Since my sister visited yesterday (and we actually talked about my 'elephant trousers' -- glad I didn't know then what I know now), I had only a few hours to work on the 486.
The seller wrote that the power consumption was too low. He was right: Almost zero is quite an achievement for a CRO. Unless it doesn't work. The neon lamp oscillator worked, so DC power was available to the SPS.
The starter circuit however was not working. The left leg of the Diac stayed close to zero. I checked for shorts and found - nothing. Which really puzzled me. In order not to bore you unnecessarily, it was, of course, a simple mistake on my side. Only much later I found that a node I had already checked indeed had a solid short to 'Neg'.
C1848, a 2 µF/150 Volts electrolytic cap. And no replacement anywhere, except - yes, if it doesn't have to be an electrolyte (and the color won't be visible behind the metal shield), there is one:
![](https://i.imgur.com/BnstSFN.jpg)
There's actually enough room for it. With my sister approaching, I can only power up once, which is answered by a relay ticking in rapid succession.
![Angry >:(](https://www.eevblog.com/forum/Smileys/default/xangry.gif.pagespeed.ic.0w4zhwjvDw.png)
Looks like there's also a short on one of the power rails.
Today at half past six I wanted to continue my repair job. Hooked a scope to TP1951 (which, according to the SM, should give strong hints regarding the shorted rail). Power on - and the damn thing comes to life!
First light! (And the sun illuminating my shirt so brightly that it almost ruins the picture.) Calibrator output (5 volts) at 1:1.
![](https://i.imgur.com/8zQD9HO.jpg)
Gentle rapping has no effect. No further tests done (time for breakfast).
However, the device is still full of our beloved tants. And the switch decks are untested yet (apart from choosing the right sensitivity, which showed no apparent problems with deck A).
With the popularity of the 485 and the unpopularity of tantalum caps around the brotherhood, there probably exists a list of them already that can be used to order replacement caps?
It surely is a rather fine CRO. If no other faults turn up, it might even get used regularly.
[And it once belonged to Valvo - another company with a beautiful logo.
![Cheesy :D](https://www.eevblog.com/forum/Smileys/default/xcheesy.gif.pagespeed.ic.KPzuH4J-TG.png)
)
![](https://i.imgur.com/LIEOirn.jpg)