denon 3801

[JR]

hello...yall might remember me trying to find problem with 3801 denon
receiver i bought that wouldnt power on...wont do anything. Mark sent
me a service manual, i tried to find problem and finally give up. I
finally sent the receiver to a denon repair shop..they called today,
said the micro processor was out and would have to be replaced before
they could further troubleshoot, and could cost as much as 760.00 to
repair. I told them nevermind and to send it back. Mark said he bet i
had a cracked circuit board.awhile back when i was trying to find
problem..any tips on how to locate a cracked board or an easy way to
check? Would i have to tear receiver all the way down and pull all the
individual boards to check?

Thanks
JR

 

[Arfa Daily]

hello...yall might remember me trying to find problem with 3801 denon
receiver i bought that wouldnt power on...wont do anything. Mark sent
me a service manual, i tried to find problem and finally give up. I
finally sent the receiver to a denon repair shop..they called today,
said the micro processor was out and would have to be replaced before
they could further troubleshoot, and could cost as much as 760.00 to
repair. I told them nevermind and to send it back. Mark said he bet i
had a cracked circuit board.awhile back when i was trying to find
problem..any tips on how to locate a cracked board or an easy way to
check? Would i have to tear receiver all the way down and pull all the
individual boards to check?

Thanks
JR

I think I was actually the first to suggest a cracked board when you first
posted. I would think that the system control micro being faulty, whilst
possible, is unlikely. I have a friend who has this "rule" that the more
pins a device has, the less likely it is to be faulty ... Just a joke, but
actually, not a bad maxim to live your repair life by in practice.

For sure, you could pull every board out and physically examine it, but
really, it just wants either fault finding properly, or giving a second
opinion by a reputable repairer. The lot you already took it to are taking
the piss suggesting $760 to repair it. That actually says that they either
can't do it, or don't want to, so are doing the old "price it ridiculously
high and he'll walk" trick.

The system control micro area is generally easy to troubleshoot for a fault
like this. You only need establish that the 5v supply is good and accurate,
the reset line is at the right level, and the system clock is running. After
that, you check for activity on the switch matrix lines, in particular,
those running to the standby switch. Make sure that they do something when
you push the button, preferably right back at the appopriate pins on the
micro, but at the switch pins will do at a pinch. After this, if all is
well, you would need to check the "power on" line coming back out of the
micro, which should toggle as a result of pressing the standby button. There
are odd little problems that could throw a spanner in the works of this
simplified procedure, but for 99% of cases, those are the checks, in that
order, that will establish whether or not there is a sytem control micro
problem. However, all this assumes that you have a 'scope to hand, and are
able to read and follow schematics and layout drawings properly.

Arfa

 

[carneyke]

Arfa,
Excellent microprocessor troubleshooting advice ! Take Care, Kevin