CA-1000 II Rebuild

Did you find any shorted output transistors ? And are they still in circuit? Are the main amp fuses installed ?
 
Is the mode switch in normal or class A? Put it in normal.And remeasure.
I cannot check now but I think it was the same in both modes. Certainly relay did not click in both modes, and I am almost sure I measured in both modes and it was the same 25/30V at OUT. And I have no fuses in main amp boards atm.
 
Did you find any shorted output transistors ? And are they still in circuit? Are the main amp fuses installed ?
Oh yeah, the original output transistors were shorted. I replaced them with the popular today's drop in equivalents On 2*93/2*94 which are there at the moment, possibly shorted now too :/
 
TR604 and TR609 still in the circuit ? TR610 and TR611 as well ?
 
Need to be all checked in both channels.
All transistors checked in one channel and all tested good on Peak DCA55. I mean every single transistor including the new outputs on the main amp pcb for the left channel.
I think faulty variable resistor would not cause such a difference in voltage? Fusistors are in specs if it matters.

So what to check now? Diodes?
Maybe I should put in fuses and see what happens?
 
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FR601,2 checked?
Maybe VR602,3?

I'm inclined to think transistors, however all tested ok.
Maybe measure voltages at pins A,B,C,S on one side.

Also by measuring the voltage drop (mV) across R618 will point to the direction of increasing voltage/problem,
ie RED probe connected to R618/TR604 node, black probe connected to TR608,9(e) node.
 
BTW, does the PNP output goes on the side where PNP driver is and vice versa? I put the new outputs as the old shorted ones were, assuming that they had been installed correctly but who knows. I think the problem started after I installed the new outputs, MJ21193G for 2SA679 (2SA566 driver on the other side of pcb) and MJ21194G for 2SC1079 (2SC680 on reverse). Just looked at schematics (previous page of this thread) and it seems ok, but maybe someone could confirm.
 
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You're just going to keep on blowing up more amps and outputs until you build yourself a DBT.
Is it ok? I will do away with the switch I think. Do I have to care about polarization in terms of live and neutral as I saw in some other schematics if I don't know how it is in my wall socket anyway? The biggest bulb I managed to get is 60W due to laws in Europe. They sell them as decoration not lighting in such wattage, so I have it really cute in 1920's style.
DimbulbSketch.jpg
 
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Definitely..
Checked all diodes, most in circuit with multimeter, seemed ok, i.e. worked one way only. Just one had to be pulled out and tested ok.
Variable resistors checked too. FRs checked.
 
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2SA679 (PNP) MJ21193
2SC1079(NPN) MJ21194

I assume the mica insulators on the power transistors were in good condition.
 
Is it ok? I will do away with the switch I think. Do I have to care about polarization in terms of live and neutral as I saw in some other schematics if I don't know how it is in my wall socket anyway? The biggest bulb I managed to get is 60W due to laws in Europe. They sell them as decoration not lighting in such wattage, so I have it really cute in 1920's style.
View attachment 957659
Yeah, pic is perfect, and don't need to worry about live/neutral or switch.
I found some amps may not get a relay click with a 60W, but you can try turning the idle setting all the way down to help. You could maybe use multiple bulbs to increase the wattage if it won't click (on a working amp).

Just means you can do a safe test each time you change something, with the bulb tester it can't draw enough current to blow outputs, and even smaller parts will take longer to burn up.
 
Yeah, pic is perfect, and don't need to worry about live/neutral or switch.
I found some amps may not get a relay click with a 60W, but you can try turning the idle setting all the way down to help. You could maybe use multiple bulbs to increase the wattage if it won't click (on a working amp).

Just means you can do a safe test each time you change something, with the bulb tester it can't draw enough current to blow outputs, and even smaller parts will take longer to burn up.
Have that DBT thing. I was messing around on main amp pcb and shorted 2 legs of a transistor with multimeter probe, the 60W bulb gave me heads up by illuminating high so kind of worked but I still blew out 1 nearby transistor and zener diode at that time :)
 
FR601,2 checked?
Maybe VR602,3?

I'm inclined to think transistors, however all tested ok.
Maybe measure voltages at pins A,B,C,S on one side.

Also by measuring the voltage drop (mV) across R618 will point to the direction of increasing voltage/problem,
ie RED probe connected to R618/TR604 node, black probe connected to TR608,9(e) node.
It's 0.07V between these 2 spots (0.39V at R618/TR604 and 0.32V at TR608/TR609)
All FRs checked. I have pulled out the output transistors now, fuses are in, the points A, B, C, S are all 49V
Double checked all transistors, all test ok.
I have 49V on TR610 B, C, E
On TR611 -49V on C and 49V B, E
 
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Apologies, don't have any real time to look at this now, maybe others will chime in.
Concern about A,B,C,S at 49V suggests something has failed open circuit or not conducting, maybe TR605.
TR610 looks faulty, I'd sort out A,B,C,S before TR610.
R618 voltages suggest problem closer to TR601,3 and D603.

Maybe measure TR603, 605 b/c/e. Probably better to wait for a thorough analysis
 
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