Are my caps leaking or glued on?

[Zuma]

Hi Folks
Hopefully you can advise me on something.
I was trying to fix my Marantz pm 54, and on checking inside i saw some resinous material around the base of some of the caps, so i assumed they had leaked and started looking for some suitable replacements. Then it occured to me that they might just be glued on.

obviously i am just a newbie at electronics otherwise i would know this sort of stuff, but if anyone can advise me it would help.
wouldn't want to change all the caps only to find that wasn't the problem in the first place

cheers

Rob

[keyne]

if it looks like resinuous material, it is probably glue...
also, electrolytics don't usually leak electrolyte (the liquid).
the phrase "leaky cap" comes from the cap "leaking" in other words passing DC current. which it shouldn't do.

big caps are often glued on because they are heavy and stress the solder joints otherwise.
hth

[Zuma]

Thanks for the advice.
It does seem to be the bigger caps that have the 'resin' around the bottom of them.
unfortunately that was the only idea i had for what could be wrong with the amp, so back to the drawing board now

[joensd]

Hi Rob,
do you happen to have a schematic for your amplifier?
I got the similar? PM-52 and am always trying to get my hands on schematics of my equipment.

What´s wrong with your amplifier?

Cheers
Jens

[Zuma]

Sorry i don't have a schematic for the pm-54, and i did look around quite a bit to find on. Also Marantz's naming scheme never seemed that logical to me so i don't know how similar it would be to the pm-52.

when i first got it (secondhand) it worked fine except for some slight volume reduction on the left channel when i wiggled the balance, but wiggling it made it work ok.

then one day I went out of the room for something and when i came back in it wasn't producing sound. After a bit of investigation i discovered that the speaker protection relays were clicking off after a few seconds. But before they click off i do get sound out of the right channel.
Also the headphone socket works all the time but only on the right channel, left channel totally dead.

wiggling the balance control didn't help

Anyway i don't wanna give up on it yet but it's probably not worth getting it professionally fixed.

[mozikluv]

hi there zuma,
when the protection circuit comes into play, it only means you a short in the right channel.

by the way i hope you dont mind my asking you this, do you any experience about audio electronics? if none, then i suggest have it repaired by competent technician. the marantz p54 would be complicated for you.

[Zuma]

thanks for the reply.

No i don't have any experience in audio electronics, and i am only going by what i have learnt as i go along. I have managed to trace the fault as far as the main circuit board, and i have found that there is a very weak signal going to the speaker terminal board that has the relays on it, on the left channel.
Thats about as far as i can go on my own, as i can see nothing visually wrong with the main circuit board. I haven't found out how much it might cost to be repaired proffensionally, but it's probably not worth it, which is why i am trying on my own.

I am however a very cautious person, and i do have some technical knowledge, so i don't think i will endanger myself, at least i hope not

[mozikluv]

ok here goes my bit solution: u said low signal on your right terminal & u hear the relay click off/on,
1. either the relay is totally defective or has poor contact
2. the transistor that drives the relay is defective
3. as to signal, compare the voltages of the good left amp to the defective right, start from the output stage, then driver stage, then pre-driver stage, the Vbe Multiplier, and lastly the input stage. (pls be careful when you check the voltages it has a positive & negative supply rail & central ground. identify first the supply lines and the grnd line.) if you find the voltage difference in any of the stages, check around it.

this suggestions is not a guaratee that it will cure the defect. there are other parameters to check. start from what i have suggested.

if you are using and analog meter be sure that the positive probe is in the positive points and the negative probe is on the grnd side. when you check the negative side be sure your positive probe is on the grnd side and the negative probe is on the negative points. if u are using a digital and it can show a negative sign even if you have reverse probes then no problem.

happy hunting