New TMB w/reverb Build

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Re: New TMB w/reverb Build

Post by foreverstrung »

OK. So here's a couple scope screenshots. Both have the V1 tube removed. Probe ground is on the output jack busbar/ground. (not input jack). The amp is off. I set the audio generator to 300mV. (I switched to #1 port, probe is set to 10x, not 1x)
SDS00029.png
Here is the measurement page
SDS00030.png
Should I post screenshots of the measurements of all the points we've gone through tonight?
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Re: New TMB w/reverb Build

Post by JMPGuitars »

foreverstrung wrote:
Fri 01/06/23 10:39 pm
OK. So here's a couple scope screenshots. Both have the V1 tube removed. Probe ground is on the output jack busbar/ground. (not input jack). The amp is off. I set the audio generator to 300mV. (I switched to #1 port, probe is set to 10x, not 1x)
SDS00029.png
Here is the measurement page
SDS00030.png
Should I post screenshots of the measurements of all the points we've gone through tonight?
No, let's focus on the jack first. Also, change your Measure settings so it shows just the ones I mentioned at the bottom. You need to hit the back button after pressing autoset for it to show everything correctly.

I wonder if there's something wonky with your shielded input wire. Try raising it off the chassis, and see if that changes anything. If not, disconnect it from the terminal strip, and connect the probe to it while floating.
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Re: New TMB w/reverb Build

Post by foreverstrung »

OK. Power is still off. V1 is still removed. Probe is in the exact same points. Audio gen is set just as it was, so is the scope, but I'm not even getting close to the same reading on the scope
SDS00033.png
I specifically chose PK-PK, Ampl, Mean and RMS in the measurement page. This scope reading as I just described above is wonky, active. I took 2 screenshots of the measurements as they were changing quickly as this reading was active
SDS00031.png
SDS00032.png
I hope I'm being thorough. I'm doing my best to post the info as I get it as accurately as possible. I don't want to waste anyones time.
I moved the shielding wire. No change. I disconnected the terminal strip with no change at all.
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Re: New TMB w/reverb Build

Post by JMPGuitars »

Post high resolution photos of your build. Also post photos of your testing setup with the amp off, but the scope and signal generator active. Post a photo of the signal generator screen as well.
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Re: New TMB w/reverb Build

Post by foreverstrung »

OK, so here's a pic of the signal generator. Plugged into and on channel 2
today1.jpg
This is the wave pattern on the scope
today2.jpg
And then this is the set up. Probe ground is on input jack busbar ground. Probe itself is on the input jack. (I get the exact wave pattern at the shielded wire @ the terminal strip, (Connected and disconnected from chassis. Same both ways). In the background we can see the AWG and scope.
today3.jpg
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Re: New TMB w/reverb Build

Post by foreverstrung »

So I had to step away for a couple days and let this stuff go. Settle down a bit. So I'm going to "ease" back into it.
One thing to note, the input jack appears to have grounded out on the chassis and this caused a ground loop which was throwing my scope off.
I'm going to go through now and the next day or 2 and meticulously clean up everything and run it through again.
Temporarily removing the FX stuff so that I've got better access to everything.
ground loop.png
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Re: New TMB w/reverb Build

Post by foreverstrung »

Back on page 14 of this thread Josh, you've got screenshots of an amp on your bench. One of the screenshots is of "PI P1 (anode)". Where exactly is this for me to probe on my build? I assumed it was the phase inverter, V4, pin 1. I'd like to get this cleared up as this is just one side of that tube and is at about 225v.
I've cleaned up much of this amp and tho my scope readings aren't as clean as the ones you've posted, I'm happy with them up to the point noted above. I'm happy because the sine waves are relatively clean and I'm keeping the 1 kHz signal
The points I've probed are. AWG, Input, V2P2, .047-56, Treble P2, Volume P2. (up to here, everything is good except for some background noise. I'll post pics of screen shots when I get past the next/last 2 positions).....So the PI P2 anode I need clarification and last, but no way the least is the output. I'm getting a poor reading and not nearly enough juice going out to move the speaker. I went through and checked all my voltages and there all still spot on.
I've got a few more areas I'd like to clean up before testing with the scope again.
So another quest for advice.
I've got a solder sucker and it does ok when I'd like to clean up a joint to resolder, but the wick braid is probably better right? Either way, once I remove the old solder, any recommendations to prep before applying new solder?
TIA
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Re: New TMB w/reverb Build

Post by JMPGuitars »

foreverstrung wrote:
Sat 01/14/23 11:02 am
Back on page 14 of this thread Josh, you've got screenshots of an amp on your bench. One of the screenshots is of "PI P1 (anode)". Where exactly is this for me to probe on my build? I assumed it was the phase inverter, V4, pin 1. I'd like to get this cleared up as this is just one side of that tube and is at about 225v.
I've cleaned up much of this amp and tho my scope readings aren't as clean as the ones you've posted, I'm happy with them up to the point noted above. I'm happy because the sine waves are relatively clean and I'm keeping the 1 kHz signal
The points I've probed are. AWG, Input, V2P2, .047-56, Treble P2, Volume P2. (up to here, everything is good except for some background noise. I'll post pics of screen shots when I get past the next/last 2 positions).....So the PI P2 anode I need clarification and last, but no way the least is the output. I'm getting a poor reading and not nearly enough juice going out to move the speaker. I went through and checked all my voltages and there all still spot on.
I've got a few more areas I'd like to clean up before testing with the scope again.
So another quest for advice.
I've got a solder sucker and it does ok when I'd like to clean up a joint to resolder, but the wick braid is probably better right? Either way, once I remove the old solder, any recommendations to prep before applying new solder?
TIA
Correct, PI P1 is V4 Pin 1. You said both P1 and P2, P1 is plate (anode) P2 is grid. Scope P1 of V4. That's the main signal path. P6 of V4 is the signal that will come from the reverb, but scoping reverb is goofy anyway, because it's reverb.

Try setting your bandwidth limit to 20M (channel button, look for options). If you haven't already done that, then it might reduce the noise.

I use the desoldering gun on my soldering station. I don't have the patience for the other stuff. If it's a good braid, it might work better. To clean stuff, desolder as well as possible, and then use a coarse brush to try and clean further. You can use a tiny amount of solder to clean as well, but that's tricky.

I'm glad to hear you're making progress!
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Re: New TMB w/reverb Build

Post by foreverstrung »

So hopefully this thread ends with a happy ending. LOL. I really got tired of dickin around and not getting anywhere with the idiosyncrasies I was finding with the scope. At one time the amp was putting out good sound but I had the reverb not performing. At all. The more I dicked with it, the better it did NOT get. Just seemed like more obsticles.So I've upgraded many of my tools and enough parts for the next build, and then just pretty much took this thing apart. De-wired and de-soldered the heaters and pots and all wires to the PCB board. Now I'm putting it all back together. I watched all the soldering videos recommended, again, plus many more, from the same outfit, that don't really apply.
One thing I did diff is that the reverb rca jacks I had installed with a washer on each side of the chassis as the predrilled holes were way too big for the rca jacks themselves. To get rid of any potential/probable continuity issues, I drilled 2 hole just next to these at the right diameter that rca jacks anchor directly on the chassis itself. Figured it can't hurt.
I'm also doing my best to get better solder connections.
Anyways, that's where I'm at with this build right now. I'm looking fwd to building the cabinet as I've got all the components, but I just can't go there till this amp is kickin.
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Re: New TMB w/reverb Build

Post by JMPGuitars »

foreverstrung wrote:
Fri 01/20/23 5:13 pm
One thing I did diff is that the reverb rca jacks I had installed with a washer on each side of the chassis as the predrilled holes were way too big for the rca jacks themselves. To get rid of any potential/probable continuity issues, I drilled 2 hole just next to these at the right diameter that rca jacks anchor directly on the chassis itself. Figured it can't hurt.
I'm also doing my best to get better solder connections.
Anyways, that's where I'm at with this build right now. I'm looking fwd to building the cabinet as I've got all the components, but I just can't go there till this amp is kickin.
Hmmm, I sent you Switchcraft RCA jacks thinking they'd be easier to solder. These are the ones I normally use: https://www.amplifiedparts.com/products ... old-plated - but if you get those, make sure they're tight and you use some kind of loctite. The solder cups are a little tricky at first, so get extras if you go that route. ;)
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Re: New TMB w/reverb Build

Post by foreverstrung »

So this morning I fired it up with dim bulb tester. Glad I did instead of being so arrogant, believing I had everything dialed in nicely, (which did cross my mind) as I found a point on V6 between pins 5 and 6 which were arcing as I had a little too much solder on pin 5. Cleaned it up, tried again and appeared good with the tester. So plugged it into the wall and found all the voltages good. Then I put it on the scope and found all these readings acceptable. Not as clean a sine waves as Josh, but much better than before.
The main thing(s) I've done diff is that I upgraded my solder station with a good suction (desoldering) tool. I rewatched the soldering videos recommended. In these videos I most notably caught how to set the tip, applying the "bridge" from the tip to the surface and then using the solder to "paint" the area concerned. One of the things I was doing wrong was thinking like soldering with a torch and pipe when plumbing. That kind of soldering, the solder follows the heat, so I would apply solder and use the solder iron tip to move the solder, rather than "painting" it on, as described in the educational videos.
Another thing I did wrong before is that after I'd solder a joint, I immediately move to the next position without giving the newly soldered point I'd just done, adequate time to fully cool allowing for possible compromised joints.
So, this is where I'm at now. I'm going to plug it in and do a sound check after everyone is up and awake. Then complete the FX stuff and give the reverb a spin.
More to come.
Thx
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Re: New TMB w/reverb Build

Post by foreverstrung »

OK. So everything is hooked up. Amp sounds amazing. Tremolo is awesome. Amp is quiet. (P90's are kinda loud no matter what). Pedal works as it should with the tremolo. BUT, i've still got the reverb problem. It hasn't changed. This is where I was at awhile back and I ended up making things worse dickin around. Like I mentioned a post or 2 back, the scope shows relatively healthy sine waves from input to output with the AWG set at 1 kHz, I've got this reading at the input to the output........So what's next for checking my reverb? I doubt you guys recall, but in this thread, awhile back, I had the reverb issue. Got a scope and an audio generator, initially for chasing down the reverb issue, but could never get past the issues I was having just following the path from input to output until I re did most everything and am back here now.
Suggestions moving fwd chasing the reverb bug would be very much appreciated.
Thx
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Re: New TMB w/reverb Build

Post by JMPGuitars »

foreverstrung wrote:
Sat 01/21/23 9:07 pm
OK. So everything is hooked up. Amp sounds amazing. Tremolo is awesome. Amp is quiet. (P90's are kinda loud no matter what). Pedal works as it should with the tremolo. BUT, i've still got the reverb problem. It hasn't changed. This is where I was at awhile back and I ended up making things worse dickin around. Like I mentioned a post or 2 back, the scope shows relatively healthy sine waves from input to output with the AWG set at 1 kHz, I've got this reading at the input to the output........So what's next for checking my reverb? I doubt you guys recall, but in this thread, awhile back, I had the reverb issue. Got a scope and an audio generator, initially for chasing down the reverb issue, but could never get past the issues I was having just following the path from input to output until I re did most everything and am back here now.
Suggestions moving fwd chasing the reverb bug would be very much appreciated.
Thx
The answer is always the same:
Voltages
Highlighter test
Photos
Sound sample

Did you redo the reverb pot? Are the RCA jacks good?

Congrats on getting everything else to awesome!
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Re: New TMB w/reverb Build

Post by foreverstrung »

Reverb issue fix.jpeg
Reverb Issue Continued.
So I got some help getting to the bottom of my Reverb problem. It appears I had an "Oscallition parasite" which overloaded the preamp stage. IDK why exactly, but it was interfering with the reverb signal but most notably, when the reverb pot was activated, it elevated the oscillation, which dropped the output and would have eventually just buggard the whole thing. It was suggested that we install a grid stopper at V4 P7. I've added a pic. It's a 10k resistor in series from pin 7 to the PCB board and a .001 cap @ pin 7 to ground.....This removed the oscillation and the reverb works great, but now I've got significant noise. Like a 60 cycle hum type noise. White noise. It's not over the top, but this amp was near silent before these modifications to repair the oscillation. Reverb 1-10, no change in the noise. Gain, yes some change in output with noise. Volume pot, hell yes......Guitar pot volume, no change in noise. Swapped cords. Swapped guitars. Same amp noise
appreciate any thoughts
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Re: New TMB w/reverb Build

Post by JMPGuitars »

I can't tell from your photo angle, but is the pin 7 grid stopper connecting to ground? It shouldn't be, and you should have something insulating it. I'm assuming it's just a bad angle next to the wire shielding, but it looks problematic.

What's that green wire that looks like it's floating doing?

Is that a capacitor to ground on pin 7?

We need to hear noise to help with it, make a demo of the noise. Longer than 2 seconds please. 😉

Also, take voltages again after cleaning up that valve.

Thanks,
Josh
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Re: New TMB w/reverb Build

Post by foreverstrung »

1) The 10k resistor is in series from pin 7 to the PCB board port marked V4P7. (This resistor was originally attached with shielded wire. I wanted to clean it up so I replaced replaced it with 20g wire. Should it be shielded?)
2) The .001 cap is from pin 7 to ground. (Is this cap part of the "grid blocker" or did my guy add that? Should this cap be in series with the 10k resistor? Do I keep it to ground?) The picture I posted earlier today shows both the 10k resistor and the .001 cap at Pin 7 of V4. Cap to ground and resistor to PCB board
3) The green wire you asked about is what connects P3 and P8 to the port on the PCB board. Small green wire jumps from p3-8 and then the longer green wire is connected to p8-PCB board
4) The voltages all check out "except", the AC voltages A, B, C and D. IDK what the hecks going on here, but there not picking up barely anything. I mean like A is 4.4v. No, not kidding. B is 0v. C and D as well. I even used another DMM and the readings were the same. I'm getting the correct AC voltage at the heaters, PT in and out, just when it gets to the cap can, I'm getting notta. I tried and retried. At least a half dozen times. I even hooked everything up and had the guitar and speaker active and checked AC voltages here and got the same readings.
5) I'm attaching the voltage chart
6) Lastly is attached a video of sound

https://youtu.be/-NhPIxDyq1g
voltage chart 3.21.jpg
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Last edited by foreverstrung on Wed 03/22/23 6:20 am, edited 2 times in total.
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Re: New TMB w/reverb Build

Post by JMPGuitars »

Try removing the cap to ground and see what effect it has.

A,B,C,D need to be read as DCV. I'll look over the rest tomorrow, it's past my bedtime.

Thanks,
Josh
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Re: New TMB w/reverb Build

Post by foreverstrung »

4) The voltages all check out "except", the AC voltages A, B, C and D. IDK what the hecks going on here, but there not picking up barely anything. I mean like A is 4.4v. No, not kidding. B is 0v. C and D as well. I even used another DMM and the readings were the same. I'm getting the correct AC voltage at the heaters, PT in and out, just when it gets to the cap can, I'm getting notta. I tried and retried. At least a half dozen times. I even hooked everything up and had the guitar and speaker active and checked AC voltages here and got the same readings.
Duh. DCV attached for ABC and D
A.B.C.D.jpg
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Re: New TMB w/reverb Build

Post by JMPGuitars »

Your B+ and tube dissipation are too high. Do you have any 5W Zeners? I would drop 15 to 20V on the B+ line. Put 2 10V 5W Zeners in series between the 1st and 2nd filter caps.

You're using a 180 ohm cathode resistor for the power tubes, correct?
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Re: New TMB w/reverb Build

Post by foreverstrung »

Your B+ and tube dissipation are too high. Do you have any 5W Zeners? I would drop 15 to 20V on the B+ line. Put 2 10V 5W Zeners in series between the 1st and 2nd filter caps.

You're using a 180 ohm cathode resistor for the power tubes, correct?
Yes, I've got 2 of the 5W Zener Diodes. Should I add a 3rd? (pic attached)
I am using 180 ohm cathode yes

What is the formula to figure dissipation?

Would this noise possibly be from the amp being too hot? Should I bring the tube dissipation down first and if noise is still present, remove the .001 cap at V4P7 to ground and see what happens? Or remove it first and recheck voltages?
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