Hi Everyone,

This is my first post on this site. I've heard alot of good things about it from the guys over on CGCC so I thought I would register and seek your help on my latest project.  This 79 Stern Meteor pin that I picked up recently.

I'll try to keep it short and I have a link to another site where I have also asked a few questions about it.  Here is the link for some history if your interested:  
http://groups.google.com/group.....3ec#8f573e6f4af903ec

When I bought this machine it had been sitting in a quansit for about 7-8 years according to the owner and he never got around to fixing it or even to opening the back box because he had no key.  He has a bunch of EM machines that are really his thing and when he got this he thought he would try an SS but never did.

Anyway, I bought it thinking it might not be too bad and to my surprise its actually in not so bad shape.  THe mpu200 has very minor corrosion from the battery which I cut out right away.  After doing the visual and cleaning it up, checking wires for rodent damage (there was some), and looking for loose wires I decided to go ahead and power it up.  All the lights came on exept for the score displays and the mpu did flash a couple time.  After researching on pinrepair.com I concluded it was stuck on the flash indicating a bad 5101 at u8.  So I stopped my testing and ordered:

:New rectifier board and battery corrosion repair kit from Ed Krycheck
:New u1,u2,u5,u6 roms

Once I received everything I installed the rectifier board and fired it up once and still got the flashes ending at a bad 5101.  I went ahead and replaced the old with the new 5105 and socket.  I thought I would power it up to see what happened and I got a solid LED light with no more flashes?  I still have the solid lit LED and I have done a few things to try to fix it with little success.

:I took out the MPU and hooked it up to a switching power supply/test bench according to pinrepair recommendations.
:I removed the 5101 and socket completely to see if I had bridged any solder, but no change,
:I replaced C23 on the solenoid driver board
:I jumpered with a screw driver pins 39 and 40 of U9 to see if the reset circuit would start but nothing
: I tested pin 40 of U9 and it stays around 5vdc.
: I grounded r1,r3 junction to ground to see if Pin 40 would go very low which it did and then high again and it went back to 5vdc
: I replace all the components of the reset circuit including Q1,Q2,Q5, cr5 and vr1 and still no change.
: daisy chaned a ground wire from all the mounting brackets in the backbox to the main ground strap
: I replaced CR44, r29, r107, c80, c3, c5, c2, cr7 and tested after each but no change.
: I resocketed all of the removable chips.
: I tested all of the diodes (cr) to see if any have gone to ground and couldn't find any.
: I checked for ground on all chips but here is a kicker and I'll try to explain further below, perhaps someone can help me out.

Ok, need a break.....

Ok, Ground I've always been tought ground is important so this was one of the first things I checked along with installing the daisy chane ground wire.  But here is were I'm left scratching my head because it strikes me as odd.
   When I check grounds on U1,U2,U5 and U6 with the power OFF I get a nice even tone from my continuity tester with one lead always on TP4(gnd).  This is also the case on all other grounds on the PIA's and CPU chips, 5101's etc.  
BUT
  As soon as I put power (12vdc) to TP2 and (5vdc) TP5 I loose my continuity tone for ground on the U1, U2, U5 and U6 roms.  If I check for vdc I get 10 to 12 volts?  I can't see this as normal but then again I don't completely understand how these chips work.  Further, when I test ground on PIA chip U11 and CPU chip U9 I get a tone that pulses, like bzzzzBPbzzzBP and that is continual, like morse code or something.  Am I somehow getting feedback or voltage into ground that shouldn't be there?

I have no problem replacing parts but I can't think of a logical reason why this would happen.  In my mind, ground is ground but I'm more familiar with house wiring than circuitry.  Help me please on this one.  

I haven't yet installed my new roms because I was sure what jumpers I had to change.  I wanted to get my LED flashing first.  

So if anyone can help me please do.  For more info on my Test Point voltages take a look at the link above.  Its all layed out there along with what the voltages should be according to pinrepair.  

Thanks alot everyone,  I really don't want to give up,

Mike

If you do decide to give up, Mindstorm88 could have that board working like new in no time for a very reasonable price. He does great work.

Of course, I commend your attempts thus far and understand why you'd want to figure it out on your own before handing it over to someone else.

Good luck.

Hey, Thanks Cooke.  I'm not quite ready to give up yet but if/when I do I'll go that rought.  Grauwulf also recommended him which is a big reason I decided to register here.  This is the first pin I've decided to tackle.  I hope I can fix it with the help of others but if not I'll have to admit defeat.  I know you and most of us enjoy fixing these whether they're vids or pins and having that satisfaction in the end when you succeed, knowing you accomplished something most could or would not have.  

Thanks,  Mike

Quoted from ancientgames

  As soon as I put power (12vdc) to TP2 and (5vdc) TP5 I loose my continuity tone for ground on the U1, U2, U5 and U6 roms.  If I check for vdc I get 10 to 12 volts?  I can't see this as normal but then again I don't completely understand how these chips work.  

Mike

I would guess that you are leaking +12VDC in the ground .  Remove F3 on the power board (in the bottom cab).  Check again your continuity for ground with power on (keep in mind that the +12 will also be missing).  If your ground stays good then you've possibly found the culprit.  You may have a failed diode on BR2 which leaks 12 VAC into the ground circuit.

Also..  Are the connectors still intact on the power board?  I've found quite a few machines with the wires soldered directly to the board but done INCORRECTLY!

Mike

Hi Mike,

I was thinking something similar but the rectifier board is new.  I replaced the old one which had wires solder on and a couple burned pins.  So I figured one from Ed Krycheck (?), recommmended by pinrepair.com would be a good replacement.  But, I took the mpu out of the back box and now I'm testing it on the bench using a switchers GND, +5 and +12 also recommended by the site.  It still does the same thing though so it can't or atleast isn't the rectifire board.  However when I remove the +12 jumper, from TP2 i do get the propper ground tone back.  So I agree, somewhere I'm "leaking" into the ground, but where? I can't find it.  I just finished replacing more resistors in the lower area below U11 but still no change.  If the PIA's or CPU go bad, do they go to ground?  I know diodes do and thats easy to test for but the other stuff isn't.  

Thanks,  Mike

Trace the +12 on the schematics.  Right I'm looking at it and it comes in on pin 12 of J4.  MAke sure there's no corrosion on J4 that's bridging pin 12 to something else.

From there goes to L1 (not likely culprit) , C2, VR1, and R112 (I think - schematics fuzzy) - all of these components are tied to ground so if they short it'll cause what you are seeing.  There's also a line that goes to the LED part of the circuit which I can't see on this poor quality schematic.  Make sure VR1 was installed in the correct orientation - this is the most likely reason for the problem.  Your board was working partially and now that you've changed components the +12 is shorting to ground - this means it's something youve changed that's the problem.

Just because you've changed some of these components doesn't make them good.  I recently bought 4 zener diodes at my local electronics shop and 3 were bad.

Mike

Well, I cant see the link from work (love that Websense!!!). What Stern is it?

...I have a soft spot for beat-to-mess Sterns... if ever you decide to get rid of it... as long as it is one I don't have, of course!!  

From the thread's title:
Stern Meteor Project-MPU 200?

What a day at work, backed up and got the truck door hung up on a solid snow drift and bent it around, frrfk!  Right at quiting time......

Anyway, Sparky its a Stern Meteor from 1979.  Nice machine in good condition but if I ever sell it I'll let you know.

And Mike, thanks for the tips.  Yeah those schematics are pretty blurry and do you think they could have labelled things any smaller.  Even with a magnifying glass I have a hard time making out what it says.  I went back and double checked everything I installed, especially the components that are only meant to go in 1 way.  I am aware of that so I was pretty careful to put them in the right way.  But this ground or leaking 12vdc problem occured after I put in the 5101 chip and socket and nothing else.  I only started replacing the diodes, caps, transistors and resistors after and tested it after each piece was installed trying to find the reason for the leak.  I even removed the 5101 chip/socket and tested each pin hole for any solder bridge I may have caused but nothing.

I'm gonna make some dinner, scim over the schematics and make some rough scetchs of the 12vdc ciruit.  If I have to I'll remove one component at a time until I find the source!!  Good quality fun!!

Good thing my wife is on nights.....

If memory serves me correctly, the 12 VDC is used for nothing on the MPU other than the reset circuit (it checks that it's at 12V before coming out of reset).  The 12V is actually  used only on the sound card.  It can't be leaking from any component like a chip.  It has to be from the reset section.

Mike

arrrg.......

Ok, now I'm really confused and I think its time I give in, or atleast ask someone who really knows what thier doing to fix it for me.  Before I make it worse, like the toaster I fixed and it now works like a space heater   Nah, just kidding....

I could just pack it in, send it away to be fix and be done with it but you guys deserve an explanation (because your tried to help me) and I deserve whatever I get...here goes.

The reason I'm done is I went back to double check those grounds to see what voltages were leaking into it and I got a reading of 10.2.......hmm,....ok my pride is going to take a sht kicken........nothing new..........but.   See, well.... this new DDM I bought is compact, no larger than a small calculater, really easy to handle, nice really.... and I'm not used to it but when I looked closer I noticed a small "m" slightly infront of the V for volts.... .....

That wouldn't be important would it?  The small "m" infront of the V is gone when I test the vdc directly at TP2, reading 12.1vdc.  It must mean MASSIVE or MAJOR or MIKE for ME.. ....  The manual doesn't actually say but I'm sure it stands for something small, tiny, maybe even mini or milli?  Whatever it is I didn't notice it before.

Ah yes, not quite as bad as when I asked what SP+ stood for on my MS Pac pinouts....yes speaker +.   ah well.

I'm going to ask mindstorm88 if he'd be willing to take it on.  Perhaps he'll pity me.

Thanks everyone, let the ribbing begin.....

Mike

Change the ROMS and all the other chips you bought..  Try a manual reset on pin 39 or 40 can't remember..

Mike