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Denon AVR 1804 amp won't switch on

davenn

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Those big caps are not from the power supply, those are output caps,

not in this case, there are no significant caps on the amplifier outputs
they are the PSU ones

The two PSU caps, C136 and C137 are each 12000 uF 63V


cheers
Dave
 

eKretz

Apr 8, 2013
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Oh wow, didn't expect that. I would have expected to see a bank in parallel. I see that you guys are totally correct now that I perused your diagram.
 

eKretz

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Those will not be cheap, BTW. I checked the price of some larger caps on my receiver (these were output caps) out of curiosity - I think they were something like $80. Mine were a pair of 22,000μF 80V IIRC. Although it sounds like they tested okay. What did you use to test them bushtech?
 

bushtech

Sep 13, 2016
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I have now tested the other 3 sizable caps around the heatsink area

Biggish cap: C144 Samyoung SMS 3300μf 35V Measures: 3675μf ESR 0.16Ω Vloss 1.9%
Medium cap: C153 Samyoung SHL 6800μf 16V Measures: 6227μf ESR 0.05Ω Vloss 2.9%
Small cap: C145 Samyoung (can't read series) 1000μf 35V Measures: 836μf ESR 0.32Ω Vloss 2.2%
 

eKretz

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I think both the 3300μF and 1000μF are suboptimal, the new caps I just installed were 2200μF and 3300μF and both measured more like .01Ω ESR. Whether those numbers are bad enough to actually cause problems is the real question.

First step for you should be to figure out exactly what's happening as far as that relay not engaging though, I think.
 

bushtech

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Agree with you. I think I will replace all 3 caps as a matter of course. Cheap insurance while the board is somewhat accessible. Am I right in assuming that I just need good caps and not top quality audio caps.? Or should I go for top quality audio caps in any case?
 

bushtech

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As far as the relay goes. Are we talking about relay RLY106 (bottom left on page 20 of the manual) It's one leg is connected to the live of CP101 (AC CORD) which is where power enters the board. So it's poised to fire whenever power is connected to the AVR.

Now here's a real redneck plan: It's a 12V relay. If I supply 12V to legs 1 and 5 (the coil) the relay should fire. My concern is that the relay is still on the board.

Can this work to test the relay?
 

davenn

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Can this work to test the relay?

shouldn't be an issue ... make sure it's a current limited PSU you use to test the relay with .... you should need more than ~ 100 - 200 mA at the most
so current limit at around 300mA

that's assuming you have a PSU you can set current max with ?
 

eKretz

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There shouldn't be any need for "audio quality" caps in the P/S section. Many of those aren't even available in higher capacitance range.


If you don't have a current limiter you could always use a small bulb to limit current if you're worried about damaging anything.
 
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bushtech

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Now for that area that I'm still very shaky on

Limiting current to 300mA
P=VI
P= 12 x 0.3A = 3.6W (I need an additional 3.6W in the circuit)

So the small automotive bulb I have is 5W
I=P/V
I= 5W/12= 0.42A Huh? Current should have dropped
Me feeling very stupid
 

bushtech

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Well, I tried it with the 5W globe. Globe goes out and relay doesn't fire
 

eKretz

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Maybe your relay is damaged then. Pull it out of circuit and double check. Wouldn't it be nice if it was just a bad relay!

The 5W bulb should limit power to 5W after it in the circuit - so the current would be limited to the ~400mA that you calculated.
 

davenn

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Well, I tried it with the 5W globe. Globe goes out and relay doesn't fire

don't know if you realised it will be polarity conscious because of the diode across it

anyway .....

Pull it out of circuit and double check.

yes, this is the next step, and then you don't have to worry about the current limiting from that 12V 1A plugpack

I was only worried about current limiting whilst the relay was still in circuit ... being worried that the test supply could damage other components on the board due to overcurrent
 
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davenn

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lets start again

can you measure AC out of that sub trans transformer ? ...... if yes, good, if no, then lock switch, CP931 or the transformer may be faulty ... not sure if it is a fuse or not

can you measure DC on the + terminal of C158 ? ... should be less than 25V ...... if yes, good, if no, then D149 or D153 may be faulty

can you measure DC on the diagram left side of IC105 ..... if yes, good, if no, then that fuse has blown

get back with those measurements .... wont matter if you have already removed the relay

any failures in that power path will stop the relay from operating
 
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bushtech

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Wow guys Thanks! Lots of stuff to work through.
Dave: Does a diode come into play? I am connecting the 12V straight to the coil legs of the relay, and I checked data sheet of relay, the coil is not polarity sensitive.
 

bushtech

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Dave, just fyi, CP 931 is a connection plug with 2 wires coming out of it leading to a little circuit board right behind the on switch on the front panel.
 
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