Mark III Repair

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emilesinclair

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i am new here so hello everyone!!

i just got into the mesa family! bought a mark iii online, but unfortunatly, i received the amp damaged (3 broken tubes) and when i switched it on (with new tubes obviously) i got no sound, very (very!) distant guitar when i dial the volume up but i heard "pop" and bursting sounds and so i switch back off the amp immediately..

i open it and saw that a part of the circuit looked burnt. 2 diodes seem to be really burnt.
i did not smell smoke when i switch the amp on.
it's an export model and since i live in france i put the selector on 220V so i guess it's all good.
i don't know what the ground switch is about, it was in the middle position.

here is a picture of the burnt circuit.
http://emilesinclair.free.fr/pictures/mark%20iii%20repair/

i recall that i had a en effect pedal and i burnt a diode someday when putting the wrong polarity. so maybe something went wrong at some time and these diodes are for protection?
i am a noob at electronics but i can solder and if i only need to replace the diodes, i can do that i guess!

thanks in advance for your time and tell me if it's the wrong place to put this topic or something else.
 
Update:

i read the manual...

it says that if i plug my guitar in the effect return jack, and that i hear sound, then V1 and V2 tubes are at fault.
i did hear sound so it looks better than i thought!
however, the sound was crackling. but maybe it is just the sound of bad tube?
or do you agree with me that the diodes looks pretty bad too ?

thanks!
 
Update 2:

the amp works!.. i feel a bit stupid but so happy it works so it doesn't matter haha..

i did not change any of the tubes, but just waited longer and not being afraid of the crackling sounds
it stops after 30 seconds and then it works normally!

someone sent me a private message and we started to talk.
he told me that the amp is oxided and need a good cleaning, so maybe it's that that causes the crackling sounds!
i will keep the topic updated.
 

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