Hi Julian, Ok, thanks. This might explain why my plus4 died earlier... from these it is obvious that the regulator is broken. I decided that I will go for the regulator that Gerrit advised. I assume however that as it is a DC-DC step down regulator I still need the graetz bridge and the 4700uF Elko Capacitor which is before the original 7805. Can someone confirm it? Thanks Istvan -----Original Message----- From: Julian Perry Sent: Thursday, September 20, 2012 2:31 PM To: Hegedűs István Subject: Re: plus4 power supply Hello Hegedűs, Thursday, September 20, 2012, 9:39:20 PM, you wrote: When replacing my C64 power supply innards with a regulated switchmode version, I noted a voltage drop of 0.2V across the power lead into the C64 under load - so the PSU needed to output 5.2V, to have 5V available at the C64. (I adjusted it by measuring the voltage of the 5V rail on the PCB, with the C64 operating). I presume it is similar on the plus4. Fortunately, the output voltage on the switchmode PSU I purchases was adjustable. It DOES raise the question - what effect high drawing devices such as the Z80 cartridge, and REU would have on the "on-pin" voltage on the 5V rail. (as to Gerrit's question - I'd be alarmed at 5.6V - that's %10 over) Julian > Hi Gerrit, > That is strange because I have measured an old C64 power supply and other > plus4 power supplies which provide 5.4v. The plus4 power supply schematic > diagram says 5.2v though. > I have checked the CPU datasheet and it says max voltage is 7v but of > course > the other components might not like it. > I know the regulator you linked here but that still needs the diode > bridges > and the 4700uF capacitor (I believe). The heat is generated by the 7805 > regulator so you are right it will be cooler (and maybe more stable). > Istvan > -----Original Message----- > From: Gerrit Heitsch > Sent: Wednesday, September 19, 2012 9:40 PM > To: firstname.lastname@example.org > Subject: Re: plus4 power supply > On 09/19/2012 09:25 PM, Hegedűs István wrote: >> Hi, >> I have done a major repair service on my plus4 power supply. Replaced >> the electrolyte and tantal capacitors, the diodes. Now it supplies 5.6v >> while before it supplied 5.4v. Is it dangerous for the plus4? What >> should be the voltage level of a normal power supply? (Note that I have >> only a multimeter and no scope so might be measurement difference). > It shouldn't go above 5.2V. You should do a complete rework of the power > supply remove the existing regulator, get a switching regulator, for > example > http://www.ebay.de/itm/290572036224 > This one is adjustable, so adjust to 5.2V _before_ connecting the Plus/4. > As a sideeffekt, the PSU will run much cooler. > If you feel _really_ adventurous, you can put a complete switching power > supply that runs on 230V and supplies 5V 2A into the empty part of the > Plus/4 PSU. The transformer will then only be used for 9V AC. > But since one has to work on 230V AC, this is only for people who know > exactly what they're doing. > Gerrit > Message was sent through the cbm-hackers mailing list > Message was sent through the cbm-hackers mailing list -- Best regards, Julian mailto:email@example.com Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2012-09-20 13:01:07
Archive generated by hypermail 2.2.0.