Brett's STE - Repair thread

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Badwolf
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Re: Brett's STE - Repair thread

Post by Badwolf » Thu Jan 13, 2022 9:24 am

Good luck RJ! It does sound very ROMish.

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Re: Brett's STE - Repair thread

Post by rubber_jonnie » Thu Jan 13, 2022 9:38 am

Badwolf wrote:
Thu Jan 13, 2022 9:24 am
Good luck RJ! It does sound very ROMish.

BW
Thank you :)
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

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Re: Brett's STE - Repair thread

Post by JezC » Thu Jan 13, 2022 11:33 am

Badwolf wrote:
Thu Jan 13, 2022 9:24 am
Good luck RJ! It does sound very ROMish.

BW
+1

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Re: Brett's STE - Repair thread

Post by rubber_jonnie » Thu Jan 13, 2022 12:12 pm

Thanks folks.

It's just been put on the bench and I have confirmed that the fault observed is a white screen, so what we knew already. Note I'm running off my bench PSU to ensure I can benefit from over voltage and over current protection.

I tested it with my diag cart, as it has a handy red light that shows all is well, seen here on my own STE for reference:


IMG_20220113_114615.jpg
IMG_20220113_114615.jpg (108.95 KiB) Viewed 118 times


However the patient has only a green light, which means generally means no TOS ROM is available, but it does have power as the green light come on. Again, this was all kind of expected.

Topside the board is clean:


IMG_20220113_115627.jpg
IMG_20220113_115627.jpg (366.04 KiB) Viewed 118 times


And under we have the original repair attempt:


IMG_20220113_115649.jpg
IMG_20220113_115649.jpg (452.4 KiB) Viewed 118 times


I've not done any diagnostics, but I'm certainly contemplating removing the existing bodge wires and sockets (Don't be sad Brett :) ) so that I can completely review the damage with fresh eyes and make a plan, however I may first just do some continuity checks and see if there is something obvious I can fix without making extra work for myself.

All things to think about, and the whole white screen thing is very reminiscent of the white screen issues I had with my own Mega ST4.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

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Re: Brett's STE - Repair thread

Post by rubber_jonnie » Thu Jan 13, 2022 1:26 pm

Just a couple of things I'd pick out here just as a warning to other people who may want to upgrade their machines.

I'm not saying this to be mean, it's just advice because I've been here myself and had to learn from it.

Firstly, if you are in the unfortunate situation of lifting a trace during chip removal, you do really need to clean the chip up afterwards.

This is one of the ROMs:

IMG_20220113_121510.jpg
IMG_20220113_121510.jpg (452.28 KiB) Viewed 110 times

You can see a trace still attached, and that whisker of a trace could quite easily short with another pin. The other thing to note is that because of the extra 'bulk' on the pin, it can damage your sockets. The same can be said of leaving excess solder on the pins, which is also visible in the picture above.

Looking at the sockets:

IMG_20220113_130912.jpg
IMG_20220113_130912.jpg (586.3 KiB) Viewed 110 times

We can see that there are some damaged inner wipers, which can lead to poor or no contact with the ROMs and a dead machine.

My next port of call will be to fix the wipers and clean up the ROMs, and see if it makes a difference. If it doesn't, then I think removing the sockets and starting from scratch may be the best way forward, otherwise I may just be fighting with damage that is hidden under the sockets.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

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Re: Brett's STE - Repair thread

Post by BrettRogersUK » Thu Jan 13, 2022 1:38 pm

I must admit that I thought I'd cleaned the pins up before inserting them into the sockets. Obviously I got ahead of myself and thought I'd done it when indeed I hadn't. :oops: :oops: :oops: :oops:

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Re: Brett's STE - Repair thread

Post by rubber_jonnie » Thu Jan 13, 2022 1:47 pm

BrettRogersUK wrote:
Thu Jan 13, 2022 1:38 pm
I must admit that I thought I'd cleaned the pins up before inserting them into the sockets. Obviously I got ahead of myself and thought I'd done it when indeed I hadn't. :oops: :oops: :oops: :oops:
I did this sort of stuff when I started off too, so don't beat yourself up Brett, if you haven't done this sort of stuff on a regular basis, then there are lots of things to trip you up. The main thing to do is learn from the process :)
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

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Re: Brett's STE - Repair thread

Post by rubber_jonnie » Thu Jan 13, 2022 10:22 pm

Ok, so I did a quick assessment/comparison of the power draw of the dead STE against my working STE, and the dead machine was about .8W-1W higher. Not sure it was 100% proof of a short, but just in case I decided it was going to be best to remove the sockets and bodge wires just to be 100% sure, and also to be sure that I wasn't missing anything under the sockets.

@BrettRogersUK I think you actually did a pretty reasonable job with your bodge wires underneath, however looking at the damage under the sockets, I think you clearly missed some stuff on the top side of the board, hence the general unhappiness and white screen.

Again, don't beat yourself up about this, we've all probably had experiences like this along the way. Probably 10 years ago I couldn't even fix an ST of any sort, now I'm fixing STs, Spectrums, Mattels, ZX81s, disk drives, well all sorts really, but I had to start somewhere, and I can assure you, I too have pulled up traces like this over the years. As long as you learn from it, it's all good.

Topside looks like this now:

IMG_20220113_212851.jpg
IMG_20220113_212851.jpg (546.17 KiB) Viewed 73 times

And the underside is like this:

IMG_20220113_212941.jpg
IMG_20220113_212941.jpg (600.18 KiB) Viewed 73 times

Finally, to the left of C632, there is another candidate for a short in the form of a little solder ball, now happily cleared away.

IMG_20220113_210702.jpg
IMG_20220113_210702.jpg (527.78 KiB) Viewed 73 times

Whilst this might look bad, I personally believe with a bit of time, this can be repaired, after all it is just damaged traces. I noted one trace going under one of the 6850s, so that has also been removed temporarily for access, and I will fit a socket when it all goes back together.

As for power, it is now drawing approximately the same amount as my working reference ST.

There are going to be quite a few bodge wires by the time I'm done @exxos but I'm pretty confident that it'll run again.

Hang onto your hats for a bodge-wire-a-thon!!
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

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Re: Brett's STE - Repair thread

Post by exxos » Thu Jan 13, 2022 10:27 pm

Holy set of missing vias Batman!
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: Brett's STE - Repair thread

Post by rubber_jonnie » Thu Jan 13, 2022 10:40 pm

exxos wrote:
Thu Jan 13, 2022 10:27 pm
Holy set of missing vias Batman!
:dizzy:
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...

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