Mesa Mk I '77 Combo 2 x 6L6 pre amp SP-3 photos or circuit

[Michael-vactron]

Hello Everyone from Mick..This is my first post,thank you for the opportunity to do so.Late in 1977 I bought a Mesa boogie MK1 50 watt combo,there were some mods to use a green bullet mic for harmonica,after more than 20 years in the wardrobe I now want to restore the original circuit for my son to play guitar.Unfortunately what was changed has been long forgotten.I contacted Mesa in the USA for help with an original circuit.The techs were very helpful but the supplied circuit did not match my amp-the circuit has a 12ax7 phase splitter driving 4 x 6L6's.My amp had a fetron [ long since replaced ] 12at7 splitter driving 2 x 6L6's.Several other sites have circuits but not quite the right one for this amp.There's no graphics or reverb and it's a 240 volt export model.What I would appreciate is some inside photos of the pre amp # SP-3 and the input jack connections or a circuit taken from one of the 2 tube models.All the power caps and resistors have been replaced.The pre-amp input voltage is 340 volts, with 100k or 47k [?] plate resistors on the 12ax7's,the unit works well but not quiet as well as it should,all the tubes have been tested on my avo mk 4 meter.The Hitachi AX7 by-pass caps have 1976 stamped on them and the serial # is A 1021.
If anyone can help me here I would be very grateful,many thanks in advanced.Mick-vactron.