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Denon DRA-300 Dead Left Channel
Denon DRA-300 Dead Left Channel
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Old 27th September 2019, 11:08 AM   #21
Mooly is offline Mooly  United Kingdom
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Denon DRA-300 Dead Left Channel
Without seeing the circuit details it is impossible to give specific advice, however you should check and confirm the basics.

The middle leg of those 0.47 ohm resistors should be within 50mv or so of ground potential (both channels). Your voltage readings above show that should be the case for that channel, but check them both.

Look to see if there is a speaker relay, and if so is it being activated to connect the speakers to the amp.
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Old 27th September 2019, 03:59 PM   #22
wiseoldtech is offline wiseoldtech  United States
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Originally Posted by Mooly View Post
Without seeing the circuit details it is impossible to give specific advice, however you should check and confirm the basics.

The middle leg of those 0.47 ohm resistors should be within 50mv or so of ground potential (both channels). Your voltage readings above show that should be the case for that channel, but check them both.

Look to see if there is a speaker relay, and if so is it being activated to connect the speakers to the amp.

Hi Mooly, it doesn't appear to use relays judging from the previous photos.
Perhaps a bad solder joint, or the speaker switches have gone bad?
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Old 27th September 2019, 07:12 PM   #23
Mooly is offline Mooly  United Kingdom
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Denon DRA-300 Dead Left Channel
Could well be Does this amp have 'pre-out and power in' jumper links I wonder.
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Old 27th September 2019, 08:15 PM   #24
22asd is offline 22asd  United States
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That's more like it

So where are you up to? Is it all working with no problems now?
You were right Mooly!! It did work.

I soldered back in the two resistors just now. I tested the speaker lines and saw the voltage jumping around on the left speaker line. Plugged in the speaker and the sound was good.

Wise might be correct about a bad solder joint : \

So glad it is finally working! Should I recap it? I have most the caps in stock already (dont have those big boys).

Last edited by 22asd; 27th September 2019 at 08:17 PM.
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Old 27th September 2019, 09:34 PM   #25
wiseoldtech is offline wiseoldtech  United States
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Originally Posted by 22asd View Post
You were right Mooly!! It did work.

I soldered back in the two resistors just now. I tested the speaker lines and saw the voltage jumping around on the left speaker line. Plugged in the speaker and the sound was good.

Wise might be correct about a bad solder joint : \

So glad it is finally working! Should I recap it? I have most the caps in stock already (dont have those big boys).

I wouldn't see the need to recap the unit, it's not that old.
Recapping things has been some kind of internet "fix all" and it's gotten out of hand.
Part of the "recapping" craze was due to products that were manufactured between 2003 and 2006, because of a bunch of stuff was breaking down because of the infamous "bad capacitor" scandal - resulting from a stolen formula that was missing a key ingredient, whereby capacitors made with that formula soon failed.
That has since been taken care of, yet the "craze" goes on - promoting paranoia about anything with capacitors.
It's nonsense of course.
Older, 1940's to early 1970's products could use a,... ahem, "recapping" to bring back reliability and improve performance.


As for bad solder joints, it happens.
Best to concentrate with a magnifying glass the whole board(s), looking for "ring joints" around soldered components and wires, switches, jacks, etc.
A ring type crack may appear, and if the part is wiggled, it will show up.
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Old 28th September 2019, 06:42 AM   #26
Mooly is offline Mooly  United Kingdom
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Denon DRA-300 Dead Left Channel
good to hear it works.

I'd agree with the comments on re-capping and also follow on and say that we see so many examples on the forum where things go wrong and an otherwise good amp ends up with multiple issues. Not saying that would be the case here... but it happens, a lot.

The comments on dries are spot on. Check out the last couple of images at the end of post #1 here for typical examples:

Sony CDP790 and KSS240 Restoration Project
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Old 28th September 2019, 07:05 AM   #27
wiseoldtech is offline wiseoldtech  United States
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good to hear it works.

I'd agree with the comments on re-capping and also follow on and say that we see so many examples on the forum where things go wrong and an otherwise good amp ends up with multiple issues. Not saying that would be the case here... but it happens, a lot.

The comments on dries are spot on. Check out the last couple of images at the end of post #1 here for typical examples:

Sony CDP790 and KSS240 Restoration Project

I'll add to those comments from that link - nice work Mooly.
A few months ago one of my Technics "Mash" CD players started annoying me.
Sometimes wouldn't read or spin up the disk.
Drove me nuts.
Diving into it, I eventually found a 1uf cap on the servo board was leaky, and read 0.4uf.
Changing it restored perfect operation again.
But man!.... was it a delicate procedure to do!


I'm retired after 45 years of professionally fixing other people's broken crap, and I want a darn rest now, but this stuff just happens anyway.
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Old 28th September 2019, 07:13 AM   #28
Mooly is offline Mooly  United Kingdom
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Denon DRA-300 Dead Left Channel
Thanks

Your Technics sounds a real 'one off' type of issue, you did well sussing that one out as those are often nightmare type faults.
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