BIG problems

Moving right along

Spent the evening transistor checking.
Left and Right channels in circuit:
Q1,2,3,4,5,6,7 check out OK except for some (R)everse bias (1.1v) at Q5 and Q7 BE jcts

Q8 Left channel: out of circuit
BE (F)orward (B)ias .1v RB .1v
BC same as above
EC FB and RB SHORTED

Q8 Right channel: out of circuit
BE FB .22v, RB open
BC RB .22v, RB open
EC FB and RB open

why the low voltage drops on these two?

Q9 Left and right, out of circuit:
BE FB .22v, RB open
BC same as above
EC open both ways

again, why the low voltages?

Q10 Left channel out of circuit:
BE FB and RB open
BC same as above
EC same as above
OPEN AT VERY JUNCTION

Unless I`m missing something Q8 left and Q10 left are the only casualties
What do y`all think?
 
Q8, Q9 are germanium. The diode jct on a germanium are much lower,.

Looks like you found the casualties.
 
Don't solder any of the transistors back in. I'm working up a care package. Need your address.
 
Should have ben a hot source then, need immersion fans for that...
 
NavLinear said:
It takes time and patience to do it right but you've got to attack at the right moment. If you do it too well your posts just might wind up in the dark and dingy area. I know - I earned the right. Just ask the mods. :shaking: :la: :shaking:
Click to expand...



Unmatched in that area, no doubt.............
 
laatsch55 said:
Don't solder any of the transistors back in. I'm working up a care package. Need your address.
Click to expand...

All of the outputs and drivers are still out, as are the 2 dead small ones.
While looking to get some TO-3 micas and paste I came across these pads that apparently don't need compound, are they any good?

P.S. Lee, you have mail.
 
Check the BR and leak test the power supply caps. DO NOT USE SIL_PADS, stick with mica and grease, way more effective and if there was ever an amp that DID NOT it's heatsink assembly LESS EFFECTIVE, it's this one.
 
laatsch55 said:
Check the BR and leak test the power supply caps. DO NOT USE SIL_PADS, stick with mica and grease, way more effective and if there was ever an amp that DID NOT it's heatsink assembly LESS EFFECTIVE, it's this one.
Click to expand...

I kind of figured those pads are not that great.How does one perform a cap leak test?
 
Emitter resistors

So I set out to test the resistors but soon came to realize my World travelled, 30+ year old Fluke 75 cant tell the difference between a .33 and .27, reading more like .4 and .5 :(

The 180R driver resistors measure well. There is however a mystery here: R41, .33 is connected between the driver and output collectors and not between output collector and driver board as shown on diagram. ????
 
R41 is exactly where it needs to be and is considered a CRITICAL part. Don't mess with it, it'll F^%$ your world up.
Check the "Reforming Power Supply Caps" in the PLWO archives.
 
If you a "Blue ESR Meter" they are great for checking low value resistors.
 
Michael, I know it's been 4 days since i said I would get the care package out. Cause---I was waiting on an amp to raid some parts. New outputs, MJ 21196's .

Care package contains,
4----------TIS-97's--matched
2----------TIS-93's--matched
2----------MPSA-93's--matched
4----------2N3439's----Q5, Q10
2----------2N5416's----Q7
2----------5K trimmer pots----R20
2----------2--KZ caps 470uf at 25 volts, with 1N4148 Gepetto fix diodes, and 2 .01uf caps to bypass the big cap.
6----------heatsinks for the TO-5 transistors. The stock are wholly inadequate.
4----------47uf at 25 volt Nichicon KZ caps for C15, C16
2----------47uf at 100 volt for C11.
2----------RCA-410 drivers
20--------MJ 21196 outputs.

Anything else?? If not , as soon as I get the shipping cost I'll PM the bill.
 
laatsch55 said:
Michael, I know it's been 4 days since i said I would get the care package out. Cause---I was waiting on an amp to raid some parts. New outputs, MJ 21196's .

Care package contains,
4----------TIS-97's--matched
2----------TIS-93's--matched
2----------MPSA-93's--matched
4----------2N3439's----Q5, Q10
2----------2N5416's----Q7
2----------5K trimmer pots----R20
2----------2--KZ caps 470uf at 25 volts, with 1N4148 Gepetto fix diodes, and 2 .01uf caps to bypass the big cap.
6----------heatsinks for the TO-5 transistors. The stock are wholly inadequate.
4----------47uf at 25 volt Nichicon KZ caps for C15, C16
2----------47uf at 100 volt for C11.
2----------RCA-410 drivers
20--------MJ 21196 outputs.

Anything else?? If not , as soon as I get the shipping cost I'll PM the bill.
Click to expand...

God bless you.
That is wayyyyy more than what I was expecting. So the amp is essentially being completely repopulated with superior transistors. Are those caps in the signal or feedback loop? Something tells me the amp will sound better than before (assuming I don't F@&K it up again:cussing:)
I`m really looking forward to getting the amp together and singing again, I`ve been tuneless for a while now and starting to get anxious :(

I`ll be checking the filter caps and BR now that I have a couple of days off, I also need to get a hold of an ohm meter that can more accurately measure the emitter resistors than my Fluke can.

.
 
Add a 10 ohm in series with what you are checking, see if that helps. Should be in it's resolution range then. I have a lot of emitter resistors. I''ll throw some in.
 
You must log in or register to reply here.
Back
Top