alright well i was getting kinda tired of the stacked massive 12x12s and coffee tables
so rather than lay on the couch and watch football (at least what we in the US call football)  I decided to build a new set up from existing lumber gathering dust

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it was very muggy and humid out....

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finally got it in and everything swapped out

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and its immediately obvious as i lay here on the couch finally watching the evening game that those 2x4 toe boards have to go

oh well not tonight

its a work in progress i suppose

looks more like some bunk beds than work space

it is def much lighter than the previous set up so that is an improvement

 

This amp is called Combo Head II, it is in a small 12 inch combo, model CMD121P Will study the  SMPS fundamentals.  Will need it, I have established that there is 120v going in, but no power being supplied to fan, preamp, etc,. 

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[Edit: Ok, I figured out a way to get photos on here. I haven't had time to open up the amp again, but I'll try to get gut pics at some point.]

As far as whether or not this is a good platform, I think it's ok. The pcb has flimsy traces and it isn't silkscreened with part numbers, so you need to do detective work to find the part you intend to replace. The speaker it comes with, the Celestion G12K-85, is a bit bright in this amp. The shelved low pass I installed (the 68n in series with the 820 ohm resistor) worked well for the G12K-85, but made the amp too dark for other extension cabs. I had to change the 820 to a 1k5.

The are some big positives for this amp. The cabinet is sturdy. Even stock the clipping circuit is sufficiently tube-like in tone. And, these are relatively cheap on the used market. Just a few tweaks and I got a great, dynamic metal tone.

I tried to post earlier. Do you want a working variac? If so PM for details.
nosaj

I could not see the schematic, so I will post the ones I have if someone is interested.
Photos would be very nice.You cannot view this attachment.You cannot view this attachment.You cannot view this attachment.   

while I got you here I am really struggling with trying to understand how to be safe with oscilloscope grounding.
I was going to put a two prong adapter on the cord to unground it but maybe that is not a good idea.
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It has been a long time since I used my scope, and my scope is a real CRO.
I usually use one ground clamp that I attach to the 0v rail, as long as the 0v rail is grounded.

All my probes have a removable ground wire so all I am left with is the probe itself, I leave one probe with the ground wire attached.
My old "cathode ray oscilloscope" is nothing like the modern units most people have today, turn it on, have a cupper, use it.

What model are we talking about ?
I have only one Mark Bass service manual, the Little Mark 2.

You have to deal with SMPS to get anywhere with these kind of amps.
see attached

another one here:  https://docs.google.com/viewer?a=v&pid=sites&srcid=Y2Fyc3UuZWR1LnBofGpiaGFsaWJhc3xneDoyYjgyY2E5OTZmN2FjZWQ0

Has anyone looked at or attempted repair on these types of amps? I bought one non working for parts for a song... but now I see the complexity of such a device .   It seems that they are stingy with schematics and all roads lead to approved repair shops. This one won't even power up... no power LED, no fan, no life at all.   Just learning about class D, fascinating stuff!

I was watching a video on my tv and took a pic of the screen

anybody recognize these guys 



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