I am going to try to repair this. Any help is appreciated.
All of the components with red arrows are confirmed blown
All of the components with red arrows are confirmed blown
An externally hosted image should be here but it was not working when we last tested it.
Do you have a variable temperature soldering iron?
Do you have a small butane torch?
Did you check for rail voltage on the blown channel when it was powered up?
In the defective channel, pull all of the 0.1 ohm source resistors and cut the output transistors free from the board. Confirm that all of the small surface mount resistors are within tolerance. The 100 ohm and 33 ohm are the most likely to have failed. There are ~20 100 ohm resistors to check.
You should replace Q321, 322, 324 and 325 even if they appear to be OK.
Do you have a small butane torch?
Did you check for rail voltage on the blown channel when it was powered up?
In the defective channel, pull all of the 0.1 ohm source resistors and cut the output transistors free from the board. Confirm that all of the small surface mount resistors are within tolerance. The 100 ohm and 33 ohm are the most likely to have failed. There are ~20 100 ohm resistors to check.
You should replace Q321, 322, 324 and 325 even if they appear to be OK.
Just got back with a rad shack torch and a better multimeter
R379 - 6.9k
R372 - 100.5
r378 - 4.39k
r370 - 99.6
r377 - 3.31m
r368 - 99.5
r376 - 3.39k
r366 - 99.5
r375 - 206k
r364 - 99.6
r382 - 4.55m
r383 - 24.1k
r384 - 59.1k
r385 - 35.6k
r380 - 2.14k
r381 - 489
r386 - 813
r387 - 31.5
r330 - 10.3
r332 - 22.4m
r345 - 99.5
r327 - 100.5
r329 - 470
r361 - 158k
r351 - 66.6k
r345 - dead
r359 - 101.9k
r358 - 20.02k
r357 - 56.3k
r355 - 15.3m
r356 - 817
r360 - 30.2k
r353 - 20.01
r354 - 509
r326 - 22.3
r350 - dead
r341 - 68.4
r349 - 46.6k
r330 - 101.2
r348 - dead
r337 - 99.7
R379 - 6.9k
R372 - 100.5
r378 - 4.39k
r370 - 99.6
r377 - 3.31m
r368 - 99.5
r376 - 3.39k
r366 - 99.5
r375 - 206k
r364 - 99.6
r382 - 4.55m
r383 - 24.1k
r384 - 59.1k
r385 - 35.6k
r380 - 2.14k
r381 - 489
r386 - 813
r387 - 31.5
r330 - 10.3
r332 - 22.4m
r345 - 99.5
r327 - 100.5
r329 - 470
r361 - 158k
r351 - 66.6k
r345 - dead
r359 - 101.9k
r358 - 20.02k
r357 - 56.3k
r355 - 15.3m
r356 - 817
r360 - 30.2k
r353 - 20.01
r354 - 509
r326 - 22.3
r350 - dead
r341 - 68.4
r349 - 46.6k
r330 - 101.2
r348 - dead
r337 - 99.7
Ok, so what I have found bad is
320
355
361
391
374
352
351
343
341
350
349
348
379
378
377
366
376
375
380
382
386
I do question these. Not sure what the tolerance is.
383 marked 2002. Tested 17.56k
387 marked 303. Tested 27.5k
384 marked 563. Tested 49.5k
Is there anything else I should be checking?
How many watts are these .1 ohm resistors?
Where is the best place online to get all these parts?
320
355
361
391
374
352
351
343
341
350
349
348
379
378
377
366
376
375
380
382
386
I do question these. Not sure what the tolerance is.
383 marked 2002. Tested 17.56k
387 marked 303. Tested 27.5k
384 marked 563. Tested 49.5k
Is there anything else I should be checking?
How many watts are these .1 ohm resistors?
Where is the best place online to get all these parts?
The ones you're not sure about are probably OK. There's likely something in the circuit that's skewing the readings. Compare these to the ones in the other channel.
Mouser is probably the best place to get the parts.
Mouser part number for 0.1 ohm:
71-LVR3-0.1
The SMD resistors are in two sizes. The smaller ones are 0805. The larger ones are 1206. You'll need to order the correct ones. Order extras. They're inexpensive. On the schematic, the ones with a 'B' suffix are 0805. The ones with a 'C' suffix are 1206.
The SMD resistors that have 4 digits are 1% tolerance components and need to be replaced with 1% components. The ones with only 3 digits are 5% tolerance and can be replaced with either 1% or 5% tolerance components.
You also need to check the protection circuit transistors. They are:
Q226
Q227
Q228
Q229
Q230
Q231
Mouser is probably the best place to get the parts.
Mouser part number for 0.1 ohm:
71-LVR3-0.1
The SMD resistors are in two sizes. The smaller ones are 0805. The larger ones are 1206. You'll need to order the correct ones. Order extras. They're inexpensive. On the schematic, the ones with a 'B' suffix are 0805. The ones with a 'C' suffix are 1206.
The SMD resistors that have 4 digits are 1% tolerance components and need to be replaced with 1% components. The ones with only 3 digits are 5% tolerance and can be replaced with either 1% or 5% tolerance components.
You also need to check the protection circuit transistors. They are:
Q226
Q227
Q228
Q229
Q230
Q231
Ok some of the transistors are bad too. What am I looking for at mouser for transistors? Got everything else ready to order.
I am ordering twice the parts I need, might need them later anyway.
Edit,
Nevermind I figured it out. Just have to wait on parts. I think I will start playing with some other stuff getting my soldering mojo going
I am ordering twice the parts I need, might need them later anyway.
Edit,
Nevermind I figured it out. Just have to wait on parts. I think I will start playing with some other stuff getting my soldering mojo going
Post the DC voltage on one of the TL494 ICs with the amp powered up (including remote). Black meter probe on chassis ground. Copy and paste the following list.
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:
Send me a copy of the schematic. Something is driving pin 4 high. 9-16 are numbered backwards.
If you used the chassis ground terminal for the reference (black probe), you may have a bad ground somewhere in the amp. The pins that were at ~0.5v should have been no more than a few thousandths of a volt above ground.
babin_perry@yahoo.com
If you used the chassis ground terminal for the reference (black probe), you may have a bad ground somewhere in the amp. The pins that were at ~0.5v should have been no more than a few thousandths of a volt above ground.
babin_perry@yahoo.com
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