Alesis adat HD24

Hi!

I'm having problems with HD24. Unit have faulty PSU and I would really need schematics. I have service manual for HD24, but it doesn't contain PSU schematic.

Kind regards,
Ivica

elektroivo said:

I'm having problems with HD24. Unit have faulty PSU and I would really need schematics. I have service manual for HD24, but it doesn't contain PSU schematic.

Click to expand...

Hi I must have the same schematics,and somewhere in there it gives the Voltages that the psu supplys,
Maybe a clue in there.
My HD24 is still going strong so never had it open,
Take some pics  of the PSU as i would like to have more info on this...and maybe
give  some pointers in the right direction.
Switch mode I suspect ?
I read somewhere they fail from overheating when sutdown but not swiched off at the rear switch....which i always do.
Possibly only bad caps ?

I'll try to get some photos... but, caps are OK.. I'll replace them tomorow, when shops are open... but, i think that transformer is problem... core is loose and foil changed colour.

sorry for delay... long holiday weekend... I've replaced caps, that didn't solve problem.
I sketched portion of circuit schematic, and realized that it is simple implementation of TOP227 IC. I've made some measurement according to TOP227 datasheet, and determined that IC's auto restart doesn't work properly. Auto restart loop should occur when PSU is out of regulation (overload, short circuit, etc). there is no such situation. So I'll replace TOP227, hoping to solve this.

Ivica

I've replaced TOP227... that reduced voltage at control pin of TOP227, but, PSU was still down. Then I've replaced optocoupler, and PSU works OK.

I've found some info on net about this matter. It is not uncommon for HD24 to start having problems with turn-on. People who replaced caps in PSU emediately when such event ocured had no problems for few years. In this case, that was not done in time, so damage was  greater.

I hope this thread would help someone in future.

best,
Ivica