New TMB w/reverb Build

[foreverstrung]

So I went thru and checked the connection of my resistors by checking at the pads. Everything appears good. I went thru it twice. Part of it a 3rd time.
I got a new pair of Sovtek tubes that I threw in and checked the voltage on everything again. I'm attaching the chart. Not much diff than with the NOS GE I had in there prior.
I can't tell by looking at this chart if anything is significantly out and/or how to move fwd. Appreciate you alls feedback on it.
I did plug it in, with the volume low, it's relatively clean and clear. Turn it up at all and it's not right. Almost sounds like a blown speaker. To be clear, this speaker is NOT blown, this is just the sound that's being produced.
Thanks in advance for your comments

[Bieworm]

Did you try a new cap can? Voltage on node B is still very low, resulting in overall low voltages in the amp...
But at least the voltages are gradually low.. so when you get that node B on par, the rest will be in the right ball park.

[JMPGuitars]

Switch OFF the tremolo with the mini toggle. Confirm that it's off. Turn the reverb volume to 0. Then record a demo so we can hear what it sounds like.

It appears that your voltage is dropping too much between A to B, so you could try a 1.5K 5W instead of the 2.2K 5W, but chances are, the issue is somewhere else in the amp.

With the amp powered off, connect one DMM probe to ground. Then test resistance to ground for every resistor that eventually goes there. For example, all cathode resistors including the power tube cathode bias resistor. Test grid resistance to ground. Look at the SCHEMATIC to see what those values should be.

If you want to rule out the speaker, you can try a different speaker. But I'm guess you're correct, and the speaker is likely fine.

Thanks,
Josh

[foreverstrung]

Switch OFF the tremolo with the mini toggle. Confirm that it's off. Turn the reverb volume to 0. Then record a demo so we can hear what it sounds like.

I don't have the toggle switches on this build. Is there another way to disconnect the tremolo?

[Bieworm]

Switch OFF the tremolo with the mini toggle. Confirm that it's off. Turn the reverb volume to 0. Then record a demo so we can hear what it sounds like.

I don't have the toggle switches on this build. Is there another way to disconnect the tremolo?

Grounding it. Put a jumper wire between the tip and ground lugs of the switching jack
If you used a cliff jack I would connect the tip and ground lugs of the other side permanently. That way you can still play the amp without footswitch without having tremolo all the time

[foreverstrung]

With the amp powered off, connect one DMM probe to ground. Then test resistance to ground for every resistor that eventually goes there.

Where is "there"? To ground? At the cap?

For example, all cathode resistors including the power tube cathode bias resistor. Test grid resistance to ground. Look at the SCHEMATIC to see what those values should be.

IDK how to do this. IDK exactly what cathode resistor is. I "think" I know, but I don't want to guess. IDK what the PT cathode bias resistor is. Here again, I "think" I do, but even if I'm right, I'm not sure how exactly to test resistance. IDK exactly which side to check the resistance. ......To save face, I could spend all night researching trying to figure it out. Easier just to humble myself and ask......How do I do this?

[JMPGuitars]

How do I do this?

No worries, you're not the first beginner looking for help here.

Look at your documentation. Look at the voltage test chart, and you will see that I included diagrams of each tube.

Your preamp tubes are "dual triodes" which means there are 2 triode tubes inside one tube. Pin 3 and Pin 8 are the cathodes for each of the 12AX7 preamp tube triodes.

You'll see on the diagram for the EL84 power tubes, that Pin 3 is the cathode. Now for the power tubes, they SHARE a single cathode resistor. That's the 5W 180 ohm resistor on the far left end of the board (assuming PT is on the left when you're looking at it).

Now look at the schematic:

power-tubes-schematic.jpg

You can see there next to the blue 4 that your 180R 5W resistor is connected to BOTH power tubes in the schematic. So you could, for example, connect the negative lead of the DMM to ground (transformer mounting bolt with an alligator clip), and then touch the positive lead to Pin 3 of either power tube. You should see about 180 ohms measuring resistance on your DMM.


I highly recommend installing the mini toggle switches for the tremolo, but I can see you don't have the external footswitch connected yet. That's ok. If you look at your docs, you can see that the switches to mute the tremolo connects Pin 7 of Valve 1 to ground. You have a brown wire coming off the board to Pin 7:

tremo-muto.jpg

If you have small clips, or if you want to tack-solder something to the turret hole next to your wire, you can connect "the grid" (pin 7) with a second wire running to the terminal strip ground lug right next to the board. Be careful not to short anything else out, especially not the plate connections (pins 1 and 6) close by. The result would look something like this:

mute-trem.jpg

A word of advice: try to comprehend what you are doing and why. Try to think in terms of preamp stage 1, instead of V1b. Try to find out what voltages you should have and why. Get used to connecting plate resistors to plate pins, instead of putting a wire between that resistor and V1 pin 1 or 6...connecting cathode resistor/cap to cathode pin, instead of pulling a wire from V1 pin 3 to that capacitor/resistor.
It's the same thing, but it gives you more insight of what you are actually doing and helps you to detect red flags before soldering.

The above is excellent advice. This will help you understand everything much better, and help make communication clearer. Not sure what pin is what? Look at the labels on the voltage chart, then reference those spots on the schematic. You'll get used to it pretty quickly that way.

Thanks,
Josh

[JMPGuitars]

Side quest:

From your photos I see that you didn't exactly follow the layout for V1:

V1-layout.jpg

In the layout, there's two 2-terminal strips, I think I sent you a 3 terminal strip for that position. One side goes to each grid of V1. The 10K from the input to V1/P2, the V1/P7 lead from the PCB to P7.

Your build currently only has a terminal strip being used for the 10K resistor, but it ignores P7. Using a terminal strip lug there makes it really easy to add in your tremolo mute switch for the front panel.

On the first page of the build guide, I included reference photos of two of my builds (Turret and PCB versions), don't forget to reference those for comparison. Here's my PCB version again:

_JMP3283.jpg

Thanks,
Josh

[foreverstrung]

https://youtu.be/8q14_kIvXCU

Sound test. Jumped tremolo out with alligator clips and reverb to zero. Guitar is at about 4-5. Volume on amp is about 3

[foreverstrung]

In the layout, there's two 2-terminal strips, I think I sent you a 3 terminal strip for that position. One side goes to each grid of V1. The 10K from the input to V1/P2, the V1/P7 lead from the PCB to P7.

Your build currently only has a terminal strip being used for the 10K resistor, but it ignores P7. Using a terminal strip lug there makes it really easy to add in your tremolo mute switch for the front panel.



On the first page of the build guide, I included reference photos of two of my builds (Turret and PCB versions), don't forget to reference those for comparison. Here's my PCB version again:

I do refer to that manual. Often. I printed a copy to view and then on my laptop to magnify pics. In my confusion, I believed I was not putting in toggle switches as I did not receive them in my pkg and then on pg 2 of this thread Bieworm stated that he does not use the switches and then you followed up with a comment that I "thought" agreed with that. (I went back and found this not to be true).....That lug, I did have installed. but had the ground to those 2 shielded wires attached. I removed it after putting them in their proper places. I'll reattach it when I put the footswitch jack back. I would never guess that the wire running to pin 7 attached to this lug without you clarifying.......
So, I do want 2 toggle switches? Attached as you show them, correct? Assuming I get this dialed in from where we are now. When I install all the FX. Correct/
Also, should I change that 2.2k 3w for a 1k 3w or do you believe it will be futile?
Also, the cap can. I have 2 extra I just recieved. Should I change out or no? Will it be a waste of time?. I ordered many of these misc components and have them on hand.
Thx

[JMPGuitars]

So, I do want 2 toggle switches? Attached as you show them, correct? Assuming I get this dialed in from where we are now. When I install all the FX
Thx

Yes, you want the toggle switches. I thought I sent you two tiny toggles in your kit? It's possibly I forgot, or I couldn't find the on/off (2 position) version you need. I know I have too many on/on/on or on/off/on options (3 position).

Either of these are fine:
https://www.amplifiedparts.com/products ... medium-bat

https://www.amplifiedparts.com/products ... older-lugs

SPDT, DPDT, SPST, or DPST is fine as long as it's only 2 position, which could be on/on or on/off. If it's on/on then you don't connect the 3rd lug to anything.

Thanks,
Josh

[Bieworm]

" In my confusion, I believed I was not putting in toggle switches as I did not receive them in my pkg and then on pg 2 of this thread Bieworm stated that he does not use the switches and then you followed up with a comment that I "thought" agreed with that. (I went back and found this not to be true)....."

I'm sorry for that statement if it would have made you doubt the necessity of it.. I didn't take it into account that it's your first build and have not calculated the level of experience you have on this topic.

That said, I personally don't use toggle switches because I use my amps live in a band situation and need to make essential stuff footswichable. Everybody who knows me is aware of me using reverb ALL the time and that tremolo is an essential option that I build in every amp.. regardless the circuit I'm working on.
However, in some situations I'd opt for a toggle switch.. but that's merely for sporadical/optional use.

In your case I would recommend you following the docs as accurate as possible. You're not in the freestyle situation just yet
I experiment a lot though.. even with the Tremolo TMB. The main reason is to see if I can add stuff that could be useful or enhance things. But an observant eye will already have seen that the extra features on my last Tremolo TMB build are not implemented into the current one, because I find them obsolete. ( series/parallel switching of V2, B+ voltage reduction,... none of those are on my list anymore for they add nothing but a less desireable tone)

I'M STILL WONDERING IF YOU HAVE ALREADY REPLACED THE CAP CAN?

[foreverstrung]

I'll replace that cap can later today. I asked a post or 2 back if I should move fwd with that.
I also added a link to a sound test as directed. Go back a few posts to listen.
Thx

[Bieworm]

I would recommend to try the cap change. If it's not, then you at least know it for sure.
I heard the clip.. sounds like crap .. reeks after a power supply issue, an issue that's obvious on the test chart

We will hunt the problem down and get it fixed! Have you got any idea how sweet that amp can sound?
https://youtu.be/DJde9deFb0M

[JMPGuitars]

You can try swapping the cap can if you want, but I'd be surprised if that's the issue.

My money would be on a bad solder joint somewhere, or a questionable tube. You could try swapping out the preamp tubes and see if that changes anything.

Thanks,
Josh

[foreverstrung]

My money would be on a bad solder joint somewhere, or a questionable tube. You could try swapping out the preamp tubes and see if that changes anything.

I've swapped out all the pre amp tubes with no change and I've rewired all the heaters and pots. That does not leave many solder joints considering I went thru the PCB board checking pad connections....... I'll go thru the PCB board again. Slow and careful, but soldering the PCB board was extremely simple. I found it very easy to complete and I went thru and verified that everything was where it was supposed to be.
I'll go thru it all again. It would have to be something I've missed already 2-3 times, or something got fried or is defective.

[Bieworm]

Just fired up my new built Tremolo TMB. It works, voltages check out.. but no reverb. I will have to dig into that.. lol

I posted a quick video on instagram. @Bieworm

Edit: found the problem. I put the coupling cap from the recovery plate to node C of the B+ instead of on the plate. Lol!

[JMPGuitars]

I've swapped out all the pre amp tubes with no change and I've rewired all the heaters and pots. That does not leave many solder joints considering I went thru the PCB board checking pad connections....... I'll go thru the PCB board again. Slow and careful, but soldering the PCB board was extremely simple. I found it very easy to complete and I went thru and verified that everything was where it was supposed to be.
I'll go thru it all again. It would have to be something I've missed already 2-3 times, or something got fried or is defective.

Fried is possible, defective is less likely. I tested everything (for value specs) prior to sending it out.

With the amp powered off and unplugged, test your capacitors for continuity.

If possible, good photos of the bottom of the PCB might be helpful.

Thanks,
Josh

[foreverstrung]

If possible, good photos of the bottom of the PCB might be helpful.

I had to pull half the amp apart a few days ago to get to the underside of the PCB board. I really don't want to do it again. It's clean. I'm not a ace solder-er, but it's clean. If I thought for a min there'd be something there, I'd take it apart again. I took it apart then to check for anything suspicious. I wish now I had photographed it

Logically I was trying to follow the schematic and before pulling that cap can, I thought I'd try changing that 2.2k resistor from the lug after the zener diodes to B+ on the cap can to 1K. It brought my voltages up. B went from 275v to 311.9 v.....everything went up closer to what the sheet called for. However the sound is still tinny. Like a blown speaker. And I tried another speaker to be sure.

I do not know all the termanology yet, so please bare with me, but the 1k resistors from pin 9 on the el84's to the terminal strip and the 2,2k to the PCB board, I removed and replaced all 3. Slow and clean.

Right now, with the 1k @ the terminal strip to the B side of the cap can, all my voltages look good, but the amp still sounds like ****.
IDK where to go from here. I've rewired almost everything

[foreverstrung]

OK. I found one .01uF yellow cap. (I can locate it in the schematics and the layout, but I don't know the correct description to identify for you guys. At least I believe I can identify the location on the schematic.) .Cap between the el84's and the v4 preamp.
Anyways, 0ne side of this cap was not soldered. So I did. Obviously.
I REALLY believed this was going to be the problem I was looking for. So much so, That I put back the 2.2k 5w resistor @ the B side of the cap can.When I did, the voltage there dropped back down to 275 (after being at 311 with the 1k resistor 3w resistor I swapped out thinking to increase voltage to the B side of the can). This is how it's in the schematic and layout. With the 2.2k 5w......However, we have the same tinny sound. It's something else.

With the amp powered off and unplugged, test your capacitors for continuity

None of the yellow "foil" caps have continuity. The other caps do. Unless I'm not checking right. Please advise.


After you guys comments, if there nothing else, I will pull the PCB board back up again. I spent the better part of saturday doing this last time. Although I did rewire/solder all new sockets. This took up most of the time
I could, I guess, solder the pads on top. Just a thought. Wouldn't be real clean, but whatever it takes.