Denial

Ah yes that makes sense. As I said the board works perfectly well.

Thank you

I have rediscovered an old tape of Space Invaders which my dad bought me back in the early 1980's. The tape is corrupted as it loads a start up screen then attempts to load machine code and never completes (I think I may have recorder over the tape at some point!) Anyway I also had a version of Aste...

I bought a working 2 prong Vic Motherboard as a test board. It works well but the oscillator has a wire attached to it. I'm not sure why. Any ideas?

I am looking for replacement SRAM for my early 2 prong PSU VIC 20.
I found some described as "SRM2114C25 EPSON 4K BIT SRAM 18 PIN DIP"
can anyone tell me if they are suitable as replacements?
My original chips are MSM2114L3RS.
Cheers

Hi Mike,

My meter only has 500 or 200 AC settings as it's just a cheapy one. I don't have an oscilloscope. The reading I get at 200AC is 09.9 steady. No apparent fluctuations.
Forgive my ignorance but does this tell me anything?

Thank you Mike I will check the ripple effect as you suggest. Where should I be checking, on the VIC chip itself?

Radar Ratrace, does not play when plugged in but as the title screen uses standard vic characters I guess it does not bypass the kernal rom

Arghhh ! 6502! I hate making typo's that make me look foolish! No worries about the pots, I just had a feeling they were gone but they haven't changed the result particularly so you were right that they aren't the problem. I do have a cartridge, Radar Ratrace do you know if that bypasses the Kernal?...

Hi Adam, Well it's been a week of further tinkering! I have bitten the bullet and replaced the two pots r7 and r32. This has not solved the problem, but they were clearly knackered because I get consistent video signal now and I get a black screen that appears to have parallel lines from top to bott...

Ok I will check those things. In the mean time I have checked the C35 which is a pot controlling the oscillator (according to what I have read) and my meter shows nothing. Should there be a voltage across it do you think or am I barking up the wrong tree?

Hi Adam, I went back to the UE11 and checked the socket which is getting 4.88v. Then I reseated the chip again and it now shows 4.88v at the pins too so I was totally wrong with that. I don't have a logic probe I'm afraid. Where is the oscillator on the board/componenet reference. The C35 is the oth...

Of course I have already tried removing the UE11 and it makes no difference so although it may be faulty, it is not the only problem.
The screen I get is dark blue flickering, not all the time. Strangely I also get a sort of white noise from the tv as well with this new VIC chip.

The UE11 on my CR Vic is showing 4.75v so I may be able to swap it, although its hard soldered to the board

Hi Adam,

I've reseated everything and used contact cleaner as you suggested. I also got a better meter as my old one only is not digital.
I get 4.88v between pins 20 and 40 on the vic chip.
BUT checking all the others again with the new meter the UE11 901486-01 is only 1.44 volts.

Hi Adam

New vic chip arrived this morning, I put it in and only a minimal change. I got a blue screen which flickers on and off.

Could it be the components do you think?