Strange noises from trainwreck clone build

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thomasks
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Joined: Sun Jan 01, 2023 4:14 pm

Strange noises from trainwreck clone build

Post by thomasks »

Good day all!
So i finished my clone build of a trainwreck express from a kit. It is great, except for the noise that I am hearing whether an instrument is plugged in or not.
The first is just background humming. When I turn on the standby switch, I can hear a buzzing that is in the background. Like you would hear from single coils with a flourescent light in the room.
Also I get a very annoying squeal if I turn the presence down toward 7 o'clock. It goes away around 9-10 o'clock. I saw a photo of trainwreck 24 on this site, and that one did not run the bonding line to ground across the pots all the way to the presence pot. But my layout showed it going all the way across the pots. So that is what I did.
Any suggestions?
sluckey
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Re: Strange noises from trainwreck clone build

Post by sluckey »

Also I get a very annoying squeal if I turn the presence down toward 7 o'clock.
This can usually be cured by swapping the PT primary plate leads at the tube socket.

The buzz could be almost anywhere. Many times it's a bad ground connection, or lead dress issue. Triple check your wiring.
thomasks
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Re: Strange noises from trainwreck clone build

Post by thomasks »

Do you mean the OT Primary windings at the power tubes? The PT goes to the power input rectifier, and the heaters at the tubes.
joeboo88
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Re: Strange noises from trainwreck clone build

Post by joeboo88 »

Yes Steve meant try swapping OT leads, he just had a typo
sluckey
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Re: Strange noises from trainwreck clone build

Post by sluckey »

joeboo88 wrote: Sat Mar 25, 2023 10:29 pm Yes Steve meant try swapping OT leads, he just had a typo
Sorry, and thanks.
thomasks
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Re: Strange noises from trainwreck clone build

Post by thomasks »

Ok, so I took the amp chassis out of the cabinet. Then I swapped the OT leads on the power tubes.
I took a wooden dowel and started chop sticking the wires and moving wires around that were close together or crossing each other to make sure that they crossed at right angles as much as possible. I still have a wicked hiss/buzz and microphonics? Whenever I tap on a pot or a wire, you can here it in the speaker. Pin 2 of the first preamp tube (V1?) is where it starts and goes all the way to the OT.
It is a high pitched sound like you are tapping on a crystal glass. And if you rub on the cloth insulation it makes a staticty rubbing sound like a dirty pot wiper.
What should I try to clean this thing up?
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martin manning
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Re: Strange noises from trainwreck clone build

Post by martin manning »

Have you tried swapping the first preamp tube? It sounds like it is microphonic. If you don't have a spare, try swapping V1 for V2 or V3 to see if there is any change.
thomasks
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Re: Strange noises from trainwreck clone build

Post by thomasks »

I rolled V1 to V2 same result. Then V3 with V2 (previously V1) and still same. I can hear the click when I switch the bright switch back and forth also.
thomasks
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Re: Strange noises from trainwreck clone build

Post by thomasks »

Sorry, I should have included the picture of the chassis.
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Reeltarded
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Re: Strange noises from trainwreck clone build

Post by Reeltarded »

The bright cap switching will tick every cycle on. Some more, some less. Louder on the larger cap and at lower volume settings.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
thomasks
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Re: Strange noises from trainwreck clone build

Post by thomasks »

Update on what I have tried:
Moved the transformer center taps to the ground side of the first filter cap. This helped, but still have hum/buzz.
I have a new set of preamp tubes and will try those out once they arrive. I ran the amp through my variac to use it as an isolation transformer to eliminate dirty AC from the outlet.
Same results. So I think it is a problem within the amp. The noise is there with no input and a 2x12 speaker cab drawing 16ohms.
Not sure what else I can do? Still getting microphonic noises when I turn the standby or power switches off. Or if I tap on the chassis.
Any suggestions are much appreciated.
ampbldr2
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Re: Strange noises from trainwreck clone build

Post by ampbldr2 »

If you are hearing humming with standby off through your speaker you may have the OT misplaced in the magnetic field lines of the PT.
I had to move my OT to get rid of it on my express build. https://ampgarage.com/forum/viewtopic.php?f=1&t=34638
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