Alpine 3553 looks very much like the 3552 on the DVD, only this one has an input/xover daughter board, plus each channel output pair has its own individual thermistor like I have not seen on any amp before.
This amp appears to ave a failed power supply with all 2SD1669s shorted from legs 1-3. (Measuring exactly 4.3 ohms on all 6)
I carefully lifte all 1&3 legs off all PS transistors and to my surprise they actually measure OK. From pads 1 to 3, I still measure 4.3 ohms.
What gives?
The amp will not power up and does not draw anything.
This amp appears to ave a failed power supply with all 2SD1669s shorted from legs 1-3. (Measuring exactly 4.3 ohms on all 6)
I carefully lifte all 1&3 legs off all PS transistors and to my surprise they actually measure OK. From pads 1 to 3, I still measure 4.3 ohms.
What gives?
The amp will not power up and does not draw anything.
OK i found a bad trace to ground. Amp tried to power up but fails.
TL494
Pin 1: 0.002
Pin 2: 4.98
Pin 3: 0.089
Pin 4: 4.96
Pin 5: 1.663
Pin 6: 3.666
Pin 7: 0.001
Pin 8: 13.75
Pin 9: 0.001
Pin 10: 0.001
Pin 11: 13.75
Pin 12: 13.75
Pin 13: 4.99
Pin 14: 4.99
Pin 15: 4.99
Pin 16: 0.001
The amp is pulsing slightly every 6~7 seconds. During which, all 4 channels appear to have some DC voltage across them. Voltage numbers on the TL494 dont change very much.
TL494
Pin 1: 0.002
Pin 2: 4.98
Pin 3: 0.089
Pin 4: 4.96
Pin 5: 1.663
Pin 6: 3.666
Pin 7: 0.001
Pin 8: 13.75
Pin 9: 0.001
Pin 10: 0.001
Pin 11: 13.75
Pin 12: 13.75
Pin 13: 4.99
Pin 14: 4.99
Pin 15: 4.99
Pin 16: 0.001
The amp is pulsing slightly every 6~7 seconds. During which, all 4 channels appear to have some DC voltage across them. Voltage numbers on the TL494 dont change very much.
Last edited:
Removed Q518. Amp powers up. +-26v rail. it appears there is no negative regulated voltage on the opAmps.
IC404
Pin 1: 13
Pin 2: 2.9
Pin 3: .25
Pin 4: .9
Pin 5: .25
Pin 6: 2.9
Pin 7: 13
Pin 8: 13
After about 5 minutes of power-on time, the ps and outputs start to get pretty warm.
I believe I just found an open/burned 1/8w resister R528 and a 1/2w R530 next to the negative voltage regulator, Q514
IC404
Pin 1: 13
Pin 2: 2.9
Pin 3: .25
Pin 4: .9
Pin 5: .25
Pin 6: 2.9
Pin 7: 13
Pin 8: 13
After about 5 minutes of power-on time, the ps and outputs start to get pretty warm.
I believe I just found an open/burned 1/8w resister R528 and a 1/2w R530 next to the negative voltage regulator, Q514
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