JMP 50w Themelo Head

[andresound]

Hi guys. I have been asked by a freind to replace the transformer (he supplied ), for this vintage amp. I am looking for detailed layouts and gut shots, to enable me to return this to as close to original as possible. The board is totally original with associated “dyed” solder joints. Obviously I will have to replace some filter caps where necessary. I will also go over the components to check for any “out of spec” culprits. Any advise or help
Would be appreciated

 

[neikeel]

Looks very original.
Sure test the passives (all +/- 10% or so but don’t be too picky at this stage).
I’d test the caps for ESR and leakage first but most would shotgun the filter caps and bias caps for correct values which is hard to disagree with in an unknown non-running amp.
I’d rewire the screens to incorporate 1k 3w Welwyn’s if you don’t have any xf2 Mullards for it.
What PT has he given you? Marstran or Merren most accurate. Merc mag ok but likely self wire so you will not be able to mount diodes on the PT HT lugs as stock (likely need to find a chassis mounted diode block). Classic Tone are quite nice but often have 10-15% high HT voltages c/w stock.

 

[andresound]

Thank you for the swift replay. Agreed on the screen resistors. Yes, the diode bridge will have to find a new “spot”. Schematic shows half bridge (2x Diode). Should be a nice sounding amp.