Top of the pile

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atari030
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Re: Top of the pile

Post by atari030 » Sun Feb 25, 2018 12:14 am

My eyesight isn't as good as it used to be. :lol: Didn't see that next to the shifter.

So RP3,4,5, and 6. Makes sense. A SIL array might take some time to find, locally. I have a few parts on order, so this one might have to get put aside till they arrive. Probably time to replace the RAM in my 130XE.

atari030
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Re: Top of the pile

Post by atari030 » Sun Mar 11, 2018 12:50 am

I decided to have a quick look at the Mega's last night, it occurred to me that the mega4 might kick over if I pulled the 1000uf cap. It did. Progressed to a ROM/RAM black screen and no longer throws rubbish up. Which leads me to believe the bulk of my issue is confirmed. Power supply. Current delivery from the PSU's I'm using. It is clear a 2amp PSU is not enough to crank the old things over properly and the original PSU was probably failing for a long time causing me to chase red hearings.

I also noticed the MMU socket on the Mega2 is a bit touchy, that can be fixed later. For now, I have to address the PSU. So I will nip down and grab a set of caps for it. I was going to replace the rectifier bridge but Jaycar don't stock the W08. I don't know how bad this thing is, but if I have to replace every component, so be it. Chris, would an RS206 be an OK substitute for the W08?

I found my 2600jr, 2600 vader and spare 130XE, parts arrived from the UK, so let the fun commence.

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exxos
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Re: Top of the pile

Post by exxos » Sun Mar 11, 2018 12:58 am

You can use almost anything which is 4amps 600v and over.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

atari030
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Joined: Mon Feb 12, 2018 12:43 pm

Re: Top of the pile

Post by atari030 » Sun Mar 11, 2018 1:04 pm

Swapped a few caps out, and the rectifier. No dice. I'll have to sit down a bit longer with this one I think.

However, I had an epiphany, I have a deceased megafile 30 lying around so I decided to pull the PSU out and have a looksee. It has a Mitsumi SR151 in it. I figure if it can run an ancient MFM/RLL HDD then a Mega ST shouldn't be a chore. Low and behold it fired over, even with the 1000uf cap installed. So there you have it, weirdo mess patterns on your screen can easily be PSU problems.

Tomorrow I will replace a few bits and pieces on the board, but it looks pretty good. The Mega4 looks to have bad ROM's, so I will play around with 6 chip sets too.

I don't know what the rating on the SR151 is, would they be potent enough to run a Mega, Chris?

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exxos
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Re: Top of the pile

Post by exxos » Sun Mar 11, 2018 1:15 pm

atari030 wrote:
Sun Mar 11, 2018 1:04 pm
I don't know what the rating on the SR151 is, would they be potent enough to run a Mega, Chris?
Would assume be similar rating to the SR98 and other PSU's.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

atari030
Posts: 50
Joined: Mon Feb 12, 2018 12:43 pm

Re: Top of the pile

Post by atari030 » Sun Mar 11, 2018 11:52 pm

If it is enough for the Mega, all good. I'll give it a re cap. Next step is reinstall the smoothing cap, drop TOS 1.04 in, put three jumpers in for ROM select, replace the reset switch, swap the PCB's of the PSU's around and put the thing back together. All I need is a bit of time.

atari030
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Re: Top of the pile

Post by atari030 » Mon Mar 12, 2018 7:00 am

Success. Man that reset switch was an absolute mongrel. Only thing left is to try the 6 chip 1.04 sets I have. 1.02 2 chip is cooking with gas, I installed a jumper to make it easier.

Image

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Image

The next conundrum is, do I modify the front of the case for the grey 1.44 that is hooked up atm or look for a big button floppy? Bearing in mind I have another Mega 4 ST that has the same off floppy problem.

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exxos
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Re: Top of the pile

Post by exxos » Mon Mar 12, 2018 10:38 am

:bravo:

Was the "failing psu" recapped ? (can't see if you said or not ?)
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

atari030
Posts: 50
Joined: Mon Feb 12, 2018 12:43 pm

Re: Top of the pile

Post by atari030 » Mon Mar 12, 2018 11:02 am

It was, unfortunately it has given up the ghost. More than just caps, it seems. I replaced the reg as well but I'm getting nada out of it. I can't get any 6 chip varieties to work, it may be the burnt roms I have aren't burnt correctly. The ULM demo sort of fires over, but no desktop. 1.02 is fine, so I'm not too bothered.

atari030
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Joined: Mon Feb 12, 2018 12:43 pm

Re: Top of the pile

Post by atari030 » Thu Apr 12, 2018 2:53 pm

Been a bit busy over the last month, chips arrived from the UK so I changed out the PMMU on the cactus 130XE, still no response, red screen of death. I will have to tackle RAM/Freddie on this one when I have more time and parts.

On a brighter note, I dug out the SEGA's and 2600's. The Darth vader still works ok but the AV mod isn't great - I will go back to that. The JR I modded years ago and could only ever get black and white output out of it. Looking at a few pics I'm wondering if it is NTSC unit and I have just been too dumb to work it out that it was outputting 60 Hz PAL..... Dumbo moment, its a PAL TIA. I haven't looked at this thing in 10 years.

Either way, all the old boxes are coming back on line and I'm loving it.

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