what direction to go in...
Well, since the supply readings were odd, and moved around a lot, I decided to pull the output transistors and focus on getting power stable. Now reading from the output of the rectifiers I have A nice steady 67 volts. If I flip the probes, a nice -67.
Ok, so I'm checking the LM317 and LM337.
LM317 adj= +12.6, in= +23.2, out= +13.9
LM337 adj= -13.8, in= -23.2, out= -14.8
Shouldn't I have plus/minus 15volts?
The LM337 is !way! hot in maybe a minute.
The CR1000-3 Diodes are putting out plus/minus 23.2 steady.
Also, the outputs were getting hot after a couple of minutes, no dc at speaker terminals though.
Well, since the supply readings were odd, and moved around a lot, I decided to pull the output transistors and focus on getting power stable. Now reading from the output of the rectifiers I have A nice steady 67 volts. If I flip the probes, a nice -67.
Ok, so I'm checking the LM317 and LM337.
LM317 adj= +12.6, in= +23.2, out= +13.9
LM337 adj= -13.8, in= -23.2, out= -14.8
Shouldn't I have plus/minus 15volts?
The LM337 is !way! hot in maybe a minute.
The CR1000-3 Diodes are putting out plus/minus 23.2 steady.
Also, the outputs were getting hot after a couple of minutes, no dc at speaker terminals though.
It appears signal is just not getting past the first card. I can trace strong audio going in, but not coming out. One of the pins seems to be the output, but audio is only there for a moment when i probe it - then it fades out. Very distorted.
I checked the voltages at the op-amps and the positive seemed week. Should the first TL072 be getting +-5 or higher/lower?
I checked the voltages at the op-amps and the positive seemed week. Should the first TL072 be getting +-5 or higher/lower?
I'm supposed to be getting one of these in the next few days. I'll see if I can answer some of the questions after I get it repaired.
I thought D291 may light up when the amp was over-driven but it didn't on the amp I have here.
On this amp, the rail voltage was 70v across the center legs of the rectifiers.
Neither LM3x7 regulator gets hot quickly in this amp.
The audio input to the class D driver board is the bottom pin farthest from the RCA side of the amp.
In your amp, check all of the op-amps to see if any are getting hot.
On this amp, the rail voltage was 70v across the center legs of the rectifiers.
Neither LM3x7 regulator gets hot quickly in this amp.
The audio input to the class D driver board is the bottom pin farthest from the RCA side of the amp.
In your amp, check all of the op-amps to see if any are getting hot.
further....
Hey, you have audio on both sides of the TL072 by the RCA inputs?
What voltages do you have on 4 and 8?
I have like -6.8 and +4.5, crooked, eh?
I though I felt something hot on the crossover board, and probed the caps on top of the board and found DC on one side of C108 and both of C109. Circled in red in pic below.
What are the outputs of your regulators (317,337)?
OOOWWWWWW!!!!!!
found the hot one, on the eq board....
my pinky will never be the same.
These sub-board assemblys aren't a bad thing if you socket them and leave room between them, but soldered in all crammed together.... 🙁!
ow, ow, ow, that #$%$$^@#!@ was hot... I was smelling it before, but the outputs and everything were heating up, and its 80 degrees here in philly, so the trees have clouded my nose, so to speak.
Hey, you have audio on both sides of the TL072 by the RCA inputs?
What voltages do you have on 4 and 8?
I have like -6.8 and +4.5, crooked, eh?
I though I felt something hot on the crossover board, and probed the caps on top of the board and found DC on one side of C108 and both of C109. Circled in red in pic below.
What are the outputs of your regulators (317,337)?
OOOWWWWWW!!!!!!
found the hot one, on the eq board....
my pinky will never be the same.
These sub-board assemblys aren't a bad thing if you socket them and leave room between them, but soldered in all crammed together.... 🙁!
ow, ow, ow, that #$%$$^@#!@ was hot... I was smelling it before, but the outputs and everything were heating up, and its 80 degrees here in philly, so the trees have clouded my nose, so to speak.
Attachments
And the question of the day, the amp has TL072s, I have some 4558s and some NJM2068s. Would you use one of those or order parts?
darn soic-8 casing...
darn soic-8 casing...
also, some pics of xover board
Thanks for the values Sean.
I always mess the number of 0's up. When converting to uf...
Here are some pics of the Crossover board. Hopefully they'll help somebody down the line. I've already put the 4558s I had where the first TL072's were, and the caps are out, but should be good for reference... I'll prolly get some TL072s; I just want to know where I'm, at on this thing.
Thanks for the values Sean.
I always mess the number of 0's up. When converting to uf...
Here are some pics of the Crossover board. Hopefully they'll help somebody down the line. I've already put the 4558s I had where the first TL072's were, and the caps are out, but should be good for reference... I'll prolly get some TL072s; I just want to know where I'm, at on this thing.
Attachments
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The regulators in this amp have +13.79 and -14.92.
Op-amp substitution can cause all sorts of unforeseen problems. The TL072s are some of the most forgiving op-amps. The 4558s are less so.
Op-amp substitution can cause all sorts of unforeseen problems. The TL072s are some of the most forgiving op-amps. The 4558s are less so.
k, so my regulator voltage are ok then. Yes, I ordered some TL072s to put in; just wanted to check my progress (check for fire and sparks, lol).
OK!
That did it; running great now.
Thanks for your help Perry and Sean, much appreciated.
I have no problems with class A, AB and most class D amps, something about the RF stuff throws me. Its like I see it and my standard troubleshooting instinct (follow the signal) goes out the window...
That did it; running great now.
Thanks for your help Perry and Sean, much appreciated.
I have no problems with class A, AB and most class D amps, something about the RF stuff throws me. Its like I see it and my standard troubleshooting instinct (follow the signal) goes out the window...
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