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midibob

Tales from Midibob's workshop SYS85

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Me too. When these dry up (ie no more donor boards) then folks will be stuffed. I wish I was clever enough to design a replacement with a PIC or whatever but I just don't have the skills.:(

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10 minutes ago, midibob said:

Me too. When these dry up (ie no more donor boards) then folks will be stuffed. I wish I was clever enough to design a replacement with a PIC or whatever but I just don't have the skills.:(

There would have to be a fair few wanted and sold before anyone would be interested in making any custom chips, and TBH there just is not that interest required in the fruit machine community as there is in other communities (your not talking 10's of chips either) even my no battery (yes no battery needed) ram chips fell flat and I only got 50 of each type made!

Edited by Andrew96_

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I remember looking in to this a while back and the big semiconductor warehouses had shed loads of them but you'd probably have to buy them by the 1000.:o Lord knows what they will ever do with them?

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8 minutes ago, midibob said:

I remember looking in to this a while back and the big semiconductor warehouses had shed loads of them but you'd probably have to buy them by the 1000.:o Lord knows what they will ever do with them?

that's if they actually had them! just the other day i searched for a custom ABI chip and one place said they had 3000 p;us! but when I contacted they actually had none! think they just do it to get inquiries and therefore peoples emal addresses!

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A couple of boards in progress. The first one had a burn up of the PSU connector and was looking a bit sorry for itself.

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Straight off with the battery and change out anything corroded. The PSU lead was really beyond repair and plug A too!
Luckily there was no track damage. Once everything was done, powered it up and it worked.:whistle: Wish more were like that.

 

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Looking much better now. Sorry the pics were taken different ways up.

The second board was in better nick but on switch on although the Alpha fired up with a battery alarm nearly all the lamps came on too. It then got as far as the game serial number then froze after 10 secs or so with an error bleep but the alpha had already frozen so no error code. At present I'm suspecting the 8279 chip which I hope to get a spare soon so I can prove it one way or the other. It's really annoying when you've used your last spare. I must remember not to do that in future!

Watch this space

Edited by midibob
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Another board came in that was untested so there was doubt whether the custom chip IC6 was going to be OK or not.

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I did a quick visual and repaired all the obvious bits like the power resistor, a couple of triacs (one missing and another almost falling off), a few heatsinks on the lamp power transistors and some of the transistors themselves. All the electrolytic caps were renewed too.

Time for power up. First thing was to check the 5v and this was found to be a bit on the low side so in with a new one and a good 5v was restored.
It booted up, which was a relief, but only as far as an ERROR 98 on the alpha (after the REPLACE BATTERY error). This is listed as a bad ROM cart but I knew the ROM cart was good? Anyway after a few switch on and off's the error went away and I eventually got into test mode. All test passed which was good news. Normal game play worked too so things were looking good.

The next day after switching on again I got the same ERROR 98 but it went after a couple of switch on's and played fine. It was looking like there was an issue when the board was cold. Directing freezer at all the IC's didn't narrow it down as once it was working it wouldn't stop working. Leave for a few hours and the same problem?
So, do I leave it  and hope it's going to be run in  a warm room. You know me, I couldn't let this one go......

Running a hairdrier quickly over the board first thing the next morning and it fired up perfectly. Directing the freezer again at various chips still didn't conclusively point to the culprit although the CPU was maybe looking a bit sheepish.:lol:

I decided to lift it and put a socket in so I could swap them about. With a new socket in, switch on and ......NO RESET!!!  Ahhhggg!!
What have I done? Tried another CPU, nope! Have I blown the custom chip? There were some outputs missing,  which filled me with dread. The spare chip was exactly the same so that was a relief. It was whilst I levered the chip out (it was in a socket already) that I saw an unwanted guest who'd set up home underneath!!

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I don't know if this has got anything to do with anything at present but I had to send in the bailiffs.

I did have a temporary battery connected during all this but it had come detatched on one wire so I thought maybe I've upset the RAM. You can tell I was getting desperate now!! New RAM, no difference. Time to have a break and a think.....

Now, it all worked before I socketed the CPU so it MUST be something there, but what?
I tapped out all the CPU pins and they all went to where they should go. Next I took waveforms from all the pins. Forcing the RESET high showed all good outputs on all DATA and ADDRESS lines.
I was just about to take a walk down to the riverbank when I thought I'd just check all the voltages on the CPU as I had a note of what a good running CPU should show. When I touched the probe on one pin it burst into life. Took a little while to realise why but see if you can spot it.....

 

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That's the CPU socket with no chip in it. You couldn't make this stuff up.

I'll put a new holder in tomorrow morning and then get back to the (possible) heat related fault.
I think I'll take up drinking!

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Brilliant work.bob and such bad luck with that socket .I assume that pin hole is filled ?

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It should have a tiny sort of circlip in it to grip the ic pin but this one was empty!! Not the sort of thing you'd check for with a brand new socket.:headache:

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Blimey that's pretty poor .just unlucky I guess and not many would check before fitting a socket

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No I don't think so. I'm sure it was from a reputable supplier. Just unlucky I guess.

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