Q603a, b, and d all measure:
B to C, 11 meg
B to E, 11 meg
C to E, around 2k
Q603c measures:
B to C, 250 ohms
B to E, 1k
C to E, 1k
B to C, 11 meg
B to E, 11 meg
C to E, around 2k
Q603c measures:
B to C, 250 ohms
B to E, 1k
C to E, 1k
I removed Q603c and measured resistance:
E to C, 2k
E to B, 1.6k
C to B, 350r
I have no idea what these should be!
It's defective. You can also check it on diode-check.
Q603C diode-check black probe on left-most terminal
Leg 1 - 2:
Leg 1 - 3:
Leg 2 - 3:
Reverse probes and re-check.
Leg 1 - 2:
Leg 1 - 3:
Leg 2 - 3:
You stated that the screw bottomed out. That must be resolved. The screws are marginal as clamps on these large transistors so you have to make sure the transistor lays down flat before tightening the screw.
You also need to remove and replace the heatsink compound. I recommend Dow Corning 340 but any heatsink compound from a reputable electronics distributor will work.
You will need to replace both the PNP transistor (this one, green) and the black transistor (Q602C). They are not available from reputable distributors (discontinued) so you will likely have to use the 2SC5200 and the 2SA1943 (equivalent to Q603C). Buy from Digikey or Mouser.
There may be another problem. The driver IC may be defective. To know for certain, you may have to install the new transistors.
For ALL testing, you should have all transistors tightly clamped to the heatsink and a 10 amp fuse in the B+ power line (or fuse holder).
Q603C diode-check black probe on left-most terminal
Leg 1 - 2:
Leg 1 - 3:
Leg 2 - 3:
Reverse probes and re-check.
Leg 1 - 2:
Leg 1 - 3:
Leg 2 - 3:
You stated that the screw bottomed out. That must be resolved. The screws are marginal as clamps on these large transistors so you have to make sure the transistor lays down flat before tightening the screw.
You also need to remove and replace the heatsink compound. I recommend Dow Corning 340 but any heatsink compound from a reputable electronics distributor will work.
You will need to replace both the PNP transistor (this one, green) and the black transistor (Q602C). They are not available from reputable distributors (discontinued) so you will likely have to use the 2SC5200 and the 2SA1943 (equivalent to Q603C). Buy from Digikey or Mouser.
There may be another problem. The driver IC may be defective. To know for certain, you may have to install the new transistors.
For ALL testing, you should have all transistors tightly clamped to the heatsink and a 10 amp fuse in the B+ power line (or fuse holder).
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Measurements:
Q603C diode-check black probe on left-most terminal
Leg 1 - 2: 0.293v
Leg 1 - 3: 0.841v
Leg 2 - 3: 0.995v
Reverse probes and re-check.
Leg 1 - 2: 0.287v
Leg 1 - 3: 0.506v
Leg 2 - 3: 0.630v
My stupid mistake on tightening down the transistor. The washer was loose even though the screw was tight. I switched screws and both tightened properly.
I have a tube of heat sink compound I bought from Radio Spares (554-311) years ago. I also have new insulating pads if needed.
I expected to have to replace all 4 sets of transistors. I take it sonically it will make no difference?
Maybe I should just buy the IC with the transistors. Probably cheap and save on shipping.
Thanks and I will report back after replacement.
The UPC1270 has long-since been discontinued. Those that are available are likely to be questionable quality.
Is the RS heastsink compound still fluid or has it dried?
The Kapton tape is the insulator (from what I can see). Is there another insulator?
I don't know if it's safe to power the amp up with the outputs out and the driver IC in the circuit. I'd suggest removing Q602C and the driver IC. Then try powering the amp up (10A fuse and other transistors clamped tightly). If you do this, make sure that there are no solder bridges between pads.
I'm not 100% sure that the recommended transistors will work but I've never had a problem with them as subs. Replacing the other outputs would be up to you. As long as the other outputs are OK, you won't have a difference in the quality.
Is the RS heastsink compound still fluid or has it dried?
The Kapton tape is the insulator (from what I can see). Is there another insulator?
I don't know if it's safe to power the amp up with the outputs out and the driver IC in the circuit. I'd suggest removing Q602C and the driver IC. Then try powering the amp up (10A fuse and other transistors clamped tightly). If you do this, make sure that there are no solder bridges between pads.
I'm not 100% sure that the recommended transistors will work but I've never had a problem with them as subs. Replacing the other outputs would be up to you. As long as the other outputs are OK, you won't have a difference in the quality.
Got that. I'll hope it is still good.
It is still as new.
Nope, just the Kapton tape. I have some Wakefield-vette insulation pads. I've never worked with Kapton tape.
https://wakefieldthermal.com/conten...lectric Phase Change Thermal Material (1).pdf
Sorry, I didn't mean that I would do that.
I get the disclaimer - and understand completely. Hard to get my head around replacing only one pair.
Looking on DigiKey, I think NPN 2SA1943n and PNP 2SSA1943N. Toshiba and have (S1, E, S) extension on each????
https://toshiba.semicon-storage.com...t_en_20150512.pdf?did=13908&prodName=2SA1943N
https://toshiba.semicon-storage.com...t_en_20150512.pdf?did=13909&prodName=2SC5200N
"Sorry, I didn't mean that I would do that."
^^ No, that was just as a precaution since the ICs are not readily available.
2SA, 2SB << PNP
2SC, 2SD << NPN
The on-semi brand will have the same case style as the original.
I don't have a clue what the numbers in the parentheses mean on the Toshibas.
The Kapton is OK as long as it's undamaged.
^^ No, that was just as a precaution since the ICs are not readily available.
2SA, 2SB << PNP
2SC, 2SD << NPN
The on-semi brand will have the same case style as the original.
I don't have a clue what the numbers in the parentheses mean on the Toshibas.
The Kapton is OK as long as it's undamaged.
Well I'll be. It works!!!!! Thanks so much Perry! I learned a lot.
You can see I hit order before you pointed out the package case was a little different on the Toshiba. They fit just fine.
The green vs black would have lessened the stress of making sure I put the NPN and PNP in the right location. Can barely see the writing on the Toshibas.
I ended up peeling of the Kapton and I used the Wakefield-vette insulation pads.
I made a little jig to get the transistors aligned just right before soldering so the holes would line up.
I'll document some voltages so I can have a reference in the future.
Thanks again!
You can see I hit order before you pointed out the package case was a little different on the Toshiba. They fit just fine.
The green vs black would have lessened the stress of making sure I put the NPN and PNP in the right location. Can barely see the writing on the Toshibas.
I ended up peeling of the Kapton and I used the Wakefield-vette insulation pads.
I made a little jig to get the transistors aligned just right before soldering so the holes would line up.
I'll document some voltages so I can have a reference in the future.
Thanks again!
The manufacturer suggests that you re-tighten the screws for this type of mounting system.
If you have a FLIR imager, confirm that all transistors are heating the same when the channel is loaded. If no FLIR, use whatever you have (touch them, if nothing else) to confirm that they are all heating evenly.
If you have a FLIR imager, confirm that all transistors are heating the same when the channel is loaded. If no FLIR, use whatever you have (touch them, if nothing else) to confirm that they are all heating evenly.
Well done with the help. PQ10 was a workhorse amp back in the day. Definitely eclipsed by newer designs but ADS put out a pantload of them, same for the PS5. That was basically 1/2 of the PQ10 with slightly different output devices -