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Mega ST2 psu failure

Posted: Sun Sep 23, 2018 12:35 pm
by Erikswe
I got myself a Mega St2 and it doesn't power up at all, nothing at all happens. I thought I would start with the PSU. It has a Mitsumi sr188 Psu. Will the PSU start without load?

Re: Mega ST2 psu failure

Posted: Sun Sep 23, 2018 12:39 pm
by exxos
Erikswe wrote:
Sun Sep 23, 2018 12:35 pm
I got myself a Mega St2 and it doesn't power up at all, nothing at all happens. I thought I would start with the PSU. It has a Mitsumi sr188 Psu. Will the PSU start without load?
No, you need to load them for them to work properly. Lots of info on my site about PSU's..

http://www.exxoshost.co.uk/atari/last/psu/index.htm

Re: Mega ST2 psu failure

Posted: Sun Sep 23, 2018 1:53 pm
by Erikswe
Thanks for the fast answer. Well I did read there and it says the PSU don't work good with out load...
I have taken it out of the ST. It looks very much alike the sr98

Re: Mega ST2 psu failure

Posted: Sun Sep 23, 2018 1:54 pm
by Erikswe
Ahhh sorry...my English must be rubbish!! I totally misunderstood your answer...sorry!!!

Re: Mega ST2 psu failure

Posted: Mon Sep 24, 2018 11:42 pm
by atari030
Does the PSU tick by any chance? I have a pair of Mega's with odd PSU faults, so I'm curious to know.

The 12v fan on mine won't kick over unless the PSU is disconnected.

Re: Mega ST2 psu failure

Posted: Tue Sep 25, 2018 6:32 am
by mikro
Yes, ticking is normal. See also here: viewtopic.php?f=9&t=937

Re: Mega ST2 psu failure

Posted: Tue Sep 25, 2018 7:19 am
by atari030
Without hijacking too much, PSU plugged in - no 5v, no fan spin. PSU unplugged 5v OK and fan spins (no tick). This happens on two PSU's and two Mega's, one PSU is recapped and had the rectifier bridge replaced, one not. If I plug in an STFM PSU - no problem, Mega's work fine. Just plain weird.

Re: Mega ST2 psu failure

Posted: Tue Sep 25, 2018 8:10 am
by exxos
I think someone else had the same problem, can't remember what thread is was though.. probably bad solder joint on the PSU somewhere.

Re: Mega ST2 psu failure

Posted: Tue Sep 25, 2018 12:12 pm
by atari030
I wouldn't have thought it would be a bad joint on two PSU's. When the garage warms up a bit I will get in and have a closer look. ATM it is pretty cold in there. :D