Denon AVR 1804 amp won't switch on

[davenn]

So the relay is 12VDC but we keep seeing 17V. Isn't that a bit odd?

it's an unregulated 17V it will drop a volt or 3 under load


OK an idea .... if not too difficult, can you remove Q117 from the board ( note its orientation) and then see if a voltage appears on the base of Q116


Q117 may be dragging the voltage on the base of Q116 to ground (0V rail)

 

[bushtech]

Heh, it's tiny but lets try

 

[bushtech]

Nope, still 0V on base. Collector voltage has dropped to 16.7V

 

[davenn]

Nope, still 0V on base. Collector voltage has dropped to 16.7V

OK
whilst that transistor is still out of circuit, check for voltage both sides of R186 a 4k7 its in the line from the CPU to the base of Q116

 

[davenn]

ohhh ..... how in pieces do you have this thing ???

the thought just struck me that maybe the CPU board wasn't connected ?
do you reconnect everything ( if boards were separated) before powering on and voltage testing ?

 

[bushtech]

OK

Could cap C159 come into play here?
Alternately reads 85μf ESR 0.14kΩ and 1151nf ESR 1.9Ω

 

[bushtech]

It's mostly together. Component video and Svideo boards removed and 1 earth disconnected

 

[davenn]

OK

Could cap C159 come into play here?
Alternately reads 85μf ESR 0.14kΩ and 1151nf ESR 1.9Ω

should be a 1 uF ... check value written on it, does it looked bulged ? is it near a heatsink ?

I don't think it would be an issue

 

[bushtech]

Yes, it's a1μf. No, not bulged, not near heatsink.

0V on either leg of R158

 

[bushtech]

and it is switched on

 

[davenn]

Yes, it's a1μf. No, not bulged, not near heatsink.

0V on either leg of R158

OK on cap


and R186 not 158

 

[bushtech]

Yes, 0V both sides on R186

 

[davenn]

Yes, 0V both sides on R186

OK





pinouts are listed on pages 8, 9 and 10

CPU board component list starts on page 41

 

[bushtech]

Well, fortunately IC201 is not a black molten mass with legs sticking up in the air

 

[davenn]

Well, fortunately IC201 is not a black molten mass with legs sticking up in the air

OK. I think I found it. If you look at my photo of my dusty avr at the beginning of the thread it's way over to the right on the underside near where the ribbon cable connector connects. Thats actually a separate board

yes it is a separate board as I said, called the CPU board


I wonder if there is any way to do a reset for the system ?? maybe have read in the service manual on the operation of the system and see if you find anything

 

[bushtech]

Will do thanks

 

[bushtech]

Doesn't look good. Have reset the macroprocessor. No change.

From ebc electronics:

3. Solid red power light on. No responce to power button or remote control.
Most likely the receiver has a problem with main macroprocessor.

 

[davenn]

Doesn't look good. Have reset the macroprocessor. No change.

From ebc electronics:

3. Solid red power light on. No responce to power button or remote control.
Most likely the receiver has a problem with main microprocessor.

ouch my worse fear

 

[bushtech]

I am seeing just under 5V on pins 88 ,89, 52-54 (difficult to be exact) but that means that power is entering IC 201 (CXP740010) which probably means this IC is stuffed.

Assuming I can get hold of a replacement IC (long shot) what are the chances of replacing this successfully (de- resolder)?

 

[eKretz]

Oh that's not good. If you can get hold of a twin receiver someone is tossing you might find it easier to swap the whole board rather than the MCU. Trying to source a new MCU would probably be a no go because the firmware wouldn't be written.