Top of the pile

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atari030
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Re: Top of the pile

Post by atari030 »

Keeping track of everything is getting to be hard work. I've been recapping all the ST power supplies I have. List goes like this;

Mitsumi SR98 x 2
ASPF34-4 x1
Tokin x1
DVE DSP-508A x1

The DVE is the only one I could get HV caps for locally. Its working a treat now. Interestingly the supplies with the most visible problems are the Mitsumi's. They looked atrocious when I pulled them out. One of them had a bulge in the 47uf 400v cap and the rest on both had leaked.

I decided to check the MegaST PSU's while I was at it. The two I have had ASPF34-4 PSU's. I decided to give the ASPF out of the big button 1040 a crack in the Mega and low and behold it worked. I'll look into that a bit more. One of the ASPF supplies is a rev 6 and has C3 installed.

I wasn't a recap skeptic, but was always figured if it ain't broke.... well, most of these PSU's had leaky caps. Its worth doing.
atari030
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Re: Top of the pile

Post by atari030 »

With so many ST's I'm still recapping seemingly ad infinitum. Also taken on an A600 and Vampire for a mate which means I'm looking at recapping a couple of A500 PSU's too. It's getting right out of hand.

I picked up another STE motherboard and PSU so I now have two in need of cases. Not sure how this keeps happening.....

On a happier note, the Aussie summer is great for retro whitening ST's and keyboards. I've had a few yellowed ones that are now back to white. It seems to take about three days on average with good results just after one day. I have a couple of stubborn ones but I will persist. At least they now look grey rather than yellow.

Fixed a pile of spare keyboards too. Slowly winning and the repair pile is getting smaller by the day.

Progress.
atari030
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Re: Top of the pile

Post by atari030 »

My has time passed. Thought I'd update as I got the MegaSTE up and running this evening. It had two significant faults, a stuffed trace on A5 from the ROM's. I buzzed it out as I suspected a ROM fault and found no continuity from the ROMs to the blitter or CPU. Reflowed that and continuity was back. Still no go. I swapped out the CPU for a 16mhz HC over the warmish 12mhz model that was in there and eureka. Diag cart reports all good and no more white screen.

It is moaning the blitter isn't installed so I have to work that out - early model, separate blitter. Beats a white screen though. I hadn't touched it in a while because I frustrated myself by attempting fixes without thinking it through and making it worse. So, tonight back to the drawing board and 1 am here we are. Another functional MegaSTE and a happy Kiwi.

I've also repaired and rebuilt the STE boards so I have another pair of nice machines on the shelf. Picked up a remake 800XL board to build as well. Dropped a HDD controller in my other MegaSTE, put the CT2b Falcon back in its original case and repaired a ton of Amiga's for a mate.

I've been in and out of here reading as time permits over the last year but lacked the will power to get back on the horse. Not much in the pre covid piles of Atari repairs left to go. It feels pretty good.

Qapla'
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kodak80
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Re: Top of the pile

Post by kodak80 »

Glad to hear you are back on the horse again and you have been fixing your Atari's. I saw those 800xl remake boards but have resisted buying one as I would need to then search for components as my current 800xl is working well since I replaced the damaged ram chips.
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atari030
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Re: Top of the pile

Post by atari030 »

After I bought it I looked at the cost of the parts. Yowzer. I did think it would be cool to try and use modern implementations where I can from Lotharek. I.e. CPU, VBXL< SRAM etc. I do have quite a few spares and a really knackered 130XE for a doner. I'd really like a 130XE remake mind you. What would be real cool is a MegaST remake board or a Falcon060.

I quickly swapped out the blitter on the MegaSTE this morning, its looking like socket problems. The menu selection is back but it bombs pretty easy. I put MegaSTE boards right up there with 130XE boards for Atari quality. The things we do. Might have to get a replacement socket.

BTW, that SCSI controller worked a treat, cheers. Much better than the Link I was running to an external HDD. I dropped a 1g Seagate in and voila. So I will have two MegaSTE's, one pretty much stock and this one. I replaced a fair chunk of the resistors as they had corroded quite badly, recapped, replaced corroded IC's.... it (sort of) kept me from going insane during the lockdowns in Melbourne. So this is pretty satisfying.
atari030
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Re: Top of the pile

Post by atari030 »

Moving along slowly, post COVID I'm spending a lot of time in the bush and little time on the bench. Anyway, I have been playing around with the MEGASTE and from what I can see I have the blitter/CPU/CACHE etc running OK. Diag cart passes everything of concern. What I am getting is 2 bombs on boot from a Language disk. Its seems to me the problem is the floppy controller. I get errors formatting, and from what I can tell it bombs loading the CPX's etc. I thought it may have been the cache or blitter but using a small auto program over the CPX's it works fine. I also noted that not all the CPX's load consistently on boot. That can be attributed to read errors from floppy.

I had socketed and switched the 7406 and the 2149. I've swapped out the 1772, both IC's I have are 02-02 chips so they should work HD - although I understand there are no guarantee's. I have switched it back to DD (JP7) just to check but still no go. I've also tried four floppies, some brand new. What is consistent is I am getting read errors off a lot of floppies and formatting is a real problem and just throws up disk errors. Also getting read errors trying to load programs from floppy, it will error and can out as per the CPX's.

So, what I suspect is the bombs are occurring due to floppy errors, not any other hardware fault. I'm hoping it isn't a DMA chip as the MegaSTE is surface mount. Will it make any difference if I'm using a Low schottky 7406 instead of the original 7406?
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exxos
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Re: Top of the pile

Post by exxos »

atari030 wrote: Mon May 02, 2022 2:54 am Will it make any difference if I'm using a Low schottky 7406 instead of the original 7406?
Not as far as I know, no.
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atari030
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Re: Top of the pile

Post by atari030 »

Cheers Chris, thought as much. This is going to take some work but considering it was dead I'm confident. Hell, its only taken me 20 odd years so far. :D
atari030
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Re: Top of the pile

Post by atari030 »

Broke the do one thing rule again last night, but made a lot of progress. I cleaned the heads on one of the floppies I was using, a new TEAC IIRC and found my box of SIMM's. So I swapped out the ram and ran YAART overnight. I ran up some disks that were prone to throwing up 2 bombs and they worked. Demos, boot disks.... so far so good. I'll punish it tonight but its looking pretty promising. I'd wager the RAM was more an influence but a head clean can never hurt. Oddly, the other RAM I used passed tests too.
atari030
Posts: 328
Joined: Mon Feb 12, 2018 12:43 pm

Re: Top of the pile

Post by atari030 »

Ok, lets for a second assume I'm a dumb arse and instead of going to bed I decided to fix the slight ghosting on my MegaSTE, now that its back up and running. Lets also assume I hooked a 10uf cap up to C506 and didn't solder it in place. Next, lets assume it slipped and shorted against L501 which resulted in a spark and now the colour output is pretty much stuffed.

Display is a very dark washed out image either RGB or composite. Mono is unaffected. Sigh. Hoping it ain't the shifter cooked.

Image
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