Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => The Newcomer's Forum => Topic started by: GeezerB on September 23, 2023, 10:54:53 AM

Title: MarkBass/Class D amplifiers
Post by: GeezerB on September 23, 2023, 10:54:53 AM
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!
Title: Re: MarkBass/Class D amplifiers
Post by: g1 on September 23, 2023, 12:17:37 PM
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
Title: Re: MarkBass/Class D amplifiers
Post by: Tassieviking on September 23, 2023, 12:35:48 PM
What model are we talking about ?
I have only one Mark Bass service manual, the Little Mark 2.
Title: Re: MarkBass/Class D amplifiers
Post by: GeezerB on September 24, 2023, 08:04:42 PM
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,. 
Title: Re: MarkBass/Class D amplifiers
Post by: mandu on October 09, 2023, 07:58:10 AM
Disconnect the SMPS and power the amp with regular transformer power supply.
The problem could be elsewhere.
Regards.