ZX Spectrum not working
Posted: Sat Jan 23, 2021 2:39 am
This is the motherboard:
https://www.youtube.com/watch?v=IzgCmldm2H4 and I found "just" these discrepancies:
1) first measure on the voltage regulator gave me arounk 30kohm and not 100+kohm (ps: and I've a 78005 not 7805)
2) tr4 measures went ok, but on tr5 I have around 0.7 on both sides if I measure in +-+ (ok), while I get open circuit on the upper couple and 0.56V on the lower if I measure -+- (while it was supposed to be open circuit and 1.2V determined by other component around anyway, as explained on the minute 10:35)
Ram and inductors measures seemed ok.
Seems to me that the problem (for now at least) might be just on the voltage regulator. What do you think? There are other measures I should try before attempting to replace it in case?
(sorry to bother but my hardware electronic experience started just recently and is pretty noob still)
This is the trembling image on the screen when on (is alternating between two patterns of random colors and black stripes):
I tried the very nicely explained initial testing procedure 1) first measure on the voltage regulator gave me arounk 30kohm and not 100+kohm (ps: and I've a 78005 not 7805)
2) tr4 measures went ok, but on tr5 I have around 0.7 on both sides if I measure in +-+ (ok), while I get open circuit on the upper couple and 0.56V on the lower if I measure -+- (while it was supposed to be open circuit and 1.2V determined by other component around anyway, as explained on the minute 10:35)
Ram and inductors measures seemed ok.
Seems to me that the problem (for now at least) might be just on the voltage regulator. What do you think? There are other measures I should try before attempting to replace it in case?
(sorry to bother but my hardware electronic experience started just recently and is pretty noob still)