mr_rye89
Veteran and General Yakker
So the emitter resistors blew (R356, R357), output darlingtons show E to C shorts, R354 got toasty, Would a short at the speaker terminals blow these?
Beomaster 2400 stupid question
- Thread starter mr_rye89
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Not if the short circuit protection (TR316 and TR317) is working...
wattsabundant
Chief Journeyman
I think you’rll find TR316 had probably failed also which explains the burnt resistor
mr_rye89
Veteran and General Yakker
Ok thanks, I have IC300/301 out and the voltage at the base solder pads reads +/-32, TR313/314 don’t show E-C shorts, but I’m wary of them too.
Im not sure what killed the right channel on this, there was a goofy pair of wires badly soldered to the speaker terminals that looked short-y and these are notorious for having the bias voltage run away due to dirty pots. In fact the left channel bias ran away but it shut the amp down (tripped the main relay), I cleand that bias pot and the left channel is fine now
Im not sure what killed the right channel on this, there was a goofy pair of wires badly soldered to the speaker terminals that looked short-y and these are notorious for having the bias voltage run away due to dirty pots. In fact the left channel bias ran away but it shut the amp down (tripped the main relay), I cleand that bias pot and the left channel is fine now
If one of the outputs shorts, the protection circuit can't do squat. The protection circuit only works when all components are functioning.
mr_rye89
Veteran and General Yakker
Ok I’m gonna test 316/317/313/314 out of circuit when I get home. I don’t wanna lunch the new output devices…..
wattsabundant
Chief Journeyman
The bias pot may be flakey, but the circuit doesn't appear to track the heatsink temperature. No need to test out of circuit. Just put the meter on the diode scale and check all the leads. Same with diodes.
nakdoc
Chief Journeyman
I've repaired a few of these and generally the darlington outputs are the only transistors that fail. Since you have it open, it is time to replace the red electrolytics.
mr_rye89
Veteran and General Yakker
I tested 313/314/316/317 out of circuit, all good. I’ll look at the diodes soon, gonna ask the client if he want the lytics replaced.
And don’t work on these, they suck to work on….
And don’t work on these, they suck to work on….
J!m
Veteran and General Yakker
Not designed to be serviced…
mr_rye89
Veteran and General Yakker
Well new outputs and emitter resistors seemed to fix it. Bias is still iffy.....
nakdoc
Chief Journeyman
The boards pivot up at right angles and fit into slots, giving easy access to both sides. I think they are easy to work on, but you have to get used to the service manuals.