Author Topic: 6128 Screen Image issue faulty DIN?  (Read 767 times)

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Offline SyntaxError

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6128 Screen Image issue faulty DIN?
« on: 03:34, 06 July 19 »
Hi,

Any advice is welcome!

Main issue:  if I apply a modicum of pressure on either the 6pin DIN Video out socket OR the 5V power in socket the screen will change colour from the normal yellow text on blue background to black and white instead.  I can even get the screen image to roll and/or disappear completely.  If I "fiddle" with either of these two cables then the image will return - however any spirited typing on the keyboard will induce the same issue again. 
https://1drv.ms/u/s!AsxahRJAP-6L3HGveaCGO5-thSKw
https://1drv.ms/u/s!AsxahRJAP-6L3HC-f8HS7ZLIELUz
https://1drv.ms/u/s!AsxahRJAP-6L3HIiA3e00z7VKSKg

Has anyone experienced this before?

Also as part of the deep cleaning process I stupidly snapped one of the small hooks under the Spacebar keycap  :doh: - therefore it sits uneven on the machine because the small retention bar underneath the keyboard tray has nothing to grab.  So if anyone could help me source a replacement 6128 Spacebar it would be much appreciated.

Background Info:
I obtained a "refurbished" CPC6128 from eBay, its a German design with Centronics IO a QWERTY layout and a natty RF shield covering the entire mainboard. 
https://1drv.ms/u/s!AsxahRJAP-6L3G_pzfWr3wKMXF1t
https://1drv.ms/u/s!AsxahRJAP-6L3G4ITE5HCHYqem62


I cleaned the system thoroughly by watching the excellent RetroManCave videos as it was filthy - hepatitis filthy (despite the sellers assurances).  One thing I noted is that there was a yellow cable running from the 5V socket via (a capacitor?!?) and soldered to the RF shield. 
https://1drv.ms/u/s!AsxahRJAP-6L3G1uZPaBEVFJohM-

I've never seen or heard anyone mention this before - what is it for?  The machine still works with it unattached.  (I needed to snip it as the RF shield could not be removed to expose the mainboard underneath otherwise).

Upon reviewing the board nothing seems loose and I cannot spot any dodgy traces on the PCB (I was expecting to have to resolder a trace on the DIN or 5V power but it checked out.  I'm using the 6128 SCART TV Connection Kit from CoolNovelties as my link to the TV.

Hope someone can please help or give some advice regards this situation inc where I could try and obtain a donor SpaceBar!


Thanks
« Last Edit: 13:20, 06 July 19 by SyntaxError »
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Offline SyntaxError

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Re: 6128 Screen Image issue faulty DIN?
« Reply #1 on: 02:17, 08 July 19 »
Quick update to this post:


Has anyone removed and re-added the 5V and 6pin DIN to and from the PCB before?
I'm thinking that if its a loose connection from both of these areas is it a case of desoldering these connections from the rear f the board and then redoing with some fresh solder to perhaps make better contact with the internals?


Also - has anyone come across a yellow wire connecting their 5V connector to the internal RF shield?  Whats that all about?  I snipped it to get access to the PCB and the CPC works fine without it.


Thanks
Living Life, Loving Retro and listening to the 8bit chiptune of the Robocop theme.... good times!

Offline pelrun

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Re: 6128 Screen Image issue faulty DIN?
« Reply #2 on: 06:59, 08 July 19 »

If it's dry joints, you don't need to remove the existing sockets - just heat each joint up with the iron and add a little more solder. If you're going to desolder the sockets entirely, you should get new replacement parts instead of reusing the old ones - partly because they'll have 30 years less crap on the conductive surfaces, and partly because it's safer to destructively remove the old ones instead of trying to desolder them properly.


The capacitor you're talking about is just a decoupling cap. Any high frequency noise coming from the computer sees it as a short circuit and gets sent to ground, instead of going up the power cable and being radiated out. Removing it won't affect the computer operation at all - like the shield, it was only added to the german CPC's to satisfy their electrical noise standards.

Offline SyntaxError

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Re: 6128 Screen Image issue faulty DIN?
« Reply #3 on: 12:19, 08 July 19 »
If it's dry joints, you don't need to remove the existing sockets - just heat each joint up with the iron and add a little more solder. If you're going to desolder the sockets entirely, you should get new replacement parts instead of reusing the old ones - partly because they'll have 30 years less crap on the conductive surfaces, and partly because it's safer to destructively remove the old ones instead of trying to desolder them properly.


The capacitor you're talking about is just a decoupling cap. Any high frequency noise coming from the computer sees it as a short circuit and gets sent to ground, instead of going up the power cable and being radiated out. Removing it won't affect the computer operation at all - like the shield, it was only added to the german CPC's to satisfy their electrical noise standards.


Thanks pelrun - looks like I have a soldering iron project for today...


Also, do you think this DIN connector would suit the CPC6128?
https://www.ebay.co.uk/itm/2-MINI-Din-Sockets-Connector-PCB-6-Pin-176/121838766174
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Offline Bryce

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Re: 6128 Screen Image issue faulty DIN?
« Reply #4 on: 12:27, 08 July 19 »
Also, do you think this DIN connector would suit the CPC6128?
https://www.ebay.co.uk/itm/2-MINI-Din-Sockets-Connector-PCB-6-Pin-176/121838766174

No, that's a mini DIN, much smaller than the DIN socket on the CPC.

Bryce.

Offline SyntaxError

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Re: 6128 Screen Image issue faulty DIN?
« Reply #5 on: 13:14, 08 July 19 »
No, that's a mini DIN, much smaller than the DIN socket on the CPC.

Bryce.


WOW good save there Bryce - thank you.. I'm about to reapply new solder to both the DIN and 5V sockets - however I'm finding replacement DIN parts quite difficult to source here in the UK as they all seem to be of the MINI variety here in the UK. 
I did however spot this Japanese import option [size=78%]https://www.ebay.co.uk/itm/2-x-Replacement-Video-6-Pin-Female-Miniature-Din-Sockets/362279751512?hash=item54598e4f58&enc=AQADAAAC4FjVrDbVsZ8oH%2F8PNHtt9VX4%2Fw7FZcmMuqsX8uaFEduV6Rl6wu%2Fl85hZnsQg%2BT7lA4X0ysj3jANAialDoJ2SCYAbkBiJrpmpRWhJkI39R1d05wQhsFJChxozPN6R40XzAOYvzbxpqQGzkkvPLE%2FyOBAkM6GP2mp3%2FgkeaiaSlKITJjTiEB4Ki31SsDrqKD396az4Hga7EuYkHogup4ppugZ4HcwQ9iq1AtekYCbtfCdh21hMEcDQDQH%2FIWr5eiYgHtp%2B6BkZESMLocabYssD7zK2H8f7GQtRNLjxDgaCwST%2BCw0jTSeuc7vBuaPEzkUyEJlVD9aCS3NW1iINLNNcthFsdeMT2JvsqXpOAFkN4foYowRnjGkmb1SPLwKmx6kOioVJT9UuqodgcqiiE2YPBrEuMK0vrhWIP%2BsvwvRg6vV6JVtUosvDRNhKJSMmTCuq7O5pzBgzSLAApzMuD2xMMG6wfF4uXmI5v6bEiLhLU04Fp8UAqruvBo2XAOtGlTXXH3ko%2F%2B0%2BUO%2BA7mCIzuPrrK9eK8HNm1cVPtlppR0vNPeKeK%2FysSuT3wpOfQbINAsH%2FjPaQqexB6Nw2wE7Ez5K0pc%2FpPwV9aKD6Pp1N6%2FPpqZHNYa09JSWf11NOIr1ObDsg2%2B9TjkMR%2FtvDE3Vxci01v0j5HwQ7iBdQTPJZE%2FCyuzXQhRmpj%2BIX%2B0hHBz1OlgSo6CphTFTn%2Bq1hE2oLI8UhK5NO3YDzDH6YlzjBuf5VQP594NDedr5EcDFzI4GJ9nQRTX9p12yttqzD8KcyBD%2BQ%2B%2FeshHZk1vWcpOKddJGHRw6sKoAHw1M7OzRbidtTe3SJZPkGErE7vx86xo2kpm3lTs2%2BdSHf8Kugny6RiAIptFnt49GzAE13wZg3c5w0T4jN%2BS%2FxDWXg9zPTIOR%2FDCPEpvH6xKMvVHXnbf6hkLuYA%2FtmSZr3mMXXw8S4SLVuTenLNDcQ426T3%2FJ3cdrTSit%2FOQ%3D&checksum=3622797515125a5e6c1ca3aa4f37b6437bd6f7e08603[/size]
Is that what I should be on the lookout for?


Also
What barrel size is the 5V socket on a CPC6128? Would a 2.1mm like the one below be suffice?
https://www.ebay.co.uk/itm/5x-10pcs-DC-Power-Jack-Socket-2-1mm-Barrel-Type-PCB-Mount-C8H5-V4A1/332751130919?hash=item4d79835127:g:PO0AAOSwilJbaOJa


Thanks

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Offline Bryce

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Re: 6128 Screen Image issue faulty DIN?
« Reply #6 on: 13:36, 08 July 19 »
This is the one used on the Classic CPC: https://www.ebay.co.uk/itm/1-X-D6-FC680806-Socket-DIN-female-PIN-6-Pin-layout-240A-angled-90A-THT/113688209381

5.5mm outer 2.1mm inner for the classic power socket.

However, I'd just resolder the originals unless they are physically broken.

Bryce.

Offline SyntaxError

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Re: 6128 Screen Image issue faulty DIN?
« Reply #7 on: 20:51, 08 July 19 »
Thanks Bryce for the heads up regards the proper sized DIN socket.  FYI upon further inspection the ports themselves appear fine (both 5V and Video DIN).  I cleaned via contact cleaner and reapplied a fresh blob of solder on each of pins on the underside of the PCB and low and behold I now have a stable picture even when I apply a modicum of pressure on the ports - excellent!


I have very little software on disk at the moment as all my CPC goodies are tied up in Tape format - however while the odd game like KungFu Master appears to work fine, Ghosts N' Goblins always gets the screen rolling and blanking out during the first element of gameplay.  The title screen is fine as is the keyboard refine keys screens.


Could this be a memory issue?  Is there something different with this game ie. 128k features?
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Offline Bryce

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Re: 6128 Screen Image issue faulty DIN?
« Reply #8 on: 09:45, 09 July 19 »
It's unlikely to be damaged RAM. Almost any RAM hardware failure will cause the CPC not to boot at all.

Bryce.

Offline 00WReX

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Re: 6128 Screen Image issue faulty DIN?
« Reply #9 on: 12:33, 09 July 19 »
This sounds like the old Frequency switching issue that certain games & demos use, and is OK on CRT's but no go on LCD's.

The old Ghosts n Goblins was noted as one of those games.


http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/6128-on-a-17'-vga-monitor/msg36317/#msg36317

Cheers,
Shane
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Offline SyntaxError

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Re: 6128 Screen Image issue faulty DIN?
« Reply #10 on: 14:40, 09 July 19 »




This sounds like the old Frequency switching issue that certain games & demos use, and is OK on CRT's but no go on LCD's.

The old Ghosts n Goblins was noted as one of those games.


http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/6128-on-a-17'-vga-monitor/msg36317/#msg36317

Cheers,
Shane


Thanks Shane - that early forum entry was a very interesting read - hopefully Robocop and Batman aren't affected by the frequency issue - I don't fancy hooking up an old CRT again to relive my youth.


Bryce good news about my RAM chips then - so far.... Now I just need to source a replacement Spacebar and then I should have a fully restored 6128 - woohoo and then its a Centronics to Edge interface so I can enjoy some of the "bolt-on" goodness that everyone seems to eventually upgrade their CPC's with.
Living Life, Loving Retro and listening to the 8bit chiptune of the Robocop theme.... good times!