GEM H6000 channel problem

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awambawamb
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GEM H6000 channel problem

Post by awambawamb » Wed Jun 22, 2011 7:51 pm

hi there
just got my hands on a GEM H6000 (click to see), an old organ/synth - it has a monotron and polytron section, and LFO controls :P - but i've experienced a weird problem. The thing is constatly making a low "beep" sound, until i mute a channel by half pluggin in a jack in the headphones plug.

photo: with noise

photo: without noise (but mono channel)

Something tell me that one channel is messed up.
When it's in "fake" mono, it works perfectly. So probably the tone and wave generators are ok... or no?

I could do little repairs but i have no clue where to start... I need help!
Thank you very much!
Max
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rhino
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Re: GEM H6000 channel problem

Post by rhino » Wed Jun 22, 2011 11:25 pm

How fast and regular is the beeping? Any chance it could be a failure in some sort of chorus/Leslie simulator circuit?
When the wise man points to the stars, the fool looks at the finger.
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awambawamb
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Re: GEM H6000 channel problem

Post by awambawamb » Thu Jun 23, 2011 11:15 am

to me more precise, it's more like a low drone sound. It's continuous, and starts as you turn on the organ. Is there a way to chek it for sure? Btw, it has a real leslie speaker inside.
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rhino
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Re: GEM H6000 channel problem

Post by rhino » Thu Jun 23, 2011 4:33 pm

60 Hz hum from power supply/power amp?
When the wise man points to the stars, the fool looks at the finger.
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awambawamb
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Re: GEM H6000 channel problem

Post by awambawamb » Fri Jun 24, 2011 1:46 pm

Here's the sampled hum/drone. not sure if it comes from the power supply, and both my laptops have a crappy soundcard. This comes from my juno-d (surprisingly, it records wav files and not a proprietary format).

http://www.mediafire.com/?p119i2ftqw3n339

how could I check if it's from the power supply? on the tuner, it says that's between a G and a G#.
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awambawamb
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Roland Juno-D
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Re: GEM H6000 channel problem

Post by awambawamb » Wed Jun 29, 2011 8:53 am

am i left alone? :(
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rhino
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Korg DSS-1
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Location: kentucky hills

Re: GEM H6000 channel problem

Post by rhino » Wed Jun 29, 2011 3:21 pm

We're still here...It's just that diagnosing electronics at a distance is often a problem.
1) one strange thought: is a bass-pedal keyer sticking?
2) You'll no doubt need a schematic diagram. What tools do you have? A signal tracer is a must.
3) locate the INPUTS of the power amps and look at the signal there. If both are OK, then likely you've found the problem: A bad decouplling cap.
4) what does the organ sound like (in the headphones) if you plug the phones ALL the way in?
5) Are you using 50-Hz power? That would put AC hum near where you said the pitch of the noise was.
When the wise man points to the stars, the fool looks at the finger.
- Confucius
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awambawamb
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Posts: 11
Joined: Mon Feb 28, 2011 6:07 pm
Real name: Max
Gear: Korg Microkorg
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Roland Juno-D
Roland HP-1600
Ibanez ATK 4 string bass
Location: near Turin, Italy

Re: GEM H6000 channel problem

Post by awambawamb » Thu Jun 30, 2011 12:16 pm

sorry for the earlier bumping :P

I'll gather all things I can and I'll tell you after. Could be a matter of weeks i think, but I'll do my best!
Also, GEM retired from market about two years ago but I've got some contacts that could help me retrieving the schemas. Yes, the higher bass pedal is sticking but i still haven't controlled it.

On sunday after the exams I'll take some time for all this...

cya soon and thanks for all the hints :)
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