Uncle Dougs Supro Tremo-Verb... Need Help!

[Mjcopp]

Hey guys. Welcome to my nightmare. This is my first time build and first time electronics endeavor. After studying for 5 months I decided on the Supro Tremo-Verb per Uncle Dougs’ 8 part youtube video series. When I first powered up, the two in-series, 330 ohm/2w cb resistors burned up and the cb cap exploded. Yikes! Not what I expected. Since then, I have been relentlessly researching and tinkering in this amp, (for the past 3 months) hoping to accomplish this on my own, but I humbly admit I need help!!! I have read over 100 threads but can’t find the answers. Please  fellas, if you can help me get this amp going, I will be most grateful.
The problems are as follows:
Very low volume, only 1-2 watts power. (Should be around 15w)
Muddy, distorted tone.
No Tremelo.
Link to schematic:
https://m.box.com/shared_item/https%3A%2F%2Fapp.box.com%2Fs%2Fu945p1s2dv7ffrok96ux52lseya2rjv4

I have traced out my wiring per the schematic a dozen times and can find no mistakes presently. I truly hope someone else can!

Voltage measurements: (schematic specs in parenthesis)

V6 5y3 nos
Pins 2&8: 379vdc
Pins 4&6: 339vac


V5 5881 new tung sol
Plate 373 (360)
Screen 370 (350)
Grid .164 (0)
Cathode 30 (17)

V4a 12ax7 nos reverb recovery
Plate 170 (120)
Grid 0
Cathode 1.08 (1.2)

V4b driver for power tube
Plate 180 (140)
Grid 0
Cathode 1.75 (1.6)

V3a 12ax7 nos reverb driver
Plate pin1 366 (350)
Grid pin2 .03 (0)
Cathode pin3 3.7 (1.2)

V3b
Plate pin6 365 (350)
Grid pin7 .42 (0)
Cathode pin8 4.08 (2.4)

V2a 12ax7 (Marshall) tremelo
Plate pin1 87-140 (140) oscillating?
Grid pin2 1.2 (?)
Cathode pin3 .3 (.4)

V2b
Plate pin6 300 (240)
Grid pin7 0
Cathode pin8 2.4 (2)

V1 12ax7 nos
Plate 231 (180)
Grid 0
Cathode 2.4 (2)

All heater filaments: 6.5 vac
B+1: 375 (360)
B+2: 366 (350)
B+3: 300 (240)
V5 Plate to cathode: 340
Cathode bias resistor: 680 ohms
Bias voltage: 30v
Plate current V5: 45.2mA
Plate dissipation: 17 watts
Plate current V1: .3mA
Plate current V4: .4mA

Pot resistances: (viewed from back of pot)
Vol R lug-Wiper: 0-497ohms  L-W: 0-285
Tone R-W: 0-465  L-W: 0-465
Trem Int R-W: 0-0  L-W: 0-256
Trem Spd R-W: 0-425  L-W: 0-458
Rev R-W: 0-90  L-W: 0-81
No Dc voltage on pots except Trem Spd showing 7-14vdc oscillating b/t L lug - ground, and Wiper – ground.

Sidenote: Uncle Doug’s final measurements with 5y3, 5881 & 656 ohm cbr were:
Plate current: 45.4 mA
C-P voltage: 333v
Plate dissipation: 15.1 watts
Calculated bias voltage of 29.6vdc
His build sounds real nice. He claims it needed no adjustments, just wired it up and Wa-lah! Beautiful tone!

Other tidbits...
NOS tubes newly purchased from kcanos tubes. 5881 tung sol brand new. Marshall 12ax7 pulled from another amp, (good tube) used in place of 12at7 reverb driver. I had a 12au7 in v2 originally, but thought it might draw too much current for the P.T. to handle? All 12ax7s have been interchanged multiple times with no changes. Light bulb limiter stays dim with 250watt bulb.

V1 pins 1&2 pop nice and loud when probed. V4 pins 6&7 pop. V5 power tube grid pin5 does not pop at all when probed. Checked all R values (within spec). Checked all ground connections for continuity, (good). P.T. voltages test good. P.T.  resistance between HVac leads to CTap (red wires to rect plates) tested 174 & 185 ohms. Replaced O.T. with a new Weber WSE15, (5k ohms). Speaker is a new Weber 12F150.

 I also shorted the tremelo footswitch jack because the footswitch I purchased was defective. Everything else is per the schematic. The biggest difference I took the liberty of changing is to use a turret board instead of strictly pt. to pt. The board was pretty at first, but after 3 months of toying with it, and changing to a star grounding scheme I hadn’t originally planned for, it is now quite nasty. You will laugh (or cry?)when you see it. No squeals, hiss or hum… just quiet, warble-less, muddy distortion.

I do not have an oscilloscope, signal generator or variac, just a DMM.
I will try to include some pics.
Please let me know what you guys think?

[pompeiisneaks]

On quick review, most of those voltages 'seem' okay, but I'd definitely like to see pictures.  What you're explaining seems to me that a few things may be going on.  1. somehow the signal is finding a path partway at least to ground more than on down the line.  You'd likely need an oscilloscope to track down where it is, and isn't.  Also, there could be connections that aren't perfectly soldered, I'd use a wooden or plastic chopstick to tap components all over the signal chain and see if things suddenly change.  If so you should reflow the solder around those connections. 

~Phil

[Mjcopp]

Thanks Phil, I'll try to get pics up later today.

[Mjcopp]

Pics:

[Mjcopp]

pics 3, 4

[Mjcopp]

Pics 5, 6

[Mjcopp]

Cab

[Mjcopp]

Panel

[pompeiisneaks]

First, the pics are a bit dark and hard to see on the top down view but form some of the side angles I think I noted something wrong.  This is just one thing I've noticed.  I'm attaching a pic to show a red line on a lead that I think is the tube cathode connection to a board and the resistor/capacitor.  The capacitor here and on all the other locations seems 'backwards'  Normally the positive side of the capacitor has the dip around the top (dimple some call it).  On yours it appears away from the tube.  I've drawn a red line from the socket on the wire to the connection I "think" is the cap.  That cap, if that lead comes from the socket straight to the cap for the cathode, is definitely upside down, and others may be the same.  The + end connects to the socket, and the - end connects to ground directly.

They all may be in backwards.  This would be a major problem.  Also it does look like a lot of the solder connections are 'grey' instead of shiny and aren't well flowed to create a solid joint. 

let me know about those electrolytic caps first.

~Phil

[pompeiisneaks]

In fact here's a pic from one of my amps before I put the board inside, I've put a red + at the positive top side and a - at the bottom and even circled on the cap where the + is to show that end is positive.  That's the side that connects to the tube pin.

~Phil

[sluckey]

Could we see your board layout to compare to the schematic?

[Mjcopp]

Phil, I had all the caps oriented as you suggested. But I read on Aikens' site that the cathode bypass caps banded end, (which I assumed is positive) goes to ground. Did I mis-understand this? Anyway, I just flipped the caps yesterday, with no change. I'm starting to think I should buy a new board and turrets and start over.
Sluckey, I will re-draw my layout and post it soon. Thanks guys.

[pompeiisneaks]

Those definitely matter, the dented end is positive and goes towards the tube sockets, the only time they can sometimes be 'backwards' is in bias circuits.  They may have been damaged.  As for the turret board, it can't easily be messed up too much.  If you want to 'start over' you could remove it, clean all the solder off the turrets with some desoldering braid and try new wires and maybe test all resistors for good values, and replace any caps taht seem to maybe be damaged in some way or don't test for their value.  I think you likely can get it as is if you're just methodical about getting good solder connections etc. 

[Mjcopp]

Layout diagram

[sluckey]

Well that certainly explains why that cathode cap exploded! Every bypass cap on the board in your pics is backwards and needs to be installed properly. They are marked to show the polarity.

I've read a lot of stuff on Aiken's site but don't recall that statement.

[drew]

^ I'm thinking MJ might have been reading this: http://www.aikenamps.com/index.php/where-to-connect-the-outside-foil-on-capacitors and mistakenly thinking that Aiken was talking about electrolytic capacitors instead of non-electrolytics.

[sluckey]

That's what I thought too. However, the article starts with these words "Some non-electrolytic capacitors have a banded end" and never mentions "cathode bypass caps banded end". The caps on Mjcopp's board have a light blue stripe that has several negative symbols inside arrows that point to the negative end of the cap.

[Mjcopp]

Ok, I'll flip the caps and report back.

[sluckey]

Ok, I'll flip the caps and report back.

Most of those caps are probably not damaged because they have only had a couple volts on them. But that 50µF that's connected to the cathode of the output tube has had 30V on it. It's likely damaged. One cap has already exploded! I would throw that cap away and get a fresh one. The amp will work without that cap if you don't have a replacement on hand but it won't be as loud as it would be with the cap.

[pompeiisneaks]

Yeah I mentioned that earlier too, they're likely damaged and you'll need to replace them.   If you put them in the right way and they still seem to 'work' it may be degraded performance and add a lot of noise or just blow up early. 

~Phil

[Mjcopp]

I ordered new caps from Doug. When they arrive, I'll install and let you know the results. Thanks guys.

[Mjcopp]

Well fellas, I replaced all the electrolytic caps as directed with absolutely no changes in sound or voltage readings. Still same muddy, distorted low volume and no tremelo. I re-flowed most of the solder joints as well. Any ideas?

[pompeiisneaks]

New updated pictures would be great, also, as mentioned a bit more light so the innards are clearer.  Muddy sound to me makes me think that possibly the tone pot is wired wrong in some way so it's always at max cut, but not sure.  If we can see pictures, we could find something else that may look odd?

~Phil

[Mjcopp]

Updated pics:

[Mjcopp]

Pots right to left: vol, tone, trem intens, trem spd, reverb

[davidwpack]

Is your shielded wire grounded? Looks like your soldering iron isn't hot enough, or maybe using to thick guage of solder.

[drew]

 "I also shorted the tremelo footswitch jack because the footswitch I purchased was defective. Everything else is per the schematic. The biggest difference I took the liberty of changing is to use a turret board instead of strictly pt. to pt. "


Is the hand-drawn layout your own work, or someone else's, or someone else's VERIFIED layout?

[davidwpack]

I'm looking at the pictures on a phone but it looks like your red wires going to your rectifier doesn't have any solder. It also looks like your 2 wires on your fuse holder are connected with solder flow. I'm not sure how your filament wiring is done either. Are you going directly to a tube socket and then to the lamp? Are you using 100 ohm resistors for a tap? Looks like a lot of your solder joints are black. Like I said, I'm away from my computer and looking on a phone but that's a few things I see.

[Mjcopp]

Layout is my own, based on Valco schematic and Uncle dougs pt to pt layout diagram.

[Mjcopp]

Shielded wires are grounded at one end. Fuse holder is good. Rect red wires have solder. I started with a 25 watt iron, recently switched to 40 watt.

[Mjcopp]

Couple questions:
Why no pop or noise when probing grid of power tube? Incorrect bias choking off tube? Problem between power tube and O.T.?
Why is B+3 voltage 60 vdc above spec? 12ax7s not drawing enough current? Why?
(V1-1:  .3mA, V2-1:  .5mA, V4-6:  .4mA)
Why zero resistance on tremelo intensity pot right lug to wiper? (Left lug to wiper has 0-256 ohms).
Does tone control look like its wired properly?

Thanks for any comments guys!

[drew]

You don't still have amp connected to light bulb limiter, right?


What are B+ voltages right at power supply caps with only rectifier tube in?


Are you sure whatever the two resistors are between B+2 and 3 are giving you 15k ohms?


Is it possible you cooked trem intensity pot trying to solder to back of casing? Have a spare one?

[sluckey]

Why no pop or noise when probing grid of power tube? Incorrect bias choking off tube? Problem between power tube and O.T.?

Sometimes you get a pop, sometimes you don't. I would not be concerned.

Why is B+3 voltage 60 vdc above spec? 12ax7s not drawing enough current? Why?

There seems to be some inconsistencies among the voltages on U. Doug's schematic. Using cathode voltages and cathode resistance for all tubes that node B3 feeds, I calculated a total of 4.3mA current drawn from node B3. But if you calculate node B3 current using the B3 and B2 voltage numbers and the 15K resistance, you will get 7.3mA. So where is the extra 3mA going? I doubt that 10µF filter cap is leaking 3mA, but who can say. I think B3 is probably higher than what's shown on the schematic. At any rate, it's not a problem.
 

Why zero resistance on tremelo intensity pot right lug to wiper? (Left lug to wiper has 0-256 ohms).

Maybe the right lug is shorted to the wiper. But that's not a problem. I would have soldered a jumper between that vacant lug and the wiper anyway. Same for the tone and speed pots.

Does tone control look like its wired properly?

yes

[Mjcopp]

Drew - not plugged into light bulb limiter.
B+ is 483vdc at nodes 1, 2, 3 and 481vdc at node 4.
Resistors at B+2-3 is 14.85 ohms.
Yes, I could have burned the pot on my initial wiring attempt, but Sluckey says its not a problem?

Sluckey - if none of these issues are a problem, what do you suspect might be causing the lack of power/volume, muddy distortion and no tremelo?

Thanks guys

[sluckey]

I suspect wiring errors or poor soldering. Let's divide and conquer. The low volume and muddy distortion are probably related. Let's tackle the tremolo first.

The changing voltages listed for V2a indicate the trem oscillator is likely working. But the trem signal is not getting through V2b to V1. One of your pics shows a green/yellow wire jumper across the footswitch jack. That will kill the trem signal. Remove that jumper and see if the trem doesn't start working.

[Mjcopp]

I don't believe it! I have tremelo! I don't understand why, but at this point I don't care. It did not work without the jumper and the footswitch now works as well. Thank you Sluckey! Whats next brother? The volume and tone is still the same. But man, you have given me hope!

[Platefire]

I've been reading all the process and I don't recall anybody mentioning double checking the tubes or trying replacement tubes one at a time. A tube could have been effected in the big blow up.

I can understand lack of experience in soldering because I've certainly been there but a lot of those solder joints look dull and not shinny but---I think it was said the joints have been re-flowed.

Mjcopp---I feel your frustration and can tell it's been a long hard road. I have had projects just as tough and seemed impossible to get working but these guys here pulled me through every time and they will you too. So just hang in there and be patient. That thing will be singing like a bird before long and you'll be grinning like a mule eating barbwire. Platefire

[sluckey]

That jumper wire was the equivalent of having the tremolo footswitch permanently turned off or having the Intensity pot always set to zero. Totally killed the tremolo signal trying to get to the grid of V2b. Why didn't it work before you put the jumper on the footswitch jack? Most likely because of all those cathode bypass caps that were installed backwards.

What's next? Tell me what output transformer you have? What speaker? Then do a complete new set of voltage readings, B1, B2, B3, and all tube pins even if the reading is zero. There should be a lot of changes now that the cathode caps are installed properly. Hopefully the voltage readings will give us a hint. And describe the sound your amp is making with a little more detail. For example, is it loud enough that you can't hear someone tanking in a normal voice if the amp is cranked? Does the amp sound clean and tone control works at low volume? Those kind of details.

[sluckey]

...grinning like a mule eating barbwire.

Yeow! That just sounds painful!

In the deep South we would have said "grinning like a billy goat (or a jackass, depending on the company you're with) eating briars". Now I've actually seen that. They will move their lips to avoid the briars touching a tender spot. They show a lot of teeth. It really looks like they are grinning. 

[Platefire]

Correction! I think your right! Think the saying is "Grinning like a mule eating Saw Briers". No mule in his right mind would eat Barbwire! Or when someone is puzzled or confused we say "He's Looking like a Calf staring at a new Gate"!

Any Rate, I know Mjcopp will be happy when it's all said and done! If it were me, I would also get out my MM and start doing continuity checks from one point to the other. One lousy solder joint can gum up the whole works. Platefire

[sluckey]

"He's Looking like a Calf staring at a new Gate"!

Don't remember that one but I certainly get it. 

[drew]

Resistors at B+2-3 is 14.85 ohms.

You want 15000 ohms. Did you leave out the "k" or is it really this low?

[sluckey]

He's been leaving out the "K" in most of his resistance readings.

[Mjcopp]

Sorry for leaving out the "K". I will do as suggested and post tomorro. I understand if folks are busy with the holiday. I'm very thankful for your help. Until then, Happy Thanksgiving.

[shooter]

Yeow! That just sounds painful!

we had a pet goat growing up, ate a $1000 worth of the rich guys pines n flowers so my dad took it to a friends farm, it died from eating nails mixed in with food stuff on the barn floor
I still keep askin my wife for a replacement

[sluckey]

I'll be around all day on Thursday.

[Mjcopp]

Hey guys, here's the latest update:
I have replaced the power tube. I have not replaced the 5y3. I have not replaced the 12ax7s, but interchanged them in all the sockets with no changes. I performed a continuity check thru entire amp and found no problems. The O.T. is a Weber WSE15. The speaker is a Weber 12F150, 8 ohm/25 watt, both brand new. The volume, when cranked is low enough to carry on a normal conversation. Thru a fender tele, bridge pup with tone at max treble plugged in high input, vol at 9:00 & tone at max treble Amp sounds slightly distorted and muddy. With tone turned to max bass - no distortion (and  much darker tone). So yes tone works at low vol. Thru low input, same results with vol. Turned to 10:00.

Voltages:
B+1:  379v
B+2:  368v
B+3:  300v

V1-1:  216v
V1-2:  .6mv
V1-3:  2.3v

V2-1:  141-173v
V2-2:  1v
V2-3:  .45v (oscillating)
V2-6:  300v
V2-7:  6mv
V2-8:  2.3v

V3-1:  366v
V3-2:  1v
V3-3:  4.2v
V3-6:  365v
V3-7:  .9v (osc.)
V3-8:  2.3v

V4-1:  155v
V4-2:  .1mv
V4-3:  1.18v
V4-6:  168v
V4-7:  2.2-2.8v (osc.)
V4-8:  2v

V5-3:  365v
V5-4:  371v
V5-5:  75-108mv (osc.)
V5-8:  31v

V6-2:  378vdc
V6-4:  378vdc
V6-6:  337vac
V6-8:  337vac

All voltages measured between ground and filament connections/lugs:  3.25vac

Thanks again everyone for your help and encouragement!
I'll keep an eye out for any barbed wire in Grandma's stuffing.

[sluckey]

You show different voltages on V3 pins 3 and 8. Those pins should be connected together and have the same voltage. Recheck these pins.

V4-7:  2.2-2.8v (osc.)

This concerns me. V4-7 should be zero volts. Check it again. In addition, I want you to check resistance between V4-7 and chassis with power off. Turn the reverb pot to zero and put one probe directly on pin7 at the socket. What have you? Don't forget the "K".

[Mjcopp]

Hey Sluckey, I measured as you requested. Then I noticed my battery was dying on my dmm. So I turned the tremelo off, kept reverb at zero and triple checked all voltages and will post any changes below.

The voltages on V3 pins 3 & 8 are indeed the same, (3.48v).
V4 pin 7 showed 0v and 130k ohms.

The only other changes:
V2-2:  oscillating between 1.0 & 1.6v
V3 pins 2 & 7:  .15v
V5-5 oscillates between 50-70 mv

I mis-labeled pins on V6, as I'm sure you realized.
V6 pins 2 & 8: 378vdc
V6 pins 4 & 6:  337vac

I hope this helps, and sorry for the bad readings.

[Platefire]

BTW-Happy Thanksgiving Ya'll

Somebody had mentioned in a previous post I think "Chop Sticking it". Not sure your familiar with this form of trouble shooting??? but it consist of having your amp chassis circuit exposed while live/hot/powered up and hooked up to a speaker. The wood chop stick is to allow you to probe the circuit without getting electrocuted---as long as you use a dry chop stick:>)

When you are probing your circuit touching solder connections, wires or whatever in the circuit might be suspect. If you were to touch a certain point of the amp and volume all of a sudden picks up from the low volume your currently experiencing, that is a possible indicator of the problem area to check out closer. It has worked for me several times in the past when a problem was hard to locate. I think it's worth a try. Just be very careful. Probe with the chop stick with one hand and keep your other hand free off the chassis.  I usually plug a guitar in while I'm doing this because if you got a shorting to ground input jack un-plugged, your input will be dead without a guitar plugged in. I think worth a shot! Platefire