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Well, one of the functions that IC24 does is to monitor the lamps for short circuit bulbs and turn off that bulb as a precaution. It does this by monitoring the voltage dropped across the mux voltage feed resistors. This is fed into a little two transistor sensor circuit which then puts a signal on pin 10 of IC24. In this case both the transistors were iffy and the signal on pin 10 was constantly low. This is then fed back to the CPU which told IC12 to send permanent wait states up the CPU's own backside! Both transistors (T68, T69) had black legs and the BC337 (T69) tested leaky. Once swapped out along with the 5.1v zener as a precaution IC12 didn't send any more pulses on pin 7 and you could see the lamps at full brightness along with all the switches now working. To say I was relieved was an understatement.

Thanks for the pictures, will be great for emulation purposes. I can dump the ROMs for you if needs be.

A little update i have hopefully got the 10p roms coming later this week i will let you know if they work ok

Maygay - Living in America Tech M1 - Rom revision 1.1 Its time to nip over the pond for a trip around America with this rare machine from Maygay. Some say it's very rare machine and some say it was a failed test, whichever it is I have no idea. Thanks goto: Wizard (RIP) for MFME M1ajay for the roms and flyer. Living In America.zip

All finished now and ready to go in my small arcade room. As you know through the earlier posts i have sorted out the mpu faults and got it all running. I also fitted new bearings to the reel deck in the end and converted it to take the new-new 10p (adjusted the mech, removed the magnet and fitted a new payout tube), and it still uses tokens. On a side note i could not believe the mpu still worked as i had it in pieces so many times whilst doing the schematic. All that was left to do was sort the cabinet...... Removed the old base which was glued and screwed on (bitch), built and fitted a new one...... Filled and sanded the top and sides, several coats of pva in the (weetabix) T moulding groove ready for new moulding. Glued a cat to the top of it 🤣 Also moved the token refill keyswitch from the top to the bottom front (god knows how many pints were lost down the back of the machine in its life). Replaced the old flourescents with led lights. Then fitted vinyl wood effect to the top and sides and new t moulding (i know the stick on vinyl is not very hard wearing but it is not going to be abused) Finished!!!!!!!!!

For anyone reading this in future, as stated above by MattyL. I swapped the very end red pin for and placed it in the next available empty slot (next to the grey on my picture). Issue solved. Thanks all for your input.

The PSU sounds like an ultra sonic cleaner! The fans seem to fail. My take is its just general case air movement... its not like a proper heat sync or critical exhaust fan but is beneficial obviously. Both power supply types can be used. You just have to unlatch the end red wire crimp and move to a spare 12v. I still think you might have another problem. I'd at least expect it to start booting. If you can use a multimeter you can measure the 5v while connected to the machine. If it dips bellow a threshold voltage I forget what so im going to guess at 4.8v-5.2v (Sega) the Scorp4 will keep reseting. Needs to be connected to the load (machine).

I think you have another problem because of the noise. Can you confirm its defo coming from the supply and not the speaker? Unserviced Scorp 4 machines in 2026 will probably have a leaking battery on the main board which most people diagnose as a power fault, so take a look at that. Film the noise if you can, I've never know a scorp 4 supply to be humming personally- x2 seems very strange/interesting. Looking at your loom, if there is a power supply mismatch- its not the destructive way around. Ive seen machines with the wiring the same as yours and with the later supply it usually manifests as something like no power to the reels... Defo shouldn't be humming.

Welcome, we’ve had loads of people called Gary join today 😅 when you inevitably try and comment, but unable to reply, pls change theme of page by scrolling to bottom. This is a common issue for years now

Maybe dump the roms and some hi res pics as don’t think we’ve this version emulated yet

I can't believe it's been over a year since the last thread but this one was a corker! This board had been to & fro quite a few times with various faults but this time it was just 'stuck in RESET'. That proved to be easy as the little voltage supervisor chip had failed. Thinking it was ready to go back, testing it the next day proved otherwise. It was now running slow, dim lamps, and the Start switch wouldn't work? 3 days later and swimming trunks at the ready for the jump in the Thames I was geting nowhere! For those who follow this thread may remember this is very similar to a fault a few posts back and this was due to IC24 (8255) which had failed. The plot somewhat thickens here as an old note stuck to the bottom of the board had all these symptoms on it and a previous repairer had alread been around that area changing chips obvioulsy to no avail. All these had to be removed as they needed tidying up and I couldn't be sure there wasn't something untowards underneath them. So once that done the same issues were still there. So what is causing the problem. Well, as was described in the previous fault, a pulse coming from IC12 (7) puts delays in the NMI line to the CPU which is used for various functions. I'm thinking it must be something to do with IC24 as it controls the lamp multiplex and the switch multiplex, but what? The chip is OK as it's already been replaced. Whilst in bed last night it came to me in light bulb moment and this morning I found it straight away. I was correct in my diagnosis that it was something to do with IC24 but up and until then didn't understand why. Now I do. What caused the issue? (just two components)

Afternoon Ron, I will take a look, hopefully it will be a simple as hoped! Thanks for the reply 👌

I did start it a few years ago, I'll have a dig through some old harddrives.