Below the description of the repairing of two Processor Technology SOL-20.

Processor Technology SOL-20 #1 Repair

Defect:

• Dead/Split Screen.

First of ALL!

• You should never replace CD4029 with HCF4029 although apparently could work and maybe it works .. on some motherboard could do bizarre defects or video glitches, like a split screen!

Components replaced and fixes:

• Replaced all IC series HCF 4XXX HCF with the right CD 4XXX series.
• Sprayed DUE-CI G-22 on all Texas Instruments IC sockets.
• Replaced wrong ic 74LS157 in place of a 74LS367 (U29)
• Rebuild broken pcb track near the caps (C15)
• Replaced wrong capacitor of 22uf in place of a 1uf (C67)
• Rebuild  bridges under the IC U46 that has seen better days.
• Replaced Capacitor (C31)
• Remake cold welding on the PSU connector and the socket of CPU Intel 8080A.
• Removed a little piece of solder under a socket (see photo)
• Replaced 74LS138 (U34) dead without reason while typing this text on the SOL-20 (FUCKKKK!!!!!!!!!)

… Some Beers… :-D

Gallery of the repair:

Processor Technology SOL-20 #2 Repair

Defect:

• Black Screen/Dead.

First of ALL!

• You should never replace CD4029 with HCF4029 although apparently could work and maybe it works .. on some motherboard could do a bizarre defects or video glitches!

Components replaced and fixes:

• Replaced all IC series HCF 4XXX HCF with the right CD 4XXX series.
• Sprayed DUE-CI G-22 on all Texas Instruments IC sockets.
• Cleaned the motherboard and connectors with Kontakt PCC (Printed Circuits Cleaner)
• Temporarily removed the IC 74LS136 (U22) which put in short-circuit the personality card and burned the 74LS04 (U24). Probably this is a “homebrew” modification for a particular Personality card.
• Replaced wrong ic 74LS04 (U23) in place of a 74LS20 (U23)
• Replaced RAM 2102 (U15)

Note:

• Many sockets not of the Texas Instruments completely rusted are previously been replaced by the owner of this computer (Alessandro Polito).

Gallery of the repair:

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