Mitsumi 68-4242a

[Bikerbob]

These are the power supplies I have in my MegaST computers (3 of 4) I have never seen these listed or tested.

The large Cap on this one is a 220ohm 200v. I can find a Panasonic 105deg good size FR series (digikey does not list esr) at this rating - very common.

Do I - or should I up the value on this one for a recap? Some of the smaller ones were a little dodgy.. this one looks great. The PSU was dead though, no fuse blown - but it had been removed not working. I get values or continuity through all tested caps and resistors, I have not tested with power or load yet.

James

anotherpsu2.jpg

anotherpsu.jpg

[DoG]

What model number does it say on the sticker underneath the metal stand the board screws into?

You should be able to find PSU schematics on https://docs.dev-docs.org/ after that.

[exxos]

Kinda looks like some revision of a SR98 to me, but not seen that exact version before.. The SR151 is totally different.

https://www.exxosforum.co.uk/atari/last/psu/index.htm

Looks like the SR98 was 68-4237?

Looks like they must have moved to a smaller opto.. then had to move the trimmer the other side of the heatsink to keep it away from the HV side. So maybe they couldn't get that older opto anymore and had to change to a alternative part towards the end of the production runs.

[Cosmic Puppet]

SNAP! I have the exact power supply on my STFM.

[exxos]

SNAP! I have the exact power supply on my STFM.

What is the model number on the bottom ?

[Bikerbob]

What model number does it say on the sticker underneath the metal stand the board screws into?

You should be able to find PSU schematics on https://docs.dev-docs.org/ after that.

Nothing not a sticker anything on any of the trays.


So what about the question of upping the value of the hivolt cap.. 220ohm 200v?? should I up that?

I have a megaST where the PO replaced it with a meanwell.. I am going to keep that in.. as its 50w and I am putting in a PAK68/3 and they suggest getting up to 50w to have all the EXTRAS. :)


James

[rubber_jonnie]

I'd be tempted to go fo a Meanwell, at the price they are a steal and if you're going to add the PAK then you can be pretty sure it'll be more than up to the job.

[Cosmic Puppet]

SNAP! I have the exact power supply on my STFM.

What is the model number on the bottom ?

It's 68-4242A

[exxos]

It's 68-4242A

Odd theres no sticker on bottom with a proper part number though, I'm just going to call is "SR98 REV1" and there, problem solved :)

[Bikerbob]

Another MegaST2 and another 68-4242a. A batch that came out of the factory with this one and went to Canada I guess.

James