SpeedyTT, black screen of death !!!! HELP

[rubber_jonnie]

I agree with @Steve regarding fractured tracks or vias too.

I've had 2 instances, a Mega ST and an Amiga 500 where manual handling of the board damaged tracks/vias invisibly causing dead machines. I managed to track down and fix the issues but I do always warn people that working on these old boards is a risk, the manual handling of them could cause unseen damage, especially if the board gets flexed at all.

I'd suggest that you need to start troubleshooting the base machine with a minimal config.

[zfrenchy]

I found something !

This is the MCU, shorted pin 81(SINT) and 82(SZ1)
But still dead black screen.

I am asking the expert, by having these two pin shorted, what part might be dead ?

both pin connected with the short to:
UA00 (DMAC chip): pin 7
U907: 74LS86 pin 10
J502 (memory connector): pin 77
JB01 (TT RAM): pin 48

20260105_192624.jpg (299.29 KiB) Viewed 182 times

[HigashiJun]

I would advise to remove the solder blob first and then check if your TT is still alive.

[rubber_jonnie]

I would advise to remove the solder blob first and then check if your TT is still alive.

I'd agree 100%, that solder blob shouldn't be there. Get it removed.

[zfrenchy]

Of course I removed it !

Still black screen

[HigashiJun]

So check the continuity on all the 6 sockets you have fitted in order to install the Speedy.

Sockets.jpg (477.86 KiB) Viewed 124 times

There must be somtehing wrong somewhere (provided you didn't fry a component).

[zfrenchy]

Yep, find where these 68 points are going to be tested !

[HigashiJun]

Good.

[zfrenchy]

Little parenthesis in my process, here is a searchable TT schematic PDF I made for facilitating the following of wire without turning pages.

https://drive.google.com/file/d/12k8qL4 ... sp=sharing

[Steve]

Little parenthesis in my process, here is a searchable TT schematic PDF I made for facilitating the following of wire without turning pages.

https://drive.google.com/file/d/12k8qL4 ... sp=sharing

This is a great resource! Thanks for sharing