G-33000 Dead right channel
- Thread starter tobyj17
- Start date
kevzep
Its all about the Music
D01 and D02 drop about 1.4v..no voltage passes the other way.
I didn't take them out of circuit.
And yes it is getting pretty big.. 18 pages..we've gotta be close to a record
OK good.
On the driver board, there is a resistor marked R901 which is a 100Ω resistor, it is on the Base of TR02/03. Check this, I don't think we have checked this one before.
Also, around TR01, check R09 (1.5KΩ), and R43 (4.7KΩ), this is the current source for the FET. Need to make sure this is working properly.
tobyj17
Comfortably Numb
both 100 ohm resistors on the back are good. R09 is good, I can't find R43??
BUT... R15 is open
kevzep
Its all about the Music
Excellent Toby.
I think it would be a good idea to check all the resistors around these current pairs TR02/03/04/05/06/07/08/09......
Maybe that accident we had has taken a few resistors out.....
R22 would be one to check too.
tobyj17
Comfortably Numb
I checked the ones around the current pairs.. those are good.
Where is R22? i can't find it..
kevzep
Its all about the Music
82Ω joining the quads of those current pairs together you just measured.....
tobyj17
Comfortably Numb
Got it.. it was hiding.. It's good at 82
kevzep
Its all about the Music
Were you turning the trimmer down the right way? You know how they turn CW to decrease the bias instead of CCW......
Just double checking Toby, I know you would have done it right, but in haste its easy to make a mistake when you see the bias skyrocket like that.
Also, is the trimmer OK, hasnt got a burned out carbon track?
kevzep
Its all about the Music
Did you replace ZD02 with a new 24V zener, if you did, put the old one back in because that is supposed to be a 12V zener.
We thought there was nothing wrong with it didnt we?
tobyj17
Comfortably Numb
tobyj17
Comfortably Numb
Thank you guys for all your help, I really owe you one..BIG TIME. No way I could have done it without your assistance. I have learned a lot from this experience, and it will certainly help in the future.
My biggest question though, is what was the original offending part? Was it the zener diode, or the resistor? :scratch2:
My biggest question though, is what was the original offending part? Was it the zener diode, or the resistor? :scratch2:
kevzep
Its all about the Music
Thats great news Toby, awesome work dude......:thmbsp:
I think ZD01 let go, and when we put the 1N4148 it surged a massive current through that network of current pairs and took that resistor out....
You must be relieved to hear it run again.....
I think we have all learned a bit from this one. The main thing is to write measurements down, follow the circuit though logically and dont jump to conclusions without working the problem and proving your conclusions along the way....
Congrats, now GET THAT THING OUT OF THE KITCHEN and PLAY IT LOUD!!:yes:
EDIT: Makes you suddenly realize the importance of those tiny Zener Diodes and what they are regulating......
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