Black screen after tos upgrade

[rubber_jonnie]

Black is worrying. White is the normal TOS fault state.

What do you get if you remove the chips altogether?

BW

Just tried this and same result it flashes to a black screen nothing else

Completely black, or black with white borders? If just black you may have a short and need to clean things up. No ROMs will be a plain white screen.

[Badwolf]

What do you get if you remove the chips altogether?

Just tried this and same result it flashes to a black screen nothing else

In that case I'd suggest getting the multimeter out and checking resistance from the 5V to GND line and checking the value of the 5V line when the power is on.

If the above results are inconclusive, I would try to revert as per Steve's suggestion.

With no jumpers present, and no ROMs, I would still expect a white screen.

BW

[Groppo91]

Just tried this and same result it flashes to a black screen nothing else

In that case I'd suggest getting the multimeter out and checking resistance from the 5V to GND line and checking the value of the 5V line when the power is on.

If the above results are inconclusive, I would try to revert as per Steve's suggestion.

With no jumpers present, and no ROMs, I would still expect a white screen.

BW

Thank you will have to pack it away for the weekend as I am away but will dive deeper with my multimeter when I get some more time. Is there a best place to take these reading from?

[Groppo91]

I have taken a photo of what I done. I do know my soldering skills suck before anyone points that out.

IMG_20220317_152832.jpg (176.11 KiB) Viewed 2670 times

[Badwolf]

Thank you will have to pack it away for the weekend as I am away but will dive deeper with my multimeter when I get some more time. Is there a best place to take these reading from?

the most obvious one is across the huge capactitor in the middle of the board, but since you're working in the region the power pins of the ROM sockets is not a bad place to try too.

Opposite corners (GND pin 16, 5V pin 32).

BW

[Groppo91]

Thank you will have to pack it away for the weekend as I am away but will dive deeper with my multimeter when I get some more time. Is there a best place to take these reading from?

the most obvious one is across the huge capactitor in the middle of the board, but since you're working in the region the power pins of the ROM sockets is not a bad place to try too.

Opposite corners (GND pin 16, 5V pin 32).

BW

Just tested both hi and lo and got 4.92V between 16 and 32

[Badwolf]

Just tested both hi and lo and got 4.92V between 16 and 32

That positive, but unfortuntely inconclusive to the actual problem, then.

I think reverting back as Steve suggested to try to get it working again with the original TOS ROMs is the next logical step.

You may wish to spend the time fitting proper jumpers to aid this.

I did a video on this topic a while back that may be of interest:-







BW

[Groppo91]

I did a video on this topic a while back that may be of interest:-
BW

Wow thank you so much that is a way better idea just need to buy some jumper pins now. I wasn't planning on stripping the board down but I guess I have nothing to lose now

[Groppo91]

Just tested both hi and lo and got 4.92V between 16 and 32

That positive, but unfortuntely inconclusive to the actual problem, then.

I think reverting back as Steve suggested to try to get it working again with the original TOS ROMs is the next logical step.

You may wish to spend the time fitting proper jumpers to aid this.

I did a video on this topic a while back that may be of interest:-







BW

Interesting I stripped down the board and noticed that when I ran my meter across w104 there was continuity between all three sockets for w104. I assume this is probably my issue. Unfortunately one of the resistor legs snapped inside the socket and I have tried for ages to get it out. Tried wick, solder sucker heat air station. Even tiny tweezers it just will not budge. I put old chips back in and tested but still no luck.

[sety]

Unfortunately one of the resistor legs snapped inside the socket and I have tried for ages to get it out. Tried wick, solder sucker heat air station. Even tiny tweezers it just will not budge.

Ooh! That's the worst when that happens. You could try just filling it with solder and sucking it out with an electric desoldering station, repeating over and over, trying on both sides until you get it. You can also try soldering another resistor leg over the top of it and then hold the iron on the solder joint and try to push the resistor leg through to push the old one out. This has worked for me a few times.

Avoid the temptation to try to drill it out with a PCB drill. The drill tip will snap off as soon as it hits the old bit of wire and you'll never get that out.

Hope this helps