Ampeg Gemini 1 G12
Moderators: pompeiisneaks, Colossal
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terryrocks
- Posts: 31
- Joined: Sun Feb 21, 2010 12:17 am
- Location: portlandia
Re: Ampeg Gemini 1 G12
Right, i did not measure 700vac. That's from my schematic. I haven't encountered another that matches.
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Ampeg Gemini 1 G12
Ok, so let's regroup here!
First confirm that the echo foot switch is open, then if you tap on the out bound side of that .47 cap before the input side of the pan with the tip of a screw driver do you hear any noise when the echo / verb control is turned up?
First confirm that the echo foot switch is open, then if you tap on the out bound side of that .47 cap before the input side of the pan with the tip of a screw driver do you hear any noise when the echo / verb control is turned up?
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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terryrocks
- Posts: 31
- Joined: Sun Feb 21, 2010 12:17 am
- Location: portlandia
Re: Ampeg Gemini 1 G12
I touched the leads on that cap, the one coming off pin 6 on the 6cg7 and it pops when I touch either end.
It also pops the same with verb channel turned all the way down
It also pops the same with verb channel turned all the way down
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Ampeg Gemini 1 G12
If that pop noise sounds like it's got reverb on it when the verb is turned up, then signal is not getting to V6, now your scope can be put to good use by stepping thru the signal chain and pinning down where it fails to pass!
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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terryrocks
- Posts: 31
- Joined: Sun Feb 21, 2010 12:17 am
- Location: portlandia
Re: Ampeg Gemini 1 G12
Ok, i'm ready to do some signal probing.
My o-scobe is up and running along with my function gen. I assume i output a sine wave from funcgen to amp, then probe after the coupling cap on each stage?
My o-scobe is up and running along with my function gen. I assume i output a sine wave from funcgen to amp, then probe after the coupling cap on each stage?
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Ampeg Gemini 1 G12
Good!
You should not need anything more than a 180 MV output from you signal generator to drive that amp to full on output stage clipping and max peak power if all off the tubes in the signal chain are in decent shape!
You should not need anything more than a 180 MV output from you signal generator to drive that amp to full on output stage clipping and max peak power if all off the tubes in the signal chain are in decent shape!
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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terryrocks
- Posts: 31
- Joined: Sun Feb 21, 2010 12:17 am
- Location: portlandia
Re: Ampeg Gemini 1 G12
Update: Problem solved!
The issue was the reverb pot. Last tech did a number on it. Replaced the pot, no problem now.
Wasn't all me. I spent a lot of time trying to crack this before setting it aside for a few weeks while I worked on other projects. Came across a retired EE who helped me troubleshoot. after an hour of trying various things, he took a hard look at the pot and said, "that's it right there". We removed the pot, connected the wires to test the idea, got a strong reverb output on powerup, then installed a new pot.
Wish I'd figured it out on my own, but much happier to learn from a master EE than farm it out to another tech.
Thanks for all the help everyone. I've learned a lot and there are still plenty of other amp issues I will try and workout in time.
The issue was the reverb pot. Last tech did a number on it. Replaced the pot, no problem now.
Wasn't all me. I spent a lot of time trying to crack this before setting it aside for a few weeks while I worked on other projects. Came across a retired EE who helped me troubleshoot. after an hour of trying various things, he took a hard look at the pot and said, "that's it right there". We removed the pot, connected the wires to test the idea, got a strong reverb output on powerup, then installed a new pot.
Wish I'd figured it out on my own, but much happier to learn from a master EE than farm it out to another tech.
Thanks for all the help everyone. I've learned a lot and there are still plenty of other amp issues I will try and workout in time.
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Stevem
- Posts: 5144
- Joined: Fri Jan 24, 2014 3:01 pm
- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Ampeg Gemini 1 G12
Yup, just like a previously botched repair on your car will get you a tow bill a half assed amp repair will get you half assed sound if at all!
Good to hear she's up and running on all cylinders, lol!
Good to hear she's up and running on all cylinders, 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!