Author Topic: 464 Version 3 board - Is it salvageable??  (Read 1642 times)

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Offline Homr836

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464 Version 3 board - Is it salvageable??
« on: 21:44, 04 April 17 »
Hi all,

I've been poking around in the loft trying to find donor parts to get my sloppy tape drive back in actio when I found this bad boy,



I can't remember messing around with it but I plugged it in anyway (Stupid, I know). The LED came on but no picture. On opening, it looked a bit grotty and the solder joints were suspect so I had a deeper look,



The underside was a bit more worrying though,





The fat red wire from the 5v socket and the tiny bridging wires on the RAM look really gash and the flux/corrosion on the RAM sockets don't bode well.

Here are my questions:

1. Should I be worried?
2. Are the extra wires a bodged repair/mod?
3. Is it salvageable?

Regards,

Homr

Online robcfg

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Re: 464 Version 3 board - Is it salvageable??
« Reply #1 on: 21:56, 04 April 17 »
You can take a look at our motherboard scans here: http://www.cpcwiki.eu/index.php/Mainboard_Versions

It seems that version 3 mainboards had many patches.

I hope you have luck and cleaning and resoldering the sockets will bring your cpc back to life.


Sent from my iPhone using Tapatalk

Offline Homr836

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Re: 464 Version 3 board - Is it salvageable??
« Reply #2 on: 22:05, 04 April 17 »
Aaahhhh, I see that it's not just my board that has shitty flux all over it.

I assume then, from the scans, that the extra wires on my board are a workaround for duff traces found during testing?

Should be worth a clean up/re-solder............
Regards,

Homr

Offline Bryce

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Re: 464 Version 3 board - Is it salvageable??
« Reply #3 on: 10:50, 05 April 17 »
That's a seriously bodged repair job. It's probably salvageable, but it would be a massive amount of work. It looks like the repairer destroyed the traces on both sides of the PCB while removing the old RAM, so the data lines had to be bridged, if he tore the vias out then it probably doesn't work yet. He did the same on the 74LS153 ICs and also filed the expansion pads away, so you would need to install centronics ports instead. I doubt it's worth repairing (and I don't often say that), keep it for spare parts.

Unfortunately I see boards in this state more often than I'd like, which is why I always say - If you're not 100% sure you can do the repair properly, give it to someone who can.

Bryce.
« Last Edit: 10:52, 05 April 17 by Bryce »

Offline ||C|-|E||

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Re: 464 Version 3 board - Is it salvageable??
« Reply #4 on: 12:43, 05 April 17 »
Wow... that is a seriously damaged one. I have never seen something similar in before  :-X

Offline Bryce

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Re: 464 Version 3 board - Is it salvageable??
« Reply #5 on: 15:03, 05 April 17 »
I was given a 6128 PCB last year where the owner had done something similar to the two ROMs. But tearing the traces wasn't enough, they then drilled the pin holes with a 1mm drill, removing the vias completely. I got it working again, but it looked shit, so I've been using it for spares since then.

Bryce.

Offline Homr836

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Re: 464 Version 3 board - Is it salvageable??
« Reply #6 on: 22:12, 05 April 17 »
Thanks for your advice gents.

I think I'll keep it for a rainy day project.............
Regards,

Homr

Offline Homr836

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Re: 464 Version 3 board - Is it salvageable??
« Reply #7 on: 20:59, 06 April 17 »
Sod it. I'm going to attempt a refurb on it.  :o

One question, the KM4164B's. Do they have to be -15 or can I get away with -10 or -12?
Regards,

Homr

Offline Duke

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Re: 464 Version 3 board - Is it salvageable??
« Reply #8 on: 21:32, 06 April 17 »
Sod it. I'm going to attempt a refurb on it.  :o

One question, the KM4164B's. Do they have to be -15 or can I get away with -10 or -12?
Good luck :) - Less ns is fine.

Offline Bryce

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Re: 464 Version 3 board - Is it salvageable??
« Reply #9 on: 21:32, 06 April 17 »
-10 and -12 are faster than -15, so yes.

Bryce.

Offline freemac

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Re: 464 Version 3 board - Is it salvageable??
« Reply #10 on: 22:01, 06 April 17 »
My one has been printed wires only one side, and have 5cm between each components on other side... what are theses 464 boards ?
« Last Edit: 22:09, 06 April 17 by freemac »

Offline Bryce

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Re: 464 Version 3 board - Is it salvageable??
« Reply #11 on: 22:13, 06 April 17 »
My one has been printed wires only one side, and have 5cm between each components on other side... what are theses 464 boards ?

Eh... No you don't. Even the original 464 prototype was a two layer PCB. However, yours probably does have 5cm between the components as Versions 1 and 2 of the 464 had a long PCB, on version 3 they shrunk the PCB.

Bryce.

Offline freemac

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Re: 464 Version 3 board - Is it salvageable??
« Reply #12 on: 22:30, 06 April 17 »
Chips were vertical on it.
Last time I opened it shall does suffer a lot. It's board is like dust.
« Last Edit: 23:14, 06 April 17 by freemac »

Offline Bryce

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Re: 464 Version 3 board - Is it salvageable??
« Reply #13 on: 23:38, 06 April 17 »
Picture or it doesn't exist. I have no idea what you are describing.

Bryce.

Offline Homr836

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Re: 464 Version 3 board - Is it salvageable??
« Reply #14 on: 00:53, 07 April 17 »
Good luck :) - Less ns is fine.

Ahh ns. That makes sense. Maybe I should read data sheets instead of thinking it was a variation on the part No  :picard:
Regards,

Homr

Offline Bryce

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Re: 464 Version 3 board - Is it salvageable??
« Reply #15 on: 10:33, 07 April 17 »
ns with the least significant digit missing. ie: -15 = 150ns etc.

Bryce.

Offline Homr836

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Re: 464 Version 3 board - Is it salvageable??
« Reply #16 on: 21:46, 18 April 17 »
UPDATE!

I've removed the 5v socket, the cap, the RAM and the mux chips. Scrubbed the flux residue off and it looks like a very very bad desoldering job, so I took a couple of pics:



The traces and vias for pin 2 on the multiplexers and pin 10 on IC113 have gone which would explain the tiny bridging wires that were in place before I started this.



The +5v pad for the power socket has been obliterated as have the traces which have been "repaired" using solder to cover what was left.

I can't see much more damage but need to have a poke around with the multimeter to make sure all the other traces are intact.

Can the damaged traces be reinstated with something like this? http://www.maplin.co.uk/p/circuitworks-conductive-pen-standard-tip-n73aa

 
Regards,

Homr

Offline ||C|-|E||

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Re: 464 Version 3 board - Is it salvageable??
« Reply #17 on: 00:16, 19 April 17 »
I tink that it does not look so terrible now that it is clean. It is still bad but recoverable. If I was repairing it myself I would definitely solder wires to replace those broken tracks rather than painting them with silver. It is probably the most robust approach. Regarding the RAM I would be soldering sockets in there and then bridging the required places with wire soldered to their pins, underneath the board. For the expansion ports I would install centronics and get rid of the edge connections and for the PSU I would just solder a relatively thick cable :)

Offline Homr836

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Re: 464 Version 3 board - Is it salvageable??
« Reply #18 on: 10:37, 19 April 17 »
Quote
for the PSU I would just solder a relatively thick cable


[/size]That would explain the big fat red wire that was hideously bodged in.

[/font]
Quote
[/size]Regarding the RAM I would be soldering sockets in there and then bridging the required places with wire soldered to their pins[/font]


[/size]They were already in place before I started, so hopefully it should come back to life once I've properly re-soldered them back on........







Regards,

Homr

Offline Bryce

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Re: 464 Version 3 board - Is it salvageable??
« Reply #19 on: 11:31, 19 April 17 »
Can the damaged traces be reinstated with something like this? http://www.maplin.co.uk/p/circuitworks-conductive-pen-standard-tip-n73aa

No, those pens make extremely unreliable connections and will only cause you issues. Solder the new sockets in place and then use jumper wires to replace the broken traces.

Bryce.

Offline Homr836

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Re: 464 Version 3 board - Is it salvageable??
« Reply #20 on: 23:32, 03 May 17 »


IT LIVES!!!

Sort of..........I've just fired her up to check the functions and the screen is full of dots



The keyboard functions normally but I can't test any tapes as the play/FF spool has snapped and I can't connect my HxC,



None of the ICs are warm/hot. Is there a bad connection somewhere?

To do:

1. Wait for the Centronix connectors and fit them.
2. Source a replacement play/FF spool. (Industrial strength evostick doesn't cut it)
3. Find some case screws from somewhere as I have mislaid the originals.
4. Install RAM upgrade.

Can anyone help with points 2 or 3 please?
Regards,

Homr

Offline Bryce

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Re: 464 Version 3 board - Is it salvageable??
« Reply #21 on: 00:03, 04 May 17 »
My bet is a dodgy address line from the CRTC or a corrupted ROM.

Bryce.