New TMB w/reverb Build

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Re: New TMB w/reverb Build

Post by JMPGuitars »

I emailed you the BOMs, and I updated the download page with the Mouser BOM.

Thanks,
Josh
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Re: New TMB w/reverb Build

Post by foreverstrung »

I’m looking at this schematic kind of like plumbing. For some reason, it makes it easier for me to wrap my head around them. Doing this and then looking at these voltages, logically, it appears that the voltage drop on the B side of the can would be stifled in between A+ and B+. But when I put a smaller resistor there, the voltage came up to where it should be, (except for V1 pin 1, it’s always remained too low.), but the sound was still crap. So we know the sound is crap and idk, but I’d bet dollars to donuts that if I was able to get the voltage up on that B side, whatever is causing it to remain low, would be the issue with the sound. But thinking like a plumber, logically, it just doesn’t make sense. Unless there’s a leak further down the line. Lowering the pressure (voltage)
Do you have any thoughts on what would cause this that we haven’t explored yet?
If no, I’ll just start from square 1 and go thru everything again. Caps, sockets, wiring, resistors.
Still, when I follow the current in from the switch, it appears to me that it’s running from A+ to B+. Can I assume that something’s draining that B side?
Thx
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Re: New TMB w/reverb Build

Post by JMPGuitars »

foreverstrung wrote:
Wed 12/07/22 10:12 pm
I’m looking at this schematic kind of like plumbing. For some reason, it makes it easier for me to wrap my head around them. Doing this and then looking at these voltages, logically, it appears that the voltage drop on the B side of the can would be stifled in between A+ and B+. But when I put a smaller resistor there, the voltage came up to where it should be, (except for V1 pin 1, it’s always remained too low.), but the sound was still crap. So we know the sound is crap and idk, but I’d bet dollars to donuts that if I was able to get the voltage up on that B side, whatever is causing it to remain low, would be the issue with the sound. But thinking like a plumber, logically, it just doesn’t make sense. Unless there’s a leak further down the line. Lowering the pressure (voltage)
Do you have any thoughts on what would cause this that we haven’t explored yet?
If no, I’ll just start from square 1 and go thru everything again. Caps, sockets, wiring, resistors.
Still, when I follow the current in from the switch, it appears to me that it’s running from A+ to B+. Can I assume that something’s draining that B side?
Thx
The logic is a little flawed there. You can have weird voltages and no issue with sound (and vice versa). Sometimes the voltage issue directly relates to the sound issue, sometimes it doesn't. Chances are, that something else is messing with the voltage down the line, and that may or may not directly contribute to the sound issue.

So let's break it down like this instead. You want to try and resolve the voltage issues, that is correct. Whether you use a 1.5K or 2.2K resistor between A and B is an arbitrary choice. You may find that after fixing all the issues, that you still want higher voltage at B, so then you would indeed want a 1.5K resistor there.

What really matters more is what is causing the voltage issue. If a pipe is leaking, or has blockage, that would mess with the water flow either way. You'd still have to go looking for a leak or a clog, and a leak is easier to find, right?

Since your components (for the most part?) are in spec, and most of the voltages aren't that far off, it's probably not a leak. So you either have a bad solder joint, or a damaged component causing your clog. Another option is a parasitic oscillation, which could be caused by how your wires are laid out.

Now, you know that replacing all the plumbing is not how you want to go about finding a bad pipe. So take your time, think logically, and make sure you have the tools you need to do the job. In this case, you made need an oscilloscope. Or you may need a better iron. Or you may need a meter that can measure capacitance. The greatest tool you'll find is patience.

Thanks,
Josh
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Re: New TMB w/reverb Build

Post by foreverstrung »

Since your components (for the most part?) are in spec, and most of the voltages aren't that far off, it's probably not a leak. So you either have a bad solder joint, or a damaged component causing your clog. Another option is a parasitic oscillation, which could be caused by how your wires are laid out.

Now, you know that replacing all the plumbing is not how you want to go about finding a bad pipe. So take your time, think logically, and make sure you have the tools you need to do the job. In this case, you made need an oscilloscope. Or you may need a better iron. Or you may need a meter that can measure capacitance. The greatest tool you'll find is patience.
Right on. I've ordered an oscilloscope.
My MM reads capacitance, but honestly, I'm still learning how to use it correctly.
We'll see where we get this wknd
Thx
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Re: New TMB w/reverb Build

Post by JMPGuitars »

foreverstrung wrote:
Thu 12/08/22 1:23 pm
Right on. I've ordered an oscilloscope.
My MM reads capacitance, but honestly, I'm still learning how to use it correctly.
We'll see where we get this wknd
Thx
Nice. What model is your meter?
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Re: New TMB w/reverb Build

Post by foreverstrung »

Nice. What model is your meter?
My MM is a Fluke 115

I've ordered a
Proster LCR Meter LCR Multimeter Tester for Capacitance Resistance Inductance Measuring Meter with LCD Over-Range Display
To better read caps. I'm having a real hard time with the Fluke

I also ordered a
Siglent Technologies SDS1102CML+ Digital Storage Oscilloscope, 100 MHz
Both are due to arrive today

Also, something interesting. Last night I was inside the amp checking things out and I did not like the location of active points of the Rotary Impedance switch. Tho they were heat shrink wrapped at the joints, they were right on top of the #7 pin of the EL84 V6, Wire from the OT. So I kind of moved some stuff around and cleared this tight connection. So I switched it on and warmed it up and the voltage on the B+ side of the cap can was up to 303.5v. Up until now, It was always 275v and I was looking for it to be closer to 310v. That's the good news. The bad news is that a guitar still sounds like poo.
I gotta tell you tho, it's nice to get a win. Even a little one like the voltage getting to a better spot. Still low voltage @ V1 pin 1. I believe I'm supposed to be between 110v and 150/v. I'm at 77v
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Re: New TMB w/reverb Build

Post by Bieworm »

I don't think little of your discovery at the B+ ... that's BIG deal!!!
V1- 6 is ok? They're connected with a 220k iirc. Confirm that resistor value.. and the cathode resistor value of V1. Also look closely at those solder connections.

I have 110V pin1 and 152V pin6. I have a 5k6 dropping resistor between C and D.. but that's because I want to approach the prototype's values.
download/file.php?id=14479&mode=view
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Re: New TMB w/reverb Build

Post by foreverstrung »

Sound check with volume about 4 all other knobs at 50%. Is this blue wire from the OT making this sound(s) @ the tube socket or the transformer? This is a new socket and I've got good pics of the solder joint. It's clean.
Appreciate the thoughts
https://youtube.com/shorts/KdMinoJDKFw
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Re: New TMB w/reverb Build

Post by Daviedawg »

You should replace that blue wire which sounds like it might have a broken conductor unless you can see that it is contacting another node under the board for example.

Dd
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Re: New TMB w/reverb Build

Post by foreverstrung »

You should replace that blue wire which sounds like it might have a broken conductor unless you can see that it is contacting another node under the board for example.
The blue wire is directly from the OT. That's what I'm wondering. If there's a problem with that line. How can I verify/test the OT?
I got my oscilloscope yesterday. Just unboxed it and have been reading and watching info about operation, but it's going to take me a good min to use this tool accurately.
Any suggestions for testing this OT would be appreciated. With scope or MM or peanut butter. Whatever works.
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Re: New TMB w/reverb Build

Post by JMPGuitars »

Swap the brown and blue wires coming from the OT to the power tube sockets.

If the problem follows the blue wire, then the issue is with the wire or OT.

If the problem stays at the original socket the blue wire was connected to, then it's wires interacting near the socket. If this is the case, see my previous comment about lead dress, color coding, and placement of wires.

If the problem disappears, cool.

Thanks,
Josh
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Re: New TMB w/reverb Build

Post by foreverstrung »

Swap the brown and blue wires coming from the OT to the power tube sockets.

If the problem follows the blue wire, then the issue is with the wire or OT.

If the problem stays at the original socket the blue wire was connected to, then it's wires interacting near the socket. If this is the case, see my previous comment about lead dress, color coding, and placement of wires.

If the problem disappears, cool.
That one of those things that make ya go "Doh!".
I really don't know why, but it sounds great now. No noise in either wire and the amp sounds right. I'm picking up some hum/noise, but it's a grounding thing i'm sure at the speaker input as activity near this point makes it stop and the amp is pretty quiet.
Very happy about this.
Bieworm suggested this a week ago. I'll never doubt him again
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Re: New TMB w/reverb Build

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Hold your horses.. I'm not that good at amp building like you think. Josh is the master and I always get good advice from him. He made me what I am today. I've never built an amp until 3 years ago...
But I'm happy it is finally sorted out. I have had a bad feeling about the output section from the beginning. But I thought the OT was ruined when you wired the B+ line wrong at first. ..
Anyway.. even though it is a cathode biased amp without NFB loop, you can still have oscillation in the output. That's valuable info for me for future problems. Nice!!!
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Re: New TMB w/reverb Build

Post by foreverstrung »

I picked up that scope that you've got Bieworm. Do you have any advice on using it? I've just unboxed it. Starting totally from zero. Any advice using this scope would be appreciated.
Thx
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Re: New TMB w/reverb Build

Post by chaliapin »

Been following this thread with interest, great news!
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Re: New TMB w/reverb Build

Post by JMPGuitars »

Bieworm wrote:
Sat 12/10/22 12:09 pm
Hold your horses.. I'm not that good at amp building like you think. Josh is the master and I always get good advice from him. He made me what I am today. I've never built an amp until 3 years ago...
But I'm happy it is finally sorted out. I have had a bad feeling about the output section from the beginning. But I thought the OT was ruined when you wired the B+ line wrong at first. ..
Anyway.. even though it is a cathode biased amp without NFB loop, you can still have oscillation in the output. That's valuable info for me for future problems. Nice!!!
Meh, I just pushed you in the right direction. Your diligence made you what you are.

You can see in the video there was a clusterfork of wires in that spot. It's not too hard for that to cause an issue.
foreverstrung wrote:
Sat 12/10/22 12:15 pm
I picked up that scope that you've got Bieworm. Do you have any advice on using it? I've just unboxed it. Starting totally from zero. Any advice using this scope would be appreciated.
Thx
You can connect a probe set to 10x at the output jack and keep the speaker connected or a dummy load (I'm assuming your probes are rated at least 600V at 10x). Then make sure your scope is setup with the probe at 10x.

If you have a signal generator, you would want a 1K sine wave around 100 to 300mV at the amplifier's input jack.

Then you can be lazy and hit the "auto" button on the scope (I assume that scope has one). The result should be a clean sine wave.

If you don't have a signal generator, you can plug your guitar in and let a note ring, or play and watch it go crazy.

Also, now that the amp sounds good, post a demo! 😀

Thanks,
Josh
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Re: New TMB w/reverb Build

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foreverstrung wrote:
Sat 12/10/22 12:15 pm
I picked up that scope that you've got Bieworm. Do you have any advice on using it? I've just unboxed it. Starting totally from zero. Any advice using this scope would be appreciated.
Thx
Not really, read the links Josh posted a while ago.. I'm totally no wizard with that thing.. I'm just doing stuff most of the time😉
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Re: New TMB w/reverb Build

Post by Bieworm »

JMPGuitars wrote:
Sat 12/10/22 12:43 pm
Bieworm wrote:
Sat 12/10/22 12:09 pm
Hold your horses.. I'm not that good at amp building like you think. Josh is the master and I always get good advice from him. He made me what I am today. I've never built an amp until 3 years ago...
But I'm happy it is finally sorted out. I have had a bad feeling about the output section from the beginning. But I thought the OT was ruined when you wired the B+ line wrong at first. ..
Anyway.. even though it is a cathode biased amp without NFB loop, you can still have oscillation in the output. That's valuable info for me for future problems. Nice!!!
Meh, I just pushed you in the right direction. Your diligence made you what you are.

You can see in the video there was a clusterfork of wires in that spot. It's not too hard for that to ....


Also, now that the amp sounds good, post a demo! 😀

Thanks,
Josh

+1 on that!!! It's the hardest part of an amp to get the wiring tidy... I'm never satisfied there, but sometimes it izz what it izz 😉😉😉

Demo! H€££ ¥eah!! 🤘
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Re: New TMB w/reverb Build

Post by foreverstrung »

https://youtu.be/tSYgtTYQM2Q
Playing like crap, but the sound is much more gooder. I didn't adjust anything tho. Everything, across the board @ 50%
Recorded with an Iphone 12
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Re: New TMB w/reverb Build

Post by JMPGuitars »

The noise you're getting is probably a ground loop caused by where/how you're muting the tremolo. You should install the switches.

How does the reverb sound? Have you tried connecting that yet?
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