Most likely AC. Be Careful. Hot to common, not hot to ground.

Check Youtube and Google for some information.

You might be better off checking inputs at boards.

LTG : )

First examine exactly WHY you want to measure these voltages?

Transformers very rarely fail - exceptionally rarely so I would dismiss them as any source of a problem unless you have some reason to suspect it/them that you aren't sharing here?

Playing with mains voltages is DANGEROUS even for trained technicians so it can be VERY bad for casual hobbyists fiddling around.

My advice is tell us what your issues are and get some solid advice before poking around "willy-nilly".

I would start by measuring all of the voltages at the OUTPUT of the power supply - they will be mostly DC voltages and will be in the manual.

I have no idea about the replacement one you are using, sorry.

Looking at your pic close up, there is no LED indicator.

if you have to ask please stay away from the transformer for safety reasons.. it wont be blown. Assuming you dont have a blown fuse it will most probaby be the MPU.

if you want to measure voltages .. see that plug at the top of the power supply? you can measure 5v at the output. looking at it the left side is 5V, the middle is ground and the right side is -12V. Without those it wont boot, although even with those it still wont boot if the mpu is dead (usually the real problem).

If you just want it to work what you really need is probably a pascal board. http://www.flippp.fr/pi1x4.php is ideal but you can also use http://www.flippp.fr/pi1.php if your cables ( interconnect/driver board etc) is ok.

what do the displays say? while its in this "flippers work when you activate game over" state?

if you have 5V i would say your mpu is broken and its pascal time. are you 100% sure you havent blown any fuses? with the machine unplugged test each one in continuity mode with multimeter

If you want to test the transformer you can check the resistances. Turn off, disconnect and test input and output resistance. The proper expected resistances should be in the manual. If those match then the transformer is not your problem.
Next I would check the voltages at the test points on the MPU. The correct voltages should be listed in the documentation TP1, TP2, ...
Even small differences can be problematic. If it asks for 5V the 4.8V is likely to cause problems.

what makes you say that? i have all the manuals and i have never noticed it ever.. can you let me know which game you know has it shown? very curious to see ..

Actually--the small transformer (which supplies all the power supply voltages) is a known failure point (under certain conditions). The original power supply has some diodes that can short out, and since there's no fuse between the power supply and the transformer, or no fuse between the transformer and main power, the transformer can act as the fuse.

http://pinwiki.com/wiki/index.php?title=Gottlieb_System_1#Small_Transformer_Meltdown

indeed .. but from the ones i see its 1 of them for every 100 than just dont work any more because of the mpu... you're perfectly correct and possibly right but my money is still on the mpu.

Nope, I don't see any LEDs. You will have to test the outputs with a multimeter.

I agree--it's certainly a rare occurrence. But the power supply was replaced for a reason, which makes it slightly more likely.

However, testing the power supply voltages will determine if it's a power issue or an MPU issue.

I would suggest measuring IC supply pins and lights first, if the voltage is not correct there then disconnect the leads from the power supply except the ones that actually power it and then retest voltages.

If the voltages are correct there with no load but fail with a load you have one set of probs - I would first look at the regulators in that case.

If the voltages are solid at the IC pins and lights then you have another set of problems, that suggests a problem after the power supply. A shorted component, an open trace/broken wire, a failed IC, etc.

If no good voltages with either test then work your way backwards from the power supply output. You can always check the output of the bridge rectifier to make sure that simple flow is working, if it isn't then check the input, etc.

And yes power transformers do fail but as said it is quite rare. You can check ohms at each winding as has been suggested (with power off!!!), you will need to look up the transformer in an online cross reference probably if it doesn't have the expected ohms printed on it already.

I'm new to pin world but not new to electronics so this is just general troubleshooting tips that may be superseded by folks here with more pin experience. However, whatever you do, be safe. Capacitors on power supplies can hold their charge to a lethal level long after power is turned off. Work with one hand on the tool (heh) and the other at your side not touching metal, don't put yourself in a position where you inadvertently create a circuit from one side of your body to the other (through your heart). Use plastic handled tools, not metal. Wear shoes with rubber soles. Etc.

anyway he wants to know so lets show him...

Screen_Shot_2016-08-12_at_1.35.23_AM_(resized).png

for reference. ground is pin 3 ( big green wire in your case but sometimes black).. the empty one at the start and end are not counted.

the right hand end is where you look ... pin 6 and 7 are 69V AC... put your meter on AC and carefully stick a lead in the back of each hole to touch the metal pins ( one lead on pin6, the other one pin7, it doesnt matter what order. it should say around 65-90V AC

if it does.. you have the display voltage and your transformer is likely fine.

use the same safety precautions you would take sticking it in a power point

now test the same two pins on the plug with it unplugged from the power supply

higher

I think you need a technician to come and help. If you can't (in a mircosecond) recognise the difference between millivolts (which you would almost NEVER have reason to be measuring in a pinball machine) and Volts then you really should be leaving it alone until you are more familiar with things - just my thoughts, it's your machine to do with as you please but it might avoid a lot of frustration, and even be cheaper than fiddling around in the dark.

Opening this thread back up. I have a stellar wars and the transformer failed because of a failed bridge rectifier. There is a mod to keep it from happening again.

The replacement transformer had all the wires cut off so I have to splice wires on. I tested the voltages tonight and had a question about how the proper way to do it was.

It tested fine with 120v ac input. On the output for example, there are 2 white wires, the schematics has 96.7 v ac on them. I took the neg and grounded it and tested each white and got 28.5 on one and 44.8 on the other. If I take the black lead on one white and red on other I get 96.7. Is that how that is measured?