Boogie Mark IIA XPHRG S/N 4689 129/01/1980 - restoration

[Marvel]

Hi all,

My first post to this fantastic forum

I got this Boogie Mark IIA some time ago but have had no time or parts to restore it, until now.

I installed a new power transformer from tubeampdoctor.com (the old one burnt, I got the amp with some toroid), replaced all the electrolytic caps (TAD, too), as well as some resistors (power amp, bias supply, one open 150k PI resistor). New set of TAD tubes as well.

I also drew the schematic in the standard format (from left to right :wink: ).

As soon as I check the reverb circuit I'll take notes of all the voltages and put them on the schem.

I'm also thinking about removing the fetron mini-circuit, but I'm not quite sure what value of the dropping resistor to go for. Any suggestions?

I'll post the pics of the complete combo (original purple tolex) as soon as I finish the amp.

Hope this small contribution to the forum helps some Mark IIA owners.

Schematic in .PDF format:
http://marvelamps.com/wp-content/uploads/2012/09/Boogie_MK2A_schem.pdf
Schematic in .GIF format:
http://marvelamps.com/wp-content/uploads/2012/09/Boogie_Mark2A_schem.gif

 

[McBarry]

Gee, I bet TAD love to see your orders coming in..hehe..
A really nice clean chassis there, and love the neat looms now.

With the fetron out, the rail sees the 33k. With fetron in, it sees 10.3k - maybe try the 33k and see what the voltages do?

That's a very clean looking PSU board too.

Can I ask, was it R41 which was dead? What symptoms - what lead U to suspect it?

Nice score, DB

 

[Marvel]

Thanks

I'm in Europe, so actually have no choice but TAD. I'm not complaining though - they're top quality IMO.

Yes, it was R41 in my schematic. I should've known there was something wrong with the PI right from the start, cos the output sine wave on the scope was not symmetrical. But I sort of disregarded it... I found the open resistor when I was drawing the schematic - I double chceked all the resistors and some of the caps with DMM, not only read the color-coded/ printed values.

 

[mark2boogie]

When it come to Boogie MKIIA, you see the few owners coming in...

I removed the FETRON switch as I needed a place for a hum balance pot, and replaced it with a 10K 2W resistor.

Thanks for the nicely traced schematic, marvel (marcin?)

A+!

 

[mark2boogie]

I'm in Europe, so actually have no choice but TAD. I'm not complaining though - they're top quality IMO.

Not IMO, marvel... I strongly suggest you to test the transformer before installing it... Otherwise see my thread about my MKIIB for more information.

A+!