Thanks again for your replies. As this is the first PET I have ever owned, I'm not sure what the differences are between the variants. The product # on my motherboard says: 320081. I had only a few moments this morning to do some quick probing around, and this is what I found. all four 7805's basically have 0 volts going in or out. So I tested the voltages between GND and at the two IN5402 diodes (CR1 and CR2 on the 320081-2 schematic). I have 8.4V going into both and less than a volt coming out! Phil On Aug 9, 2009, at 4:32 AM, Ethan Dicks wrote: > On 8/8/09, B Degnan <email@example.com> wrote: >> Phil, >> What version of the PET 2001 do you have? Is it a 2001-8 or a >> 2001-16/32N or a 2001-32B? I forget from the beginning of this >> thread. > > My understanding is an 8K Static PET, based on the board number he > gave earlier. That's what I've been using to shape my replies. > >> If you have a later 2001 model, I found this comment in some notes I >> have "..check the voltages from the anodes of the diodes CR10,11,12 >> located alongside the heatsink. VR6 regulator supplies the -5V to >> the >> dynamic RAMs. > > Later PETs do have a 7905 and I've tested the voltage at TP10. The > PET of this thread has three 7805s in TO220 packages, not one 12V and > two 5V regulators in TO3 packages. Different sections of this board > are driven by each regulator (I gave the grouping earlier). You have > to check all three since they are not tied together. If none are lit > up, and you know you have enough AC voltage coming out of the > transformer (8VAC ought to be enough), the next thing to check is the > rectifier diodes and maybe the large (though not as large as later > PETs) filter cap. > > It's a simple linear power supply. There are only about a dozen > elements to check, and half of them are only suspect if you have power > but it's bad power (too much ripple, noise, etc). You can make a > really simple 5V PSU with just a source of about 8-9VAC, an > electrolytic cap for a filter, a small ceramic or tantalum as a bypass > cap for the 7805 and the 7805. That's more-or-less what a static PET > has, but times three. > > -ethan > > Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2009-08-09 01:46:52
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