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I was actually asking about what these two points were, without the typo.

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Great tones come in small glass jars!

I got so frustrated I just decided to do a complete rebuild. I should be done tonight and I will post results.

Now that's an Extreme Makeover!!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Unfortunately, same results. I replaced all 3 preamp tube sockets. I did not replace all the resistors and caps on the board, but I moved all the underboard jumpers to the top and all the underboard turret connections to the top of the board so they can be seen clearly. I converted it back to plexi specs since that was what was working before this mess started.

Voltages:
122.7vac from wall
304vac at the 2 pins on recto
340 vdc at the cap can

voltages along the board, left to right. The first number is what mine is, the second is what it should be;
12/11.8
311/340
180/217
178/220
55/62
82/75
53/52
244/272
165/180
1.5/1.5
126/155
128/155
.9/1.0
.9/1.0
V5 has 326vac at pin 7
v4 has 326vac at pin 7
v2 has 165vac at pin 1
340vac at the cap can



Another thing I noticed is when the is guitar plugged into regular channel, and that volume turned all the way down, if I adjust the volume and gain on the plexi channel, it puts a lot of “hissing “ through the speaker even though I am not plugged into the plexi channel.

Again the problem here is a loud buzz, it is on both channels, all 4 inputs, and it goes up and down with the volume/ gain controls. It sounds like a grounding issue, but I have checked all the grounds many times and they measure 0.2 or 0.3 ohms. I have chopsticked this thing and nothing is making any noise.

I really think it has to be a bad/ wrong component, I really took my time and carefully checked each and every joint.

Please let me know what you think, this is driving me bonkers. I was about to start on a tc-15, but I cant do anything til I get this off my bench.

Thanks,
Jon

The voltages are off but not as much as I thought they were before. I thought the PI was way out before but this looks more reasonable.
Is there sound at all or just hum/buzz?
And reading over the thread again, does this happen with only the guitar plugged in?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

There is sound with the guitar plugged in, and it is silent when the guitar cable is removed.

I believe this is how the amp should behave. IIRC the jacks are wired so they shunt the signal to ground when no cable is in. Then you don't have noise when the amp is just sitting around.

I'd check your input jack wiring, jumpers on the board, jumpers on the pots.

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Is the hum there all the time the guitar is plugged in and it just gets louder when you turn up the gain/volume?
Or does it go away when you turn down the volume?
Is the hum 60 cycle?
Is it a constant tone or is it white noise?
Have you tried a known good 6CA4?

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Tele's make the best noise

That sounds correct and the voltages seem close so what happens when you try another cable or instrument?

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Is the hum there all the time the guitar is plugged in and it just gets louder when you turn up the gain/volume?
Or does it go away when you turn down the volume?
Is the hum 60 cycle?
Is it a constant tone or is it white noise?
Have you tried a known good 6CA4?

The hum/buzz is always there when the guitar is plugged in. It varies when I turn up the gain/volume. When you turn the volume all the way off it goes away.

Please forgive my ignorance, but how do I identify 60 cycle hum?

When I use a different cable of guitar the result is the same.

plug a speaker into a 6.3 vac cct or into a wall socket if you have one that will handle 1500 w plus.
Its a low frequency steady tone, B 2nd fret on the A string on a bass. On a fretless it would be some cents below the 2nd fret.

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Fantasy Noise is what my shop of dreams is called and was the only way to beat my addiction, like many here I suffer from G.A.S.


Tele's make the best noise

If you plug the guitar cord in without the guitar is the noise still there?
You have correct B+(340) on the switch side of the can and everything else is down.
If you pull the tubes and measure voltage as you would on start up are there any that are way out
I would expect to see pin 7 on V4/5 pretty much the same as the can voltage

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Fantasy Noise is what my shop of dreams is called and was the only way to beat my addiction, like many here I suffer from G.A.S.


Tele's make the best noise

- What happens when you turn down the volume and tone controls on your guitar?

- Is the buzz there on both channels?

- Does it follow whichever channel you plug the guitar into?

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May have a breakthrough. Plugged into regular channel, turned volume all the way down, and there was still lots of sound coming through the speaker. I thought I may have had this happen before. What would cause this to be an intermittent problem?

Ok, lots of chopsticking and it is definitely in the pots. I can get the noise to go up and down, it never really goes away. But the solder joints are good.

Is there something that can be wrong with the pots that is not cold joints?


Does this give anyone any clues?

yes

Can you measure an DC voltage on any of the pots / on the 'back' side of the coupling caps to see if there is a leaky coupling cap. All pots cant possibly by bad , or it's a wiring issue.

For fun, plug in a cable and NO guitar - what happens??

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

The problem then appears to be coming from your guitar. It may have a grounding fault and/or need internal shielding.


Or even better, take a jack plug with a 10k resistor soldered across the terminals and inside the shell, where the guitar cord would normally be soldered. Plug that into the amp. If you still get buzz, then there's probably a fault with your input jack wiring/grounds.

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Removed volume pot from regular channel. I could tell one of the terminals on the pot was loose. Hooked up meter to the center terminal and the loose terminal. Turned the pot to max and it would show about 500k ohms. But when I wiggled the alligator clip connecting the meter lead to the terminal, it would show the pot as open, with no resistance. Ok, so I know the pot is bad and I am definitely going to replace it tomorrow. Could this cause the buzz I was getting on both channels?

It's posible if the grid to the PI in the Normal channel was left open in this case it would pick up a hum. Let's just hope so!

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

I doubt it - although it could have helped make things worse on the Normal channel. So please check out my previous post.

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Great tones come in small glass jars!