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midibob

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  1. midibob

    Derby's hidden electronics gem (RF Potts)

    Tottenham court Road and Lisle St were the holy grail for surplus stuff back in the 60-70s. You could spend all day going in and out of the multitude of places. I'm sure I went in Proops many a time. I've not dealt with RF Potts I don't think? Sinequanon I regularly buy from.
  2. midibob

    PC-92 test rig

    Now I'm a bit stuck and could do with a little help before I go and jump in the Thames! When I changed all the transistors around the battery area I suspect I've misread one and put in a NPN instead of a PNP. Q6 is the suspect and it may have been a BC 327 whereas I read it as a BC237. Drawing out that section of the diagram would suggest my mistake. Doh! Can someone confirm? Also what is Q?, I can't read the number as it's been placed directly over a via! Tracing the paths on this board is a nightmare there are more via's than you could shake a stick at and so many underneath chips.
  3. midibob

    PC-92 test rig

    Things are moving slowly but definitely in the right direction. My first issue was a bad ROM! It measured 43 Ohms from pin 1 to 28 not sure how it passed the CRC check in the burner?? Since I've connected up the 50v AC I now get a short tone on switch on. Not sure what the connection is but without it there's nothing? As I'm using my Arduino as a dummy reel set I see the motor outputs pulsing, dividing and feeding this back to to reel sensor inputs stops this after a few seconds so I'm happy the reels would have indexed. I still can't get anything sensible on the 7 segment display as it pulses for a few seconds shortly after the tone goes off and then stays solid once the reels have indexed. Most of the decimal points are showing so I think I may have the segments wired incorrectly. I've tried reversing them but just get different segments of rubbish. I think I should be seeing it end up on all 0's? Unfortunately the pages are missing in the Proconn manual on here so it's all guess work. I'm now using 777 Heaven and have a couple of versions and they both have the same characteristics on boot up so I'm happy they are good. One other good thing is the 53V rail has now been restored with no ill effects, which is a relief! There's no activity on any lamps though so I could still have a bad PIO although I'm a little hesitant to start swapping things out just yet. Grounding out any of the switch returns or connecting them to the switch feeds doesn't have any effect although all the feeds are pulsing and the inputs are all getting back to the PIO. There still doesn't appear to be any activity on the meter outputs either coming from the sound chip? I've since found out this code doesn't use an alpha, nor did a couple of others I tried, so I had been chasing my tail here looking for a non-existant fault. That's the trouble when you don't know the machines or have access to one for reference. It looks like there's a bit more involved to the coin mech side as I don't have any voltage on the coin sensor inputs. The Proconn manual shows a simple 5v feed via a resistor pack but the PC92 has a couple of transistors controlling the voltage feed. So, still a way to go.
  4. midibob

    PC-92 test rig

    You're a little teaser Louie The pleasure factor is a lot higher if you can crack it yourself, it has to be said. I was wondering what that switch did, I'm using 256K as that is the size of the files. Of course this isn't mentioned on the Proconn diagrams as it wasn't fitted due to no ROM socket. OK on the RESET, that's good to know it runs at a lower voltage otherwise I'd be chasing my tail looking for a fault that doesn't exist. I should be receiving a known good ROM shortly so at least that will eliminate one unknown in the equation. I'm sure all my A&D lines are good but I don't want to start swapping out any more bits now until I know I have a ROM that's good. I've just found out this morning that the extra ports on the 8910 look like they drive reel 6! Onwards and upwards.
  5. midibob

    PC-92 test rig

    Not at this rate, I'm struggling with a suitable ROM at present. I suspect most of the ROMs I've downloaded need a sound card which is why they appear not to do anything? I'm going to need some help so if anyone can chip in (no pun intended) with a game version that doesn't need a sound card, and I can download from somewhere, I'd be very grateful. Once I have a known booting system then I can crack on, at the moment I'm groping in the dark. With the ROM I'm currently using which I think is Jackpot Jungle, according to the hex dump, on switch on the Alpha pulses about six times and shows this. The 7 seg does sometimes vary but it's never anything readable as such. I'm guessing I've got the correct segments wired to the right connections? After this nothing happens, there is activity on the switch ports but nothing on the meter feeds so I assume it's not getting that far?
  6. midibob

    PC-92 test rig

    Hi chaps, My summer project this year is to get a test rig together for PC-92 boards. With a donated board I've started putting together a few bits to try and get it running. As I don't know this tech at all (yet) it's proving a challenge although there are similarities to MMM which I've worked on.The Proconn manual in downloads it almost the same but I've yet to find any wiring diagrams so working out the switch matrix, 7 seg displays and alpha is mostly poke and hope. I've never seen test software for this tech either although it must exist somewhere I'm sure. So far I've stripped down the RESET cct and associated bits near the battery as there were lots of green legs on the transistors. Only one resistor fell apart but it was good to get them all out as the solder had gone crumbly anyway. New battery rivets have been put in and the associated track mended. I've picked up some good tips from Andrew and Louie Bee especially Andrew mentioning about the 53v lamp feed. I found that the board was highly conductive even though it looked fairly clean. When cleaned with a cloth the old tobacco film was found to be quite extensive and the slightest bit of humidity would lead to voltage readings being picked up on the surface of the board to ground!! I dread to think what would have happened if I'd applied the Lamp voltage. The good news is, so far, it does boot and with a Jackpot Jungle ROM I get characters coming up on the 7 seg display and on the Alpha not that they make any sense. I have two other ROMs 8xCash and 777 but neither of these appear to do anything. Of course I may have the wrong code and also, I've got no idea how this tech is meant to boot? There are no sounds of any description ie alarms and I don't think the meters are being activated either so the AY-3-8910 might be knackered. The RESET voltage only rises to approx 3.4v and I'm not sure why as yet but it does appear to be re-setting OK. Vbatt is good at 5v. Things I'll need help with are :- What is the boot up sequence? I assume it will try to sense the meters then alarm if disconnected. Does the alpha display the code version immediately on boot or does that come after the meter check? Same with the 7 seg, should that be showing me percentage or something readable. Are there any links that need to made on the switches (like JPM Sys80) for it to do anything? I only have the single ROM fitted I assume the ROM cart socket isn't always necessary? Here's a pic of the board midway during surgery. I'll post some more when I get further down the road. I'll hopefully get around to producing a modified schematic for the PC-92 as we don't have one and I'll collate any other info gathered that might be useful.
  7. midibob

    Parvulux motor to mains help

    Hi Rich, If all else fails you could try here... https://www.parvalux.com/resources/faqs TECHNICAL Where can I find wiring diagrams for your AC motors? You can request a wiring diagram from our sales team
  8. midibob

    Sys80 I/O Rev 4

    Hi all, Search has turned up zilch but I'm looking for a schematic of the Rev 4 I/O board. It's got a few differences with an extra 74LS138 for IC19 instead of the 74LS10. Thanks Bob
  9. midibob

    Anti Static bags

    You'll find there are at least two types of anti static bags, one for boards in transit and another for boards already in an ESD controlled area. Make sure you get the right ones.
  10. midibob

    Pcb laqueur

    I found the best thing is a ladies nail curing lamp. Mine was only a tenner a few years back and it only takes half an hour, a lot less time than waiting for a sunny day!
  11. midibob

    JPM, my view from the inside. Frank Bird.

    I'm sure everyone is loving these old memories so keep with it. Thanks Bob
  12. midibob

    Scorpion 1 Issue 4

    I don't recall ever seeing a Scorp 1 with that resistor? As you now know it's not listed on the diagrams here so there must be an updated one out there somewhere. You're probably going to have to wait till somebody chirps up that's got a later revision board. I wonder if there are any other mods from the earlier boards?
  13. midibob

    MPU4 Test Jig Software

    I've just realised the display says 50Hz , fancy missing that. I could have sworn it said S00Z.
  14. midibob

    MPU4 Test Jig Software

    I've not seen that error before but I notice you don't have a plug on the serial port! You'll need to connect pins 2&3 together or you'll get an RS232 fail message. Oh, you must have the meters connected too.
  15. midibob

    BWB Line Up

    This might be what you want Steve... Line up info
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