I replaced 2 TIP35Cs in one channel and used 75344Gs in the power supply. When I power it on now the relays engage and then disengage and it is stuck in protect.
The channel opposite the one I replaced outputs in is getting hot quickly. There are no shorted TIP35/36Cs and the TIP42/41Cs are not shorted. Not sure what to check next.
The channel opposite the one I replaced outputs in is getting hot quickly. There are no shorted TIP35/36Cs and the TIP42/41Cs are not shorted. Not sure what to check next.
What is the DC voltage on the emitter resistors for both channels when it goes into protect. Place the black meter probe on the secondary center tap or one of the non-bridging speaker terminals.
I get +13v on one channel and +12.9 on the other, black probe on secondary center tap, red probe on output side of emitter resistors.
I get +13v on one channel and +12.9 on the other, black probe on secondary center tap, red probe on output side of emitter resistors.
Also, the sec. center tap trace was burned from the crossover card to where the non-bridging speaker terminals meet and to the 2 film caps All of that has been redone.
If you bypass the crossover card, do you still have DC?
Do you have both positive and negative regulated 15v?
Do you have both positive and negative regulated 15v?
The crossover card is bypassed and it is generating + and - 15v. ~+13v DC is still present at the emitter resistors.
Post the DC voltage on the two op-amps near the RCA jacks.
IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
pThe reading change depending on how long I have been testing. When cool it powers up and for a moment you see -15v and +15v, all the rest zeros. After a second or two they read this (all + voltages):
IC# U1
Pin 1: 13.5
Pin 2: 13.5
Pin 3: .4
Pin 4: .8
Pin 5: 15
Pin 6: 13.5
Pin 7: 13.5
Pin 8: 13.5
IC# U4
Pin 1: 13.5
Pin 2: 13.5
Pin 3: .4
Pin 4: .8
Pin 5: 15
Pin 6: 14.1
Pin 7: 13.7
Pin 8: 0
After it warms up it goes back to +15v, -15v, and all others zeros. If I turn it off and back on it stays that way until I let it cool down for a few minutes, then I can get the above readings. Also, it seems that the channel I did not repair now stays cool and the bank I did not replace (tip36c) in the channel I repaired is now getting hot the fastest.
IC# U1
Pin 1: 13.5
Pin 2: 13.5
Pin 3: .4
Pin 4: .8
Pin 5: 15
Pin 6: 13.5
Pin 7: 13.5
Pin 8: 13.5
IC# U4
Pin 1: 13.5
Pin 2: 13.5
Pin 3: .4
Pin 4: .8
Pin 5: 15
Pin 6: 14.1
Pin 7: 13.7
Pin 8: 0
After it warms up it goes back to +15v, -15v, and all others zeros. If I turn it off and back on it stays that way until I let it cool down for a few minutes, then I can get the above readings. Also, it seems that the channel I did not repair now stays cool and the bank I did not replace (tip36c) in the channel I repaired is now getting hot the fastest.
You need to determine why pin 4 has no -15v. Confirm that you have negative rail voltage feeding the input of the negative voltage regulator as long as the power supply is operating. Then confirm that you have output from the regulator as long as you have input to the regulator.
It does produce -15v at first and again after a few moments. Are you saying to investigate that during the 10 or so seconds it does not produce -15v?
Ok, apparently it was my mistake. I had B+, Rem, and GND connected and flipped my power supply on so the primary caps were not charged when Rem was supplied.
If I power the PS on with Rem disconnected and then connect Rem both of the op amps read:
0,0,0,-15,15,0,0,0
One channel has 0v DC, the other has +.4 and rising. The amp attempts to come out of protect and the transformer buzzes and it goes back to protect. That is at the emitter resistors.
If I power the PS on with Rem disconnected and then connect Rem both of the op amps read:
0,0,0,-15,15,0,0,0
One channel has 0v DC, the other has +.4 and rising. The amp attempts to come out of protect and the transformer buzzes and it goes back to protect. That is at the emitter resistors.
Ok, nevermind, I take that back. It must have been warmed up again.
I see about +40 and -40v at the regulators while the -15v reg produces .8v. After the "warm up" the rail voltages drop to ~35v+- and the -15v comes up.
I see about +40 and -40v at the regulators while the -15v reg produces .8v. After the "warm up" the rail voltages drop to ~35v+- and the -15v comes up.
Sorry for all the re-posts but these symptoms are the strangest I've had to deal with.
I just hooked both oscope probes to the regs. On a cold power up the rail voltage goes above + and - 40v and I see + and - 15v. Suddenly, after a second or two, the rail voltage drops below 40 and -15v goes to +.8v. After another 10 seconds or so I see both rail voltages drop slightly again and a fraction of a second later -15v is back. Both rail voltages drop slowly until some of the outputs are too hot to touch.
I just hooked both oscope probes to the regs. On a cold power up the rail voltage goes above + and - 40v and I see + and - 15v. Suddenly, after a second or two, the rail voltage drops below 40 and -15v goes to +.8v. After another 10 seconds or so I see both rail voltages drop slightly again and a fraction of a second later -15v is back. Both rail voltages drop slowly until some of the outputs are too hot to touch.
Reduce the biasing (bias pots fully counter-clockwise) so the outputs don't draw any current and observe the voltages again.
Do the outputs stay cool and do the voltages act differently?
What are they using for the 15v regulators?
Do the outputs stay cool and do the voltages act differently?
What are they using for the 15v regulators?
With the bias' down the outputs stay cool.
The rail voltages are a steady +35, -35. The -15v regulator has +.8v on the output pin and it never goes to -15v like it used to.
The regs are Motorola 7815CT/7915CT. The regs are now heating up but I believe that is normal.
The rail voltages are a steady +35, -35. The -15v regulator has +.8v on the output pin and it never goes to -15v like it used to.
The regs are Motorola 7815CT/7915CT. The regs are now heating up but I believe that is normal.
- Status
- Not open for further replies.