Mesa Dual recto Questions

[Valvehead]

Hopefully theres a couple of ya familiar with these , Ive never been inside one.

Ive got a Dual Recto Solo head here, the board is dated 2000 . None of the online scems seem to match up as far as the B+ caps in the preamp .

This one has 7 , 10uf/450v all on the first half of the preamp section . The scems show 4 - 30uf caps, am I missing something? I dont see any 10uf/450 on the schematic.

Anyway, the amp has a loud ,nasty buzz/hum that goes away when V2 is pulled . I have swapped out ALL the tubes. Im guessing a filter cap along the rail ?


Plate voltages dont match the scem either . Im getting :
V1 (1) 179v , (6) 227v
V2 (1) 235v , (6) 306v

0 volts on the first 4 grids.

[Pedro Vecino]

Hello. If the amp is Dual three chanels itīs less probable that it has problems with filter capacitors. Verify the transistor (J175) that controls the assignment of 470K grid resistor of v2A. Is paralled to that resistor and if is damaged (I have seen several times) it produces the effect that you say.
Regards

[Tubis]

I have the right schematic if you like?

[Valvehead]

ill look at that Pedro. I dont see a J175 on the scem so far


yes Tubis, send to 493dart AT gmail.com . Thanks

[Tubis]

ill look at that Pedro. I dont see a J175 on the scem so far


yes Tubis, send to 493dart AT gmail.com . Thanks

Mail in the box.

[Valvehead]

got the mail. thanks!

so J175 , is that a Mosfet or ?

its stamped:

175
C236 AD

[Gtr_tech]

got the mail. thanks!

so J175 , is that a Mosfet or ?

its stamped:

175
C236 AD

Jfet switch

[Valvehead]

it wasnt J175...