use them later.

Our goal at this point is to get the amp back up and running but without the remote control. I still want a good set of voltage readings. And we need to verify that the amp still works as it did before, although the volume will be low.

[1blueheron]

OK, I think I can handle that.  My time tonight will be limited and I will be off the grid over the weekend helping with cleanup effort in North Carolina.  I will try to post up any progress I make tonite.

As to the thoughts of which preamp...

I have some questions here in choosing.  My son primarily plays strats.  He and I prefer a full, thick tone and he tends to play more classic/hard southern rock,  Van Halen, Pink Floyd, 38special, Dire straits,Mark Knopfler,  David Gilmore,  type tones.   This may change over time but that's where he is at right now.  He is not into jazz, blues, or metal.

So I guess we fall somewhere between a Fender and a Marshall as far as overall sound charachter.  The Ampegs we have heard seem to generally fit in this category but I know very little about the tonestack configurations from a sonic perspective and use.  A little book work says I would probably lean towards a baxandall stack for functionality?  However, I like the sound and flexibility of the tone controls on Greis 5 which I understand is a Champ with modified AA764 tone stack?

I have not heard the ampeg b12n played on anything but a bass guitar.  How does it break up?  Any sound clips?

As for use, this amp will primarily be for home or school assembly use.  He is not playing in a band over drums or clubs.  It doesn't need to be loud.  More concerned with quality and flexibility, than qty of sound. 

I don't fully understand tube gain stages and how overdrive/distortion works in a tube setup.  Is  all of the gain developed in the first stage carried through by a multiplication factor with the second stage, or does a lower mu tube in the second stage damper gain or become overdriven by the first stage?   

 On the Rockola project you used (2)6SN7, (2) 6L6 setup. Fender AB763 preamp which is interesting to me based ono the sounds you describe.
 do you have any sound clips of it?

" I wanted to stay with the 6SN7, even though it's a medium mu tube, just to see if I could get away with it. I figured that if this amp could provide loud jukebox music from a ceramic phono pickup thru a meduim mu gain stage and cathode follower, it should be able to make a loud guitar noise through two medium mu gain stages. Sounds logical, right?

So, I simply duplicated the first gain stage and sandwiched the Fender tone stack between them. I was pleasantly surprised! It all worked very well together. I did add a raw control to the tone stack. And I put a switch on that 5KΩ field coil simulator. With that switch open, the B+ at nodes B and C increased about 80 volts, getting a little closer to the blackface sound. Just close the switch for a browner sound."

 

What is the difference between this and the (2)6SL7, (2) 6L6 setup?  Is it just more gain with the 6SL7's?  From what I understand the first stage should be low noise high gain correct?  Could the 6SL7 we have be moved to V1 for and then use a 6SN7 I have as V2 rather than another 6SL7 for V2?

I am trying to do a lot of reading on theory to understand this and wrap my head around it...  If you have some recommended primers to help me understand how the gain stages work please send a link.

[1blueheron]

New can cap is mounted and connections soldered up.  Volume pot and input back in place and I put sleeves on the legs of the caps that could touch anything else.  Will post a picture of it all tomorrow.  Thanks for your continued patience and support.  I feel like I'm making headway!

[sluckey]

He and I prefer a full, thick tone and he tends to play more classic/hard southern rock,  Van Halen, Pink Floyd, 38special, Dire straits, Mark Knopfler,  David Gilmore,  type tones.

Hey, I like those too, except for Van Halen.

The Ampeg has a warm, clean sound, a little creamy when pushed hard (Think "Long Cool Woman in a Black Dress"). The Rockola with the Fender preamp with the added raw control into cathode biased 6L6s will give you a good clean sound or a gritty slightly overdriven sound with some added compression. This is probably closer to the stuff you like. BTW, my Rockola runs two 6SL7s and two 6L6s. I switched out the 6SN7s shortly after building it and just never updated the web page. I would expect your amp to sound a lot like my Rockola if you choose the Fender preamp.

The reason I've suggested these two preamps is because I know the circuits I used will work well. And either would be pretty easy to stuff into your chassis. I don't have any sound clips.

[1blueheron]

OK, I guess we will go with the Rockola setup then. 

I will save the 6SN7 tubes and maybe later use them for a Moonlight build or something like that.

Here are pictures of last nights work.  I noticed some solder splatter shows up in the photos, I will make sure I get that all out before powering up and testing.  I think it all came out pretty nicely and the cap looks good sitting there.  Looks kinda like a black rook sitting there in its corner square with pawn in front , and the bishop king and queen...  Not sure why I thought of that, random thoughts...

I removed the red lug 6 jumper.

Can is in place and wired up.

Question on AC power cord.  I replaced the old cracked 2 wire cord with a 3 wire.  It it OK to ground the green wire on the chassis?  Should it run to the central chassis ground point or just the nearest convenient location?

Provided this all passes inspection, I guess I can take new readings when I return Sun. eve or Monday.

[1blueheron]

And here is the underside.

[sluckey]

That looks great! The green wire in the power cord needs to connect to chassis. Put a ring lug on the green wire and fasten to chassis with a nearby power transformer bolt/nut. Look at the attached pic. This is what I envision the mains wiring to look like.

The resistor on the cap can... Is it red/red/orange (22K)? On my monitor it looks like the orange band could be a yellow band.

Tell me about the wire you used for the cap can. That's not low voltage wire such as you would use for a HVAC thermostat, or sprinkler system, or door bell, is it?

1. The next step will be to power the amp on and measure the voltages on the cap can at points A, B, and C.

2. Then temporarily disconnect the orange wire from R16 and remeasure the voltages on the cap can at points A, B, and C. Reconnect the orange wire when done.

3. Finally, measure the voltages for all tube socket pins.

After voltage measurements, connect a guitar to the input jack and see if the amp sounds similar to what you heard before.

[1blueheron]

OK, I will get the green wire soldered to a lug and put it on the PT transformer bolt/nut.  That will be very convenient.

The resistor on the cap can was taken out of a new package that said 22k on it but in honesty I did not check it with ohm meter or check the color bands closely.  I will confirm its value and make sure is correct and replace if need be.

The wire I used for the cap is definitely not thermostat doorbell type wire. It is a 18AWG stranded/tinned wire. Looks very similar to MTW type wire.  I will strip a piece back and take a picture of it so you can see it. I do not know the specs on the insulation.  It is heavier than any of the other wire presently in the amp.  Is the concern current/voltage carrying capacity or insulation temp/breakdown?  I can replace with known spec wire if needed.

[sluckey]

Here's a parts list for everything you need for the mod. I highly recommend Hoffman's parts. You can get the 6SL7 from AES...

     https://www.tubesandmore.com/search/node/6sl7

[1blueheron]

Sluckey,

Thanks! That list is great.  I will try to get it ordered ASAP.   Just got back in town late last night and was pretty wiped out.  We had a flash flood Sat. eve while I was out of town that took out part of our driveway so  I have to play a bit of catch up and get that fixed and the grass mowed, but hope to get back on this very soon.  Might be able to get the voltage readings tonite or tomorrow night.

 

[1blueheron]

I was able to get the ground wire from the mains bonded to the chassis and the 22K resistor put in last night.  Then I powered it up and took some voltage readings.

Here is what I came up with:

A= 415V
B= 346V
C= 260V

V1
Pin 3= 97V
Pin 8=3V

V2
Pin 2= 132V
Pin 3= 2V
Pin 5= 101V

V3
Pin 3= 407V
Pin 4= 346V
Pin 5= 1V
Pin 8= 26V

V4
Pin 3=409V
Pin 4=346V
Pin 5=0V
Pin 6= 389V
Pin 8= 26V

V5
Pin 2=415V
Pin 5= 415V
Pin 6=26V

[1blueheron]

I plotted voltages on drawing.