C64 250407 rev c

The PSU is original to the unit I received. OHM for the C64? Just to make sure the traces are still functioning? The system's LED turns on, but no video.

Testing the power switch. Got it. Sorry to hear the PSU is dead. That makes no sense really, if the power supply is 'dead' then no chips would be getting warm. Testing the power switch is tricky, ohming it out will not tell you the full story. If it has one microscopic patch of decent contact it will look fine with the few milliamps the multi-meter will put through it.

To test it properly you should have a known good power supply attached and then measure the voltage drop across the switch.

If you see more then 0. Ideally you would test the power supply both open circuit no load attached and then with a dummy load power resistors selected to draw close to maximum amount of current the supply can put out. With a multi-meter and this set up you can get an idea if the voltage output is 'OK', and stays 'OK' for minutes of use the voltage can spike up as the power supply warms up.

Commodore 64

You can't see the ripple voltage though voltage not stablewhen the capacitors break down the output can look OK at first and then develop a lot of ripple voltage. I've been working on a video on this subject for the last couple of weeks.

It will show a dummy load you can build, how to test supplies, common faults, etc. Thanks to some Lemoners sending me their bad power supplies I have a good range of faults to show. I'm not a video making guru so give me another week or two to get it finished up and on YouTube. I tested the IC chips as well to see what the voltage was and it was too damn low.All caps are good brand, long life types.

Please note: The values originally fitted by Commodore can vary slightly from their own schematics! Please check the listed contents of the packs against those on your particular board. Where there is a difference it's normally only a capacitor's rated voltage and that should not matter, but if you require a substitution just leave a note with your order in the Special Instructions box during checkout - or contact me if unsure.

Please choose Pack 2 or Pack 4 instead if this is the case with your C Pack 5. Pack 6. Pack 7. A, B, 3 or 4 with a uf capacitor at C63 - this is the most common type. It consists of:. If you require a pack with differing caps, contact me and I'll see what I can do. The C64's modulator can be thought of as a single replaceable unit but it is possible to open it up and replace the capacitors if desired.

Other variations exist, if your modulator has a different part number to those previously mentioned please check its components before ordering.

Note: The voltage rating on the original caps varies - those above marked as 10v may be 7. This is irrelevant - the voltage used in the modulator is only 5v, so anything above that will be fine. Basket: 0 Items. Site Menu. It consists of: 1 x 2. Please check if you need different types. Capacitor Pack for the later II disk drive assy no For mainboard: 3 x 10uf radial electrolytic capacitors Also included, for the motor control PCB: 3 x 10uf, 2 x 4.

Assy 250407 Rev. C #1

Please check if you need any different types. Capacitors for re-capping the C64 c modulator. Restore key mod capacitor It has been found that replacing C38 with a 4. Products: Click on the product thumbnail for an enlarged view.GitHub is home to over 50 million developers working together to host and review code, manage projects, and build software together.

Work fast with our official CLI. Learn more. If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again.

It is a universal solution that fits and is electrically compatible with both the C64 and C64C without having to change components on the board or run jumper wires for power. It is easy and inexpensive to build with only a single, small PCB and all through-hole components.

This allows for the best possible compatibility with a wide variety of different board revisions, VIC chips, aging components and monitors. I have not tested it, but I believe it should also be compatible with Bwack's KU board as well since it uses the standard longboard RF modulator.

It is not compatible, however, with the early revision boards with the 5 Pin AV Output. This revision uses a different modulator pin layout, and the video signals are not combined in the modulator.

Kicad files are available for you to view or modify as you see fit. Gerber files are available that can be uploaded directly to your favorite PCB fab to make your own boards, and a complete Bill of Materials BOM can be found here with example parts from Digikey.

I strongly recommend building the entire board, if you choose to do so, there are a few components that can be omitted in different situations to decrease the cost at the expense of features and flexibility.

The trim pots used to adjust the luma and chroma are the most expensive components in this project. I highly recommend using them, but if you choose, you may jumper the solder bridges on the back of the board to bypass the trimmer pads and install Ohm resistors for R4 and R7. This won't give you the precision adjustment of the trimmers, but it will be close enough for most configurations. You can experiment with different fixed value resistors between K Ohm if you want to change fixed output levels.

Once you have your PCBs and all your components, soldering them together should be pretty straightforward. You can use the schematic or the BOM to place the right value parts in the right place.

From a soldering standpoint, it is easiest to assemble the components starting with the lowest profile first and then work your way up. This would be mean soldering the resistors and inductor first, then the ceramic caps, the diode, electrolytic capacitors, transistors and voltage regulator, and finally, the jumper block.

The jumpers can then be installed on the headers in the appropriate configuration. Finish off by removing the flux residue with some cotton swabs or a brush and isopropyl alcohol. First, you need to remove the old RF modulator. This can be a bit tricky as the large metal can will suck the heat right out of the iron. The new board can then be installed one of two ways. The first is soldering it directly to the motherboard. For this, you can solder two.

I recommend sticking small rubber feet near the rear of the board to help support it. You can slide two feet under the front of the rf modulator replacement to keep the pcb level and evenly spaced all the way around while you solder the headers from the top side. Trim the excess length of the header pins off and slide out the rubber feet.

For a nicer finish, reflow the solder joints after you have trimmed them.A, Rev. From this version and forward, the Commodore 64 board had an 8-pin video jack. Heatsinks and thermal tape have been bought from the Retroleum.

c64 250407 rev c

Capacitor C38 51 pF has been replaced by a 4. Instead of swapping the keys, small labels were added to indicate the new characters. The case is in pretty good shape and the number on the side just adds to the authenticity of the machine. Excellent oldschool computer. Thanks Neal! I think we had machines from IBM with green text. Hey MtnBuffalo, very informative post about the board. Some years ago I came into posession of a used C64, with this board revision. You highlight C38 being replaced to fix a problem with the Restore key.

Hi SegF4ult.

Some early 250407 working rev boards

I can perfectly understand your confusion regarding C In this picture you can see the original underdimensioned capacitor link. The color coding on it indicates that it is a 51 pF. I have a similar board that I am going to completely overhaul, except mine is a W 94HB. For instance, in my video block, C86 is a mica capacitor but there is a resistor also from it to the trace leading to R There are some other idiosyncrasies as well. Did you have similar issues? So, the question is now, how would I go about this overhaul?

I would also change the voltage regulators at VR1 and VR2 to make sure that the board gets correct voltages. Thanks for the tips. It works except the SID chip produces no sound, voltages seem right, plugs, continuity, etc but the previous owner must have stored it someplace where something could dissolve some of the outside of the ceramic caps. All components, except maybe ferrite beads as I cannot find those specs, will be replaced by more modern ones ceramic disk with MLCC, electrolytic with better ones, resistors with better ones, and so on.

But, yeah, I will get around to doing those mods you mentioned and replace the SID if it is actually dead. I suppose they were put in order to avoid some interferences, am I right? Are those required for RF shielding or does it not matter any longer? Even though they could be made of metal, they were usually made from tin foiled cardboard wrapped around the motherboard. The carboard definately worked more as an insulator and not as much as a heat remover! In later version motherboards e.

Assythe modified RF shields were made from metal and did add some cooling to the larger ICs. I have not experienced any burned chips using this approach. B Assy Rev. C Assy Rev. A Assy Rev.After running the diagnostic tests on one of the bad 's it gave me readings on the alignment which is confusing, bad sectors and also errors. I adjusted the speed which was not far off at all but no matter what I do on the alignment it keeps giving me different results from test to test. So I decided to test one of my good 's which will do anything I ask of it and it gave me out of alignment results also, or at least I think they are.

I can't figure out what they are meaning with these results especially when a couple tracks in the beginning are bad then maybe 15 or so are good, then 3 or more bad ones again.

On the Sector test that shows that I have 22 bad sectors, what am I suppose to do to fix that? I guess what I am saying is having test results are meaningless unless you know what to do with them. Here are a couple pics of some results. Could someone maybe explain to me what they are saying? When did you clean the head s last on the diskette drives? You might as well clean them as well with isopropyl alcohol and see what happens. I just cleaned them last night and also the top pad and rails.

BTW, all of these drives have been sitting in boxes in a garage for the last 25 years. Note that the 'clO1' thing is cee el capital-oh one. I'll try it again in the morning. If so, how is that adjusted? If it is a disk formatted on that drive then the results will not be accurate.

To answer your question, yes that is a problem that it is reading track 2 when attempting to read track 1. Sometimes when a drive is out of alignment it could still read and write its own disks. If you have a factory disk you can be reasonably sure it was produced on a properly aligned drive.

Make sure it is write protected then use that disk to test the alignment. I'm going to do some testing now and I'll return with the results.

I do think the bad drive needs to have the track 1 adjustment. I did tests on the bad drive and then a drive I use that can do anything I ask of it which tells me it's good to go even though it showed some alignment problems. Here are the results with comparisons of both drives.

Tip: Get C64 Forever for super-comfy C64 emulation with pre-installed games, demos and other goodies! View previous topic :: View next topic. I have 6 's and 3 of them are having problems mostly not being able to load a game or make a copy of a disk so I got this Diagnostic cartridge to see if it would help me get them up to par again.

Back to top. Try these commands: Code:. Is that one whole command or is each line a separate one? Ahhh, I thought that was a 1 and a zero. Looking at the data on that 1st alignment test, the 1st set is saying track 1 but reading track 2, is that maybe a problem of the head not going far enough to get to track 1? What disk are you using when you run this test? I am using a disk that is blank like it says to put in there. The reason I ask is that if you format a disk on the drive you are testing then use that to test with, it won't be accurate.

I understand, I was just doing what it told me to but you are correct.The serial reset line is directly connected to the CPU so that you can use a serial reset button to reset the C64 and all serial devices [This is an assumption, because this is the case with the succeeding version A]. The following is an enumeration of features that all old boards including have in common: RAM: 8 pcs. Can you verify that the CPU reset is directly connected to the serial reset?

Version A CR [ Help! Schematics wanted! A, REV. B, REV. It is the first C64 board using an 8-pin video jack, all newer boards use this connector. You can recognize this particular board by looking through the expansion port viewing from behind, it is on the left side. Version B [ Help!

c64 250407 rev c

Then the VIC-II's alignment has been changed from vertical to horizontal, so that pin 1 is in the lower left corner.

In some revisions, the resistors R29 and R30 have piggybacked diodes, which seem to be protecting two lines of the serial port [? What is the revision of the 'piggyback' boards? Version B-2 [ Help! Picture wanted! Their new locations are CR9, How can you tell this version from prior versions without opening the case?Then I started checking the voltages.

The LED pin is 4. The S1 switch is OK On pin 1 shows 1.

eBay C64: Numerous Faults \u0026 Repairs (250407)

On Datassette port I get 4. Any clues of what might be failing or where to test? Many thanks in advance! Any clues of what might be happening?

c64 250407 rev c

I have installed another power switch just in case, but the problem still. Looking forward for your wise tips Thanks!! Yes, I have used the dead test cartridge but it doesn't do anything. Just black screen. Would like to know how to test CR4, and if it is damaged, would it be possible to use a CR4 from a motherboard that I have it as spare CR4 looks different on this one. In case it is damaged, could I use a CR4 from a motherboard that I have as spare?

And also you will not have AC going into the rectifier. If your fuse is not blown, check the line filter at L4. Input should be around 10VAC output slightly less. If you have AC going in and not out L4 is bad. Maybe bad solder joint. Tip: Get C64 Forever for super-comfy C64 emulation with pre-installed games, demos and other goodies! C64 mainboard issue.

View previous topic :: View next topic. Back to top. Have you confirm the switch is actually outputting the AC. Do you have 10V AC at User port pins 10 and 11? All times are UTC.


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