Yes, one tip on each !
If the drive amp side of the pan is working and you have a good amount of sound coming from the speaker than you be reading ac signal voltage on that input side pan rca, in fact if you have another amp you can drive another amps input and also prove out that you have pan drive signal as I am assuming that you do not have a O- scope!
Ampeg Gemini 1 G12
Moderators: pompeiisneaks, Colossal
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Stevem
- Posts: 5144
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Re: Ampeg Gemini 1 G12
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 do have an o scope, just not much practice with it.
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Stevem
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Re: Ampeg Gemini 1 G12
Ok, it's time to start using it then, do you have the instructions for it?
Just to be on the safe side and not harm the scope with a dc voltage hook up a . 22uf to .001uf 600 volt cap to a section of wire hooked to the scopes test probe tip and use that unhook lead / end of the cap to do your probing of the circuit unless you have confirmed by test with a meter that you have no dc voltage above about a volt !
Be sure when probing a powered up amp to not have any part of your body touching the chassis and you will be safe from shock!
Just to be on the safe side and not harm the scope with a dc voltage hook up a . 22uf to .001uf 600 volt cap to a section of wire hooked to the scopes test probe tip and use that unhook lead / end of the cap to do your probing of the circuit unless you have confirmed by test with a meter that you have no dc voltage above about a volt !
Be sure when probing a powered up amp to not have any part of your body touching the chassis and you will be safe from shock!
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
All voltage measurements are relaive to ground except the heater pins.
Voltage after c30 is 11vac
Voltage between heaters is 12v
In other voltage tests:
V3, my 7199 phase inverter shold read 84v on pin 8. However, i'm seeing 46v
V4/v5 both 12ax7 should read 185v on pin 6. They are reading 156v.
V6 the 6cg7 should be 205v on pin 6. I see 293v.
Pin 8 should be 4.5 and I see 6.2v more than 20% out of spec.
And v7 a 12ax7 should read:
Pin 1 130v. I see 90v
Pin 3 1.5v. I see .6v
Pin 6 100v. I see 190v
Pin 8 0.6v. I see 4 v
Voltage after c30 is 11vac
Voltage between heaters is 12v
In other voltage tests:
V3, my 7199 phase inverter shold read 84v on pin 8. However, i'm seeing 46v
V4/v5 both 12ax7 should read 185v on pin 6. They are reading 156v.
V6 the 6cg7 should be 205v on pin 6. I see 293v.
Pin 8 should be 4.5 and I see 6.2v more than 20% out of spec.
And v7 a 12ax7 should read:
Pin 1 130v. I see 90v
Pin 3 1.5v. I see .6v
Pin 6 100v. I see 190v
Pin 8 0.6v. I see 4 v
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Stevem
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- Location: 1/3rd the way out one of the arms of the Milkyway.
Re: Ampeg Gemini 1 G12
Man something is really F ed up with the original G12 schematic I found online as I can not see how the on the effect channel the dry signal gets around the reverb circuit, no less how the output of the none effect channel gets its way to the PI!
So you have 11 volts of signal coming out of the drive amp at the down stream side of C30?
If so than the foot switch is not shorting it out to ground and since you said you can hear yourself tapping on the pan then you should have reverb as you posted back that the resistance checks I gave you proved out, I am at a bit of a loss now!
So you have 11 volts of signal coming out of the drive amp at the down stream side of C30?
If so than the foot switch is not shorting it out to ground and since you said you can hear yourself tapping on the pan then you should have reverb as you posted back that the resistance checks I gave you proved out, I am at a bit of a loss now!
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: Ampeg Gemini 1 G12
Does your schematic look similar to one of these?Stevem wrote:Man something is really F ed up with the original G12 schematic I found online as I can not see how the on the effect channel the dry signal gets around the reverb circuit, no less how the output of the none effect channel gets its way to the PI!
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Stevem
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- 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
Yea, there Ya go, that second schematic is the one I glanced at too fast to see those 3 nodes for the dry signal, thanks!
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've replaced the two electrolytics on v7 and nothing blew up.
Then today I powered her up and started tap components and leads with a chopstick. I found about 10 different spots on the turret board where it seems the solder joint is bad. These are all toward the center of the board where a lot of flexion takes place. Makes sense to me.
Should i just reflow, or remove the old solder and replace?
The old stuff sure gunks up my solder sucker fast. Maybe my iron isn't hot enough.
Then today I powered her up and started tap components and leads with a chopstick. I found about 10 different spots on the turret board where it seems the solder joint is bad. These are all toward the center of the board where a lot of flexion takes place. Makes sense to me.
Should i just reflow, or remove the old solder and replace?
The old stuff sure gunks up my solder sucker fast. Maybe my iron isn't hot enough.
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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
Most times I try to get as much of the old stuff out first, to the point where I will flow in new solder just to get some flux into the old stuff,but it can be a pain so I would say just reflow it first and check if you then still get noise!
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've just realized that my schematic doesn't completely agree with the voltage chart. There don't seem to be any really early gemini schematics floating around.
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terryrocks
- Posts: 31
- Joined: Sun Feb 21, 2010 12:17 am
- Location: portlandia
Re: Ampeg Gemini 1 G12
Sluckey, mine more closely matches the first one that says patent pending at the bottom. Mine also has that.
A huge difference with my schm is that the voltage right before rectifier is 700vac. Yours says 280vac.
A huge difference with my schm is that the voltage right before rectifier is 700vac. Yours says 280vac.
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terryrocks
- Posts: 31
- Joined: Sun Feb 21, 2010 12:17 am
- Location: portlandia
Re: Ampeg Gemini 1 G12
700VAC into a full wave bridge will give you about 990VDC unloaded B+! That's obviously wrong.A huge difference with my schm is that the voltage right before rectifier is 700vac. Yours says 280vac.
280VAC would give about 395VDC unloaded. That's in line with the 360V at Node A input capacitor.
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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
How hell are you measuring 700 volts ?
That amp uses the same PT 110 as do 4 other Ampeg amps from that era, how are you placing the leads of your meter, and how do you have it set?
That amp uses the same PT 110 as do 4 other Ampeg amps from that era, how are you placing the leads of your meter, and how do you have it set?
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: Ampeg Gemini 1 G12
I don't think he measured that. He read it on the schematic that's glued to his cab.