Spectrum Computing

I've cleaned the board multiple times with alcohol. Those bridges weren't there before. Maybe they have come from my workdesk? I have not cleaned it for a while. Some of those may look like bridges but they are just reflections of the soldering mask that has melted away due to my bad soldering skills.

I don't know what to do.

Everything I have replaced:
1)electrolytic capacitors
2)the entire lower ram
3)zilog z80 cpu

Slauri wrote: ↑Fri Feb 14, 2020 6:15 pm Hi everyone, i got 2,98 volts on the pin 1 of the lower ram. The other voltages were good.

Yestreday i measured the -5v rail the voltage was much lower.

Pin 9 5.01 volts, pin 8 12.14 volts, pin 1 4.80 volts (lower ram)

Almost 9 volts

My probes are too big to get in there. But i'll try.

The ULA warms up so much that it's painful to press your finger against it for over 5 seconds.

I already have the lower ram replacement board soldered in

Hi everyone, i got 2,98 volts on the pin 1 of the lower ram. The other voltages were good.

Recapping was the first thing i did.

I noticed an another problem. If the machine had been on for a while the top section of the screen would start to flicker a bit, and after a few minutes the top section would go nuts. It just went out of sync and flickered even more. At that point I disconnected the power cable and cooled down the v...

>>You also do not appear to have any colours on screen. I was just adjusting the trims before I recorded the video. >>You can tell that the CPU is running, by the border mostly being white. Yes. Before i replaced the CPU or the lower ram the border would stay black and it wouldn't do anything when I...

The machine had been on for a while already. I pressed the reset button multiple times and this happened: https://youtu.be/PVr2weWOylE

The picture changes when the ULA heats up.

On the ULA pin 13 there is only 3.17 volts. On the pin 14 there is almost perfect 5 volts. Is this normal?

Can i replace the ZTX213 transistor with ZTX750 or ZTX753?

I tested the voltage on the ROM and it was good. I'll replace the tr4 too. Is there any equivalents to the ZTX 650 transistor?

Any other ways?

Is there any way to test the ula?

Oh, it heats up in under 15 seconds.

The power supply might actually be the culprit, because the picture is much different after swapping out the entire lower ram and the cpu. It still shows garbage but is it normal for the ULA to heat up in the center in under 30 seconds?

Nevermind, my universal power supply has a 9 volt option too.