Date: 2006-11-16 08:33:56
Hallo Bill, > The 6545 chip (Cathode Ray Tube Controller) in this picture > is hot to the touch, probably is bad. I am currently searching > for a replacement. I know some ICs can become very warm but IMHO the 6545 is not one of them. I don't have a spare either but this could do the trick: Two years ago I have been experimenting with the Motorola 6845 wondering why that one doesn't work inside a 8032. And to be honest, I still haven't any idea. But during these experiments I took a Hitachi 6845 out of the box and suprise.... that one worked fine! And so did the UMC version. All three worked fine on a PC MGP card but all Motorola 6845's refused to work on a 8032. Having a reliable source of 6545 replacements, I quit the research. Remark: I never tested it on a 8296. > Note also that the processor is a 6502 A, not a "B" like other > 8296's. Would be slower? No. The A means it is the 2 MHz version, the B means 3 MHz version. This means they can run reliable at these frequencies. The 8032 is only a 1 MHz system so the 6502A should run very fine. Remark: I wonder if the A, and especially the B, is made for these frequencies or are they justed tested. A 80486-33 running on 25 MHz is much cooler then the original 80486-25. One idea of reducing the heat output in, for example a 1541, could be replacing the parts with their A or B versions. > 2) could the display be causing the problem? You failed to mention the bee-de-bee-de-bee beep at start-up. So I presume that it didn't occur. And that isn't a good sign either. > 3) Any diagnostic ideas? All the brooken 8296's I met so far had all the same major problem: bad PLA's. Your luck: replacements exist, IIRC Jens Schönfeld sells them. There even exists an EPROM replacement, no URL at hand. A not so hi-tech solution: start swapping parts with another 8296. In some cases a 8032 will do as well (6522, 6502, 6545, 6520). The B700 won't do as it is 2 MHz IIRC. For the next one you need an osciloscope: replace the upper ROM with an EPROM filled with NOP's and JMP $F000 at $FFF7. This should produce square waves at the address lines A0..11. Taking this idea a step further: use a EPROM filled with a diagnostics program, one that outputs the result at the userport. Problem: I don't have such a ROM and if others cannot help you, you must program your own one. A hi-tech solution: I myself repaired quite some 6502 machines using my debugger,<www.baltissen.org/htm/debugger.htm>. I simply compared what the 6502 was doing against the source code. That enabled me to detect bad RAM, bad 6522's etc. A logic-analyser will do as well of course but I don't think you have that laying around somewhere (me neither). Good luck! -- ___ / __|__ / / |_/ Groetjes, Ruud \ \__|_\ \___| URL: Ruud.C64.org De informatie in dit e-mailbericht is vertrouwelijk en uitsluitend bestemd voor de geadresseerde. Wanneer u dit bericht per abuis ontvangt, verzoeken wij u contact op te nemen met de afzender per kerende e-mail. Verder verzoeken wij u in dat geval dit e-mailbericht te vernietigen en de inhoud ervan aan niemand openbaar te maken. Wij aanvaarden geen aansprakelijkheid voor onjuiste, onvolledige dan wel ontijdige overbrenging van de inhoud van een verzonden e-mailbericht, noch voor daarbij overgebrachte virussen. Stichting Pensioenfonds ABP is gevestigd te Heerlen en ingeschreven bij de Kamer van Koophandel Zuid Limburg onder nummer 41074000 The information contained in this e-mail is confidential and may be privileged. It may be read, copied and used only by the intended recipient. If you have received it in error, please contact the sender immediately by return e-mail; please delete in this case the e-mail and do not disclose its contents to any person. We don't accept liability for any errors, omissions, delays of receipt or viruses in the contents of this message which arise as a result of e-mail transmission. Stichting Pensioenfonds ABP, having its registered office at Heerlen, is registered in the Traderegister of the Chamber of Commerce Zuid Limburg (Maastricht), the Netherlands, registration number: 41074000 Message was sent through the cbm-hackers mailing list
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