[rescue] urgent need for Sun Hi-Res monochrome monitor (or repair

[Geoffrey S. Mendelson]

Greg A. Woods wrote:

> One of the electrolytics may be dry, and perhaps one of the diodes is
> shorted (there's even a bridge that gives low resistance readings in all
> directions while in-circuit).  If I can find suitable test loads I may
> try fixing this one on the bench, but I must say I'm no expert in SMPS
> troubleshooting (though I've recently read about all there is to read on
> the subject on repairfaq.org and other referenced sites).  I doubt I
> have enough good replacement parts in my "shop" though so it really
> would be nice to know what I need to buy before making many trips to the
> store.....
> 
> The other two exhibit what is apparently a classic failure mode where
> the SMPS makes an ever-repeating whining clicking noise.  One would
> eventually "warm up" and work, but as of this morning it now makes a
> fainter and faster cycling noise which takes quite some time to fade off
> after the line power is removed.

IMHO once a SMPS starts sparking or clicking, they are beyond economical
repair. The problem is that the designers put in just enough "self
defense" electronics to prevent it from bursting into flames, but not
enough to save the critical components. So when you see sparks or hear
clicking something went wrong and took many other components with it.
:-(

Before you go about fixing these things see if you can locate a wiring
diagram and hopefully get a PC supply to power it.

> FYI the SMPS module is a little 5x6.5" motorola board labeled PSM-7458.
> I can apparently order one of those for $20 from:

If it works with the PC supply, you can then make a decision to be a slob
and have the PC supply out back (or with long enough wires under the table),
or buy a new power supply.

You should look at the faq (www.repairfaq.org I think) and ask on 
sci.electronics.repair. There you will find people who do fix these things
day after day. (as opposed to me who just figures out who to fake them)

Geoff. 
-- 
Geoffrey S. Mendelson
Bloomberg L.P., BFM (Israel) 2 hours ahead of London, 7 hours ahead of New York.
Tel:  972-(0)3-754-1158 Fax 972-(0)3-754-1236 Email: gmendelson at bloomberg.com