Help with WHITE screen issue

[Linzino]

I have a serial IEC button for the C64, can I use it on my Vic/VC 20s?
Can I use it for the purpose of testing the white screen issue?

I have removed the (tested the working VIC1), cleaned the socket with (abundant) contact cleaner (KONTAKT 60)
and I have resat the chip correctly into its socket. I have also sprayed the contact cleaner on the legs of the soldered 7402 TTL chip.
I still get a white screen.

[mrr19121970]

I have no idea what a serial IEC button is. If it works on a C64 then it works on the vic20 too.

You need to get your soldering iron out to fix your issues. Contact cleaner spray really is a long shot.

[Linzino]

Hi

Summary: WHITE screen and VIC1 checked OK.

I have bought 2 SN74HC02N (from the same seller). Are they pin-to-pin compatible with the 7402??
I have managed to cleanly remove the 7402, install a socket and SN74HC02N.
With either SN74HC02N I get a BLACK screen (no sound, my SD2IEC lights up at start-up but no commands are received)

If I re-insert the 7402 I still get a WHITE screen.
The sockets of the VIC1 and 7402 seem OK (I have tested the continuity of the lines and sockets)

What else should I check or replace?

Should I start with the 6502 which is soldered? I have some spare working 6502...

Linzino

[mrr19121970]

To me it seems your SN74HC02N NOR gate is faulty. You can test with a prototyping board, wire, LED+resistor and +5v DV

See http://images.datasheet.hk/pdfimages/00 ... 600001.gif

[Linzino]

I have tested with two different chips.
They produce a BLACK screen instead of the WHITE screen.

Are they pin to pin compatible?
Should I buy from a different seller/site?

[Linzino]

Remark:
The two SN74HC02N are brand-new.
Both produce a black screen instead of the white screen.

Could this come from a different problem? Like a failing 6502?