identifying phono PSU Transistor (resolved)
I have an Alice Phonopak 1 preamp which has developed a low level buzz.
I am quite happy this is not an earth loop hum and on further investigation, lifting out the pcb, it looks to me like a transistor got a bit hot.
The power supply looks simple enough, altho I don't have specific understanding of everything I am more than capable of replacing such components but I could really use some advice about what the transistor is and if you agree with me that one looks fried, and any other comments to help me along my way to getting this fixed. If it is fried? what else do I need to know?
Very many thanks in advance, photos at google if you have a moment.
https://goo.gl/photos/HwToEqFEJM7944P58
I have an Alice Phonopak 1 preamp which has developed a low level buzz.
I am quite happy this is not an earth loop hum and on further investigation, lifting out the pcb, it looks to me like a transistor got a bit hot.
The power supply looks simple enough, altho I don't have specific understanding of everything I am more than capable of replacing such components but I could really use some advice about what the transistor is and if you agree with me that one looks fried, and any other comments to help me along my way to getting this fixed. If it is fried? what else do I need to know?
Very many thanks in advance, photos at google if you have a moment.
https://goo.gl/photos/HwToEqFEJM7944P58
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If the regulator's output voltage is normal, the regulator is likely to be ok.
First make sure the problem is in the unit, and not external. If so, it might
be a bad capacitor or solder joint.
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If you have a suggestion as to how I can check that I would be greatful. I am able to use a meter without a problem, the joints do look a bit suspect and I am tempted to re solder them, but before I did that I wanted photos of how they appear at the moment. To me they look a bit fried....thus suspecting the component may be damaged.
I have now found a PDF file and data sheet for the component which is a help
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Your photos show the electrolytic caps to be highly suspect due to the effects of heat. I would replace all those for what they cost. The plastic sleeve shrinking is a classic giveaway.
Check out CPC for all the parts. Free delivery on orders over £5.00
https://cpc.farnell.com/?catalogId=...t4FxyQBZK3eBv4ZpbqzY7kfqwFZ2n rf7xiJKg4/HOSde
Check out CPC for all the parts. Free delivery on orders over £5.00
https://cpc.farnell.com/?catalogId=...t4FxyQBZK3eBv4ZpbqzY7kfqwFZ2n rf7xiJKg4/HOSde
More... its normal for PCB material to discolour from heat.
(The regs may well be OK, those caps look to be the real problem. For what the regs cost though I would replace the lot. Just search for 7815 and 7915. They are IC's, not transistors. Any of the versions offered are suitable
7815
7915
Don't buy these parts off Ebay. To many fakes around)
(The regs may well be OK, those caps look to be the real problem. For what the regs cost though I would replace the lot. Just search for 7815 and 7915. They are IC's, not transistors. Any of the versions offered are suitable
7815
7915
Don't buy these parts off Ebay. To many fakes around)
Mooly, very many thanks indeed.
I have a CPC account so no problem there, I am happy to replace the parts to preserve this great phono amp.
I use it at home, so I have a nice little project to work on now, should I replace anything else?
Thanks for taking the time to help me out. It's much appreciated.
I have a CPC account so no problem there, I am happy to replace the parts to preserve this great phono amp.
I use it at home, so I have a nice little project to work on now, should I replace anything else?
Thanks for taking the time to help me out. It's much appreciated.
I'd just stick to fixing the fault initially which is almost certainly those caps. Looking at the brand of those caps that I can make out, and which seem to be <NOVER>, well lets say it might be worth replacing all the electrolytics but fix the fault first.
Make a list of the caps and select suitable replacements based on value, voltage, size and pitch (pin spacing). Go for 105C rated parts rather than 85C for those in the power supply.
Make a list of the caps and select suitable replacements based on value, voltage, size and pitch (pin spacing). Go for 105C rated parts rather than 85C for those in the power supply.
and good luck.- Status
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