Solved! Technics SU-Z990 operational issues

[windows-xp]

Hi all,

Recently I've encountered some issues with an old (late 1980's) amplifier I decided to get going again. For example, when the unit is turned on there is quite a loud spike that is heard through the speakers when the relays click on. This is also heard when selecting another input, turning the volume up or down and when it is turned off. It's also worth noting that there was a small amount of liquid spilled on the unit many years ago, but it was repaired in quick time and has operated fine since then. The unit does work, on all inputs too, this is the only issue.

So I ask what could this be? I've got a few ideas but whether or not they're true I'm not too sure.
And, is it worth repairing it.

All help appreciated.
Many thanks,
Nicholas

 

[americanaudiophile]

Sounds like you have some DC on the speaker outputs.
Might be a DC blocking cap or an adjustment on the amp board.
You can get the service manual here
https/www.hifiengine.com/manual_library/technics/su-x990d.shtml

 

[windows-xp]

Sounds like you have some DC on the speaker outputs.
Might be a DC blocking cap or an adjustment on the amp board.
You can get the service manual here
https/www.hifiengine.com/manual_library/technics/su-x990d.shtml

I thought that would be the problem but hoping it was not.
I busted out the voltmeter and took some measurements. You're right, there certainly is DC there. The highest peak I measured was 1.565 volts! There's something definitely not right there.
I'll pull it apart, have a look at a few components and see what I can do.
Thanks for the repair manual too.
Cheers for your help,
Nicholas