Audio left channel silent

[Ludes]

Hi.. I'm new to this forum; or actually any forum... so please excuse my lack of online "jargon"...

I recently got an old Garrard receiver\amp.
I was a big fan of Garrard turntables back in the day... and actually still have one packed away.

   So I really want to find out why this Garrard Model 528 isn't
putting any sound out the left channel.
  I have a strong electronics background, but no experience with audio.  I can identify and test components.. Strong soldering skills.. and a decent rework station.
  I don't have an oscilloscope, I do have a good meter and variable power supply.


   I'm hoping someone here has fixed failed channels before, and can tell me where to start.


Thank you

[tpowell1830]

Welcome to the forum, there are many audio folks here.

You really need the schematic for the channel in order to be able to troubleshoot, or you could take a look in the box and start tracing the circuit and watch for obvious flash marks or smoke trails.

If you get the schematic, then post it here as well. Pictures can also be helpful.

[Armadillo]

Firstly, I suggest you do the obvious and basics like swop the input signal cables, clean all the mechanical switches with contact cleaner, swop the speakers etc...

[vk6zgo]

Your good channel is your best diagnostic aid
To start with, all the DC voltages should be the same on both channels.
Swapping things over also helps.
An Oscilloscope makes signal tracing a breeze, but you should be able to " bodge up" a signal tracer using the audio stages of an old radio or similar.

[Ludes]

Thank you for your replies..

I did try all the obvious tests.. cleaned volume and balance pots.. swapped speakers etc.. Right side sound beautiful, left side is silent.

Then I opened it up and looked for broken wires, blown fuses, etc..

Tracing backwards the speaker outputs go into the board next to the transformer.

I'll try to hunt down a schematic but I'm not hopeful since it's old and the company changed hands several times before folding.

One of the caps inside the heatsink feels slightly popped.. I ordered some already. Not sure if it could even possibly be that but it was only $2 for 5 so I gambled.

[Armadillo]

I would say you are moving into the right track.
The capacitors would be the right things to do especially those smaller electrolytic caps.
If its bulk, change it, considering the age.

But as for "completely silent", something should be opened otherwise it should at least "hiss", "crack" or "hum".
Check all types of fuse, resistor fuse or something like that.
Do a mirror voltage measurement or mirror ohms measurement, at least some.   

[Ludes]

Yeah... I'm worried that I'm not getting a hum or a faint "pre-amp" sound out of that channel..

I pulled the board next to the transformer off the chassis and started looking at the bottom...
There are some power transistors mounted to that heat sink.. and they all look brown and overheated on the solder side of that pcb.   

But if it was one of those the right side would have failed also? 

Those 2200uf 16v caps will be here in a few days.. I'll keep ya'll updated..

Thank you for your help...
 

[lordvader88]

Can u take a little speaker/earbud and attach it between chasis and/or gnd, and a capacitor,  and following between output and audio source, just carefully touch the cap to points to see if u hear any music ?

[Ludes]

Those caps came today.. I'll R&R them tomorrow morning.

[Ludes]

Well I finally got around to R&R'ing that capacitor.. And it worked.
Beginners luck I guess..

It works great now.. both channels..
I replaced the right side Cap as well just for preventative maintenance..

I am so in love with the old tech.. sounds so much better!

Can anyone recommend a good starter book for Audio Electronics?

[lordvader88]

So problems fixed

If u want a cheap and very small oscilloscope I'd recommend a $20 DSO138. It's far more than a toy(like some on here might say) and works up to 200Khz well enough for some stuff. AND IT'S $20.

I have 4 CRT scopes but none of them are isolated from mains earth. Three DSO138 runs off a 9V battery or in my case a 12V transformer. So I can probe away.