I have an RX-570 here that keeps popping the outputs and have no clue where the SM Transistors are to defeat the BLOW Line in it. According to what I've read in other dealings with this thing, Q7401 and Q7406 are the SMTs in question, but they're not on the amp boards, are invisible or I'm going blind. The entire amp module is brand new, so you can imagine I was pretty suprised (enraged really) when I fired it back up and it killed the thing. I had a 100w light bulb in there to keep it from self destructing as well, but it didn't help.

I want to rule the entire amp module out, since it was new and still got toasted. I replaced the outputs and the 220ohm resistors as well as everything else on it are all still good. But now really have no idea where to start looking externally for whatever is kicking the "protection circuit" (term used very loosley) on. Every other one I've ever messed with had an open resistor or two and shot outputs, and that repair alone fixed them up, but this things deciding to be a nightmare. If anyone has any ideas or info I thank you a ton in advance.

There are really some of those piles of crap still out there?

"RDC" wrote in message
...

I have an RX-570 here that keeps popping the outputs and have no clue
where the SM Transistors are to defeat the BLOW Line in it. According
to another post I read, Q7401 and Q7406 are the SMTs in question, but
they're not on the amp boards, are invisible or I'm going blind. The
entire amp module is brand new, so you can imagine I was pretty
suprised (enraged really) when I fired it back up and it killed the
thing. I had a 100w light bulb in there to keep it from self
destructing as well, but it didn't help.

I want to rule the entire amp module out, since it was new and still
got toasted. I replaced the outputs and the 220ohm resistors are all
still good on it. But now really have no clue where to start looking
externally for whatever is kicking the "protection circuit" (term used
very loosley) on. Every other one I've ever messed with had open
resistors or shot outputs and that repair alone fixed them up, but this
things deciding to be a nightmare. If you have any ideas or info I thank
you a ton in advance.


--
RDC

The surface-mounts are there - they are just hard to find. A nagnifying
glass helps to find the board markings.
These units can be blown by a bad cassette motor or any power supply voltage
being low.
When you find 7401 and 7406, short the E-B junctions.

Mark Z.

Yep, and you wouldn't believe how attached to them some people are. I can understand the attachment to a piece of electronic equipment, but not to a crappy one. Some people figure because it cost close to $1000 when they got it 12 years ago that it must still be worth that much. Those two things combined make for a "hard to steer down the right path" type of person. So they'd rather have it fixed than listen to reason and put that money toward a nice receiver.

Thanks Mark, I was hoping you'd see this since it was an older post of yours that had the info. Are you saying these are on the Front amp board? or are they located elsewhere? I've been all over both amp boards and there are no Q74xx at all on these, Q71xx and Q72xx on the Rear/Reg/Protect Board, and then Q75xx and Q76xx on the Front Board.

Thanks again.

"RDC" wrote in message
...

Mark D. Zacharias Wrote:

The surface-mounts are there - they are just hard to find. A
nagnifying
glass helps to find the board markings.
These units can be blown by a bad cassette motor or any power supply
voltage
being low.
When you find 7401 and 7406, short the E-B junctions.

Mark Z.


Thanks Mark, I was hoping you'd see this since it was an older post of
yours that had the info. Are you saying these are on the Front amp
board? or are they located elsewhere? I've been all over both amp
boards and there are no Q74xx at all on these, Q71xx and Q72xx on the
Rear/Reg/Protect Board, and then Q75xx and Q76xx on the Front Board.

Thanks again.


--
RDC

They're there, just almost impossible to find. One in on the front amp
board, one on the rear amp ass'y. I'm not quite sure how to steer you to
them. I have a couple similar modules laying around at work, but I'm not
sure if any of them are from a 570.

E-mail my work e-mail direct at:



and reverse the domain name.

Maybe I can take a pic and e-mail it to you.


Mark Z.

Email sent, I attached pics of the boards I'm dealing with also.