Denon AVR 1804 amp won't switch on

[bushtech]

Not sure what you mean by twin receiver


But not totally convinced that it's mcu. On switch on red led flashes 8 times and then goes solid. Don't know if it's gone into a protection mode. I have seen that if voltage is not present on rails it will go into protection mode



Currently trying to figure out how you check the rails for voltage

 

[eKretz]

Just another of the same receiver. Find one that's trashed somewhere other than the MCU if that ends up actually being the issue and just swap. Sorry can't help much with the circuit tracing - my internet is piggy-backed off a cell phone hotspot right now and I can barely load a web page let alone try to download that service manual. I can't read the diagrams being posted very well either, the resolution is too low.

 

[bushtech]

Investigation continues. I pulled the relay, previously I had taken the cover off the relay to see if it kicked in. Checking continuity on the coil I noticed that the coil wire had broken. Now it might have broken with all my fiddling on the board previously or it might have broken earlier causing the problem with the AVR that started this thread.

Now, just tying a knot in the coil wire does not give me continuity, realized that the coil wire has to be coated. So new question, how do I strip the coating off the two broken ends of the copper wire?

 

[davenn]

Investigation continues. I pulled the relay, previously I had taken the cover off the relay to see if it kicked in. Checking continuity on the coil I noticed that the coil wire had broken. Now it might have broken with all my fiddling on the board previously or it might have broken earlier causing the problem with the AVR that started this thread.

this sounds a little unusual maybe you damaged it when you removed it ? as a test you did for me
back a bit proved that voltage was present either side of the relay, so what ever happened to it has happened since that test

Now, just tying a knot in the coil wire does not give me continuity, realized that the coil wire has to be coated. So new question, how do I strip the coating off the two broken ends of the copper wire?

indeed


generally just heating the ends of the wires with the tip of the soldering iron with a little solder on the tip will burn off the coating
( sometimes depends on the coating) if that doesn't work it will have to be scraped off


Dave

 

[bushtech]

I have managed to solder the 2 ends of the coil wire together. I also found that the relays contacts wre burnt and not making contact. Bent the one leg slightly and they now make contact when the coil is powered.

But set will still not power up

 

[bushtech]

I have found 2 places that can supply CXP740010 chip. Now are all CXP740010 chips equal software wise or do companies who use these use their own custom software?

 

[davenn]

I have managed to solder the 2 ends of the coil wire together. I also found that the relays contacts wre burnt and not making contact. Bent the one leg slightly and they now make contact when the coil is powered.

But set will still not power up

OK ... well the contacts are switching mains voltage 115 or 230 whichever it is that you have, cant remember

when the coil is powered ? ... whilst removed from the board ?

remember the system wont power up if there is no voltage appearing on the base of Q116
and we had already proved that wasn't happening

 

[davenn]

Now are all CXP740010 chips equal software wise or do companies who use these use their own custom software?

as was mentioned by eKretz, some time earlier, it's possible that the cpu is programmed specifically for that piece of gear .... I cant answer that for sure ?

 

[bushtech]

220V 50Hz

The relay now connects when I power the coil whilst it's not on board. So even if there was voltage on the coil the relay would not have connected power through because the contacts couldn't make contact.

But no voltage on coil when inserted on board and I power up

And am I correct in saying that no voltage on base of Q 116 is caused by the cpu not directing voltage there and this is the cause of the problem.

 

[bushtech]

And I suppose even if you could flash the software on the old chip onto the new chip there is no guarantee that the software on the old chip is not corrupted

 

[davenn]

And am I correct in saying that no voltage on base of Q 116 is caused by the cpu not directing voltage there and this is the cause of the problem.

that is the most likely cause

The only things we haven't done is prove that there is voltage on the relevant pin of the cpu
That is, from the 7805 regulator to the cup
and that the output voltage from the cpu is getting all the way back to the base of Q116


that is checking to make sure there is continuity in the tracks and interboard connectors between those 4 points

 

[davenn]

And I suppose even if you could flash the software on the old chip onto the new chip there is no guarantee that the software on the old chip is not corrupted

and the chances of there being a way to read the firmware on the old chip is probably somewhere between zero and none at all

 

[bushtech]

I have seen on some site that the 7805 is a possible suspect

 

[davenn]

I have seen on some site that the 7805 is a possible suspect

yes but you tested that for me and it was putting out 5V

 

[bushtech]

So glad you know what we were doing. I will check for continuity as you mentioned. Thanks

 

[davenn]

that 5V regulator also supplies the cpu with its operating voltage

 

[bushtech]

I am battling to follow the route from the base of Q116 to the CPU. The base leg connection splits into 3 immediately. Th first connection is not it as it goes straight back to bottom leg of Q116 via a resistor R107. But which one of the other 2 connections should I be following.

Q116 is just to the right of Relay RLY106 on the bottom left of page 20 of the manual.

Help/advice would be appreciated

 

[davenn]

I am battling to follow the route from the base of Q116 to the CPU. The base leg connection splits into 3 immediately. Th first connection is not it as it goes straight back to bottom leg of Q116 via a resistor R107. But which one of the other 2 connections should I be following.

Q116 is just to the right of Relay RLY106 on the bottom left of page 20 of the manual.

Help/advice would be appreciated

will get back to you soon, haven't forgotten you, been rather ill with hospital visits

 

[bushtech]

Ouch! Hope it's not serious. Best wishes

 

[bushtech]

And if anybody can answer my question in post #35 it would help me enormously. Would hate to break something while investigating how they seperate