| clayton |
| When I got this amp it would not power on. Took of cover & c19 had blew up. Q5 is connected to c19 & it also was bad. Replaced both and now it powers up but it will only run for about 5 min then the power led starts going dim and sound stops coming out. If I connect & disconnect turn on wire led trys to come back on but then goes back dim. If I let it sit for a few min it will come back on. By the way c19 & q5 are part of the turn on. Any suggestions on what needs to be checked? |
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| Perry Babin |
Compare the voltage on the SG3526 when it's working properly and when it's shutting down. That may help you to trace the source of the problem.
Also check the voltages on the 555 and the 6 pin opto-coupler.
There's a small driver transformer just behind the power transformer. Resolder the leads on it on the top 'and' the bottom of the board.
Q5 is part of the regulator circuit. It controls the amount of current driven into the driver transformer.
If I'm not mistaken, the remote feeds Q1 which delivers power to the 3526. |
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| clayton |
I was not able to get it to power up all the way. Led comes on then goes dim right away. Anyway here are the readings I got with it like this.
SG3526
pin 1: 5v pin 2: 0
pin 3: 4.2v pin 4: 4.66v
pin 5: 5v pin 6: 0
pin 7: 0 pin 8: 4.96v
pin 9: 3.65v pin 10: 4.98v
pin 11: 12.25v pin 12: 5.2v
pin 13: 0 pin 14: 11.9v
pin 15: 0 pin 16: 0
pin 17: 0 pin 18: 1.8v
555 timer
pin 1: 0 pin 2: 12.25v
pin 3: .4v pin 4: 12.25
pin 5: 12.25v pin 6:.01
pin 7: .01v pin 8:8.18v
6 pin opto-coupler
pin 1; 7v pin 2: 6.4v
pin 3: 0 pin 4: 0
pin 5: 12.25v pin 6: 0 |
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| Perry Babin |
| Pin 17 should have 12v. Trace it back to see if you can determine why voltage isn't present. It appears that it may go through a resistor. The resistor may be open. |
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| clayton |
I was able to get it to power up long enough to get my readings.
SG3526 had only 2 changes pin 15 is 5.1v & pin 16 is4.4v pin 17 stayed at 0v. The opto-coupler pins 1,2 & 3 went to 24v.
Thge resistor connected to pin 17 of the SG3526 is fine. I got a reading of 18k |
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| Perry Babin |
| I'm relatively sure that pin 17 must have ~12v for the IC to operate. Are you sure you're not mistaken on the pin numbers? |
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| clayton |
| My bad I was reading pins 10 - 18 backwards. Pin 17 has 12v with & without it functionig properly. Pins 12 & 13 are the only one that change when amp is working. Pin 12 is at 4.4v & pin 13 is at5.1v. Sorry about the confusion. |
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| Perry Babin |
13 and 16 should have the same voltage. If one goes to 0v, the other should also.
What other component connects to pin 12? |
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| clayton |
| I am not sure but there is only one trace on the top of the board that goes under the ic. I think this connects to pin 12 The trace goes to either a 50ohm or 51ohm resistor. When measured it reads 50ohm. The only reason I am not sure of its value is the first band on the resistor is either green or blue,both look the same to me (guess I might be a little color blind or need glasses). The other leg of the resistor goes to pin 17. Form that point it splits off & goes to 2 caps by pin 17 & going the other way it goes to another resistor. This resistor measures 18k ohm in circuit. According to the color code it should read 26k ohm. |
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| Perry Babin |
| If you're unsure about the connection between pin 12 and the resistor, use your meter to confirm that there is a 0 ohm connection between them. If the other side of the resistor goes to pin 17, there's no point in tracing it further unless the voltage on pin 17 is dropping. |
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| clayton |
| Pin 12 does not connect to anything. Pin 17's voltage stays the same. |
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| Perry Babin |
That makes sense since pin 12 is the sync input/output and there is no other oscillator for it to sync with.
At this point, I think you need to go back and confirm all voltages (working and not working). Be as precise as possible and confirm all voltages.
Working
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 17:
Pin 18:
Not Working
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 17:
Pin 18: |
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| clayton |
Here are the measurements:
Working
pin 1: 4.98
pin 2: 0
pin 3: 4.2
pin 4: 4.66
pin 5: 4.98
pin 6: 0
pin 7: 0
pin 8: 4.96
pin 9: 3.84
pin 10: 1.83
pin 11: .01
pin 12: 4.19
pin 13: 5.04
pin 14: 11.62
pin 15: 0
pin 16: 5.03
pin 17: 10.7~11.7
pin 18: 4.98
Non working
pin 1: 4.98
pin 2: 0
pin 3: 4.23
pin 4: 4.66
pin 5: 4.98
pin 6: 0
pin 7: 0
pin 8: 4.96
pin 9: 3.84
pin 10: 1.832
pin 11: 0
pin 12: 0
pin 13: 0
pin 14: 11.62
pin 15: 0
pin 16: 5.02
pin 17: 12.25
pin 18: 4.98 |
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| Perry Babin |
| If this is accurate, it looks like the IC is defective. I don't know this IC as well as some of the others but I know of no way that this IC can be forced to turn off one output while leaving the other on. |
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| clayton |
I retested all the pins & got better readings this time. I also noticed that when both channels are driven, in working state, they would fade in & out alternately. The left more than right channel. On previous power ups I was only useing the right channel.
This time it while runnig it popped the 15amp in line fuse. Volume maybe 1/4 way up. Speakers are 8ohm home speakers if that makes a difference.
Working
pin 1: 4.99
pin 2: 0
pin 3: 4.21
pin 4: 4.68
pin 5: 5.01
pin 6: 0
pin 7: 0
pin 8: 4.96
pin 9: 3.68
pin 10: 1.823
pin 11: 0
pin 12: 4.46
pin 13: 5.44
pin 14: 0
pin 15: 0
pin 16: 5.43
pin 17: 12~13
pin 18: 4.99
Non Working
pin 1: 4.98
pin 2: 0
pin 3: 4.2
pin 4: 4.66
pin 5: 4.98
pin 6: 0
pin 7: 0
pin 8: 4.96
pin 9: 3.65
pin 10: 1.823
pin 11: 0
pin 12: 4.47
pin 13: 5.35
pin 14: 12.25
pin 15: 0
pin 16: 5.51
pin 17: 12.68
pin 18: 4.98 |
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| Perry Babin |
The voltages are essentially identical except for pin 14. I think it was also ~12v when you took the readings for the non-working list. Without the voltage on pin 14, pins 13 and 16 couldn't have output.
If the rest of the voltages are accurate, there may be a bad connection between the 3526 and the driver transformer. Resolder the connections on the driver FETs (near the 3526) and the driver transformer. If those don't solve the problem, the regulator control module could be the problem. |
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| clayton |
| I have already resoldered the driver transformer. Will resolder driver fets this afternoon. If it is the regulator control module,do you know what the part # is? |
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| Perry Babin |
The regulator module isn't available. You'd have to send the amp to TIPS to have the module replaced ($150).
You need to re-check pin 14 when the amp is not working properly to determine whether it has voltage or not.
If you want to 'bypass' the black box (regulator module), pull the regulator transistor (under the board) and replace it with a 120 ohm 1 watt (or larger) resistor (see image below). This will allow all of the circuits to function except the regulator. The amp will not produce full power but if both channels play normally and the amp doesn't cut off, you can be relatively certain that the reg module is the problem.
http://bcae1.com/temp/IMG_2840b.jpg |
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| clayton |
I did like you said & removed the module. Looks like thats my problem. Amp powered up right away. Worked like a charm. Thats a sucks not being able to purchase the module!
Just out of curiosity, what would happen if I were to leave the resistor in? |
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| Perry Babin |
| It won't produce rated power. This is simply to eliminate other possible problems. Screw it to the sink and let it play for several hours to be sure there are no other problems. |
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| clayton |
I understand that it won't prodce full power. I just wanted to know if the amp would be able to operate normally( just not full power) . Would there be any other draw backs?
Should I run radio at 1/4, 1/2 volume, when I test it ? |
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| Perry Babin |
I don't think the volume level is important. It's an old amp and could have other problems that may not show up unless it's on for a while. There are almost certainly a few electrolytics in the audio section that need to be replaced.
If you are not going to pay to have TIPS repair it and if you can't find another module, it may be possible to build a regulator circuit. It probably won't work precisely like the Linear module but it should regulate the rail voltage.
I'm not sure how much power the amp will deliver with the resistor in place. I've only used this (resistor subbed for transistor) for troubleshooting an amp with a defective module. |
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| clayton |
Tanks for the help. It was a good learning process for me.
Now I have to decide if I want to spend that much on this amp or not! |
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| clayton |
After putting the module back in, to send amp off for repairs, it started working.
I am thinking that there could have been a cold solder joint on the module.
I see why you only used the resistor for testing purposes now. The rail voltage with the module is around 39v. With the resistor in place there is around 50v. |
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| Perry Babin |
| A higher value resistor would have produced lower rail voltage. |
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