Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by JMPGuitars »

perplexd wrote:
Thu 02/16/23 5:26 pm
JMPGuitars wrote:
Thu 02/16/23 5:18 pm
Did you install R34?
I did not.
Try it and see if it affects your issue.
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by perplexd »

JMPGuitars wrote:
Thu 02/16/23 10:49 pm
perplexd wrote:
Thu 02/16/23 5:26 pm
JMPGuitars wrote:
Thu 02/16/23 5:18 pm
Did you install R34?
I did not.
Try it and see if it affects your issue.
OK, I put in R34 and the issue seems to be gone! Smooth all the way up the pot travel. Even with the long plate phase inverter tube.
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by JMPGuitars »

perplexd wrote:
Fri 02/17/23 11:29 am
OK, I put in R34 and the issue seems to be gone! Smooth all the way up the pot travel. Even with the long plate phase inverter tube.
Nice! I figured that would do the trick.
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by perplexd »

I soldered the 220k in now the hum is back. Ugh.
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by JMPGuitars »

I just listened to your clip. It sounds like you might have a parasite trying mess with you. With R34 in place, do you still get radio signal testing voltages?
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by perplexd »

I am not getting any radio signal tonight. I get about 53 volts on each coupling cap going into the phase inverter rather than the 52 and 62. I found that the voltage at the bias resistor drops about 4-5 volts as I swing the channel 2 volume control, it does not drop at all when I swing the v1 volume control
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by JMPGuitars »

perplexd wrote:
Fri 02/17/23 9:15 pm
I am not getting any radio signal tonight. I get about 53 volts on each coupling cap going into the phase inverter rather than the 52 and 62. I found that the voltage at the bias resistor drops about 4-5 volts as I swing the channel 2 volume control, it does not drop at all when I swing the v1 volume control
Ok, so it sounds like R34 at least helped a little.

My suggestion is to get the volume knob in a position that the issue is obvious. Then you can try chopsticking some wires and see if that has an affect on it. For example, see if moving that grid wire into different positions with the chopstick has any affect on the hum noise.
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by perplexd »

Okay I think we are on to something. I found that the yellow wire connected to Pin 2 of V3 affects the hum and was able to get it to go away by pulling it out away form the other wires. Checked the voltage on the bias resistor while while turning volume pot and it doesn't drop anymore. It finally sounds better when volume is at 6 or above, like more headroom. So maybe either a solder issue on the tube socket or lead dress?

BUT now I hear a high frequency ticking when the guitar is plugged in either channel. It stops when the guitar volume is all the way down or unplugged.
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by Daviedawg »

It could be guitar finding RF pickup from lights, a computer or related gear or even a watch. Move your guitar away from anything and switch off lights to see what happens.

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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by Bieworm »

I was taking a new build nearly apart once… turned out to be the 20 foot Planet Waves cord I was using
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by perplexd »

I think you’re right. When I went back and powered on again the ticking was gone. I think I might be able to button this thing up and play now!
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by Bieworm »

Ever since I only use 10 foot cords… plenty enough for me. On stage I want to be close to my amps anyway
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by JMPGuitars »

Bieworm wrote:
Sun 02/19/23 4:30 am
Ever since I only use 10 foot cords… plenty enough for me. On stage I want to be close to my amps anyway
I haven't used anything longer than 10' in decades. I dunno how much it matters, but I was told you start getting signal loss at 20'.
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by Bieworm »

JMPGuitars wrote:
Sun 02/19/23 1:22 pm
Bieworm wrote:
Sun 02/19/23 4:30 am
Ever since I only use 10 foot cords… plenty enough for me. On stage I want to be close to my amps anyway
I haven't used anything longer than 10' in decades. I dunno how much it matters, but I was told you start getting signal loss at 20'.
The problem I had wasn’t tone loss… I picked up radio and rewired the input wiring, every grid wire,… turned out to be the 20 inch extremely well double shielded planet waves cord. Go figure… that was the antenna😎
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by JMPGuitars »

Bieworm wrote:
Sun 02/19/23 5:01 pm
The problem I had wasn’t tone loss… I picked up radio and rewired the input wiring, every grid wire,… turned out to be the 20 inch extremely well double shielded planet waves cord. Go figure… that was the antenna😎
Did you try extra grid stoppers? Damn you shielding that acts like an antenna!

BTW- I'm curious. If you take that same 20' cable, mark one side amp, and one side guitar. Then make sure the shield is only connected to the amp side ground. I wonder if that would cure the problem. (it probably doesn't matter which side it's connected to, as long as it's only one side)
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by Bieworm »

JMPGuitars wrote:
Sun 02/19/23 5:06 pm
Bieworm wrote:
Sun 02/19/23 5:01 pm
The problem I had wasn’t tone loss… I picked up radio and rewired the input wiring, every grid wire,… turned out to be the 20 inch extremely well double shielded planet waves cord. Go figure… that was the antenna😎
Did you try extra grid stoppers? Damn you shielding that acts like an antenna!

BTW- I'm curious. If you take that same 20' cable, mark one side amp, and one side guitar. Then make sure the shield is only connected to the amp side ground. I wonder if that would cure the problem. (it probably doesn't matter which side it's connected to, as long as it's only one side)
Too late… I made 2 cables out of that one… looong ago😁
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Re: Diagnose Static/Egg Frying in Trinity 18 Watt Plexi MkII

Post by perplexd »

Solved! I tidied everything up, put the chassis back in the amp and played for an hour without any issues. I am finally at peace. Thanks again for working through this with me. :D
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