| Posted By
ManicMiner1977
on 2025-04-02
14:10:15
|  Black Screen Plus 4
Hi All,
Had a fully working Plus4 6 months ago. Tried it again recently and only a black screen @ 50 hertz visible.
I suspect it may be faulty RAM but before removing and socketing all chips does anyone have any suggestions?
A bit of background prior. I noticed the original psu was emitting some strange voltage levels. I modded the socket to a standard C64 and use my known working psu but get the same results. I have checked for shorts on the RAM, CPU, TED etc. There doesn't appear to be any.
I did notice a hard short at Q4. I removed it, tested out of circuit and no short. Checked all via @ Q4, no short. Re-soldered voltage regulator and no short?
Checked voltages @ user port. All 5v present no 9v AC but 5v DC present instead.
No visible signs of damage on circuit board.
I tried removing the 2 roms with the software as noted from another post which made no difference. I also tried my diag rom in the kernel socket but again a black screen.
That's currently all I have done before proceeding further. If anyone can suggest basic things to check I'd really appreciate the support. |
|
Posted By
SukkoPera
on 2025-04-02
14:36:52
| Re: Black Screen Plus 4
Sorry if this might sound harsh, but my recommendation is: stop doing random things and send it to someone who knows what they are doing. You are only making things worse. |
|
Posted By
ManicMiner1977
on 2025-04-02
15:09:30
| Re: Black Screen Plus 4
Fair enough |
|
Posted By
GreatWhiteRetro
on 2025-04-02
20:12:06
| Re: Black Screen Plus 4
My first black screen plus/4 was just a bad PLA, similar to the PLA problems longboard C64s often had. Barring locating a known good PLA, the GAL PLA seems to be a suitable replacement.
Adrian Black demonstrating the thing. Plenty of eBay vendors selling these.
https://www.youtube.com/watch?v=S7e1MGJwGvI
The fact you're getting 50 Hz video suggests the TED IC is OK still.
No 9VAC? Is that an original power supply? Those things might not be the safest, so see if you can find a NuBrick or something. Apparently The Retro Channel at YT demonstrated that the plus/4 power connector may be replaced with a C64 power connector, allowing the use of (modern) C64 power supplies.
TRC plus/4 with RF replacement and Luma Bypass, time stamp jumps to C64 PSU connector:
https://youtu.be/nuEED8dxTzs?t=1754 |
|
| |
Copyright © Plus/4 World Team, 2001-2025. Support Plus/4 World on Patreon |
