Vibrochamp insanity!
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Vibrochamp insanity!
Ok this is the same champ I posted about with the Tremolo issue that I finally fixed.
From the start of this repair the amp had a distorted fuzz tone to as each note faded out at any volume level.
This type of issue I have always found to be caused by a tube or a speaker, but not with this amp!
Here is a list of what I have tryed to resolve the issue which still is taking place.
In no peticular order here's what I have tryed out.
1) tubes, no go.
2) speaker, no.
3) power supply filters, no.
4) install a good known output transformer from my own 100% fine Vibrochamp,no,
5) replace V1 tube socket, no.
6) replace output tube socket, no.
Jump out all 3 tone stack caps one at a time even after they tested good for ESR, no go.
7) jump first gain stage right to the output tube, no.
check grid load off of input jacks, no.
9) unscrew and lift the tag board up off the insulator board, no.
10) check / test my newly installed cathode bypass caps and jump with new ones even though the ones I put in tested good, no.
11) test a ton of circuit points to other circuit points to test for stray resistance, no.
12) jump the volume pot out, no.
13) check all other grid load resistors in the audio path, no.
I am flat out of things to try here so anybody got any suggestions because I could have built 3 of these amps in the time I have been messin with this thing!
From the start of this repair the amp had a distorted fuzz tone to as each note faded out at any volume level.
This type of issue I have always found to be caused by a tube or a speaker, but not with this amp!
Here is a list of what I have tryed to resolve the issue which still is taking place.
In no peticular order here's what I have tryed out.
1) tubes, no go.
2) speaker, no.
3) power supply filters, no.
4) install a good known output transformer from my own 100% fine Vibrochamp,no,
5) replace V1 tube socket, no.
6) replace output tube socket, no.
Jump out all 3 tone stack caps one at a time even after they tested good for ESR, no go.
7) jump first gain stage right to the output tube, no.
check grid load off of input jacks, no.
9) unscrew and lift the tag board up off the insulator board, no.
10) check / test my newly installed cathode bypass caps and jump with new ones even though the ones I put in tested good, no.
11) test a ton of circuit points to other circuit points to test for stray resistance, no.
12) jump the volume pot out, no.
13) check all other grid load resistors in the audio path, no.
I am flat out of things to try here so anybody got any suggestions because I could have built 3 of these amps in the time I have been messin with this thing!
Last edited by Stevem on Mon Mar 18, 2019 4:00 pm, edited 1 time in total.
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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Re: Vibrochamp insanity!
Oof.... jump all points out to another working amp.. if you get to the pi and It all works... build a new one.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
Re: Vibrochamp insanity!
Is it that faint buzzy sound that cuts off suddenly just before the note fully fades? You might try shielding the leads to the tone controls. If you have multiconductor shielded cable, you can put them all in one shield. It's worked for me on some Fenders.
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Re: Vibrochamp insanity!
No, even if you play a staccato note the fuzz tone is there for a half a second and like I posted I fully jumped the first gain stage output right to the input of the output tube, thru a cap of course so that cuts the whole tone stack and all it's cabling out of the picture.
Thanks for these replys though!
Oh, and sorry I could not erase the smile face in my first post for some unknown reason!
Thanks for these replys though!
Oh, and sorry I could not erase the smile face in my first post for some unknown reason!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Vibrochamp insanity!
That's because this forum interprets 8 ) as a smiley face. There, see, I solved one issue for you!
I build and repair tube amps. http://amps.monkeymatic.com
Re: Vibrochamp insanity!
May be time to get serious about board replacement. You can get a VibroChamp G10 eyelet board from Hoffman for $12.53.
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Re: Vibrochamp insanity!
Yes, but it just now having to talk the customer into going for what amounts to full rebuild!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Vibrochamp insanity!
not sure what year you are dealing with I did a brown face a while back and the B+ voltage was around 100 volts to high
I changed the PT to a new one great.
I changed the PT to a new one great.
Re: Vibrochamp insanity!
Just thinking out loud....
When you jumped from the first triode to the output did you disconnect the tone stack or just turn volume down and jumper around it? Did you disconnect the coupling cap from the grid of the 6v6?
On the Vibro Champ I mentioned in your other thread I ended up using a "listening amp" to find the problem.
When you jumped from the first triode to the output did you disconnect the tone stack or just turn volume down and jumper around it? Did you disconnect the coupling cap from the grid of the 6v6?
On the Vibro Champ I mentioned in your other thread I ended up using a "listening amp" to find the problem.
Deric®
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Re: Vibrochamp insanity!
The eighth thing you do is always funny anyhow.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
Re: Vibrochamp insanity!
Did you try to Isolate the vibrato section? I had a Princeton with a similar problem.
If it don't get hot and glow, I don't want it !
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Re: Vibrochamp insanity!
Yes, when I bypassed the the whole second gain stage and the tone stack I used a new coupling cap at the input to the 6V6.
Once I got the Tremolo issue resolved I pulled out that tube for all the other test I posted about so the Trem section I would think could have no bearing on the issue since all the Trem does is wiggle the bias voltage on the preamp tube cathode that I bypassed.
The amp is a 65 and all the voltages are are within 15 volts of what they should be so I see no issue in that regard either!
Thanks to all once again for the brain storming!
Once I got the Tremolo issue resolved I pulled out that tube for all the other test I posted about so the Trem section I would think could have no bearing on the issue since all the Trem does is wiggle the bias voltage on the preamp tube cathode that I bypassed.
The amp is a 65 and all the voltages are are within 15 volts of what they should be so I see no issue in that regard either!
Thanks to all once again for the brain storming!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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- Posts: 4576
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Vibrochamp insanity!
I gave up on this though I did not want to, but my labor time on it was up to 5 hours so it went back to the customer now working instead of being dead,but not to my liking!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: Vibrochamp insanity!
The later VCs added a cap from the grid to the cathode of the 6v6. I removed mine since it was surely sucking tone. The result was a buzzy oscillation riding most notes. I changed the grid wire to that 6v6 to shielded and the buzz went away. Mine is 1974.
If it says "Vintage" on it, -it isn't.
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- Posts: 4576
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Re: Vibrochamp insanity!
This was a 1965 VC and never had that cap to deal with parisitic oscillation, but my next move would have been what you did .
I was going to try placing a 50 pf 500 volt silver mica cap across the plate and or the plate to grid, or the Cathode as you did as they all can help or cure that issue.
I at that point had none left in stock and was not going to rip one out of one of my own amps!
I big help with this issue should have been when I fully jumped out the tone stack and second gain stage, and then ontop of that moved the output tube coupling cap right onto the output tube socket and the 220k grid load resistor also.
Many times in silverface amps , or any amp with oscillation issues removing inches of grid lead length in favor of plate lead length will get rid of the issue at its root and adding tone sucking small bypass caps will have to be done.
I was also about to try the trick of raping a few turns of wire around the output tubes cathode lead and the hooking that up to the plate to add some inducted feedback.
Oh well, if the amp comes back I am recharged now and ready for it, lol!
I was going to try placing a 50 pf 500 volt silver mica cap across the plate and or the plate to grid, or the Cathode as you did as they all can help or cure that issue.
I at that point had none left in stock and was not going to rip one out of one of my own amps!
I big help with this issue should have been when I fully jumped out the tone stack and second gain stage, and then ontop of that moved the output tube coupling cap right onto the output tube socket and the 220k grid load resistor also.
Many times in silverface amps , or any amp with oscillation issues removing inches of grid lead length in favor of plate lead length will get rid of the issue at its root and adding tone sucking small bypass caps will have to be done.
I was also about to try the trick of raping a few turns of wire around the output tubes cathode lead and the hooking that up to the plate to add some inducted feedback.
Oh well, if the amp comes back I am recharged now and ready for it, lol!
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!