Help repairing LA-610 SE that is distorting when compressing

[Rockman]

I just recently got hold of a la-610 signature edition for really cheap well knowing that the compressor had some issues, which i hope some up you more knowledgeable types might be able to help me troubleshoot:

here is what i know:

1) when set in the bypass mode everything works just fine and sounds really nice (as a 610 does)

2) when switched to comp or limit and peak reduction is set low it sounds fine.

3) once peak reduction is turned up so compression is audible (the meter shows 5-7db peak reduction) there is a audible distortion is the mid/treble area.

4) i have tried swapping V2-V5 for other tubes (without biasing V5 though) one at a time and it did not seem to fix the problem.

Any bright ideas on what the issue might be and how to fix it, for starters if anyone knows which tubes are related to the compression circuit and which are related to the preamp it would help a lot as it would narrow down the area to be tested (solder joints resistors etc)

 

[shabtek]

What if the metering circuit is disconected?

 

[Rockman]

Dunno, will check (you men just disconnect the wire connectors from the metering board?)

And out of curiosity, how would the meter cause distortion. BTW the meter works fine on input /output metering

 

[Rockman]

I disconnected the meter itself and the problem persisted

Should i have disconnected more than the meter itself ?

 

[CJ]

does this model have the T4 opto modules? 

 

[Rockman]

Yes it has a horizontal mounted T4 module (with a black box mounted over it)

 

[Rockman]

Bump.... yes well, issue is still not fixed, i have been accepting the Non-compressing LA610 as is.
If any of the bright minds in here have some ideas im all ears

 

[pucho812]

you could try and replace the t4 if you have spare and see if that resolves anything. You could also check for faulty solder joints and or failed components.

 

[Rockman]

ok, yeah. after testing the tubes  i'm down to either the T4 or perhaps a faulty cap?

In case anyone feels like listening in on the noise here is what the unit sounds like with GAIN -5, LEVEL 6, output GAIN 7 (with and without PEAK REDUCTION at 3.5)

https://soundcloud.com/johan_simonsen_abildgaard/sets/la610-se-comp-issue

 

[pucho812]

ok, yeah. after testing the tubes  i'm down to either the T4 or perhaps a faulty cap?

In case anyone feels like listening in on the noise here is what the unit sounds like with GAIN -5, LEVEL 6, output GAIN 7 (with and without PEAK REDUCTION at 3.5)

https://soundcloud.com/johan_simonsen_abildgaard/sets/la610-se-noise-when-compressing

have you contacted UA about this?

 

[Rockman]

Good point Though the unit is out of warranty, they might have an idea where such a fault could lie.
Being based in Denmark, shipping it to US and back would not an option, so i did not think to write them.

 

[pucho812]

Good point Though the unit is out of warranty, they might have an idea where such a fault could lie.
Being based in Denmark, shipping it to US and back would not an option, so i did not think to write them.

it never hurts to ask the source.  I did a bench stint for a pro audio manufacture. When you sell enough of the same units, you can pin point common issues and how to address them.

 

[David Kulka]

Likely the T4 is bad.

 

[rackmonkey]

David's seen enough of these to know. Get a new T4 and see if that does it for you before you waste time on anything else.