AudioSource AMP200 - help needed

[Jiji]

hi everyone,
my AudioSource AMP200 stopped working yesterday. I was listening @low volume and it just stopped. I pushed the power button and I heard a pop. Opened it.
The fuse is fine but a 104 ceramic cap smoked. it is located on the power board. can't find the schematics anywhere -as far as i can tell, the same schematics are used by a few different manufacturers (audiosource, OSD audio, etc) and the board is the same for the AMP200 and AMP300.

I replaced that capacitor. the amp still doesn't power up. so far I managed to measure some voltages coming from the transformer and it seems fine. the wires that go to the amp/preamp are labeled (15V, 24V, power, etc) and it seems the voltages here are zero or too low.

any advice or schematics would help me, thanks for your time, have a nice day!


edit:
*as seen in the pic
1- cap 104 replaced
2- AC is coming from the transformer
3- NO AC or DC voltage
4- i don't remember right now

*some heat coloration can be seen on the back of the power board, marked it in the pic

*2 more pics for whoever is courious how the inside of a AudioSource AMP200 looks like. I had a hard time finding any pics so I'm posting some....

[Jazz P Bass]

Start by checking the bridge rectifier for shorts.

This uses FET's on the output section, si I would also check those for shorts.

Note: disconnect any load (speaker) until you suss out what is wrong.

[Jiji]

@Jazz P Bass thank you for your reply,

the bridge rectifiers don't show like being shorted w/ my DMM. I have a few, they're all cheap and they all show different resistance values when I measure, but none showed a short.

the big one is a kbpc25-04w (RD02) and the smaller one is a gw rs202m (RD01). there are also a kia 7815a (IC01) and a 7915pi(IC02).
all the resistors show some value except R01 & R02 (lower right-mid of the pic). They might be a 1 Ohm resistors (brown/black/gold/gold/space/white) but don't show any value when measured for resistance.

somebody is looking thru some documents, I have hope will find a schematic...

[The Dude]

If you look at the second picture, the solder joints on IC01 and IC02 are clearly in need of attention. Have you resoldered those?

[Jiji]

If you look at the second picture, the solder joints on IC01 and IC02 are clearly in need of attention. Have you resoldered those?

thank you, I will edit the post. I took the picture after I took them off the board.

[The Dude]

Gotcha then.

(Making some inferences from the pictures) I would first work on the 24V supply. This is needed to turn on the relay for the other supplies. The 24V supply appears to be developed by the small bridge rectifier. There is a center tapped transformer plug that goes through 2 resistors (R01 and R02) to the smaller bridge rectifier. Is there AC on the smaller transformer plug? Does it get to the center pins of the BR? If not you have at least one/maybe two open resistor(s). If there is AC on the rectifier and no DC out, the rectifier is likely bad.

Edit: If the resistors are open, check the BR for shorts before you apply power or you may burn up the resistors again.

Edit again: I just re-read your post #3. You say R01 and R02 "don't show any value". For future reference, please say either infinite or 0 ohms, or you could use shorted or open. The meter shows a value one or the other. It helps to know which.

[Jazz P Bass]

Not uncommon to see low resistance value resistors on a supply like that. (47- 100 ohms)

They are there to go open when trouble occurs downstream.

Trouble does not limit the problem to the bridge rectifier.
Any over current draw will send them open.

[DrGonz78]

Sure looks like a lot of cracked solder joints on that power board. I would at least re-flow the worst offenders just to get that part out of the way.

[Jiji]

Sure looks like a lot of cracked solder joints on that power board. I would at least re-flow the worst offenders just to get that part out of the way.

@DrGonz78 thank you!
I will retake a close look. As far as I can tell the board has a generous amount of solder -looks like a manual labor- and the joints do not look weak. I will recheck. Not being proficient in repairing electronics, that's one of the first things I check... cold joints.

here are some more pics by a different user. last post on page. everything looks messy, but not like somebody was in a hurry...
http://diyaudioprojects.com/Forum/vi...0bd525df45cc30

[Jiji]

I've got the schematics today for the AMP200/300
should I post a print-screen of the power board schematics?

I will recheck tomorrow the suggested components for shorts and also the voltages and write everything down.
as of right now, only the 2 resistors seem to be bad (open).
just as Jazz P Bass has said earlier, the schematics I have says "R01 = 1[Ohm] 1/4W(FUSE)"

[nickb]

I've got the schematics today for the AMP200/300
should I post a print-screen of the power board schematics?

I will recheck tomorrow the suggested components for shorts and also the voltages and write everything down.
as of right now, only the 2 resistors seem to be bad (open).
just as Jazz P Bass has said earlier, the schematics I have says "R01 = 1[Ohm] 1/4W(FUSE)"

Screen shots don't come up well - better to simply just post the file ('Go advanced' and use the attach icon).

[DrGonz78]

@DrGonz78 thank you!
I will retake a close look. As far as I can tell the board has a generous amount of solder -looks like a manual labor- and the joints do not look weak. I will recheck. Not being proficient in repairing electronics, that's one of the first things I check... cold joints.

Yeah I have posted a couple close ups of what looks like cracking around the filter cap joints. The soldering on that power board reminds me of a Pyle amp that I worked on once before. From my experience when the soldering looks like that there can also be some cold joints too. Mainly I was addressing more of a preventive issue of re-flowing solder on those main filter caps due to cracking issues.

edit:
*as seen in the pic
1- cap 104 replaced
2- AC is coming from the transformer
3- NO AC or DC voltage
4- i don't remember right now

I am confused by "3- NO AC or DC voltage". Please explain that better.

[The Dude]

......just as Jazz P Bass has said earlier, the schematics I have says "R01 = 1[Ohm] 1/4W(FUSE)"

I don't doubt you, and I could certainly be wrong, but you may want to double check that. Those look larger than 1/4W to me.

[The Dude]

......Thus without me rambling on .....

Too late.

[g1]

How about the TL(power of ten)DR version?