Educator 64

[RobertB]

     Ray has given his diagnosis of the E64, "I also checked the Educator64 and it does have a bad tube... very low emission, so a brightener wouldn't help. It just got used to death as the screen burn indicates."
     Then he provides some info, "FYI: the analog video board in the Educator is totally different than the PET digital display board."
     Finally, he provides some solutions, "I did some quickie research on the Educator tube, an Amperex M31-334GR 12" green phosphor CRT. One Internet site listed that tube for about $200. Ouch!"
     He continues, "PETs like the 8032 used a similar M31-331GH for their monitor CRT. One site listed that number for a more reasonable $70. It's also a green screen 12", and the pinout is the same. I don't know the difference in those tubes but if I had to guess, I'd bet it's the persistence of the phosphor... how long the image lasts since the last vertical refresh. A long persistence tube might look smeary if used for video but if I had one of the PET tubes, I would try it."
     He will continue looking for solutions.

          Hmm, maybe I should bring him one of my 8032s
          so that he could try out his theories,
          Robert Bernardo
          Fresno Commodore User Group
          http://videocam.net.au/fcug
          The Other Group of Amigoids
          http://www.calweb.com/~rabel1/
          Southern California Commodore & Amiga Network
          http://www.sccaners.org

[RobertB]

     An update from Ray Carlsen... everything is repaired!  Ray has really outdone himself this time.  Here is his solution for the video problem of the E64, "I found a tube for the Educator, a black & white tube out of an old portable TV set stored in the Carlsen archives (a four car garage that never housed a car). Once in a great while, I find it pays to hoard this stuff. ;-) The tube is an identical electrical match but required a bit of engineering to make it mechanically fit the cabinet. The result looks great. The monitor electronics needed a bit of TLC: a few bad capacitors were changed and board repair was required because of overheated components."
    I think a black-and-white screen is an acceptable replacement to the original greenscreen.  Anyways, if you really want green, you could attach some green cellophane over a pair of glasses.    It was nice to think about trying to get a color screen in there, but the engineering to get that screen and control board in there would have tried Ray's patience.  
    More from Ray, "I noticed some of the keys need a hard press to make them work. (snip) A good cleaning took care of it."  I never even noticed that the E64 keys needed work, probably because the original screen was so dim that I couldn't see if there was any response shown on the screen.
    Even though there is a lot of space in the E64, as a precaution, Ray put heat sinks on the MPU, PLA and SID.
    Ray also discovered this, "Somewhere I read that there were two versions of the Kernal for the Educator. The one that's in there looks like the standard C64 one. The alternate version apparently defaults to a setting that allows software to work that would otherwise look bad on a black and white TV or monitor. If it's important to you, and you can point me to a source for the other ROM, I'll get it and burn you another Kernal."
    As a poor teacher in the early 1980's, I used a regular brown C64 with a black-and-white t.v., and it seemed to do well.  I've passed on putting in the alternate Kernal in the E64.
    I was concerned whether the repaired E64 monitor components would overheat again in the future.  Ray answered, "Well, those big resistors normally run pretty hot. It doesn't harm them but it does eventually cause the board to blacken and it weakens their solder connections. What I did was reinforce those areas and move other components away from the heat producing ones. As much as that computer has been used, I'd say that monitor will outlive us all just as it is. :-) "
    I'll pick up the E64 in June.

                Blockparty 2010 on April 16-18,
                Robert Bernardo
                Fresno Commodore User Group
                http://videocam.net.au/fcug
                July 24-25 CommVEx v6 2010 - http://www.commodore.ca/forum
                and click on ComVEX

[RobertB]

     The Educator 64 came with a warning label on the side which said not to connect an external monitor to it.  I asked Ray about that, and here is his response.
     "I did some experimenting with the Educator output and found that it will run both monitors at the same time although the video on both has reduced contrast. The external monitor, as expected, displays in color. The VIC chip video output is isolated and buffered by a transistor inside the RF modulator so there is no danger of overloading that IC. Since there are no schematics of the C64 modulator internals, I did a bit of reverse engineering on one and found the transistor (one of six) that drives the video outputs. With the added load of an external monitor, that transistor runs a tiny bit warmer than normal but well within its ratings. I wouldn't have a problem running it that way. As I said, the only drawback is that the video level to the monitors is reduced. You can compensate with the contrast and color controls on the external monitor. The Educator monitor has only the external brightness control... its contrast control is on the inside."

                 Thanks, Ray, for the info,
                 Robert Bernardo
                 Fresno Commodore User Group
                 http://videocam.net.au/fcug
                 July 24-25 CommVEx v6 2010 - http://www.commodore.ca/forum
                 and click on ComVEX
             

[RobertB]

     I also wanted to know about the power output on the E64, i.e., how many amps output at 5 volts, 9 volts, and 12 volts?  Ray gave a general answer, "Judging by the size of the PS components, I'd guess it's no more powerful than the original black brick, although it would be more reliable since the 5V regulator for the 64 board is on a big heat sink. The 12 volt supply is probably good for more than the internal monitor, but I really don't know how much. There is only one big transformer to run everything, and it seems to be conservatively rated."

                 Truly,
                 Robert Bernardo
                 Fresno Commodore User Group
                 http://videocam.net.au/fcug
                 July 24-25 Commodore Vegas Expo v6 2010 -
                 http://www.commodore.ca/forum
                 and click on ComVEX

[RobertB]

     Yesterday, I picked up the Educator 64 from Ray Carlsen.  He said that he "replaced bad picture tube with white phosphor type, replaced bad capacitors on monitor board and reworked board for loose connections.  Replaced overheating components with "beefier" ones for longer life."  He put on custom heatsinks on three or four of the E64 chips, going so far as to label them with the name of the chip underneath.  The installed CRT was shimmed into place, and its picture is sharp and bright.  Hooray!

            Ah, it's a wonder!
            Robert Bernardo
            Fresno Commodore User Group
            http://videocam.net.au/fcug
            July 24-25 Commodore Vegas Expo v6 - http://www.portcommodore.com/commvex

[Rorshach]

Truly excellent news Robert.  I am glad to hear of another uncommon piece of commodore gear going back into service.

[RobertB]

     Well, for a common piece of hardware, Ray Carlsen has just sent me his diagnosis and fix for a 1701 monitor (I had picked up the E64 and had given him a 1701 which had been labeled, "No color".)  Ray's fix was inventive.  This is what he wrote, "I found the problem with your monitor. Someone had gotten into it and there were several things wrong including what they did to it. The main problem was a failing device called a high voltage divider that is part of a device called a flyback (aka, the high voltage transformer). The divider portion of the flyback supplies a voltage needed by the picture tube. Flybacks are not available except from another scrapped monitor and I don't have any junkers. I decided to see what I could figure out to bypass that failing part, and I did. It's a little added circuit that steps up another source voltage to the required value and feeds the tube separately. I cleaned and reset all the internal controls (they were heavily "diddled") and the monitor works fine now. It still needs a good scrubbing on the outside.
     I'll pick up that monitor at the end of the month when I'm in the Pacific NW again.

               Writing from England,
               Robert Bernardo
               Fresno Commodore User Group
               http://videocam.net.au/fcug
               July 24-25 Commodore Vegas Expo 2010 - http://www.portcommodore.com/commvex

[RobertB]

     The Educator 64 is back at Ray's place again.  I delivered it last Saturday.  I described the E64's problem which occurred at the July 24-25 CommVEx.  When powered up from cold, the E64's screen is all jiggly and very unstable.  After I described the problem and drew some pictures for Ray, he figured that it was a horizontal sync problem.  With his guarantee on each of his repairs, he will look into what's causing the condition.
    I'll pick it up from him during Thanksgiving.

            Back in California for a few days,
            Robert Bernardo
            Fresno Commodore User Group
             http://videocam.net.au/fcug
             The Other Group of Amigoids
             http://www.calweb.com/~rabel1/
             Southern California Commodore & Amiga Network
             http://www.sccaners.org

[RobertB]

     I picked up the E64 from Ray on Thanksgiving Day.  In a small slot already on near the volume control knob, he installed a switch which would turn off the internal monitor (just in case you didn't want to run it with an external monitor at the same time).  He also resoldered the monitor's board connections and installed a new horizontal sync IC.  More and more custom all the time!
     This time I left him a MSD SD-1 drive to repair.  The SD-1 was not recognizing any disk being inserted; in fact, its disk activity light stayed lit all the time, though there was no drive activity.  This MSD is different in that it has *two* CMD JiffyDOS chips in it.  Very different!

          Truly,
          Robert Bernardo
          Fresno Commodore User Group
          http://videocam.net.au/fcug
          The Other Group of Amigoids
          http://www.calweb.com/~rabel1/
          Southern California Commodore & Amiga Network
          http://www.sccaners.org

[Rorshach]

Hello RobertB

I am glad your 1701 is working well now.  Whoever did that misguided "repair" is very foolish indeed. The flyback is the highest rated voltage source in the entire monitor as it provides the acceleration voltage for the CRT. Voltages in this area of a colour minotor can easily reach 26Kilovolts, and yes theres a reason it rhymes with "Killervolts". Fooling around with that circuitry out of blind ignorance can and does send people one of two places, the Hospital or the Morgue.

[RobertB]

     Recently, Ray Carlsen repaired a PET 64 board which seemed to differ from the board in my E64.  The Educator 64 that Ray mentions below is mine.  This is what he said on comp.sys.cbm about it --


From: Ray Carlsen     
Date: Jan 15, 6:44 pm

Hello all,
     I have not been on comp.sys.cbm in a long time but I've been repairing Commodore gear for a few decades now. I retired last year but I intend to continue with Commodore as long as I have spare parts on hand.
     I recently got a 1982 C64 board (326298) in for repair that came out of a PET64 (aka 4064). The owner lives in Japan, so to keep costs down, he sent only the board. It was built without a SID chip, produces  no color and has no RF unit as it was designed to fit in a PET case with its internal monochrome monitor. The Kernal is a 901246-01  but the other ROMs are standard C64. One very peculiar item... the VIC was a 6597! I never heard of that IC and can't find any information about it.
     This board had no power socket (it was hard-wired to the PET PS) so I installed one to test it with a standard C64 PS. The board had many bad chips (PLA, VIC, one CIA, all RAM, and BASIC ROM) but I was finally able to get it going again. I never heard of a 6597 so I subbed a standard VIC (6567) and got the opening screen on my monitor. Tests of all functions were OK and I installed my "computer saver" just to be safe.
     The repaired board was returned to the owner. He states that the board doesn't produce a picture on the internal monitor but that an external monitor plugged into the A/V port does, so we know the board is working. With no previous experience on a PET64, I assumed its monitor was designed for a PET computer and so needs separated H and V sync as well as the video. There is a small interface board wired between the composite video of the C64 board and the monitor. I suspect that board generates the necessary signals for the PET monitor. As I said, without previous experience, these are only guesses. Now, what about that peculiar VIC?
     I recently repaired an Educator64 (C64 board in a PET case), which is similar to the PET64, but that had a complete C64 board with all standard IC's and all normal functions intact. Its monochrome monitor was designed for composite video and didn't need the little interface board used in a PET64. An external monitor plugged into the A/V port of the Educator produces a color picture.
    Now some questions... does anyone have a PET64/4064 -exactly- like the one I repaired? I need to know what would happen if a 6567 VIC chip were installed to replace the 6597? Would it produce a picture on the internal PET monitor? If necessary, I'm ready to send someone a standard VIC chip to find out. Any information would be welcome. Thanks in advance!


From: Ray Carlsen     
Date: Jan 16, 11:34 am

> I think I saw a message long ago on the CBM Hackers list from
> someone who had reverse engineered the extra board used to feed the
> monitor. I searched but could not find it. Perhaps you should post a
> request there?

That's a good idea, Steve. I'm always interested in saving and passing along information even if I never need it again myself.

> BTW, I'm pretty sure there was never a 6597 chip. It is probably
> just mis-labelled...

I thought of that and you might be right. The chip is clearly marked, no smudges or other irregularities on its face. I'll hang onto it until I know for sure it's really bad. It does nothing in that board or my "standard" C64 test board but I've been fooled before. I never throw
anything away. ;-)

(snip)


From: Ray Carlsen     
Date: Jan 16, 9:03 pm

> Nice to "see" you at comp.sys.cbm... I've visited your website many
> times and your repair articles are very helpful.

Hi, Sam. Thanks for the feedback. I put up all I could gather to help people when I couldn't assist personally and it ended up being a rather unique source. :-)

> About a month ago I bought one of those boards very cheap on Ebay

Thanks for the photos and the schematic! That verifies what I needed to know, that the original PET monitor accepts TTL level digital video and separated sync signals. So, the little board in the PET64 does the conversion from a single composite video signal out of the C64 board to feed the PET TTL monitor.

> Because I'm a Commodore collector and a PET64 is hard to find I made
> a "PET64" for myself. replaced the keyboard and motherboard and added
> a monochrome monitor with composite input.

I'll bet Commodore's interest in that model was mostly financial... using whatever they had left in stock to make a working computer. Like the Educator, my guess is it was targeted to schools and perhaps business users. Could anyone back then have guessed their efforts would have such fervent followers at this late date?

> A good picture inside the PET64 is here to see:http://www.dickestel.com/images/expo221.jpg
> The interface board is the same as I have..


From: Ray Carlsen     
Date: Jan 17, 12:45 pm

> So many bad chips on the board of the PET64 owner in Japan.. Must
> have something to do with a bad PSU ?? And maybe for that reason the
> video interface board is also damaged ?

Sam,
     The user is somewhat savvy about electronics, so I had him load test the supply. He said the 5V regulator seems to hold steady over time so that almost rules out a bad PS. Just to be safe, I installed my computer saver circuit on his C64 motherboard. The only other cause of that many failures is if someone got into that computer and started carelessly poking around. A surge could certainly have damaged the interface board along with the motherboard, but the monitor itself is also suspect. I wish the guy had a scope to verify the signals out of that sub-board. I don't think he's ready to dig into the monitor himself. His C64 board works now but he still has a non-working system and I can't fix it "over the phone". Bummer.


From: Ray Carlsen     
Date: Jan 17, 12:52 pm

> Definitely a weird looking board, but it looks like you could solder
> in a SID chip if you really wanted to.

David,
     Yep. It's an old but standard 64 board with some of the parts "missing". When I found so many ICs bad, I thought about swapping out the entire board, but this guy wanted it as original as possible. It also appears there are some parts missing that would have been used to generate color... also not available on this board. I took on this project mostly because I had never seen one of those computers before.

It was/is quite a learning experience. I don't mind that at all. :-)

Ray