Exxos 4MB Ram Upgrade for C070789 - Different Issue

Upgrade your RAM from ST to Falcon.
kbjunkie
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Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by kbjunkie »

Hey all,

Started a new post about the 4MB EXXOS RAM upgrade that I recently had issues installing (and getting working with the 1MB/4MB switch) as this is a new issue..

I decided just to heed general advice and not worry about the 1MB/4MB switch, soldered the link on the RAM upgrade board for 4MB and all was good. Until today.

Today the STFM was switched on and I get a light blue screen with thick vertical black bars:
Screenshot 2024-05-14 21-45-02.png
Screenshot 2024-05-14 21-45-02.png (1.03 MiB) Viewed 292 times
The PSU in the STFM was recapped about 8 months ago - and all voltages tested today are good.

I've checked the install of the RAM board (which has been working fine for a couple of weeks now with constant use) and that's all good too.

I've taken out both PLCC chips, checked and cleaned the sockets and the chip pins and reinstalled them.. I've taken the shifter out and re-seated it too.

Can anyone point me in the right direction on what to check out next?

Thanks,

kbjunkie.
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Re: Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by kbjunkie »

A quick update...

I noticed that one of the 3 68R resistors that need fitted wasn't soldered properly and was hanging loose at one side. I've completely removed it and fitted another. Also checked for shorts and all is good.

Now all I get is a white screen and no boot. Tried with my Gotek - nothing and even fitted a floppy drive back in and neither will even attempt to boot. Leaving it for a while with no disk and it still doesn't boot into the desktop..
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Re: Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by exxos »

That bad resistor contact was a probable cause of your odd switch issues. But now you seem to have another problem.

You need the diagnostic cart to find out what the problem may be. But it sounds like if bad soldering is in the mix, I think your machine needs professional diagnostics and repair now.
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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: Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by kbjunkie »

Been involved in electronics for 30+ years - my soldering is good :-) I've checked all the traces across the desoldered ram chips and your new board for breaks/shorts and all is good there too.

The resistor was not soldered properly as I soldered it in place once the machine was partially re-built as I'd forgotten to do it - so it was tacked temporarily across the pads.

The diagnostic card I have was one purchased from yourself exxos - and I've never really had much luck getting it to work. Cleaning the edge connector with IPA doesn't help and it will frequently just not work. I'll give it another go I guess.

I may build a cart and put the diagnostics on it once more and carry on.

The bad resistor wasn't the issue with the switch. I replaced the resistors after all that mucking around with the RAM board. :-)

Is there anything else that could be causing a white screen with this RAM board?

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Re: Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by exxos »

The bad resistor wasn't the issue with the switch. I replaced the resistors after all that mucking around with the RAM board. :-)
But if you remember I suggested there was some floating signal as the fault with the switch made no sense. So indeed you did have a floating signal, and was likely the cause of your switch troubles. Just having your hand near a IC can alter its state when a signal is floating.
kbjunkie wrote: Wed May 15, 2024 9:15 am Is there anything else that could be causing a white screen with this RAM board?
White screen can have multiple causes, such has bad contents on the GLUE / ROM, bad reset circuit / switch. I think you have gone from installing a RAM board to troubleshooting your whole machine now.
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: Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by rubber_jonnie »

With a white screen that's often due to ROM issues, I'd suggest that by pulling and cleaning the PLCC chips you now have a bad contact either on the GLUE or MMU and the ROM can't be accessed.

I'd suggest you pull both and tweak the socket pins and also spray with something like Electrolube or Deoxit before reassembly. It's really easy to upset these sockets.

Generally I have noted that with a white screen the diag carts don't work, but you could try to get a serial cable hooked up to a PC with a terminal program like Teraterm and see if it gives any diagnostics over serial.
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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
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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Re: Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by kbjunkie »

But if you remember I suggested there was some floating signal as the fault with the switch made no sense. So indeed you did have a floating signal, and was likely the cause of your switch troubles. Just having your hand near a IC can alter its state when a signal is floating.
I replaced the resistor after I had decided to give up on the switch. The original resistors were in the board - I measured them out of circuit and one of them was low, so I cut it out and tacked a new 1% 68R resistor in place - but after the issues I had with the switch.
White screen can have multiple causes, such has bad contents on the GLUE / ROM, bad reset circuit / switch. I think you have gone from installing a RAM board to troubleshooting your whole machine now.
I wonder if it is an issue with the TOS ROMS or the GLUE then. I may just bite the bullet and replace the sockets since I have a few spares here. I'll take the advice and check the reset circuit too.
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Re: Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by kbjunkie »

With a white screen that's often due to ROM issues, I'd suggest that by pulling and cleaning the PLCC chips you now have a bad contact either on the GLUE or MMU and the ROM can't be accessed. I'd suggest you pull both and tweak the socket pins and also spray with something like Electrolube or Deoxit before reassembly. It's really easy to upset these sockets.
I've done that already - pulled the chips, cleaned the pins of the chips and the socket and added a little Deoxit - no joy.
Generally I have noted that with a white screen the diag carts don't work, but you could try to get a serial cable hooked up to a PC with a terminal program like Teraterm and see if it gives any diagnostics over serial.
That's a good idea - I'd forgotten about the serial output - I may try that but I reckon that my diagnostic cart has met it's maker. I may just build one :-)
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Re: Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by stephen_usher »

With regards to the cartridge port, I've found the best way of cleaning it is to fold an A4 sheet of paper three times (or four... basically trying to make it the same thickness as the cartridge PCB) and spray it with contact cleaner and then gently insert the corner into the slot and rub in and out. You will have to do this along the whole slot and not rub side-to-side as this can bend the contacts.

The slightly rough surface of the paper will gently polish the surface of the contacts, removing corrosion, but not erode the metal.
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Re: Exxos 4MB Ram Upgrade for C070789 - Different Issue

Post by rubber_jonnie »

kbjunkie wrote: Wed May 15, 2024 10:59 am
With a white screen that's often due to ROM issues, I'd suggest that by pulling and cleaning the PLCC chips you now have a bad contact either on the GLUE or MMU and the ROM can't be accessed. I'd suggest you pull both and tweak the socket pins and also spray with something like Electrolube or Deoxit before reassembly. It's really easy to upset these sockets.
I've done that already - pulled the chips, cleaned the pins of the chips and the socket and added a little Deoxit - no joy.
Generally I have noted that with a white screen the diag carts don't work, but you could try to get a serial cable hooked up to a PC with a terminal program like Teraterm and see if it gives any diagnostics over serial.
That's a good idea - I'd forgotten about the serial output - I may try that but I reckon that my diagnostic cart has met it's maker. I may just build one :-)
But have you tweaked the socket pins as well as cleaning them?

This is what I meanviewtopic.php?f=17&t=1484&hilit=PLCC

Sometimes cleaning is not enough.
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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