Mesa Mark III, What is this...?

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jkkkjkhk

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I opened my blue stripe Mark III today to take a look around and snap some pics to compare to other gut shots. I found this weird little box that I can't find in any other mark III's. Anyone have an idea what this is? The board around it looks burnt and the solder job isn't the cleanest so assuming it's not stock. To anyone who knows these amps, does everything else look stock to you? blue stripe, simulclass, reverb, GEQ.





Thanks for any help

Edit: after looking around a bit I've finally realized my blue stripe is actually a green stripe. Pretty cool, now I'm interested to hear how different triode is.
 
The "weird little box" is a wirewound resistor. It is part of the power supply for the channel switching.

Schematic calls for a 680ohm 1w in that spot but when that blew up whomever did the fix probably threw in what they had. If the channel switching works ok I wouldn't be too concerned about it.

The amp also had a couple other resistors flame out up near the rectification diodes in the upper left corner. You can see the charring on the 2 remaining metal films and the shoddy soldering on the new components.
 
jkkkjkhk said:
I opened my blue stripe Mark III today to take a look around and snap some pics to compare to other gut shots. I found this weird little box that I can't find in any other mark III's. Anyone have an idea what this is? The board around it looks burnt and the solder job isn't the cleanest so assuming it's not stock. To anyone who knows these amps, does everything else look stock to you? blue stripe, simulclass, reverb, GEQ.





Thanks for any help

Edit: after looking around a bit I've finally realized my blue stripe is actually a green stripe. Pretty cool, now I'm interested to hear how different triode is.

Same answer as Rig-Talk, blown resistor in LDR supply.

Per previous response, stock is 680 Ohm - 1W.

Mine blew out as well about 25 years ago.

I did the same thing and replaced with 5W, but used a carbon and prettied it up a bit.
 
Thanks for the replies guys, good to know nothing is messed up.

Jupa: Thanks for pointing out the other burns. Is it anything to be of concern? Everything works as I imagine it should.
 

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