MegaST - something recient.

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Bikerbob
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MegaST - something recient.

Post by Bikerbob »

Hey all, having issues with my MegaST project board. I am sure this is something self inflicted, this board has been out of a case and moved around and played with a lot.
I can start it up from dead cold. works for a min or two.. or if I run the Diagcart.. I get a pass on everything for the first min or two.. then I have these.. issues.. now.. the one with the 1m memory is an indicator I think because the machine has 4m and when first into diag.. shows 4mb..so .. maybe an issue with the mmu itself?

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exxos
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Re: MegaST - something recient.

Post by exxos »

PSU ?
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Darklord
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Re: MegaST - something recient.

Post by Darklord »

On his BBS I think he commented that he had swapped out that Mega ST's P/S with
another P/S from a known working Mega ST...
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Re: MegaST - something recient.

Post by stephen_usher »

Sounds like a dry joint or broken joint to me.

As something warms up something expands the the connection is broken.

Then again it could be a memory chip on the way out.

Cold spray is the way to go to try to locate the place where it's temperature sensitive.
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Re: MegaST - something recient.

Post by exxos »

Ah, I keep telling people about this. Just because the power supply works in one machine does not mean it will power another reliably.

I could easily have 200 PSUs here which will power up a STFM fine, but fail every time on a STE. Its why it is important to service them. If the mandatory fixes have not been done then people are just asking for trouble right from the start.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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Re: MegaST - something recient.

Post by Bikerbob »

So if I had to guess from the msgs I am thinking memory? IT is an area of the board I fussed with? I put new chips in.. and installed sockets.

SO.. can I just remove a ROW? or two Row? is there a way to try and identify it?

What do you mean by cold spray?

James
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Re: MegaST - something recient.

Post by Bikerbob »

exxos wrote: Thu Oct 28, 2021 4:00 pm Ah, I keep telling people about this. Just because the power supply works in one machine does not mean it will power another reliably.

I could easily have 200 PSUs here which will power up a STFM fine, but fail every time on a STE. Its why it is important to service them. If the mandatory fixes have not been done then people are just asking for trouble right from the start.
Yes I hear you Exxos, I have multi MegaSTs .. it is a psu from a megaST going into it.. I am not saying it could still NOT be.. but seems like a cold joint or something... going bad.. IF I was to check the psu.. am I just monitoring the +5 +12? I cannot scope it right now.

As for the manditory fixes.. I was just using this board to test the whole cloudy/Storm/Lightning thing.. and have a number of the fixes here ready to install when this went bad.. IF I can get it up and running again.. I will do a lot of them.

james
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Re: MegaST - something recient.

Post by rubber_jonnie »

BTW, do you have a bench PSU you can run it off? It would help knowing that your power is solid.
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800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
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Re: MegaST - something recient.

Post by Bikerbob »

rubber_jonnie wrote: Thu Oct 28, 2021 4:25 pm BTW, do you have a bench PSU you can run it off? It would help knowing that your power is solid.
No the only thing I have are PSU from PCs .. 300w 400w etc psu. It was one of those - smaller 110w that I was running the machine on. As a test I put the another psu from a MegaST in .. same result.

With all the movement I have put it through, I would guess its a cold, or poor joint, or maybe something "going" bad, just hoping to get an idea where to look.

The erros I have got one the diag cart.. is there any documentation as to what they are?? where I go?

James
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Re: MegaST - something recient.

Post by rubber_jonnie »

Bikerbob wrote: Thu Oct 28, 2021 5:13 pm
rubber_jonnie wrote: Thu Oct 28, 2021 4:25 pm BTW, do you have a bench PSU you can run it off? It would help knowing that your power is solid.
No the only thing I have are PSU from PCs .. 300w 400w etc psu. It was one of those - smaller 110w that I was running the machine on. As a test I put the another psu from a MegaST in .. same result.

With all the movement I have put it through, I would guess its a cold, or poor joint, or maybe something "going" bad, just hoping to get an idea where to look.

The erros I have got one the diag cart.. is there any documentation as to what they are?? where I go?

James
I have, I think, three Mega ST threads on here (Sorry I can't find them ATM) and at least one goes into the RAM checks of the diag cart.

Also, you sometimes see different stuff over the serial port, so worth trying that too.
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
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