Help needed with very old, rare, computer CRT display

[scokljat]

Hello,

I'm retro computer collector and I got an ultra rare, 30 years old computer to restore and repair. It's Ivel Z3, an Apple2 compatible from ex. Yugoslavia. There are maybe 100-200 units ever produced mostly for army, most of them destroyed during the war. This one is one of two units we know still in existence, S/N 23.

Now to the point,

On the video board for CRT, I noticed some possibly leaky caps. I don't want to switch the unit ON before I'm sure everything is OK. The caps look quite different than what I use today, and I'm even not sure what type of caps to use for replacement. I tried to check them with ESR4.0s in circuit, but on some caps I get some nonsense reading. Maybe I should measure them out of circuit...

What do you think, should I replace all these caps? Take a look at the pics, there is some visible leak or corrosion on two small 10MF/30V caps (C1 and C13). What capacitor type is that?? These big blue electrolytes are OK, but I worry about all these small axials...

When restoring retro stuff, I like authenticity even on component level, but in this case I prefer funcionality ;-)

Any help is more than welcome!

Thanks and Cheers!

Suad

[Behemot]

Re: Help needed with very old, rare, computer CRT display

As for replacement, I would suggest Tesla capacitors. Not sure about the smaller ones, but the bigger are known holders for tens of years, most fo them are still good today. They have been manufactured here (former Czechoslovakia).

[ben7]

Re: Help needed with very old, rare, computer CRT display

Replace all electrolytics.

The small leaking ones are likely wet-tantalum capacitors.

Be aware that the Flyback transformer is old, and prone to failing.
(They let off a LOT of disgusting toxic smoke)

When your ready to power the unit up, keep a ballast in line with this (such as a 40w light bulb). If there is a short, the ballast (lightbulb) will help keep things from exploding/frying.