Display issue on rev 6A motherboard with DIVMMC Future

[Vyprman]

I have a rubber key spectrum which I have been restoring.
I received the system along with a ZX81 and a +3 model both of which have now been restored to full working order and I thought I had done hte same with the rubber key model.

The machine has had capacitors replaced, a new keyboard and membrane and a new metal backplate for the keyboard as the old one was dinged to hell and back and peeling off. I also performed the capacitor od for the modulator to allow composite video.

I then bought a DivMMC Future direct from TFW8B and am seeing an odd issue.

Basically when the unit powers on I get a normal display, when the DivMMC is activated, the display gradually dims, the picture is still visible and I can load and run software but the display is very dark.

Thinking it was a power issue, I replaced the 7805 regulator and the PSU with new versions but still seeing the same issue.

Where would be the best place to start troubleshooting?

[1024MAK]

My best suggestion is to test the voltage on the 12V rail while the symptoms are present.

Mark

[Vyprman]

Looks like it was the DC Barrel connector, I swapped it from another Spectrum that is undergoing repairs and the display stays birght.. I suspected the barrel because the system would not power on properly if the Adapter was plugged all the way in.
New barrel has been ordered and added to the list of bits needed to fix the other board.

[1024MAK]

Good that you have found the problem

And thanks for letting us know what you found.

Mark