Leak Delta 30 cracking, humming and popping

[jsmac]

Hi all,

I've recently acquired a freebie Leak Delta 30 from one of the members of this forum. Unfortunately, the right channel has a pretty aggressive sounding crackling and popping sound when the amp is turned on. As the volume is turned up the sound gets worse and then it goes away when the dial gets to about 12 o'clock.

Both channels also have a pretty noticeable humming/buzzing coming from the speakers.

The crackling/humming occurs even when there is nothing connected to the amp other than the speakers.

I'm really at a loss as to where I should begin with isolating and addressing these problems and so would appreciate any thoughts and advice.

Thanks.

Scott

 

[reddish75]

Start by cleaning the switches and pots with deoxit and see where that gets you.

Secondly replace the main psu capacitors and see what that does to the humming/buzzing on both channels.

 

[jsmac]

Thanks, Chris.

I'll order a Deoxit kit and see how I get on.

Replacing the capacitors sounds like a somewhat more involved job so a bit more research will be necessary.

Thanks for pointing me in the right direction. Knowing what to ask google makes these kind of repairs so much more straight forward.

Cheers.

 

[SergeAuckland]

If you're anywhere near East Anglia, I'd be happy to replace the caps for you. I have a Delta 30 myself, so am familiar with the circuit. Nice amplifier, capable of decent results into efficient loudspeakers.

I echo the suggestion to clean the pots and switches, although without getting inside my Leak again, I thought that the volume and tone control pots were sealed. If so, then a crackly pot may need replacing.

S

 

[jsmac]

Thank you, Serge. I may well take you up on your offer. I'm in east London so not too far away.

I can't tell for certain from the pictures of the inside of the Delta 30 on Google whether the pots are sealed or not. I guess that I'll have to open it up and have a look.

Thanks, again.

 

[SergeAuckland]

Looking at this image from Google, they don't look sealed so you should be able to squirt in some contact cleaner.

The 6 large capacitors should also be easy to change, but I'm happy to do it for you if you prefer.

S.

 

[JPG]

Hey, that's my photo (pre re-cap).

Cleaning the pots is a good idea, especially as your crackling seems to be improved as you turn the volume pot. However it'd be worth re-seating the PCBs. Mine was popping loads, and it seems that it was mostly the PCB edge connectors. IIRC I tightened up the contacts a touch by pinching them together with a small screwdriver. Be gentle though, they're not the most robust metal. And don't go overboard, or they'll scrape the PCB a bit. Cleaning the all the connectors with de-oxit or similar is probably a good idea: the plating isn't very corrosion resistant IME.

If you do go for a full re-cap, watch out for the PCB traces lifting - they're very heat sensitive. Otherwise it's all pretty simple stuff.

Finally, check that the fuses are the right type - 1A quick-blow IIRC. If they've been replaced with higher value or time-delay fuses you're far more likely to pop the output transistors in the case of a short on the output.