Clean 1 issue on a Mesa Quad Preamp

[Hexa]

Hello,

I'm a new owner, of a mesa quad preamp, for now two weeks. This preamp is absolutely perfect for old mesa boogie sounds I was looking for )

What is less good is the sound on the clean 1 channel (which is set to be really clean on my side) which is decreasing and becomes crispy after, between 20 and 60 min of playing. Sometimes it comes down and up again :? . It's only the clean 1 of channel 1 which is having this issue ... channel 1 drive sound seems not to be affected :?

Yesterday, I've changed tubes for new JJs on BOB advices (Eurotubes) ... but the problem is unfortunaly still present (

The first infos I was able to get on internet are focusing on a tube socket bad solder or a LDR opto cell issue

What do you think about ?? Did someone got the same kind of issue with his Quad preamp ?? (I'm trying to get a maximum of information before doing anything in the Quad :wink: )

Many Many thanks in advance

Seb

 

[Gregwor]

It's rare in my experience to find a Mesa with bad solder joints but check them. Otherwise it could be your LDR's or caps on ch 1. I don't think it's a voltage supply issue as your 2 channels share the same plate voltage.

... ??? I dunno.

 

[Hexa]

Thanks for the reply Gregwor...

Actually I've ordered some LDR VLT5C1 and will try to replace all opto cells related to channel 1...
The problem is it's not something totally broken but something not working well :?

 

[Hexa]

LDRs were the culprits ... after changing all of them, the quad is back again to his original sound