X68000 Ace HD - Red Video Signal Died? UK Repair Options?

[cauterize]

Hey all,

I recently purchased my very first x68000 after several years of research and uncertainty.

After the system arrived I waited for both the Sanwa video adapter and a floppy drive with some blank disks (so I could get some software written to them in Win98).

All seemed to be going well after I had a few games running just fine in 31khz on my CRT monitor. Then all of a sudden the red channel in the video just seemed to disappear.

Dispite trying different monitors, turning the system on and off, and countless other things too, I'm still missing the red no matter what I do.

I'm assuming that the system is in need of a recap (mainly the video board), which is something I was afraid of. As much as I appreciate the advice on this board here about doing it yourself, my soldering skills are woeful and I'm reluctant to put this new purchase at risk. The last project I attempted saw a PC Engine Duo-R nearly taken to extinction...

Is there anyone in the UK that is able to repair these systems? I'm more than happy to pay for parts and servicing - but in the meantime I'll be messaging the seller as this system was only bought a week ago

Thanks
Adam

[neko68k]

Maybe it's the adapter. Or the cable.

[kamiboy]

Yeah, a faulty cable or adapter is more likely to be the cause than capacitors.

But regardless of that, the PSU has to be recapped on the towers, there is no getting around it. Furthermore, the Ni-Cad battery has to be changed as well. Neglecting either of those things is tantamount to machine suicide.

[cauterize]

Thanks for the replies, but you've made me realize one thing I forgot to mention.

I tested the issue with two different VGA leads, the two Sanwa adapters I have, and two different monitors. Each time round the whites on screen we're very blue, with red missing from the picture.

The monitors and cables (minus the adapters) were then tested with my PC and appear to be working fine sadly.

Really worried about this now 

[eidis]

 Hi Cauterize !

Leaked capacitors can lead to corroded or eaten traces near them. This failure can be repaired while taking minor impact on motherboard esthetics and you will probably have to take your X68000 apart and see what is going on inside.

How to open X68000
http://gamesx.com/wiki/doku.php?id=x68000:how_to_open_x68000

Keep the scene alive !
Eidis

[cauterize]

Hey Eidis,

Thanks for the reply! I was wondering if you were still around Unfortunately I have both some good news and some bad news.

I took apart the Ace HD and had a look inside. Everything from what I could see appeared to be fine. The video board showed now signs of corrosion at all, which had me rather puzzled. I reconnected everything again and decided to boot up the system.

Surprisingly the video signal was back to a clear RGB signal - with the insert disk prompt appearing in black and white. However, it only stayed that way for around 10 seconds. After that, the red signal dropped out once more and the picture went back to being very blue.

Looking inside the system once more I noticed three pots on the video board. Twisting these appeared to change the R, G and B values, but again the R one didn't seem to change as it was still not being output.

Sadly I'm back to square one with a broken video signal... Any more ideas?

Cheers,
Adam

[eidis]

 Hi Cauterize !

This sounds like an intermitent signal which could be caused by cold solder joint or poor contact. The best way to diagnose them is by checking for continuity with a multimeter. There could be a lifted pin at the connector where the video board plugs in. Also I would highly advise you to replace all capacitors in your X68000, if it has not already been done, before doing any further testing. The original capacitors are way past their lifetime. The ACE is built to last and replacing through hole capacitors is very easy on them.

Keep the scene alive !
Eidis

[Monstermug]

Missing colours is normally the result of faulty capacitors at locations C4, C9 and C8.  C4 being in charge with Red.  You can actually test these capacitors in circuit with a ESR meter.   Be warned though, these capacitors are on a massive ground plain.  You need to heat up the Negative legs of these capacitors pretty hot to remove the solder.

If this doesn't fix your problem the signal goes back via a few resistors and then transistors at Q1 and then into pins 29 (Red output) of the Video amp M51387P.  This signal is fed from Pin 4 of M51387P chips and then follows back via a few resistors and smoothing caps to the 74LS07 buffer and then to VR pot at VR1. 

If anybody is interested, changing capacitor at location C4 and socketing a new Video amp fixed the problem.  Red is now showing.