New TMB w/reverb Build

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Re: New TMB w/reverb Build

Post by Bieworm »

Here's my 3rd build, well a total make over of the Tremolo TMB. This is what I refer to as the prototype. It's the first operational Tremolo TMB ever. Look at my progress, most credits go to Josh for nearly whipping me like a slave. If there's one thing I call a talent of Josh is that he can really rub your face into the mess you made... you'll thank him later for doing so :D :D :D
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Re: New TMB w/reverb Build

Post by JMPGuitars »

And here I thought I was being restrained and kind in my feedback. I guess that's why Belgium has the best chocolate. 😉😉 🤣🤣🤣🤣🤣
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Re: New TMB w/reverb Build

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My input wired:
16692254565566867703406055371915.jpg
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Re: New TMB w/reverb Build

Post by foreverstrung »

Great Pics
Dim bulb tester question.
I'm not sure I'm getting the right bulb. i've tried 2. Both incandescent. 1st one rated 50w-100w-150w. It's the one I used on the first trial with the amp start up. I tried it with my 74 Vibrolux and then on a Hot Rod Deluxe, first, before using it on the TMB build. Both when fired up, lit up and then faded to a very very dim light. So when the TMB did the same when I took the voltages, I thought it was fine as the other 2 amps were fine......Well, fine enough to test for voltages anyways........So since I'm going thru everything again with a fine tooth comb on the TMB, I thought I'd go ahead and build another tester. Nice and clean, with a diff incandescent bulb. 100w.......Same thing with the 2 amps. the vibrolux lit brighter then faded to a very dim light immediately and the Hot Rod just stayed a very dim light. I had to turn off the overhead lights to see it.
Is this ok? Everything I'm reading about these DIY testers is that when everything is cool, there's no light, at all. I know I've wired the tester together correctly, but either I'm not using the right bulb or there's something wrong with the other 2 amps I've got here now. OR, of course, something else I'm completely missing
Also, fyi, I did not fire up the TMB yet. I've not finished going thru it all yet. Just trying to be prepared
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Re: New TMB w/reverb Build

Post by Bieworm »

I cant' comment on that but I have a different kind of light bulb current limiter.

It's a 250W Halogen yard beam light. I attached it to a power brick, where in the circuit also resides. It works perfectly and never lights up whatsoever, unless there is a short in the amp. Works for me...
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Re: New TMB w/reverb Build

Post by Daviedawg »

In my experience the bulb goes bright on switch on, immediately starts to dim, then stays at a low dimness after that. Variables in dimness depend on the power of the bulb versus the power of the amp. I use mine on the floor beside my desk out of bright light. So that you see it quite dim without straining.

What you describe is what I have experienced. If it stays bright something is wrong. Switch off right away.

Dd
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Re: New TMB w/reverb Build

Post by foreverstrung »

Happy Thanksgiving.
Grateful for y'alls help
Ran a 2nd voltage test. After installing the voltage dropping diodes. Then I rewired all the pots. Just because they were not really pretty. I went through all the tube sockets. Thoroughly. A few times with a large lighted magnifying glass and as they are "sketchy" and not real pretty, there is no grounding.
I went through the layout diagram and highlighted all the connections. I've been taking long segments of time and reviewing the schematics. I do understand (see) how the flow of the drawing goes. All that being said, I powered it up with a dim bulb tester and then directly to the wall and let it warm up. I got some better readings (because of the zener diodes) and some are still not cool.......I'm really wondering if I didn't damage something at the PI with that surge the other day when testing pin 2. I'm still not getting anything. In fact all my PI numbers suck. Is there a chance I burned something up.
As for the other pre amp tube sockets, even tho they appear clear and connected as should be, I'm going to rewire all of it. Valves V1-V5. I've got replacement sockets coming tomorrow. I'll just rewire the entire heater section. Then run the highlighter thru everything again. But as I do this, do you guys have any ideas about the possibility of frying something? Like I said after the first voltage test, When I measured V3 P2 on the PCB board there was a loud output and I caught the MM read high, briefly. like .5 seconds n it was gone. Since then, nothing. No sound, no reading.
Also, the HV1 and 2. Am I not measuring them correctly? I've marked the reading I got. Something is no bueno.
Thx
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Re: New TMB w/reverb Build

Post by foreverstrung »

Pics of the Zener Diode(s) install and new 221k resistor and pic of new wire on pots.
Also, doing the highlight review I found 2 mistakes. Looking at the numbers above, does not appear like it made too much of a difference tho
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Re: New TMB w/reverb Build

Post by Bieworm »

Did you try other tubes?
What's up with node B on the B+??? Maybe your cap can is corrupt?
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Re: New TMB w/reverb Build

Post by foreverstrung »

HV1 is 306 and HV2 303. I was testing in DC with the voltage sheet posted tonight. When I went thru other correspondence, I found Josh mentioned that.
I've ordered some new components and like I said, I'll rewire the heaters completely. I picked up a couple cap cans just in case and for another project after this. That B side being so low bothers me. That is a 2.2K resistor, I checking it with a MM tonight and it checked out. As I was cautioned, do not guess, but if the cap can is bad, I'm prepared. If it's not, I've got a couple extras. After cleaning this all up, I'll do a highlight trace again carefully.
That PI still bugs me tho. It's wired correctly. V1 as well. It's not getting the voltage expected Maybe new sockets will help. I very well could have f'd them up.
I've swapped tubes in these spots a few times. And I've bought some new tubes too
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Re: New TMB w/reverb Build

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What value zener diodes did you use? Are they oriented correctly? First short the zeners between the cap can and the solder terminal by bridging it with a wire and alligator clips. What is the voltage now for B? Where did you measure A? Before or after the zeners? It should be after, so on the solder terminal.

If the voltage on B does not increase substantially I am almost certain that the cap can is the problem of the screen voltage being abnormally low. It must be leaking DC to ground, pulling down the voltage substantially. Try to replace it first, before doing anything else. Try not to overheat the caps when soldering.

We need hi res pics of the entire build. Here's a link to the thread when I built my 36W Tremolo TMB with the 1st version of the PCB. There are some hi res pics in there that might be useful? Check it out..
FWIW, I had NO issues whatsoever with this one.. it sounded dead gorgeous from the 1st flip of the switch. I think it was the first amp I ever built that was good to go from the start. As a matter of fact, I was a bit disappointed it was ready from the start.. I was prepared for the troubleshooting ritual which is mostly a part of the process.
I fell into a hole :D :D :D :D

viewtopic.php?p=250045&hilit=My+36W#p250045
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Re: New TMB w/reverb Build

Post by foreverstrung »

What value zener diodes did you use? Are they oriented correctly? First short the zeners between the cap can and the solder terminal by bridging it with a wire and alligator clips. What is the voltage now for B? Where did you measure A? Before or after the zeners? It should be after, so on the solder terminal.


If the voltage on B does not increase substantially I am almost certain that the cap can is the problem of the screen voltage being abnormally low. It must be leaking DC to ground, pulling down the voltage substantially. Try to replace it first, before doing anything else. Try not to overheat the caps when soldering./quote]
I ran the zener diodes in the correct direction. The first voltage test I did, without them, the B side was 256v. With them, it's 242v. Now the A side it brought the voltage down as expected. 1st time without was 378v and then with the diodes it's 350v.......I did measure at the solder terminal.
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Re: New TMB w/reverb Build

Post by JMPGuitars »

Voltage at A is good, Voltage at B is not. The only thing that is between there should be a 2.2K resistor.

With the amp off, measure the resistance of the 2.2K resistor. If it measures good, then lift (disconnect) the wire connecting B to the terminal strip. Measure the voltage at B. It will likely be higher than expected, unless there's a different issue.

Alternatively, you could also try a different pair of power tubes and see if that changes anything.
Bieworm wrote:
Fri 11/25/22 2:03 am
FWIW, I had NO issues whatsoever with this one.. it sounded dead gorgeous from the 1st flip of the switch. I think it was the first amp I ever built that was good to go from the start. As a matter of fact, I was a bit disappointed it was ready from the start.. I was prepared for the troubleshooting ritual which is mostly a part of the process.
I fell into a hole :D :D :D :D
lol, poor fella. Hahahaha

Thanks,
Josh
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Re: New TMB w/reverb Build

Post by foreverstrung »

[
quote]With the amp off, measure the resistance of the 2.2K resistor. If it measures good, then lift (disconnect) the wire connecting B to the terminal strip. Measure the voltage at B. It will likely be higher than expected, unless there's a different issue.

Alternatively, you could also try a different pair of power tubes and see if that changes anything.
After removing the wire I've got 400v on the B side.
On the A side, I now have 400v before Zener diodes (@ the terminal strip) and 429v after the diodes (@ the can A side).
New tubes ordered. I'll move fwd with these heater re-do-ing.
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Re: New TMB w/reverb Build

Post by foreverstrung »

So that last post showed what the voltage is when I remove the red wire from the B side of the cap can. IDK what this means exactly, but the voltage did increase like Josh said it would. So I put it back in place.

Then I rewired all the pots. Cleanly and with intent. Pic included

Then I removed all the tube sockets and rewired it all. Cleanly and with intent. Pics included. I also lifted the PCB board to make sure there were no unwanted kinks or connections.

I've gone thru with a highlighter 3 times now, (the more recent after rewiring the new tube sockets).

The B side of the cap can is still low. My readings are better, but I think one thing that is confusing me when taking readings is that the voltage sheet has V1-V5 and the actual amp has V1-V6. For a beginner like me, it's confusing. V4 on the voltage sheet is actually V5 in the amp and V5 on the sheet is actually V6.....I assume V1 is actually V1, but is V4 actually the PI and not V3 as the sheet shows? If so, that would explain many of my poor readings, tho it does not take away that the B side of the cap can is so low.

appreciate your help
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Re: New TMB w/reverb Build

Post by JMPGuitars »

foreverstrung wrote:
Sun 11/27/22 4:39 pm
The B side of the cap can is still low. My readings are better, but I think one thing that is confusing me when taking readings is that the voltage sheet has V1-V5 and the actual amp has V1-V6. For a beginner like me, it's confusing. V4 on the voltage sheet is actually V5 in the amp and V5 on the sheet is actually V6.....I assume V1 is actually V1, but is V4 actually the PI and not V3 as the sheet shows? If so, that would explain many of my poor readings, tho it does not take away that the B side of the cap can is so low.

appreciate your help
Hi Dave,

You're using the wrong voltage chart. You need the reverb version: files/JMPGuitars_18_Watt_Tremolo_TMB_Re ... _Chart.pdf

First, a warning, don't measure continuity on a live (powered) amplifier. If you measure continuity on the output transformer powered off, you will get continuity. In a live amp you only measure resistance (NEVER continuity), and you have to do so very carefully, and only with equipment rated to do so.

Second, don't measure continuity on the speaker, measure resistance. The speaker is 16 ohms (nominal), which isn't necessarily enough for your meter to not think there's continuity. Test the speaker disconnected from the amp for resistance and see what it measures.

For some reason, you're images are much lower quality when you upload them here. Try emailing me the full size images.

Thanks,
Josh
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Re: New TMB w/reverb Build

Post by JMPGuitars »

I'm posting this response to your photos publicly because the feedback will help others as well.

Tell me what’s wrong with this picture:
shield.jpg

Looking at the board makes me question the soldering a bit:
soldering-on-pads.jpg

You should probably (and very carefully) go through this stuff with the power cord disconnected. To start, measure resistance by touching only the pads, not the component leads and see if they read as they should. If not, then you know you have a bad connection (assuming it's not in parallel with something else).

I dunno if you know the terminology for PCBs, but pads are the gold circles at the ends of the holes (vias):
naked-pads.jpg
Thanks,
Josh
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Re: New TMB w/reverb Build

Post by foreverstrung »

OK. Got it. Shielded wire to the PCB board. Makes sense.
That F'd up PCB board pic is pretty much just that area. I forget why now, but I disconnected/reconnected there a couple times. Kind of butchered it. My next smaller tip does not get hot enough.
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Re: New TMB w/reverb Build

Post by JMPGuitars »

foreverstrung wrote:
Sun 11/27/22 5:58 pm
OK. Got it. Shielded wire to the PCB board. Makes sense.
That F'd up PCB board pic is pretty much just that area. I forget why now, but I disconnected/reconnected there a couple times. Kind of butchered it. My next smaller tip does not get hot enough.
I use 2.4mm on the whole thing. The trick is to first heat the pad, add a tiny bit of solder to create a heat bridge, then once that melts into the pad, paint on the proper amount of solder to make your connection. It takes time, and practice, and good equipment. If your soldering iron is holding you back, it's time to get a new one.

Either way, it's essential now to make sure you have the connections you need by measuring values between the pads.

Thanks,
Josh
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Re: New TMB w/reverb Build

Post by Bieworm »

You are getting closer to the essence now, that's good. It's a learning process...and I guess you soak up the knowledge gradually.
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.
Hope this made sense 8)
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