bhf@mtuxo.UUCP (b.freedman) (12/15/86)
I have a c64 with what appears to be a dead power supply. Can they be fixed? Does anyone have an extra to sell? Where can they be picked up in the central Jersey area? Thanks for any help. Barry
sands@usiv03.dec.com (12/19/86)
In response to the C64 Power Supply question: If you remove the cover from the power supply there is a fuse inside buried down in a bunch of goop. It is possible that it may be blown. If not pick up a copy of Compute's Gazette which deals with the Commodore 64. In it you will find a ton of adds from shops that repair the C64. Most are mail order, but it is possible that one may be near you. Rgds Larry Sands Digital Equipment Corp. Southwest Area Field Service Sales Support
wtm@neoucom.UUCP (Bill Mayhew) (12/26/86)
Toys-R-Us routinely stocks replacement power packs for the C-64. I have about 6 C-64s to take care of in one of our labs. The power packs made in the last couple of years are potted in plastic, which makes servicing even the fuse pretty nasty. If I remember right, the Toys-R-Us model was good for 5 amps and cost "only" $29. You might also thumb through the back of Byte Magazine in the ads. I think Jameco Electronics has a C-64 power pack in the same price range. For a few bucks extra, they should be able to get it to you in just a couple of days by 2nd day air UPS. Jameco also stocks replacement VIC-2 chips, PALs, SIDs, etc for the C-64. My experience has been that the SID seems particularly sensitive to overvoltage, and will burn out relatively quickly. Use care when monkeying with the power for your C-64 that you keep the voltage to 5.0 volts maximum! (on Vcc, that is.) By the way, when the new 256K ram pack for the C-64 comes out, it will include a new power pack to accomodate the additional power required for the memory cartridge. Also, thanks Commodore for making the power pack for th C-128 decent. It was about time that the fuse was made accessible without taking a chisel to the plastic blob! --Bill Bill Mayhew Division of Basic Medical Sciences Northeastern Ohio Universities College of Medicine Rootstown, OH 44272 USA phone: 216-325-2511 (wtm@neoucom.UUCP ...!cbatt!neoucom!wtm)
grr@cbmvax.cbm.UUCP (George Robbins) (12/27/86)
In article <342@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes: > > The power >packs made in the last couple of years are potted in plastic, which >makes servicing even the fuse pretty nasty. > >Also, thanks Commodore for making the power pack for th C-128 >decent. It was about time that the fuse was made accessible >without taking a chisel to the plastic blob! > >Bill Mayhew The potted power supplies are a result of trying to sell the same system/supply in Canda as the US. The Canadian safty testing outfit (CSA) thinks that "NO USER SERVICABLE PARTS" means no user replacable fuse. If the power supply fuse were replacable, then the whole mess needs to be certified in a different category. There is also some tie-in with whether or not a 3-prong plug is required. -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)
scott@max.u.washington.edu (09/24/89)
My power supply for the C64 has broken down, and I am thinking of repairing it myself. I was able to find all the necessary parts to try to fix it except one, the tranformer. So I have two questions in regards to the transformer. I hope someone will be able to answer them. 1. How is it likely that the transformer is the culprit in the break down? 2. Where can I buy a transformer that has the same specification as that of the one used in the C64 power supply? Thanks in advance, Scott Stephen
prindle@NADC.ARPA (Frank Prindle) (09/25/89)
A transformer can really only fail one way - a winding opens up, usually from excessive heat melting solder at some point where wires are joined. Oxidation and a cold solder joint eventually cause the winding to open. Of course, if you dead short the thing, it can also melt the wire itself depending on the rating of the transformer. A C64 transformer actually has two independent windings, and you'll not likely find one exactly like it. Replace it with one 6V, 2A transformer (for the 5VDC supply) and one 9 to 12V, 2A transformer (for the isolated 9VAC supply). Older C64s draw about 1 Amp from each of the 5VDC and 9VAC supplies, while newer ones draw more from the 5VDC supply and less from the 9VAC supply. Sincerely, Frank Prindle Prindle@NADC.arpa
Geoffrey.Welsh@p0.f171.n221.z1.fidonet.org (Geoffrey Welsh) (09/25/89)
> From: scott@max.u.washington.edu > Message-ID: <7296@max.u.washington.edu> > My power supply for the C64 has broken down, and I am thinking of > repairing it myself. I was able to find all the necessary parts > to try to fix it except one, the tranformer. So I have two questions > in regards to the transformer. I hope someone will be able to > answer them. > > 1. How is it likely that the transformer is the culprit in the break down? > 2. Where can I buy a transformer that has the same specification as that > of the one used in the C64 power supply? 1. Negligible. 2. As far as I know, Commodore uses a custom-wound one (they're cheap in sufficient volume). Chances are that the failure is in the voltage regulator. This may or may not help you, depending on how old your power supply is. The first ones (in the larger cases, with vents in them) can be opened, but the newer ones (smaller, solid "blocks" with plastic fins) are poured full of epoxy, so that you'd destroy the innards while trying to get at the parts. If you have an older one and the voltage regulator is at fault (i.e. there's at least 8V going in and anything but 5V coming out), then you could replace it with part number LM323 (I'm sure there are others, but that's the one I have ued successfully). Beware of pinouts; even if the case looks the same, the in, out, and ground pins may be arranged differently! If you want to build a new supply from scratch (using cables salvaged from the old one), that should be easy using two transformers. The 10V power line requires only 1A typically, so you won't have a hard time finding a part for that. Supplying the voltage regulator is a bit more tricky. You want the input to be above 7.5V for the regulator to work, but every extra bit over that means more power dissipation in the form of heat. Buying an 8V transformer and putting it through a bridge rectifier won't work, since the voltage drop accross two diodes is enough to drop 8V below the regulator's operating input level. On the other hand, a rectifying transformer (in the form of a centre-tap transformer with one diode) has a lower voltage drop... perhaps someone with a bit more experience than I can tell you what values to look for, since my solution was brute force (expensive heavy-duty parts, BIG heat sink - but I got a power supply that ran two and even three computers at a time as other supplies died out!) NOTES: It wouldn't be a bad idea to put a 5.2V Zener diode between the 5V output and ground. Put a fuse "inside" the loop created if the Zener cuts in, so that the fuse'll go if the regulator ever dies & cranks full voltage at the C64. Don't fall to the temptation to buy one hi-current 10V transformer to feed both the 10V AC and 5VDC lines; the C64 internals do not expect the AC lines to have any voltage or signal relative to GND or +5. The effects of not observing this expected isolation range from mild (VIC chip displays off patterns on screen, even when C64 power is off; fuse inside C64 blows) to disasterous (blow most major LSI chips int he C64). Put a large filter capacitor on the INPUT side of the regulator (1,000 microFarads per amp of expected current - I used a 4700 uF myself) and a small capacitor (perhaps the exxperts can suggest an appropriate value?) on the output side. This will give a steady voltage to the regulator and help reduce noise amplification by the regulator, respectively. Hope I've been helpful, informative, or entertaining. -- Geoffrey Welsh - via FidoNet node 1:221/171 UUCP: {{uunet!}watmath!xenitec!}zswamp!171.0!Geoffrey.Welsh ARPA: Geoffrey.Welsh@p0.f171.n221.z1.fidonet.org
bas@wuibc.UUCP (Barry Siegfried) (09/25/89)
In article <7296@max.u.washington.edu>, scott@max.u.washington.edu writes: > My power supply for the C64 has broken down, and I am thinking of . . . > 1. How is it likely that the transformer is the culprit in the break down? > 2. Where can I buy a transformer that has the same specification as that > of the one used in the C64 power supply? I once had a problem such that it took longer and longer for the C64 to power up after turning it on. It turned out that one of the capacitors in the power supply needed to be replaced; the transformer was fine. I don't know what the replacement transformer is. Barry Siegfried (bas@wuibc.wustl.edu)
mikemo@opus.uucp (Mike Mo) (09/26/89)
Scott:
About your power supply, I have some personal experince that may be useful.
I repaired two C64 power supply before. None of them had a bad transformer.
Their common problem is the 5V regulator. After I changed the failed regulator
they all worked fine. My response to your questions is as follows:
1. Transformer does go bad if it is shorted internally, but it is very rare.
2. If you need a replacement transformer, it should have 120V primary, two
secondary winding, two 9V 2A windings would be fine or try to use an 18V, 2A
center tapped secondary (break the center tap, so it is two 9V 2A windings).
For transformer part number please see Radio shack catalog?
Good Luck!
/* Disclaimer: McDonnell Douglas has nothing to do with my opinions *//* Mike Mo */
/* McDonnell Douglas Tymnet */
/* San Jose, Ca */
/* (408)922-6032 */
scott@max.u.washington.edu (09/27/89)
Thanks to everyone for the advices given in regards to the power supply. After reading your comments, I realize there are number of ways in which improvements can be addred from the original power supply like adding a led power indicator, fuse, small built in motor motor fan, etc.. If possible, could someone who has a schematics of a good improved version of the C64 power supply post the schematics here. I will appreciate it very much. I am sure that there are alot of other people who are in need of such schematics... tahnk thanks in advance, Scott Stephen
jbh@mibte.UUCP (James Harvey) (09/29/89)
In article <7445@max.u.washington.edu>, scott@max.u.washington.edu writes: > Thanks to everyone for the advices given in regards to the power > supply. > > After reading your comments, I realize there are number of ways > in which improvements can be addred from the original power supply > like adding a led power indicator, fuse, small built in motor > motor fan, etc.. > > If possible, could someone who has a schematics of a good improved > version of the C64 power supply post the schematics here. > I will appreciate it very much. > I am sure that there are alot of other people who are in need of > such schematics... > > tahnk > thanks in advance, > Scott Stephen Since there have been several posts here concerning power supply problems for the C64, I thought I would dust off this old article I had. Took a while to find it. I still see these Coleco supplys advertised from time to time. I have also seen them under a quite different part number, apparently Coleco second sourced the unit. I know of one C64 hacker who has used dozens of these, he makes them up for friends. I have been using one for years now with no problems whatsoever. -------------------------------------------------------------------- The following is the text of an article that I placed in the Michigan Commodore Users Group newsletter in November, 1986. I am posting it here because I know USENET people are always interested in a bargain. -------------------------------------------------------------------- Twelve Dollar C64 Power Supply ------------------------------ If the Commodore 64 has a weak spot, it is surely the power supply. Mine started to act up last spring. After an hour or so of calling BBS numbers, the screen would suddenly scramble, and the computer would lock up. I noticed that the red Power LED on the 64 would dim, indicating power supply failure. I know of at least six people that have had identical problems in various degrees. Some were failing within ten minutes of turn-on. Mine would take two hours and then fail only with the additional load of an RS232 interface. A friend told me of his success in using a surplus Coleco Adam power supply model PS 72559 with his 64. This is a well designed circuit with at least twice the iron in the transformer and three times the heat sink of the Commodore unit. It is large and ugly, measuring 3" x 8" x 9", and comes on an open chassis as it was originally mounted inside the Adam printer. There is a separate primary on/off switch, and all the 115 volt wiring is safely covered by a separate metal shield on the bottom. The regulators are 723 types driving 2N3055 pass transistors and appear to have overload protection built in. The following are the results of my investigation and use of the supply. Some of this information was obtained from the JAMECO data sheet. These are the connections to the nine pin D plug that comes with the unit: Wire Color Pin Voltage Amps ---------- --- ------- ------ Green 1 Ground ---- Yellow 2 -5 VDC 200 Ma Orange 3 +5 VDC 3.0 A Red 4 +12 VDC 2.9 A Brown 5 +12 VDC 1.0 A -None---- 6 Bare Wire 7 No Connection Violet 8 No Connection Blue 9 No Connection Connecting the Coleco Supply to a C64 ------------------------------------- Snip the leads from the grey cable with the D type nine pin connector that comes with the supply. Remove the entire cable and discard it. You will use only the plus five volt source (orange wire connected to E9 on the circuit board), and ground (green wire to E11). Cut or unsolder the two green wires from the transformer pins 7 and 8. This will furnish the 9 volts AC required for the 64 VIC chip. Now you must decide whether or not to destroy your old 64 supply to get the proper cable, or obtain one elsewhere. I went elsewhere, as my 64 supply was still working to some degree. You can make a cable with four conductor wire and a seven pin DIN plug, or possibly you can obtain a defunct supply from one of the computer stores that takes trade-ins. I believe a dead supply can be had for five dollars. The DIN plug alone can cost $2.50. This is the power supply connector that plugs into the jack on the right side of the 64. YOU ARE LOOKING AT THE PINS. Pins C, D, and F will be missing on the plug, but the socket in the C64 has all seven. * * * ** * * ** * * A B * * * * * * * * C D * * * * * * * * F G * * * * H * * * * ** * Now you must make the connections from the Coleco supply to the seven pin DIN plug. Use an ohm meter to verify the wires if you are using a Commodore cable as the colors have been observed to vary. Connect the following: DIN Pin Voltage Comes From Coleco ------- -------- ----------------- A 9 VAC Transformer Pin 7 B 9 VAC Transformer Pin 8 G +5 VDC Orange wire or E9 H Ground Green wire or E11 Possible sources for the PS 72559 are: JAMECO Electronics, 415-592-8097 R & D Electronics, 813-772-1441 Hosfelt Electronics 800-524-6464 Electronic Parts Co. 313-893-3228 They may be available locally, consult your Yellow Pages under Electronic Equipment and Supplies. Prices range from nine to $18 plus shipping. I have been using the big, ugly Coleco supply since July and am totally satisfied. The C64 uses only about a quarter of the units capacity so it barely warms up. I simply screwed it upside down to the bottom surface of my computer table. Four other people I know are using the converted units with perfect performance. Disclaimer: You MUST verify the connections and voltages before attempting to use the adapted power supply. YOUR COMPUTER WILL GO UP IN SMOKE if it is wired wrong so if you are not sure of your work, get help from someone who has fourty years of experience in electronics, is a working Nuclear Scientist, a Registered Professional Engineer, or an EDS employee. I will not be responsible if you detonate your 64 doing this modification. Jim Harvey, 18538 Inkster Redford, Michigan, 48240 -- Jim Harvey | "Ask not for whom the bell Michigan Bell Telephone | tolls and you will only pay 29777 Telegraph | Station-to-Station rates." Southfield, Mich. 48034 | ulysses!gamma!mibte!jbh