where to buy LDR to fix my Mark IV lead channel problem

[Nico66]

From mesa directly? Any help please

 

[Bugeyed Earl]

I bought a handful of them from Allied Electronics recently, they're around $6 each.

 

[sduck]

Allied is about the only place in the US you can get them. There's another place in europe, don't remember the name. Mesa is the biggest buyer of vactrols in the world - about the only other group of people using them in any quantity is modular synthesizer makers - I think Buchla is the second biggest buyer.

 

[Nico66]

Thanks guys! I have switching problems with my Mark IV B. When I switch to lead channel from the switch selector in the back of the amp, i get not gain but a soft sound sure not correct. Also the lead gain red led don't blink so it must be a problem with some LDR optocoupler I guess. Is there a way to test them individually in the circuit? Any help will be welcome. I don't have any Mesa service Center in my country.

 

[Bugeyed Earl]

I replaced mine because there were only four in the amplifier, so it was a cheap fix, but I didn't attempt to test them in the circuit. If I had done that, I would have found that they were not faulty after all. From what I've read, LDRs don't fail very often.

 

[sduck]

Yes, just replacing them is probably easier than testing them. However, in the mark iv there are a LOT more than 4 - maybe 10 times that number of them. And they're stacked up in various places, so messing with them in any capacity is a huge undertaking. Really, your best bet is to send it back to Mesa - but that's a long way from you, so I don't have any better answers, - sorry!