Stern SS Meteor (Stern, 1979) Power problem

[RobertG]

The problem is that the score displays don't illuminate. I have found a voltage problem on the Solenoid driver/voltage regulator board. The section that is supposed to have 185v output only has 2.4v. The input has 235V. All of the transistors tested good but I replaced them anyway. No change on the output. I need help finding the problem. See attached

 

[pinballdaveh]

The problem is that the score displays don't illuminate. I have found a voltage problem on the Solenoid driver/voltage regulator board. The section that is supposed to have 185v output only has 2.4v. The input has 235V. All of the transistors tested good but I replaced them anyway. No change on the output. I need help finding the problem. See attached

Sometimes when the transistors blow they will take out resistors also. Is this voltage test done with the j2 output jack unplugged?

 

[RobertG]

Sometimes when the transistors blow they will take out resistors also. Is this voltage test done with the j2 output jack unplugged?

There is a 0.5v increase at TP2 with J2 unplugged. Note I did replace the 22K resistor at R51 because it looked crispy but it did test OK after removal.

 

[pinballdaveh]

There is a 0.5v increase at TP2 with J2 unplugged. Note I did replace the 22K resistor at R51 because it looked crispy but it did test OK after removal.

I don’t want to start guessing about what to change. I remember working on a board that the wiper of the pot broke off, disabling the regulator part of the circuit, allowing full voltage at the output. It seems like Q21 isn’t working or allowing voltage to pass thru.
You might want to consider sending the board out for repair Or changing the displays for the new LED type that doesn’t need the high voltage section to work since the plasma glass replacements are getting harder to find.

 

[RobertG]

I don’t want to start guessing about what to change. I remember working on a board that the wiper of the pot broke off, disabling the regulator part of the circuit, allowing full voltage at the output. It seems like Q21 isn’t working or allowing voltage to pass thru.
You might want to consider sending the board out for repair Or changing the displays for the new LED type that doesn’t need the high voltage section to work since the plasma glass replacements are getting harder to find.

The RT1 pot tests OK. I changed out Q21 Q22 Q23. All the old parts tested OK after removal. I'm stumped.

 

[RobertG]

I don’t want to start guessing about what to change. I remember working on a board that the wiper of the pot broke off, disabling the regulator part of the circuit, allowing full voltage at the output. It seems like Q21 isn’t working or allowing voltage to pass thru.
You might want to consider sending the board out for repair Or changing the displays for the new LED type that doesn’t need the high voltage section to work since the plasma glass replacements are getting harder to find.

Update. I found that when I turn the power off the voltage at TP2 jumps up to about 170v, close to what it should be, and then slowly starts to drop at the capacitor discharges. What could cause this circuit to work when the power is off but not work when the power is on.

 

[pinhead1]

did you do basic check for bad connections on the power and ground.
bad ground or a ground wire too small can do all kinds of strange things.
check the power coming out of the wall plug.

 

[RobertG]

did you do basic check for bad connections on the power and ground.
bad ground or a ground wire too small can do all kinds of strange things.
check the power coming out of the wall plug.

I checked the ground by doing an Ohm check between all the ground test points I could find and the ground going around the case. The highest Ohm reading was 0.2 ohms of resistance. Strange I have. Another thing I just found. I put a scope on TP2 where I should have 180v and when I first turn on the machine I have a 6v saw wave for a few seconds and then it goes to 2v+-.5v ripple when the flipper relay activates. (I hear the click). Another thing I found by accident. If the fuse for the 43v bus is blown then I get 70v on TP2. Is there some connection between the 43v section and the 180v section that isn't on the schematic. Another note. I believe that the schematic I have for the power board doesn't match the board that is in the machine. Someone has been inside this machine before I got it.

 

[pinhead1]

in your first post you said you have voltage problems and changed out all the transistors.
what about the capacitors and diodes.....
capacitor from google-----
In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other.....
diodes....
A diode is a two-terminal electronic component that conducts current primarily in one direction. It has low resistance in one direction and high resistance in the other. Wikipedia
did you unplug the machine from the wall then
1. use some fine sandpaper on the contact switches then
2. spray contact cleaner on switches and contacts if it has contact switches like car points.
you replaced transistors with no changes.
at this time it could not hurt to check for bad caps then diodes.....
it's 45 yrs old.....maybe you have bad caps and diodes or maybe some other old components that have failed.

 

[pinhead1]

one more thing to consider.
it's been blazin' hot.
i remember awhile back someone else in maintenance and repair had problems with power supply because it was hot summer.
everybody is using their AC, fans, swampers and whatever they have.
this puts a tremendous draw on the transformers on the poles that supply the juice to the house.
it's very likely there might be a power drop when everybody starts their AC and coolers up.
take a reading at the wall plugs early morning before the heat then again in the peak hours of the day
when everybody is using their AC and coolers.

 

[RobertG]

one more thing to consider.
it's been blazin' hot.
i remember awhile back someone else in maintenance and repair had problems with power supply because it was hot summer.
everybody is using their AC, fans, swampers and whatever they have.
this puts a tremendous draw on the transformers on the poles that supply the juice to the house.
it's very likely there might be a power drop when everybody starts their AC and coolers up.
take a reading at the wall plugs early morning before the heat then again in the peak hours of the day
when everybody is using their AC and coolers.

Now that I have access to an oscilloscope I have found that the 11.9V DC has a serious high frequency ripple in it. Not something that shows up on my cheap little volt meter. So that does point to a capacitor problem. New caps on order. I am now suspecting that the ripple is leaking across to the 185v regulator circuit because of the effects of induction somewhere in all the wires that are tied together. That would explain why the 185V suddenly works briefly when the power is turned off (running off the stored power in the cap). On another note I did find that the bridge rectifier for the 43v was only half working.

 

[pinhead1]

xllnt, good catch Rob.....you mentioned you had voltage drops in some of your previous threads.
thats when i suspected the possibility of bad caps or diodes.
good luck....
before you start it up again look at the power and gound connections to make sure they are good.
what is the power reading on your meter out from the wall plug before peak hours in the early
morning or late night and during peak hours demand in the heat of the day?

 

[RobertG]

The power at the wall is 120v +- 1v. I'm in an area with very stable power. I was so focused on the high voltage circuit not working and everything else seemed to be working and voltages were OK with a volt meter I didn't consider that voltage problems elsewhere could be affecting the high voltage. As a test I pulled the fuse on the 11.9v and the 185v works. I don't have any number displays but I figure that is because the circuits powered by the 11.9v was now not getting power for my test. Now to wait for parts.

 

[RobertG]

Update. Replacing the cap on the output side of the 5v regulator fixed the 185v

 

[pinhead1]

Update. Replacing the cap on the output side of the 5v regulator fixed the 185v

is it finished and playing ok or still waiting for more parts?

 

[RobertG]

It seems to be working OK except for one score display that is only showing digits in the 10s position. It seems like all digits are trying to display in that one position. Moving the display around and the problem follows the display. Another problem that did go away was a low pitched hum the machine always had.

 

[pinhead1]

It seems to be working OK except for one score display that is only showing digits in the 10s position. It seems like all digits are trying to display in that one position. Moving the display around and the problem follows the display. Another problem that did go away was a low pitched hum the machine always had.

yeah, good job.
i would like to play that old EM.
i played triple action, quick draw, time zone, frontier and few more i can't remember at my local bowling alley
down the street.
there are a few 90s SS machines local i play sometimes.
i think they are NM on elm st, addams family, strange encounters and few more.
have not been that way in a while
flippers work ok?
flippers should be strong and jet the ball through the spinner back to the top.
is it in nice condition?

 

[RobertG]

Flippers flip ok but occasionally the upper flipper gets stuck in the flipped position. And one drop targets drops from any vibration.

 

[pinhead1]

Flippers flip ok but occasionally the upper flipper gets stuck in the flipped position. And one drop targets drops from any vibration

can you get the parts??
maybe you could pull the plug, lift the PF and spray some contact cleaner to see if it helps.
could be just dirty from age.

 

[RobertG]

I haven't looked closely at the flipper yet. But it's working pretty good for a $75 purchase. I got it on a "my wife says get rid of it now" sale.

 

[pinhead1]

I haven't looked closely at the flipper yet. But it's working pretty good for a $75 purchase. I got it on a "my wife says get rid of it now" sale.

you bought that PB machine at a get rid of it garage sale for $75!?
the SS (solid state) machines might be a little easier to fix.
keep looking for parts.
it was probably at an arcade or bowling alley.
it got played out.
they got a new machine.
that's how it worked at my local bowling alley.
i played PB...there were no video games yet.
after about 3-5yrs it was getting played out from everybody especially on league night every night.
all the kids were in the rec area playing PB and this was before video games.
if you want look for some pb techs in your area.
i know a few PB repair techs in my region.
i'll make a call to see if they can get parts then i will give you the # if you want.

 

[RobertG]

Yep :) It helps to have a pickup truck too.

This machine does have a lot of wear and some non-standard repairs inside.
But it now has a nice easy life in a smoke-free air conditioned environment.
So far I am able to find parts. The harder part is exercising my high school electronics class education from 40 years ago.
At least the manual came with schematics unlike devices you buy today.