----- Original Message ----- Sent: Friday, August 19, 2016 3:22 PM Subject: Re: cbm 8032 motherboard + atx power supply > On 19/08/2016 20:28, Steve Gray wrote: >> +5V, +9V, +12V, -5V regulated to the main board >> +9V, -9V, +16V unregulated to the expansion power connectors >> according to page 11 of the schematics..... I think you got it a bit wrong, there is no regulated +9V, ohny unregulated. -- Christian Dirks Toast_r@Idealine.info ---------------------------- I don't think everyone is aware that unlike Apples and in fact most other computers, the older PETs do not actually have a discrete power supply per se. There is a transformer and a filter cap that plug into the main board and everything else (bridges, diodes, regulators, filter & bypass caps etc.) is on the board. The board is supplied with 9VAC and 16VAC; from those it generates: +5V regulated (the main supply, around 4-5A), using one or two regulators. +12V regulated for the DRAMs -5V regulated, also for the DRAMs +9V unregulated for the cassette motors and it supplies +9V, -9V and +16V unregulated on the power expansion connectors. If you don't mind some drilling, cutting traces and adding jumpers on the main board then a slightly modified AT or ATX supply would do the job; as mentioned elsewhere, if it doesn't have the -5V it's easily derived from the -12V. There are several approaches, more or less neat and with more or fewer modifications. If you want a plug-in (no mods to PCB) switching solution then you would need three voltages: +9V at around 4-5A +16V at around 1A -9V also around 1A or less. They're not critical and don't have to be regulated, so you might get away with merely disabling/modifying the regulation on an AT(X) supply and using that. m Message was sent through the cbm-hackers mailing listReceived on 2016-08-19 22:00:03
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