First: Disconnect all peripherals. Disconnect the keyboard and try again. The computer should come up, you just won't be able to type anything. Second: There are 4 voltage regulators on the system board. They controll different sections of the system board. If one of them is bad, parts of the computer will not work, but other parts will. You will need to check the schematics on funet to find the test points. They may be labeled on the system board as TP1 through TP4. TP2 should be 12 volts, the others should be 5 volts. Third: I assume you have a 4032-12, since you say it beeps. The keyboard is controlled by the 6520 at UB2. It may be defective. Fourth: Even with the keyboard disconnected, the computer should come up with the usual power up message and give the correct number of bytes free. If it does not, you probably have a bad ROM or memory chip. A less likely possibility is a bad line driver on the address or data busses. On Mon, 17 Jan 2000, [ISO-8859-1] Marko Mäkelä wrote: > Hello Brian, > > > Thanks for the reply! It's a Commodore CBM 4032. When I turn it on, It > > makes a shrill beeping sound for about a second then displays all the > > correct bootup info. It also shows "ready>" at the bottom. > > Really "ready>" and not "ready."? The code for the ">" sign would be > 0x3e, while "." is 0x2e. This could mean a failure in the memory chip > connected to the processor's data line D4 (1 << 4 == 0x10). The chip > probably has faulty bits also at other addresses, but luckily the system > starts up pretty far nevertheless. > > > I opened it up and and probed the back of the keyboard connector with a > > multimeter. When I press a key, the voltage will drop by a few tenths of a > > volt. > > I don't think it's a problem with the keyboard. The keyboard lines are > arranged in a matrix. If you really suspect the keyboard, you can measure > the resistance between a row and a column line (disconnect the keyboard > from the mainboard first) and press the corresponding key. The resistance > sould be around 100 ohms (anyway less than 1 kilo-ohm). And if it really > was a keyboard problem, I'd rather suspect the electronics that drives and > reads out the keyboard matrix lines. > > I sent a copy to the cbm-hackers list, in case someone else has any ideas. > You can send your further questions to the list address. > > Marko > > - > This message was sent through the cbm-hackers mailing list. > To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi. > - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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