exxos's Atari, Amiga & retro forum

I just found something interesting, take a look at the middle via here:


The trace has a neat cut at the 12 o'clock position, and I can assure you it's really not noticeable to the naked eye. Thank god for hi-res cameras in mobile phones and high quality image processing on laptops!!

rubber_jonnie wrote: 13 Jan 2022 22:48 I just found something interesting, take a look at the middle via here:

Yikes ! When I've done repairs like that where the via and track top and bottom is broke, is solder a body's wire to the track on top, poke through the hole and solder on the bottom. That way you kinda made a new via. But also have to be quick when soldering pins in the hole as to not melt the solder on the tracks. But not so simple when doing many track repairs like that.

I think you can get prototyping vias . I've not used them. But would allow bodge wires to be wrapped around them without poking them through the holes. I wouldn't trust damaged vias either. So may be worth just drilling them out and replacing them. :shrug:

EG
https://www.instructables.com/Repairing ... -on-a-PCB/

exxos wrote: 13 Jan 2022 23:42

rubber_jonnie wrote: 13 Jan 2022 22:48 I just found something interesting, take a look at the middle via here:

Yikes ! When I've done repairs like that where the via and track top and bottom is broke, is solder a body's wire to the track on top, poke through the hole and solder on the bottom. That way you kinda made a new via. But also have to be quick when soldering pins in the hole as to not melt the solder on the tracks. But not so simple when doing many track repairs like that.

I think you can get prototyping vias . I've not used them. But would allow bodge wires to be wrapped around them without poking them through the holes. I wouldn't trust damaged vias either. So may be worth just drilling them out and replacing them. :shrug:

EG
https://www.instructables.com/Repairing ... -on-a-PCB/

Yes, I had considered putting the wires through the hole too, but using something like kynar and wrapping it round the pins. What i will probably do is lay the new wires in place and use lacquer to hold them in place, so even if the do get too hot, they should stay in position and cool down ok without moving. Lot's to think about.

I did wonder if replacement vias were available, and I'll have a look at the page, cheers :)

Wow! Never even noticed that cut track. But then again, I wouldn't be looking for it. Great catch! I think that's why there was a black bodge wire attached to it, there wasn't any continuity between those pins and I think that's why I put the bodge wire in.

There maybe some hope yet! 🤣🤣

Thanks for everything you're doing. It's very interesting! Sorry I made a complete balls up of the thing!🤣🤣🤣🤣

Regards,

Brett

BrettRogersUK wrote: 14 Jan 2022 01:36 Wow! Never even noticed that cut track. But then again, I wouldn't be looking for it. Great catch! I think that's why there was a black bodge wire attached to it, there wasn't any continuity between those pins and I think that's why I put the bodge wire in.

There maybe some hope yet! 🤣🤣

Thanks for everything you're doing. It's very interesting! Sorry I made a complete balls up of the thing!🤣🤣🤣🤣

Regards,

Brett

Don't worry, these things happen.

I always like to review what I'm working on to try and come up with a plan, so anything like this always gets close up photos and a look with the microscope. Now it's possible the cut track isn't an issue because you're using 28 pin and not 32 pin ROMs, BUT it still needs to be repaired as the socket will cover it.

The other issue that can happen is that many people will use a screwdriver to pry components from the board and that can sometimes cause damage like this as the screwdriver edges can be sharp and cut the thin copper.

I have a specific chip lifter that is a bit like a mini crowbar, but it has very smooth edges and because it's curved too, it doesn't tend to cut when you use it to lift. You still have to be careful, but it is a lot safer than a screwdriver.


Luckily it seems to be that in most cases the damage is restricted to one end of the trace, so there is at least one end to work with, which is always a good start.

FYI I intend to fit sockets to the ROM slots, I think if I was to install the switcher it would make it a lot harder to repair in the future if it came to it. Both my STEs have a socketed switcher, so I know it is workable, and it will just about fit under the FDD with some care.

Next step will be to clean up the ends of the traces that remain and see if there is enough to solder too.

It's going to take a while though!

Given the level of damage I would be inclined to assume that all the traces are damaged on those ROM locations, fit sockets and then patch wire every pin to a known good location. I know that's 16 data patch wires and 16(?) address wires plus power, /CE etc. but it's the only way to be really sure that you've got everything.

stephen_usher wrote: 14 Jan 2022 10:46 Given the level of damage I would be inclined to assume that all the traces are damaged on those ROM locations, fit sockets and then patch wire every pin to a known good location. I know that's 16 data patch wires and 16(?) address wires plus power, /CE etc. but it's the only way to be really sure that you've got everything.

Yeah, it's one of the ideas buzzing around in my head right now, and one of the reasons I'm not rushing to start repairs. I may only have one shot at it, so I need to be sure I'm going to get it right.

Yikes! But definitely still fixable.

I've used a custom cartridge port adapter to bypass internal ROMs before. Bit of a faff if you haven't got the kit, I appreciate, but it can be quite a good tool to develop as you get most of the address lines and all the data lines routed out 'for free'.

An emutos cart build (configured for 0xE00000) and a bit of a fly wire from the chip enable line(s) and you could probably persuade any eprom-carrying cart you might have to boot you up.

It's a way of proving the rest of the board is working before investing all that repair time.

BW

Badwolf wrote: 14 Jan 2022 12:25 Yikes! But definitely still fixable.

I've used a custom cartridge port adapter to bypass internal ROMs before. Bit of a faff if you haven't got the kit, I appreciate, but it can be quite a good tool to develop as you get most of the address lines and all the data lines routed out 'for free'.

An emutos cart build (configured for 0xE00000) and a bit of a fly wire from the chip enable line(s) and you could probably persuade any eprom-carrying cart you might have to boot you up.

It's a way of proving the rest of the board is working before investing all that repair time.

BW

Sounds like an interesting prospect, do you have any links or other details?

@BrettRogersUK Just to help you understand that sometimes older machines can sometimes be 'lacking in quality', this is a shot from my 600XL:


If you look at the 2nd hole in from the right, on the top row, you can see a pad is missing. It didn't come off when I removed the socket, it was simply never there. However, the via and the trace are in one piece and buzz out ok once the new socket was soldered in place.

The pad is also missing from the 7th pad in from the right, but because it had no tracks on the topside, when it's soldered it works just fine on the bottom with no repairs.

These things are fragile and often poor quality from the outset. STs do tend to be a lot better than 8 bit machines, but they all do suffer from cheapness built in!!!