C103225 REV.2

STFM motherboards.
KD4CBM
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Joined: 05 May 2023 23:13

C103225 REV.2

Post by KD4CBM »

Here is my C103225 REV.2 STFM board awaiting mandatory upgrades and 4 Meg upgrade.

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exxos
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Re: C103225 REV.2

Post by exxos »

:thanksyellow:

One of those odd revisions I don't seem to see very often.
MacTech05
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Re: C103225 REV.2

Post by MacTech05 »

KD4CBM,

That is same motherboard I have in my 1040 STFM. You don't happen to have a schematic specific to the motherboard, do you? I am trying to locate the Reset circuit capacitors so I can replace them.

Thank you
Randy
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rubber_jonnie
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Re: C103225 REV.2

Post by rubber_jonnie »

MacTech05 wrote: 28 May 2024 08:05 KD4CBM,

That is same motherboard I have in my 1040 STFM. You don't happen to have a schematic specific to the motherboard, do you? I am trying to locate the Reset circuit capacitors so I can replace them.

Thank you
Randy
From what I can see looking at a bunch of schematics, the reset circuit is much the same across all boards and uses a 556 IC labelled either U2 or U37, so you'll be looking at the electrolytic caps surrounding that and that are connected to it.
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...
MacTech05
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Re: C103225 REV.2

Post by MacTech05 »

rubber_jonnie,

I will check that out.

Thank you.

Randy
MacTech05
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Re: C103225 REV.2

Post by MacTech05 »

rubber_jonnie,

Thank you for the info on finding the Reset Circuit capacitors on my 1040 STFM. While I still have not found a schematic for my 1040 STFM motherboard, I did find and download a different 1040 STFM motherboard schematic. Based on your information, I found the Reset Circuit capacitors immediately on the schematic and on my motherboard. I have replaced the capacitors.

Thank you!
Randy
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rubber_jonnie
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Re: C103225 REV.2

Post by rubber_jonnie »

MacTech05 wrote: 06 Jun 2024 13:34 rubber_jonnie,

Thank you for the info on finding the Reset Circuit capacitors on my 1040 STFM. While I still have not found a schematic for my 1040 STFM motherboard, I did find and download a different 1040 STFM motherboard schematic. Based on your information, I found the Reset Circuit capacitors immediately on the schematic and on my motherboard. I have replaced the capacitors.

Thank you!
Randy
:girldance:
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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