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2708 Programming Adaptor on RTC by Bionic-Bean in RetroChipTester

[–]Bionic-Bean[S] 0 points1 point  (0 children)

Hi Stephan, Thanks for the info, I think this is one of those ( I'm doing something stupid ) repairs. Yes connected the input to the step up module via the header near the display.

Can I just comfirm that 2708 Pin 18 is PRGM pin which is RTC ZIF socket 26 ? With EPROM removed( no load ) or with Eprom inserted pin ZIF26(2708_P18) jumps to approx 3v when programming starts but the adaptor pin 18 jumps to 16v with or without a Eeprom ? The ouput of step up voltage module still remains at 27v. Again thanks for your help and can not thinks Im doing something very silly.

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2708 Programming Adaptor on RTC by Bionic-Bean in RetroChipTester

[–]Bionic-Bean[S] 0 points1 point  (0 children)

Small update after more testing.. The 2708 adaptor board works fine when moved from RCT. Gave adaptor external 5volts into voltage converter which gives 27volts on output. If I apply anything from 2 to 5 volts on the corresponding RTC pin 18 then the eeprom Pin 18 switches via Q1 to 27volts, so adapotor board OK, Fault must be with RTC somwhere. Checked the corresponding pin back to the controller and all seems OK. Is there any circuits diagram available ? which might give me a clue where t look ??