Dead x68000 compact power supply , need help!

[gypsie]

Hi everybody.

My x68000 compact stop to work suddendly.

When i push the power button, nothing happen. There is no light on the front panel.

I've tested my 68k with another PSU and it works perfectly.

So the PSU must be dead...

I've checked inside the psu, everything is in good visual condition (no leaking capacitors).

The fuse is OK !

Do you thing that replacing the caps could revive the psu ?

This is the picture :



Thanks for your help!

Gypsie

[eidis]

 Hi Gypsie !

Almost 80% of all failures are caused by the capacitors. In this case they are way past their expected lifetime so they need to be replaced. The following link might help.

X68000 Compact/030 PSU Schematics
http://nfggames.com/x68000/Schematics/PSU/X68000_Compact_030_PSU_Schematics.pdf

Keep the scene alive !
Eidis

[gypsie]

Thank eidis, but i'm afraid to do caps replacement for nothing (it's long to do and big capacitors are expensive)..

[BlueBMW]

Typically capacitors will revive a dead / dying compact PSU.  Definitely worth a shot.

[gypsie]

Ok i will do it.

[RetroRepair]

As eidis stated, even if they are ok it's worth doing as if they do leak they will likely short and destroy the PSU. Of course some just dry out but better safe than sorry.

All capacitors will fail at some point, it's just a matter of how and when. These are getting on for 30 years old so...

[caius]

More than capacitors I think you should check zener diodes (especially the one marked as 'ZD12' on schematics, it seems this is very prone to failure on this PSU model) and MOSFET (2SK1101).

[BlueBMW]

Or you may consider just going ahead and doing a PICO PSU swap on it.

[gypsie]

More than capacitors I think you should check zener diodes (especially the one marked as 'ZD12' on schematics, it seems this is very prone to failure on this PSU model) and MOSFET (2SK1101).

Interesting. I will check that.

Thanks

[gypsie]

Found ZD12 but can't find mosfet 2sk1101 (Q1 on schematic)

[caius]

There should be.Maybe it's marked 'K1101' or has been replaced with an equivalent one.

[gypsie]

Mosfet q1 found. I will test them.

[gypsie]

Do you have informations about ZD12 and mosfet 2SK1101 ? voltage, type etc...

Is it the good one : http://www.ebay.fr/itm/2SK1101-FUJI-SEMICONDUCTOR-TO-220-/200913256568?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item2ec75d0078

Thanks

[caius]

Do you have informations about ZD12 and mosfet 2SK1101 ? voltage, type etc...

Is it the good one : http://www.ebay.fr/itm/2SK1101-FUJI-SEMICONDUCTOR-TO-220-/200913256568?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item2ec75d0078

Thanks

Regarding ZD12 , it's a zener diode with a breakdown voltage of 15V.I think the one on Compact PSU is 1/4 Watt but you can go up too (1/2 Watt).
As for 2SK1101 (30V 10A), as Lydux said, there are new equivalent  with same or higher specs than this discontinued N-channel MOSFET.One of these is a IRF740, very cheap and reliable, I used it in my Compact PSU and it's still working.

[gypsie]

Can't find on the web IRF740 30v 10a. Only 400v 

[lydux]

Don't bother on characteristics ! 400v is the breakdown voltage from drain to source pins (Vds). Anything higher than 110v will do the trick.
30v is the gate to source voltage (Vgs) which is the interesting one here.  As the zener diode ZD1 between gate and source is rated 15v, it will limit voltage to Vgs to this value. This is the minimal Vgs you have to check for. But consider 20v because of voltage overshoots occuring sometimes due to the zener diode.

There is only one IRF740 reference and is rated 20v on Vgs and 10A on drain current (like 2SK1101).

So just go the any IRF740 you can find !

[caius]

Yes, sorry, I misled you saying 30V.As Lydux said IRF740 will do the job, specs are equivalent to 2SK1101, this last has only higher drain-source voltage, 450V against 400V but in this PSU we have maximum 110V  so gor for IRF470.

[gypsie]

Thanks guys!