tonygvng

Active member
Aug 19, 2023
8
8
25
Visit site
Hello, i recently got an Harman Kardon PM635 UWB dual system amp and no matter what the left channel doesn't work: tried plugging the source in tape, cd, tuner and no luck, the left channel doesn't work neither on the headphone jack or the speakers (both system 1 and 2).
Any suggestions? Thanks in advance.
 

camcroft

Well-known member
Hello, i recently got an Harman Kardon PM635 UWB dual system amp and no matter what the left channel doesn't work: tried plugging the source in tape, cd, tuner and no luck, the left channel doesn't work neither on the headphone jack or the speakers (both system 1 and 2).
Any suggestions? Thanks in advance.
It's an old amp so anything inside could have gone. Just a thought as components in old equipment do sometime go.
 
  • Like
Reactions: WayneKerr

camcroft

Well-known member
it was stored in perfect conditions and i powered it for the first time since 2005/2008 but thanks for answering.
It could be anything like the solder joints have deteriorated . As above find a repairer. I have a Harman Kardon amp in the loft from the 80,s last time years ago that I fired it up it worked fine. They made some good equipment in those days sadly not anymore as if I am not mistaken they belong to Samsung now. It could well be a simple fix maybe a loose connection.
 
Last edited:
  • Like
Reactions: WayneKerr and Gray

Gray

Well-known member
I have a Harman Kardon amp in the loft from the 80,s last time years ago that I fired it up it worked fine. They made some good equipment in those days
They sure did, I had their PM650 amp, capable of a 39 amp peak current output (and it sounded like it).

@tonygvng if you're anywhere near Essex, get it to me - (C&G 224 certificates say that I know what I'm doing - even if I don't 🙂)
At the very least you'll get a free diagnosis - and (almost certainly) a cheap repair and service.

Otherwise, be sure to get an estimate from whoever. Don't pay more than £60.
(If repairable (it will be) I'd do it for half that or less....just for fun 👍)
 

tonygvng

Active member
Aug 19, 2023
8
8
25
Visit site


They sure did, I had their PM650 amp, capable of a 39 amp peak current output (and it sounded like it).

@tonygvng if you're anywhere near Essex, get it to me - (C&G 224 certificates say that I know what I'm doing - even if I don't 🙂)
At the very least you'll get a free diagnosis - and (almost certainly) a cheap repair and service.

Otherwise, be sure to get an estimate from whoever. Don't pay more than £60.
(If repairable (it will be) I'd do it for half that or less....just for fun 👍)
i am in Italy but thanks anyway for the offer
 
  • Like
Reactions: Gray

tonygvng

Active member
Aug 19, 2023
8
8
25
Visit site
Hello again, another question, i noticed that the amp transformer gets pretty hot after like 30 minutes at 1/3 of the volume , around 50°C/122°F.
is it normal or should i worry about it? thanks.
 

Gray

Well-known member
Hello again, another question, i noticed that the amp transformer gets pretty hot after like 30 minutes at 1/3 of the volume , around 50°C/122°F.
is it normal or should i worry about it? thanks.
You could check that service manual (and any labelling on the transformer itself) for any mention of operating temperature.

I wouldn't worry though, as long as the amp has plenty of ventilation - with nothing obstructing bottom and top vent holes in the casework.

If there were some excessive power consumption due to a fault, a fuse should be first to go.
 
Hello again, another question, i noticed that the amp transformer gets pretty hot after like 30 minutes at 1/3 of the volume , around 50°C/122°F.
is it normal or should i worry about it? thanks.
Is that the transformer itself, or the casing above it? 50C is ok, but you’d not want it much warmer on the casing. You’ll see in Stereophile reviews they test amplifiers for temperature and over 50C isn’t that rare.
 

tonygvng

Active member
Aug 19, 2023
8
8
25
Visit site
Is that the transformer itself, or the casing above it? 50C is ok, but you’d not want it much warmer on the casing. You’ll see in Stereophile reviews they test amplifiers for temperature and over 50C isn’t that rare.
the temperature was measured on the steel casing under the transformer with the lid closed
 

Jasonovich

Well-known member
Jul 28, 2022
1,115
680
2,070
Visit site
Yeah it sounds like something has failed on the output stage, it could be dry solder and if it is just that, it should be easy to repair. It could even be corruption of the left and right outputs, where the two are 'touching', so two becomes one.

You could if you feel comfortable doing it, open the case lid and have a look inside. Does anything smell like it's burnt or can you see areas that look like it has melted? Also check the integrity of the soldering and simple joints. Don't touch anything, just gaze over for anything that may be the cause of the problem,
Please and I know it's obvious, do make sure the amplifier isn't connected to the mains and NEVER put your fingers under a capacitor (you'll get a nasty kick, God knows how many times I done that building PCs!)

Best to have it checked out by someone qualified.
 
Last edited:

WayneKerr

Well-known member
Yeah it sounds like something has failed on the output stage, it could be dry solder and if it is just that, it should be easy to repair. It could even be corruption of the left and right outputs, where the two are 'touching', so two becomes one.

You could if you feel comfortable doing it, open the case lid and have a look inside. Does anything smell like it's burnt or can you see areas that look like it has melted? Also check the integrity of the soldering and simple joints. Don't touch anything, just gaze over for anything that may be the cause of the problem,
Please and I know it's obvious, do make sure the amplifier isn't connected to the mains and NEVER put your fingers under a capacitor (you'll get a nasty kick, God knows how many times I done that building PCs!)

Best to have it checked out by someone qualified.
Keep up Jason, he's fixed it :)
 
  • Like
Reactions: Al ears

TRENDING THREADS

Latest posts