rlb@ncsu.UUCP (Roger Lee Banner) (07/05/84)
I am posting this for a friend who is having trouble with his C64.
First off, he has not been able to get a control C () to work or ever
appear on his monitor. Has anyone else had this problem? Does anyone
have suggestions on how to fix it?
Second, he is also having trouble rewriting corrected programs to disk.
How is this done? Also, how can he delete a program from disk?
I am inexperienced with the C64 and could not help him.
Thanks,
Roger Banner
ncsu!rlbabc@brl-sem.ARPA (Brint Cooper ) (11/30/85)
Help! I have a friend's C64 before me. Upon power up,
nothing happens except the drive runs for a few seconds. The
pilot light appears to come up to full brightness initially,
then suddenly becomes dim.
I have "heard" that there are chronic C64 problems that appear
after the machine is one to two years old. Is this one of
them? I'll begin the usual troubleshooting (sans schematics)
in the meantime, but would appreciate any hints.
Has anyone seen this or something similar?
Brint Cooper
ARPA: abc@brl.arpa
UUCP: ...{seismo,decvax,cbosgd}!brl-tgr!abc
--
Brint Cooper
ARPA: abc@brl.arpa
UUCP: ...{seismo,decvax,cbosgd}!brl-tgr!abcwkb@cbsck.UUCP (William K. Brummett) (12/02/85)
(Sacrifice to the line-eating bug.) > Help! I have a friend's C64 before me. Upon power up, > nothing happens except the drive runs for a few seconds. The > pilot light appears to come up to full brightness initially, > then suddenly becomes dim. > ... > Has anyone seen this or something similar? > > Brint Cooper > ARPA: abc@brl.arpa > UUCP: ...{seismo,decvax,cbosgd}!brl-tgr!abc I, too, have experienced what you are desribing. In my case, it was the power supply that was causing the trouble. Specifically, the 5-volt regulator failed and was feeding almost 8 volts into my 64. To check for this problem, unplug the power supply from the AC outlet and from the 64. Plug it back into the AC outlet and measure the voltages on the output plug that connects to the 64. You should read +5VDC and ground on one pair of pins and 9 V*AC* on another pair. (Sorry I can't be more specific here. I don't have access to my documentation right now. Apparently there are at least two versions of this plug, one with four pins and one with seven (3 unused?).) If one or both of these readings is off, you need a new supply. After ascertaining that the supply is at fault, determine what sort of supply you have. The newer versions are square, sealed, and completely filled with some sort of hardened resin or epoxy. The older ones are about 30% larger, have tapered sides and ventilation slots, and are held together with screws. If you have one of the newer versions, you're SOL. Buy a new supply. If you have an older supply, AND it's the 5VDC that's off, there's a cheaper way to go. Remove the screws on the underside of the supply and open the casing. Inside you will find a transformer and a small circuit board. The black object bolted to the metal heat sink with three leads attached to the circuit board is the regulator. Unsolder it from the board and disconnect it from the heatsink. You will replace it with a variable regulator from Radio Shack (an LM-217, I think). Note: do not try to use a common 7805 regulator, as the current requirement of a 64 exceeds the output of a 7805. The 217 is soldered into the holes left by the old regulator, only shifted one hole to the left. The old regulator was some proprietary design and had a wierd pinout. The far left pin of the reglator is connected to the far right hole with a piece of wire as shown: | LM-217 | |____________| ||__||__||___ `---||--||--,\ || || || Circuit board holes -> () () () Connect the new regulator chip to the metal heatsink. To the right of the regulator on the circuit board is a resistor. This must be removed and replaced with a small potentiometer (I used a miniature 5K multi-turn). With the supply plugged in to an AC outlet (be careful!) adjust the pot until the appropriate pin on the output plug reads +5 VDC. Reassemble the case and you're done. If you are unfortunate enough to have one of the newer, sealed units, all may not be lost. I had one originally, but was able to get an older, used one from a dealer's service department. They told me it was broken and gave it to me for five bucks, but it worked just fine when I replaced the regulator. By the way, I had considered just building a whole new power supply from scratch, but it turns out that the transformer used is somewhat wierd also. It has one winding that supplies the the 9VAC at about one amp and another completely separate 9V winding that is center-tapped and half-wave rectified to feed the 5-volt regulator at about an amp and a half. I would have needed two separate normal transformers to duplicate this. I don't really know why the two are isolated like that, unless Commodore plays tricks with different grounds inside the 64. Anyway, I hope this helps you out. __________________ \_|_______________|) ________/^\________ | | `,--,-\_____/-----' W. Keith Brummett __|_|_____|_/_ ~ AT&T-NS/Bell Labs /__ ======||=(- Columbus, Ohio `----------- {anywhere}!cbosgd!cbsck!wkb "I'm not sure, but I think we've been insulted." ... "I'm sure."
wrc@whuts.UUCP (CLEGG) (12/03/85)
> Help! I have a friend's C64 before me. Upon power up, > nothing happens except the drive runs for a few seconds. The > pilot light appears to come up to full brightness initially, > then suddenly becomes dim. > > I have "heard" that there are chronic C64 problems that appear > after the machine is one to two years old. Is this one of > them? I'll begin the usual troubleshooting (sans schematics) > in the meantime, but would appreciate any hints. > > Has anyone seen this or something similar? > > Brint Cooper > > ARPA: abc@brl.arpa > UUCP: ...{seismo,decvax,cbosgd}!brl-tgr!abc > > -- > Brint Cooper > > ARPA: abc@brl.arpa > UUCP: ...{seismo,decvax,cbosgd}!brl-tgr!abc I had a similar problem with my friend's c64. I found that the 5 volt regulator that is located in the power supply let loose. The voltage on that line varied anywhere between 4.5 up to 9.5 volts. The led on the computer is tied directly to this line and is the reason that it varies. The bad news is that this 5 volt line feeds all of the RAM and most of the other logic chips and if this voltage goes too high then kiss all those chips goodbye. Even if thay all didn't go, it will be very difficult to find the ones that did go. Your best bet in this case is too get repaired by a dealer. There are some places that replace the entire board for $55.00 which isn't bad considering that the price of some of the individual chips is as much as $30. One other thing is that the power supply is not repairable as it is potted and the components can not be accessed. Befor you go too far I would recommend that you put a voltmeter on the 5 volts from the power supply. It should measure almost exactly 5 volts and not vary. Good luck Bill Clegg
jerem@tekgvs.UUCP (Jere Marrs) (12/05/85)
> In my case, > it was the power supply that was causing the trouble. > > By the way, I had considered just > building a whole new power supply from scratch, but it > turns out that the transformer used is somewhat wierd also. > It has one winding that supplies the the 9VAC at about one > amp and another completely separate 9V winding that is > center-tapped and half-wave rectified to feed the 5-volt > regulator at about an amp and a half. I would have needed > two separate normal transformers to duplicate this. > That is a viable route - the two transformers. I had one that way. Hook one up to the 9VAC pins and the other to a regulator (LM-309?) that can handle about 4A. The increased current capability is useful if you add such things as IEEE interfaces and 80-column adaptors. A better way - and this is what I ended up doing - is to replace the +5 supply by one of those small switching power supplies and use a 9V transformer for the AC requirements. I used a 10V transformer (door bell) with an (EPD? EDP?) 5VDC, 4.0A switching power supply and it worked beautifully for the year-and-a-half until I got my 128. I was using both the BusCard II IEEE interface and the BI-80 80-column converter which drew more current than the 64 alone. It's not as cheap as the linear power supply, but I think the reliability factor is increased orders of magnitude. Jere M. Marrs Tektronix, Inc. Beaverton, Oregon tektronix!tekgvs!jerem