so I am in some real deep stuff here.

I've been trying to test my Star Trip cocktail power supply. The manual ( http://mirror2.ipdb.org/files/3605/Game_Plan_1979_Star_Trip_Repair_Manual.pdf ) explains what voltages should be at each test point, but I was really struggling as it didn't have a board layout showing their locations.

So I found another site ( http://www.beerorkid.com/pin/Gameplan%2077-85/ ) that showed me the information (page 22)

My problem is that I can't check the test points - I don't have them!

The regular board should look like this:gpps4.jpg

My board looks like this: 20150429_202308.jpg

Yes, someone replaced the circuit board with components mounted on a piece of plywood and hard-wired together. The power supply seems to be mostly working but none of the solenoids come on at all so I wanted to test it.

I can't figure out where to put the multi-meter. Can anyone who can read the circuit diagram give me some pointers?

thanks viperrwk!

I was really trying to understand why someone would do such a thing, unless the board had corroded so badly it needed to be thrown out. I guess that makes sense...kind of....

Thanks for the info - I am going to give it a try!

The fuses are good.

It looks like my problem is voltages. According to the diagram, measuring voltages at the fuses, from the transformer side:
1) 3A slow blow, should be Line AC - did not measure
2) spare
3) 5A, should be 12V running through it. I measured 12V - good!
4) 5A, should be 7V running through it. I measured 3V - not good
5) 10A, should be 28V running through it. I measured 14V - not good
6) 5A, should be 6.5VAC - did not measure

It looks like the 7 and 28V circuits are running at half their voltages.

is this something fixable? or is it time to start trolling CL for a replacement P/S

Bizarre, I should probably take a few hundred hours and learn basic circuits

I'm going to check at the board connectors.. but it sounds like they *may* be ok, if the voltages at the fuses are at exactly 1/2.

Unless its a dead wire it might mean the solenoid board is toast - the original problem is none of the solenoids will fire.

Thanks viperrwk.

I'm reading through the guide. One thing not mentioned is how exact the power should be. When I test power at the pin connector between power supply and sdu, I am not getting 3xactly the power the circuit diag shows. I dont know if this is significant or within tolerance.

when I check pins 4 and 1,2 ... I get 12v matching circuit diagram
pins 4 and 12 give 33vac instead of 24
pins 4 and 13 give 27v instead of 24
pins 4 and 15 give 5v. Matching circuit diagram

is that within tolerance or could that have destroyed something on the sdu?

Not entirely sure how to measure the voltage at the coils!

I did find reference to checking the ac ripple on the power supply. The article ( beerorkid.com/pin/Gameplan 77-85) said to set my meter at vac and check across the 11000 mfd big cap on the power supply board. I should only see .2 vac on it.

it didnt say to check with power on or off, I assumed with power on.
mine shows 30 volts ac when powered on and measured across the two connectors (hard to see in pic but I have it set at 50VAC.) After a few min of being powered off it still shows about 2vac.

I am either doing it completely wrong or that capacitor is seriously toast!
Does this sound reasonable?

20150514_194159.jpg

As a separate issue, I thought I would try and check a few transistors on the processor board with my new Atlas DCA55 which says it is easy to use. Just connect it and it figures everything out.

I checked transistor 31 (2N 4403 transistor) and the transistor 32's (2N 3904 transistor) - it shows 2 of them as transistors and 2 as not (see pictures.) I assume I should pull them off the board and check them while isolated. Note the previous repairs on the board, including a wire where a corroded trace used to be!

IMG_7753.JPGIMG_7746.JPGIMG_7749.JPGIMG_7751.JPG

Dang. I was afraid of that

Thanks Viperrwk, I am 100% in agreement with you - I have no interest in randomly pulling components just to test them.

I'm going to replace the big cap just in case.. then spend some quality time with your shotgun guide. It looks like my problem (no solenoids or numbers display) is not a power-supply problem, so the next guess will be the processor board

I am trying to figure out how to proceed on this star trip. It appears it is not a power supply problem.

with everything back in place and connected....when turned on all 6 lights on mpu light, test points on mpu board show correct voltwges, game sounds work, displays work.

pressing test gives lights - ok
test again gives display cycling -ok
test again gives solenoids -no errors but not a single solenoid fires

I've checked power and fuses. 24v to mpu is good.flippers work, scoring works, scoring off bumpers works but not one solenoid fires.

any idea what might cause this? A failed ic. Are there any voltage test points I can check on the sdu-1?

Progress! The fuse under the playfield was missing. Replaced with 3amp slow blow and it popped immediately when turned on. Multimeter says it has 29 volts across it. But at least it is progress

No worries, I really appreciate all your help on this. The table has never worked, I know nothing about pinball or electronics! that's what makes all of this so fun. I am learning something new and having a blast.

The table pops the playfield fuse about 1/2 second after the game-over sound plays. I didn't see any coils move but everything else works - playfield lights, flippers and digits display.

So I unsoldered all the coils and their diodes, checked each one and they seem fine (5.5 and 8 ohm.) Checked each and every switch and all are open. I powered it back up with every solenoid still unconnected and it popped again - back to the store for more fuses, lol.

In looking over things carefully, I noticed one of the switches seems to have a diode missing (see red circles in the middle of the image - the switch on the right has one (disconnected for testing) and the one on the left does not. I need to check the playfield schematic to see if it is supposed to be there and see what else I may be missing.
IMG_7775.JPG

Just wanted to report - that you are a freaking genius!

That coil was burned looking and shows only 2.5 ohm on the meter. When I turned the table on with it disconnected, it did NOT blow!
IMG_7776.JPG
I reconnected a couple of coils and verified they are working. This is real progress!

btw - I had forgotten another coil as well, there is one inside the playfield that shoots the ball from the center exit over. I didn't see it because it is kind of hidden inside the double-layer playfield. Fortunately it is ok and works.

I am sooooo excited!
Mark