Question Harman Kardon Amplifier

[tonygvng]

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]

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.

 

[tonygvng]

it was stored in perfect conditions and i powered it for the first time since 2005/2008 but thanks for answering.

 

[JDL]

If you particularly like the amp and want to keep it, it seems you'll need to find yourself a repairer. If not, it's probably time for a replacement.

 

[tonygvng]

If you particularly like the amp and want to keep it, it seems you'll need to find yourself a repairer. If not, it's probably time for a replacement.

It was my grandfather's so i will get it repaired, but thanks anyway.

 

[camcroft]

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.

 

[Messiah]

Have to ask - is the balance control in the centre and not on the right channel?

 

[tonygvng]

Have to ask - is the balance control in the centre and not on the right channel?

the balance is in the center, turned all to the left it plays on the broken channel at like -80dB even if i crank up the volume to the max

 

[Gray]

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]

---

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

 

[tonygvng]

UPDATE: looked at the service manual, cleaned the pots, resoldered a disconnected wire and everything works fine.
Thanks for everything.

 

[Gray]

cleaned the pots

And all signal switches 👍

Great stuff, good for many more years.

 

[nopiano]

UPDATE: looked at the service manual, cleaned the pots, resoldered a disconnected wire and everything works fine.
Thanks for everything.

Brilliant, well done. And congratulations for spelling HK correctly - that’s quite rare too!

 

[tonygvng]

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]

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.

 

[nopiano]

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 case temperature, fully assembled, or the transformer with the lid off?

 

[nopiano]

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]

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]

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.

 

[WayneKerr]

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

 

[Al ears]

Keep up Jason, he's fixed it

However, to my mind, it is still running too hot.

 

[Jasonovich]

Keep up Jason, he's fixed it

Apologies I should have read through all the threads

 

[nopiano]

the temperature was measured on the steel casing under the transformer with the lid closed

Oh, then in that case I’ve no reference point. But you should be able to touch that without discomfort, so personally I’m not sure it’s an issue. But if you checked it previously…