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Denon AVR 1804 amp won't switch on

bushtech

Sep 13, 2016
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Grabbed the remote yesterday to switch on the amp, pushed button and nothing happened:(. Checked remote working by shining it at my phone camera and pressed button = working. Opened unit, checked fuse = working.Checked power cable, 220VAC arriving on board and red pilot light lit up as usual.

I wanted to insert a photo here but can't find the option so will try again in a second post.
 

bushtech

Sep 13, 2016
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AVR1804ps1.jpg
Upload file not visible, probably my rubbish internet connection.
Anyway, the plug at A supplies power to the transformer at B.With the unit on, if I pull the plug at A and probe the pins I get no voltage there. The plug at C supplies power to a small board at D, there is power there as pulling that plug kills the red pilot light.

Can somebody suggest what I can check. There is no burnt smell, but I don't hear the relay which normally clicks when I switch on
 

bushtech

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One of the 2 big caps near A and C is slightly bulged on top. Do they come into play at switch on or only later when amp is being used?
 

davenn

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One of the 2 big caps near A and C is slightly bulged on top. Do they come into play at switch on or only later when amp is being used?

they will most likely be smoothing caps in the PSU section
replace them both. If one is already bulging it is stuffed and the other one if probably not far from it
 

bushtech

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Thanks davenn. Could they be the cause of the amp not switching on or do I need to keep digging? I see they are Samyoung DL (DL =audio) 63V 1200μf 85C caps. Quite big 31mm dia x 63mm. Going to be nearly impossible to find in South Africa. Have already checked RS here. What would be a decent replacement or should I try for Samyoung again?
 

davenn

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Thanks davenn. Could they be the cause of the amp not switching on or do I need to keep digging? I see they are Samyoung DL (DL =audio) 63V 1200μf 85C caps. Quite big 31mm dia x 63mm. Going to be nearly impossible to find in South Africa. Have already checked RS here. What would be a decent replacement or should I try for Samyoung again?

I wouldn't worry too much about brand unless you can find online evidence that they are bad.
Also if possible use 105 deg temp ones.

get in there with a 1" paint brush and a vacuum cleaner and get rid of all the crap on the board, it's really yucky. It may help you find hidden faults.
Suspect every electro cap that is in a position with respectable voltages across them or ones close to heatsinks << I can see a few
 

bushtech

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Thanks again davenn. Will do on the cleaning. Most of the replacement caps that I have found so far with my sucky internet connection are much smaller. Can I go to 1500μf and stick 2 of them in parallel?
 

bushtech

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It doesn't look as if Samyoung make this cap anymore. The closest one I can find is 3300uf here: https://www.samyoung.co.kr/download/large/DL.pdf

So I will probably be looking for a cap from a different manufacturer. I will go for 105C as davenn suggested but how far can I venture from the original spec. Voltage and capacitance wise?
 

davenn

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Thanks again davenn. Will do on the cleaning. Most of the replacement caps that I have found so far with my sucky internet connection are much smaller. Can I go to 1500μf and stick 2 of them in parallel?

you can parallel 2 x 1500 to get 3000 if needed. are there some ~ 3000uF ones in there ?

but how far can I venture from the original spec. Voltage and capacitance wise?

as long as the voltage is the same or higher, it wont be a problem .... and try and stay within ~ 10% of the value of the existing one
 

bushtech

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Ooops, I obviously don't know what I'm talking about. I was concerned about the much larger size of the original 1200μf caps. I thought if I got 2 x 1200 and stuck them in parallel I could equate to the larger sized caps.

When you say ~10% are you talking voltage or capacitance?
 

bushtech

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10% doesn't leave me much room = 1320μf. My big concern is the size difference. Orig caps 31 x 63mm. The ones I'm seeing are generally less than half the size
 

eKretz

Apr 8, 2013
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Smaller won't hurt. Larger can be a problem if there is not enough space for them. Newer higher quality caps are usually a lot smaller than older ones.
 

davenn

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10% doesn't leave me much room = 1320μf. My big concern is the size difference. Orig caps 31 x 63mm. The ones I'm seeing are generally less than half the size

A 1500 cap will be OK instead of a 1200uF

a smaller value, as eKretz suggested, specially if significantly smaller value, will be a problem in PSU circuits where they are used for smoothing as
they wont give the same filtering amount and it will lead to more ripple on the DC rail(s)


Dave
 

bushtech

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I could probably modify the snap in connectors to make it work
 

bushtech

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Scrap that. Min qty =800, Not in stock, lead time 11 weeks

Back to the drawing board
 

eKretz

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Yes, davenn misunderstood my comment, which was in regard to physical size (as bushtech mentioned as a concern in the post right before mine). Definitely do not go lower in capacitance when replacing caps. As Dave previously noted - slightly higher capacitance is okay, and higher voltage is okay.
 
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