First post, by Imperious
I purchased this Cypress scaler from a UK based Auction house Ebay site for roughly $70 Australian delivered, which is a good price for one of these.
Unfortunately it's dead as a Dodo apart from the fact that the power Led lights up.
I got about $60 of the $70 refunded, I think You don't get the Auction house fee refunded. That sucks a bit but they don't want it returned so I'm
going to see if I can fix it.
I purchased this model as I know it's compatible with 720x400 Dos resolution, based on a Youtube clip out there.
The reason the LED lights up is it's directly connected to the DC jack.
After some poking around with the multimeter I found that after the switch IC the 5v rail is 19.3 ohms to ground. From there the
rail goes off to 2 3.3v regulators as well as a 2.5v regulator. There is a 1.8v regulator but that is fed from the output of the 3.3v regulators.
The regulators outputs are all ok and none have any low resistances to ground. The 19.3 ohms is also across any capacitors on the 5v rail.
I initially started removing a capacitor as well as the DC jack to get at the 8 pin switch ic (Fet) which I thought might be the culprit. As it turned out
the Fet does not have any pins to ground so that cannot be the problem. I next removed three of the regulators but the 19.3 ohm is still there.
Eventually I found that there is a diode on the underside that measures 19.3 ohms and after removing it the low resistance to ground is gone.
Tomorrow I'll stop into Jaycar and pick up a new DC jack, and if lucky I might be able to find a 6.8v zener and capacitor at work. Ill update this once I
have got the parts and fitted them as well as put the 3 regulators back.
Atari 2600, TI994a, Vic20, c64, ZX Spectrum 128, Amstrad CPC464, Atari 65XE, Commodore Plus/4, Amiga 500
PC's from XT 8088, 486, Pentium MMX, K6, Athlon, P3, P4, 775, to current Ryzen 2600.