Have both a DE845 and DE945 and also have the service manual. Neither
unit will power on. The 845 had chattering power and I found bad solder
joints in the display board. After repairing those, the unit ran for
about a minute and a half then shut down...never to restart. All fuses
are good, and the standby power circuit seems to be working fine. When
pushing power button nothing happens (front panel or remote). So, I'm
assuming there is a problem with the standby circuit. According to the
schematic, the main power x-former is off until the the standby relay
is switched on, so ruling out that area. Is there a built-in protect
that prevents unit from coming out of standby? I took voltage readings
earlier but will recheck them one I get home and post them. BUT, if
memory serves, I had 5vdc out from some terminals and 10-13V on the
collector of Q901 which supposedly powers the relay (RY901). I'm
looking for guidance on how to approach this problem. I'm proficient
with O-scope, DVOM, ESR meter, and general electronic repair. Just
never messed with audio receiver/amps before. Thanks,

Alex

"427Cobraman" wrote in message
ups.com...
Have both a DE845 and DE945 and also have the service manual. Neither
unit will power on. The 845 had chattering power and I found bad solder
joints in the display board. After repairing those, the unit ran for
about a minute and a half then shut down...never to restart. All fuses
are good, and the standby power circuit seems to be working fine. When
pushing power button nothing happens (front panel or remote). So, I'm
assuming there is a problem with the standby circuit. According to the
schematic, the main power x-former is off until the the standby relay
is switched on, so ruling out that area. Is there a built-in protect
that prevents unit from coming out of standby? I took voltage readings
earlier but will recheck them one I get home and post them. BUT, if
memory serves, I had 5vdc out from some terminals and 10-13V on the
collector of Q901 which supposedly powers the relay (RY901). I'm
looking for guidance on how to approach this problem. I'm proficient
with O-scope, DVOM, ESR meter, and general electronic repair. Just
never messed with audio receiver/amps before. Thanks,

Alex

Very first thing is to make sure that no front panel buttons are being
accidentally pushed by slightly wrong assembly of the front panel. Make sure
that all buttons move, and click.

Assuming that there is no attempt by the main power relay to close, when you
try to turn it on, you can try forcing it, by temporarily shorting the
collector to the emitter on the relay driver transistor. DO NOT have any
speakers connected to it at this time. If unit then appears to come up ok,
check all of its display and operation functions. If anything here seems not
to be working correctly, chances are it's a system control problem, possibly
related to the work you already did on the front pcb. If all is still
looking good, check across ALL speaker outputs for DC. If there is any, then
check power supplies to output stages carefully. Some of these big amps
monitor the power supplies, and if anything is wrong, block operation,
although that's only a potential issue if the main power relay does close
momentarily. If everything is still looking ok, you can give it some input,
and see if the outputs look normal on all channels, on a 'scope. If this
looks good, you can risk some speakers, and then carefully recheck all
functions. If there are any noted problems, they should give you a clue as
to where to look. If it all appears to be working ok, then the only
circuitry that you then need to concentrate on, is the relay drive, back to
the system control micro, but check the circuit around the system control
micro carefully, for any pins that may have a power up blocking function.
With the standby supply present, and the system control idling, you should
be able to verify that there are no incorrect inputs to the micro.

Arfa

Arfa Daily wrote:
"427Cobraman" wrote in message
ups.com...
Have both a DE845 and DE945 and also have the service manual. Neither
unit will power on. The 845 had chattering power and I found
bad solder joints in the display board. After repairing those, the
unit ran for about a minute and a half then shut down...never to
restart. All fuses are good, and the standby power circuit seems to
be working fine. When pushing power button nothing happens (front
panel or remote). So, I'm assuming there is a problem with the
standby circuit. According to the schematic, the main power
x-former is off until the the standby relay is switched on, so
ruling out that area. Is there a built-in protect that prevents
unit from coming out of standby? I took voltage readings earlier
but will recheck them one I get home and post them. BUT, if memory
serves, I had 5vdc out from some terminals and 10-13V on the
collector of Q901 which supposedly powers the relay (RY901). I'm
looking for guidance on how to approach this problem. I'm
proficient with O-scope, DVOM, ESR meter, and general electronic
repair. Just never messed with audio receiver/amps before. Thanks, Alex

Very first thing is to make sure that no front panel buttons are being
accidentally pushed by slightly wrong assembly of the front panel.
Make sure that all buttons move, and click.

Assuming that there is no attempt by the main power relay to close,
when you try to turn it on, you can try forcing it, by temporarily
shorting the collector to the emitter on the relay driver transistor.
DO NOT have any speakers connected to it at this time. If unit then
appears to come up ok, check all of its display and operation
functions. If anything here seems not to be working correctly,
chances are it's a system control problem, possibly related to the
work you already did on the front pcb. If all is still looking good,
check across ALL speaker outputs for DC. If there is any, then check
power supplies to output stages carefully. Some of these big amps
monitor the power supplies, and if anything is wrong, block
operation, although that's only a potential issue if the main power
relay does close momentarily. If everything is still looking ok, you
can give it some input, and see if the outputs look normal on all
channels, on a 'scope. If this looks good, you can risk some
speakers, and then carefully recheck all functions. If there are any
noted problems, they should give you a clue as to where to look. If
it all appears to be working ok, then the only circuitry that you
then need to concentrate on, is the relay drive, back to the system
control micro, but check the circuit around the system control micro
carefully, for any pins that may have a power up blocking function.
With the standby supply present, and the system control idling, you
should be able to verify that there are no incorrect inputs to the
micro.
Arfa

Could just be the micro isn't getting any power. A regulator might have
died, a crystal might be intermittent, and I'm thinking there were a couple
1 ohm power supply resistors that would go bad on these. I'll check.

Mark Z.

427Cobraman wrote:
Have both a DE845 and DE945 and also have the service manual. Neither
unit will power on. The 845 had chattering power and I found bad
solder joints in the display board. After repairing those, the unit
ran for about a minute and a half then shut down...never to restart.
All fuses are good, and the standby power circuit seems to be working
fine. When pushing power button nothing happens (front panel or
remote). So, I'm assuming there is a problem with the standby
circuit. According to the schematic, the main power x-former is off
until the the standby relay is switched on, so ruling out that area.
Is there a built-in protect that prevents unit from coming out of
standby? I took voltage readings earlier but will recheck them one I
get home and post them. BUT, if memory serves, I had 5vdc out from
some terminals and 10-13V on the collector of Q901 which supposedly
powers the relay (RY901). I'm looking for guidance on how to
approach this problem. I'm proficient with O-scope, DVOM, ESR meter,
and general electronic repair. Just never messed with audio
receiver/amps before. Thanks,

Alex

OK, I was wrong about the resistors - guess I was thinking of a different
model.

Check Q1205 on the digital board and make sure it's putting out around 6
volts or so - and check D1211- it could be open or have been breaking down
under load - which kind of seems like your problem. Make note of whether the
micro is getting hot, or is stone cold. Could be an important clue.

Mark Z.

OK. Here's an update. I tried the front panel board from the 945 in
the 845 and it worked great. I checked continuity on all of the
switches on the bad board and none are shorted. I'm guessing a new
board is in order. What is a good source for sony parts? I've used
mostly pac parts but they don't seem to show this part, let alone many
sony replacement parts.

Alex

"427Cobraman" wrote in message
ups.com...
OK. Here's an update. I tried the front panel board from the 945 in
the 845 and it worked great. I checked continuity on all of the
switches on the bad board and none are shorted. I'm guessing a new
board is in order. What is a good source for sony parts? I've used
mostly pac parts but they don't seem to show this part, let alone many
sony replacement parts.

Alex

If you've got the skill to have undertaken the repair in the first place,
and have managed to successfuly transplant the board from the '9 to the '8,
then I wouldn't give up quite yet. You say that it initially worked, so
there's a good chance that there's not a lot wrong. As the other poster
said, now you know for sure that the problem is in the system control, check
the clock generator crystal for activity with a 'scope, check that the 5v
actually reaching the Vcc pin on the micro is accurate and clean, and check
that there is activity on the switch matrix lines, just to make sure that
there is no leakage across any of them, even though no switches appear to be
actually closed. Have you checked this one with the remote control ? You
might need to use the remote which matches the board ie from the '9, unless
you know for sure that both remotes work both units correctly.

Arfa

"427Cobraman" wrote in message
ups.com...
OK. Here's an update. I tried the front panel board from the 945 in
the 845 and it worked great. I checked continuity on all of the
switches on the bad board and none are shorted. I'm guessing a new
board is in order. What is a good source for sony parts? I've used
mostly pac parts but they don't seem to show this part, let alone many
sony replacement parts.

Alex


You're really going to have to troubleshoot it down further than just the
board. First of all the board may very well not be available, and if it is,
it's going to be expensive (over 100.00 maybe closer to 150.00 - I'll
check.)

Mark Z.

"427Cobraman" wrote in message
oups.com...
Thanks for the encouragement boost. I would normally shoot deeper, but
I lack the SMD solder/desolder tools I'd need, especially the micros on
there. I've done chip resistors and caps, etc. with a standard iron on
occasion, though. I did see that crystal there and will check it out
as well as the switch matrices. The remote is actually from the 845.
...the adventure continues...


There is a guy over here who has created " Beer's Maxim " ( his name is
Beer ). It basically states that " The more pins an IC has, the less likely
it is to be faulty ". Over the years, I've found this to be a pretty good
thing to keep in mind. On many occasions, I've condemned a micro, because
it's easy to do. With the best will in the world, none of us mere mortals,
no matter how experienced in the world of repairs, TRULY understands the
black magic, sorcery and esoteric shenanigans, that go on inside a
microcontroller IC, so when one doesn't work, we always condemn it. On the
occasions when I have actually replaced such an IC - and you can do it
perfectly successfully with ordinary workshop soldering equipment - it has
cured the problem on probably fewer than 20% of the occasions. Almost
always, unless there is a definite reason for the IC to be bad, such as
lightning damage, screwed internal software ( people trying to hack DVD
region protection etc ) or your 'scope probe having slipped ( !! ), the
problem turns out to be something simple, elsewhere. Often, an input to the
micro is wrong - even the /reset line. If you've got the time and
inclination, I would recommend checking all of the pins on the micro on the
working board, and noting the conditions on them, and then comparing to the
bad board.

Also, as you previously did work to this board, involving soldering, check
carefully, all over the board, with a strong magnifier, just in case a
whisker of solder has flown off the end of the iron, and lodged across
somewhere. Also check that there are no bent pins on any connectors, or
damaged foil fingers on the ends of any flexiprints going to the board. It's
amazing how often secondary faults, are caused by something you've done
yourself ...

Arfa

Well, all switch matrices checked out as well as supply voltages and
oscillators. ESR'd all electrolytics. The only thing that was off is
the LED drive circuits 1,2, and 4 on IC102. On the good board, these
are all at 4.7v when unit is powered off, regardless of state when in
operation. On the bad board, all are at zero. I wouldn't think these
would affect general operation, but who knows. I've checked, and a
couple other eyes have checked for cracks, solder bridges and bent
pins...everything looks good. I'm at wit's end. I'm sure I'll get
motivated to dig around some more after a nice cold brew. Link to
diagram:
http://www.archive.org/download/Part...atic/de845.gif

"427Cobraman" wrote in message
oups.com...
Well, all switch matrices checked out as well as supply voltages and
oscillators. ESR'd all electrolytics. The only thing that was off is
the LED drive circuits 1,2, and 4 on IC102. On the good board, these
are all at 4.7v when unit is powered off, regardless of state when in
operation. On the bad board, all are at zero. I wouldn't think these
would affect general operation, but who knows. I've checked, and a
couple other eyes have checked for cracks, solder bridges and bent
pins...everything looks good. I'm at wit's end. I'm sure I'll get
motivated to dig around some more after a nice cold brew. Link to
diagram:
http://www.archive.org/download/Part...atic/de845.gif

Hmmm. That's interesting. The anodes of the LEDs are connected to B+ via
their 150R limiter resistors. The cathodes are connected back to pins 1,2,4
on the micro. On the good board, in standby, the pins - ie the LED
cathodes - are all at very nearly B+, which is exactly as you would expect.
In standby, the LEDs will want to be off, so the driver transistors,
internal to those pins, will be turned off. Now look at the situation with
the bad board. The voltage at the three IC pins can only be low as a result
of two conditions. First, the internal driver transistors are on. BUT, if
this is the case, then the LEDs must be alight, as we know that there should
be B+ on their anodes, even when the unit is in standby. The second
condition which would lead to there being no voltage on the IC pins, AND the
LEDs not alight, is B+ missing at the back side of the 150R limiter
resistors.

It's hard to see how this could be the case, if all of the other voltages on
the micro are correct. Never-the-less, it would be my best guess, as being
the case. Although you can be pretty sure from your measurements so far,
that B+ itself is established and correct, I'd give reasonable odds that
it's not everywhere it should be. I think that the missing voltages at the
LED drive pins are a big clue. My next move would be to check that B+ is
present at the junction point of the three limiter resistors and C120 and
pin 1 of IC105. Keep us posted on your findings.

Arfa

Well, it looks like B+ is not available on the ckt with the good board
until unit is powered up, yet there is 4.7 volts at the pins on the IC
while in standby. I've pulled all but 3 hairs out of my head trying to
shoot as well as understand how this circuit is supposed to work. I
also went and double-checked all voltages coming into the card via
ribbon cable and everything checks out. *sigh* Incidentally, the owner
said he is willing to pay for a replacement card if all else fails.
Luckily he's a very patient neighbor! It's $95 bucks for the durned
thing. Again, I appreciate all of the guidance and encouragement!

Alex