LSS schematic / help?

Classics and Specials

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tubeydude
Mark I
Posts: 43
Joined: Tue Mar 20, 2007 2:44 pm
Location: santa ynez, CA

LSS schematic / help?

Post by tubeydude » Thu Sep 30, 2010 1:03 pm

Hi all,

I am looking to find a schematic of the LSS. I've found a couple of the classic, but I've got an amp here that needs repair after redplating a couple tubes. This is after a tube shorted and probably caused the damage. Screen grid resistors and grid resistors all replaced already. I think one or more of the cathode resistors have also been taken out, but it is pretty tough to see where the signals are going with the density of the board. Anyway, any help would be great.

Are there any known issues with LSSs redplating tubes? I'd also like to check the bias supply.

Thanks,
'91 Mk IV
'09 Mark V
'89 Studio Pre

tubeydude
Mark I
Posts: 43
Joined: Tue Mar 20, 2007 2:44 pm
Location: santa ynez, CA

Re: LSS schematic / help?

Post by tubeydude » Fri Oct 01, 2010 4:24 pm

Bump...

Anyone? It looks like the LSS is Cathode biased. (at least there is no negative voltage on the grids) However, I can't tell how many resistors are connected to them. There is also a relay that takes a couple in and out of the circuit. That is how the bias points are likely changed when switching power levels/class operation.

But, I'd really like to see a schematic to verify what I can surmise by looking at the complex board.

I've got a call in to boogie and they of course told me that I would not be getting a schematic from them. That's ok I understand their position. Hopefully the tech can let me know what and where the likely faulty component is.
'91 Mk IV
'09 Mark V
'89 Studio Pre

thom
Mark II
Posts: 91
Joined: Mon Dec 29, 2008 9:25 am
Location: Leicester, England.

Re: LSS schematic / help?

Post by thom » Sun Oct 03, 2010 10:11 am

Sorry. I tried to get the schematic also, from Mesa's UK distributor. Turned me down flat..........

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