Jump to content

Fixing my Royal Exchange mpu3… stuck in reset!!


sp1971
 Share

Recommended Posts

I already have a couple of working mpu3 machines but no experience of fixing anything inside the metal box.  I decided to have a go at building some experience so I’d have the confidence to try and fix any issues that might arise with my working machines. I purchased a non-working Royal Exchange and didn’t pay a lot for it but reasoned with myself that if my project failed then I could always sell it on or break it for spares.  But I only want to preserve it and get it working!! I have no contacts to call on for help, but I’ve found this forum is a brilliant resource for people like myself who are willing to have a go.  I’ve been logging everything I’ve done so the following posts detail my journey so far.

The story so far part 1…

Power on and Royal Exchange not working, only 2/3 flo tubes lit.  I replaced the ST111 starters and all the flo tubes, then checked/replaced all the PSU fuses.  The mpu3 board is a Mod 5 with a daughter board and 6117 RAM. No battery on the board but it was evident the old battery had leaked and done some damage as there is some masking missing.  Someone has previously cleaned the board up, but upon first inspection I found quite a few green legged components, also T60 had a broken leg and C41 was missing.  I replaced T60, T61, C41 and R92 – R95.  I also cleaned between tracks with a fibre pencil and mopped up with IPA.  Checking the white power plug I found that the 12v return pins 1 & 9 had burnt.  I then fitted a bypass lead to 0v on the board as suggested elsewhere on this forum.  I checked pin voltages on the white power plug and all OK. I fly wired a NiMh battery, confirmed 5v at the link and pin 24 on 6117 which dropped to 2.4v on power off. After cleaning all the plugs I connected the board and switched on… it booted but was stuck in reset.  Reels stepped up & down and remained stiff, optos lit and display was now showing ‘Resetting RE 4.0’.

  • Like 2
  • Thanks 1
Link to comment
Share on other sites

The story so far part 2…

I replaced further corroded components R84, R85, R87, R97.  Changed D44 & D45 for P600B.  Further cleaned between tracks and around soldered plugs.  Continuity checked all plugs. All plugs then sprayed with contact cleaner, reconnected board and switched on… now resets and goes into attract. Machine plays, but no sound, and meters working intermittently. Tested speaker in another mpu3 and working OK so I replaced T11 and R33 and sound now working.  For a couple of weeks I was playing the machine daily and would leave it in attract for at least 4 hours.  I then started to get an issue with the machine resetting itself randomly when in attract or being played.  After doing some research on this forum I decided to focus on the Auto Reset circuit.  I replaced T57 – T59, C46, R75 – R78, R80 – R82, and removed T56 & T62 to disable the Anti-Spark circuit. I refitted board and now all working OK and no more random resetting.  All fine for a couple of weeks until I started getting reel judder and independent movement on Reel C.  This was happening when warmed up say about 25 plays after switch on, and would do it in attract or whilst playing… sometimes it would eventually give a Reel C Alarm.

  • Like 1
Link to comment
Share on other sites

The story so far part 3…

After some more research on here I decided to change the Reel C driver transistors T47 – T50 BCX38C, and I checked OK for 330R across the pins on RP7.  I also changed the old looking C1 – C3 regulator board capacitors whilst the board was out. I then just connected the board up with the white power plug and confirmed the regulator board voltages and the board 5v link and D44/D45 voltages, all OK. I then connected up white power/yellow/aux1/red/red/green leads and no boot… just ‘CCCCCC’ on display. Removing red/red/green gave me ‘Resetting RE 4.0’ but stuck in reset.  Replacing red/red gave me the same but with green connected I got either ‘CCCCCC’ or other garbled characters on the display. It was at this point I believe I started getting lost because I decided to look closer at the green plug and work backwards.

  • Like 1
Link to comment
Share on other sites

The story so far part 4…

I checked for 5v at green plug pins 6, 7, 8, 9 and no 5v at pin 6.  Looking at RP8 there was 5v at pin 4 but not at pin 13.  Also no 5v at IC17 pin 15.  I replaced RP8 and T55 BCX38C and no change but now I’ve got 5v at green plug pin 6 but no 5v at pin 8. I then replaced IC17 LS138 & C41 (next to IC5) as I noticed it was damaged. Test and back to no 5v at pin 6 but 5v is back at pin 8.  I replaced IC5 6821 and still no 5v at green plug pin6/IC17 pin 5/RP8 pin 13. I’m now getting ‘Resetting RE 4.0’ with white power/yellow/aux1/red/red/green leads connected but it’s still stuck in reset.  Reels step up & down on power on but don’t spin. I have no idea if the reel issue is fixed, maybe the no 5v at one of the pins is supposed to happen? I started thinking that currently being stuck in reset may be unconnected to the green plug, and I have a separate issue somewhere within the Auto Reset circuit?

  • Like 1
Link to comment
Share on other sites

The story so far part 5…

With just the white power plug connected I tested the following in the Auto Reset circuit…

C36 10.23v across.  I read elsewhere on this site that it needs to be 10.6v to release reset?

R75 0v across

R97 10.22v each side measured to 0v

R77 15.88v and 10.22v measured to 0v

D41 15.92v and 10.25v measured to 0v

I replaced T57 – T59, D41 & D42, C36, and C40 (as noticed dry joint)

I then connected up white power/yellow/aux1/red/red/green leads and nothing… just corrupt text on display.  Unplugging red/red/green and try again I now get ‘Resetting RE 4.0’.

Retesting Auto Reset circuit with just the white power plug connected…

C36 now 10.84v

R75 still 0v

R97 now 10.86v each side

R77 now 15.54v and 10.86v

D41 now 15.46v and 10.87v

I then replaced R79 as I haven’t done this previously, and also changed R90 (as noticed it was corroded).

Testing with just white power/yellow/aux1 connected and I’ve now just got garbled text on the display.  Frustrating as it feels like I’m going backwards!!

  • Like 1
Link to comment
Share on other sites

The story so far part 6…

Previously when the machine was working and running in attract I had probed each pin of the 6117 RAM and IC9 & IC24. I had recorded what I found for each pin to keep for future reference.  Probing these IC’s again now has thrown up the following differences… IC9 LS138 pin 6 and 6117 RAM pin 21 are now High (previously pulsing).  I saw that IC9 pin 6 connects to the VMA line and the only other connection to this is IC1 pin 5 which was also high.  I didn’t have a clue!!

Before going off at a tangent I left everything for a week or so then re-read these notes.  I’ve only had the garbled text on the display since changing R79 so I decided to remove and replace R79 again.  There was some masking missing on the 0v track under where its sitting on top of the board, so I resolder making sure it’s away from that. Testing with white power/yellow/aux1 connected and I’ve now got ‘Resetting RE 4.0’ back. I probed the RAM IC’s again and all pins are back to when the machine was previously working and running in attract.

I then connected up white power/yellow/aux1/red/red/green leads and back to just corrupt text on display but reels A & B step at power on then nothing.  No optos lit but reels are stiff.

I then removed R79 and T59 to enable a manual reset.  Now with white power/yellow/aux1/red/red/green leads connected and power on gives all reels judder once moving slightly up or down. Reels are stiff but no optos lit. Display just shows garbled text.

Manually jumping between 0v and ‘R’ causes all 4 reels to step up twice, then reels remain stiff with optos lit. Display is now showing ‘Resetting RE 4.0’. So I’m back to where I was before changing all the Auto Reset components… but now have to do a manual reset to achieve this.

So that’s where I am today.  Apologies for the lengthy posts.  I’m trying but obviously lacking the technical knowledge needed so I would be grateful for any suggestions please for my next steps.  Is there anything else I can measure/check to try and establish why it’s still stuck in reset?

Cheers, Steve

  • Like 1
Link to comment
Share on other sites

Welcome to the world of frustrating MPU3 faults.:lol:

A few things you need to check, the 500HZ osc from the 555. Both the 10K timing and duty cycle resistors can go out of limits as can the big 0.1uF cap. Do IC9 and IC24 show any signs of the green plague on their legs, if so replace them (in sockets). The RAM sockets can be an issue as they are the 'stamped'  type but due to the fact you have the daughterboard you can't fit the more reliable 'turned' ones. Sometimes contact cleaner will work but again any signs of the green stuff, whip em out! Don't forget to clean the legs of the daughterboard too and check the state of the actual RAM chip socket.

The ROM cart socket can give you grief too if it's dirty or lost tension on the pins. A bit of contact cleaner and a very fine (and I mean 'very') emery board works wonders. Also if the little silver key spacer is broken (very common) the cart can just be out of alignment enough to stop it booting or at least become intermittent.

See how you get on with that.....

  • Like 5
Link to comment
Share on other sites

Many thanks for the pointers Bob.

I have only previously ‘tickled’ the ROM socket connections with a fibre pencil and sprayed with contact cleaner so I will try your emery board suggestion.  The key spacer appears to be ok on inspection.

I don’t have access to a scope to measure the 555 so I will order a replacement 555, along with replacements for C33 and C34 which I also don’t have.  What I can replace today is R67 - R69 and C32.

The pins on IC9 & IC24 don’t have any green legs. I will give all the pins and all that area a good clean up anyway, and the same for the daughterboard.

I do have replacements and turned pin sockets ready to fit for IC9 & IC24 so if there’s no improvement after replacing everything in the 555 circuit I will try that next.  The only reason I haven’t done this already is that I’m unsure about soldering the turned pin sockets as I noticed a few of the pins also need soldering on top of the board.  I will do a bit of research on that!

  • Like 2
Link to comment
Share on other sites

The via's will take care of that! They are the rivets that join the top and bottom tracks together. You only need to solder from the bottom and capillary attraction will do the rest.

  • Like 1
Link to comment
Share on other sites

45 minutes ago, midibob said:

The via's will take care of that! They are the rivets that join the top and bottom tracks together. You only need to solder from the bottom and capillary attraction will do the rest.

Thank you... that's a relief!!

Link to comment
Share on other sites

  • 2 weeks later...

The story so far part 7…

I had replaced R67 - R69 and C32 whilst still waiting for my replacement 555 timer and caps for C33 and C34 to arrive. When I measured the resistors I’d removed R67 & R68 were spot on but R69 only measured 8.1K instead of 10K.  I gave the ROM socket connections a good clean up along with the RAM chip legs and sockets/connections on the daughter board.  I then connected up white power/yellow/aux1/red/red/green leads and got nothing… turns out I had no 5v at the link which I traced back to the regulator board.  The output from the UA78H05 regulator was only 1v.  Luckily I’d already purchased a couple of LM323K’s as spares, so I fitted one of those and it gave me a tidy 4.98v whereas the failed regulator used to give 5.14v.  Retested again with white power/yellow/aux1/red/red/green leads connected and manually jumping between 0v and ‘R’ gave me no improvement, still stuck… All 4 reels initialised then remain stiff with optos lit. Display showed ‘Resetting RE 4.0’.

Today I fitted a new 555 in a socket and changed C33 and C34. Tested again as above and no improvement.  I then changed T57 and T58 again, and refitted T59 and R79 to re-enable auto reset. Testing this gave no reel movement and display just showed garbled text.  I tried the manual jump between 0v and ‘R’ even with T59 and R79 fitted and all 4 reels initialised then remained stiff with optos lit. Display showed ‘Resetting RE 4.0’ and still stuck.

Probing about in the reset circuit I’m reading…

C36 11.08v across

R75 0v across

R97 11.12v each side to 0v

R77 16.02v and 11.1v measured to 0v

R81 16.1v and 0.95v measured to 0v

D41 16v and 11v measured to 0v

D42 10.56v and 1.5v measured to 0v

If anyone has any ideas then please let me know?! 

I’ve removed T59 and R79 again for now.  Next steps for me today are removing IC9 and IC24 and fit replacements in sockets.

Link to comment
Share on other sites

Does the RESET circuit function correctly, sounds like it doesn't? It should go to approx 0v on switch on and then after about a second switch to 5v. You shouldn't need to 'jump' the RESET obviously but I would make sure that part is all working first as it will save you time. Depending what mod state you have will depend on what parts may be faulty.

Moving on to the no boot is where it can get tricky. Assuming your ROM chip is OK, test by substitution, then you are getting in to logic probe or even scope territory. I wouldn't recommend a scatter gun approach either of swapping all the support chips (unless things get desperate, been there a few times) as that can lead to all sorts of added problems of pad lifting, broken vias etc unless you have all the right gear of course.

It'll be a good idea to do IC9 & 24 anyway as you may hit lucky. Watch you don't pull any pads off though as some of the pins are soldered both sides

  • Like 3
Link to comment
Share on other sites

Thanks Bob.  I’ve now changed and socketed IC9 and IC24.  Still no change testing with ROM cart in and just white power/yellow/aux1 connected. Display was blank until I did the manual jump and then I got ‘Resetting RE 4.0’.  Logic probe on each pin of 6117 RAM and IC9 & IC24 gives me the same readings as I’d recorded for reference when the machine was previously running in attract.  Reset line is currently sitting at a steady 4.98v. For whatever reason the display is now showing ‘Coin Alarm’ which I’ve only seen once before and that was yesterday.

I’ve checked the ROM cart in another machine, and it boots and spins the reels before giving a ‘Reel D’ alarm which I guess is because it’s a 3 reel AWP.

I’ve just powered off and back on and Reset line goes straight to 4.98v… dips for a split second when I do the manual jump then back to a steady 4.98v.  I would assume it should sit at 0v at power on until I do the jump?  Given that putting T59 and R79 back in yesterday to re-enable auto reset failed I am also thinking something must be wrong in this circuit.  I have already changed T57 and T58 again so I’ll try changing D41, D42, C36 and C46 again, and also put T59 and R79 back in.

Link to comment
Share on other sites

No, it should start at 0v and then switch to 5v after approx 1 second ish. No point keep changing the transistors as it's unlikely they are bad again.  Looking back through the thread I see you had removed the spark circuit so that's eliminated. The timing of the RESET pulse is set by R76 and C36 which you can monitor by reading the voltage from R76/T57 to ground on switch on. It should start at a low voltage and rise to somewhere 12-15v if I remember. If that's happening then T57 should be switching when it's collector voltage reaches the threshold of the 9v1 zener on it's emitter which in turn switches T58 on and T59 off....bingo 5v on the RESET line.

  • Like 2
Link to comment
Share on other sites

Thanks again Bob.  I’ve rebuilt the Reset Circuit again this afternoon, and also put T59 and R79 back in.  Upon testing I’m getting garbled or no text on the display, and the voltage at the R76/T57 junction climbs quickly to 14.86v at switch on.  I am getting 5.26v almost instantly on the RESET line.  I’ve spent time this evening mapping out voltage readings to 0v at various points within the Reset Circuit as per the attached pic.  I’m just hoping this may highlight something to your experienced eye? After this I logic probed the RAM chips again and they gave the same outputs as when the board was running. RAM voltages are a solid 4.98v. Cheers, Steve.

 

RESETcctVoltages.jpg

  • Like 3
Link to comment
Share on other sites

Thanks Bob, yes I see what you mean.  Due to working I’m unable to have a proper look at this until the end of next week, but I couldn’t resist doing a bit of continuity testing tonight.  All the transistors meter OK on the diode test.  The T59 and T58 emitters have continuity as expected, the soldering is OK and they link via a single track on the underside of the board. Crucially, what I did find is the solder joint on the top side of the board for the T59 emitter does not have continuity to the 0v track!!  So I’m keeping my fingers crossed that fixing this will give me a result 😐

T59badjoint.jpg

  • Like 2
Link to comment
Share on other sites

 Share

×
×
  • Create New...