Do a reset on the mpu. Do you have power to the displays (you should see a glow at bottom)? Move the hinge door, & wiring (do displays come back)? Gently touch wiring top left of mpu (maybe bad contacts) for displays. If this doesn't help post some pictures.

If the game is booting and playing, it's probably power problems.
Check the rectifier board first. You need the switched illumination bus and the HV . Measure the voltages on the rectifier test points and post them here.

looks like your missing the high voltage fuse, next to big blue cap.

Yes you are missing the fuse on the solenoid board for high voltage. The pictures helped a lot, like the hack wiring! In North America the small fuse is not available, so we move the fuse holder end up a hole & use a standard glass fuse.

The high voltage fuse is located to the left of the big capacitor, in the circled area here:

1522519185.png

OK, there are multiple problems going on here.

A couple of basics to get you going. Most if not all voltage readings you will be measuring are going to be DC. The DC position on the meter is usually marked something like -..---..- while ac is marked ~. For ground you can use the ground braid running through the game or the frame (unless somebody ungrounded it.)

Lets start with the HV circuit. I can barely make out the HV fuse on the SD board. It looks like someone could not find the miniature fuse the board requires and wedged in a standard fuse off to the side of the fuse holders. Measure the voltages to be sure.
You should have 230v at TP4 of the SD board and 190v on both sides of the fuse holder. There should also be 190v at TP2 on the display panels.
No matter what you measure you need to modify the SD board with a new fuse holder spaced to hold a conventional sized fuse to make future service easier.
Another important mod is to replace the 2 large capacitors on the SD board. If they are original they should be replaced. The date should be printed on them. They look original from the photo.

Moving on to the switched Il bus. That is supposed to be 6.3v DC that runs to all the switched, (computer controlled), lights on the backbox and playfield. In the photos it appears to be out. The Sw IL bus comes direct off the rectifier board. TP1 should measure 6.5vDC and you are reporting it as 3.8v above. But you reported previously it was present?? What does it measure at the lamps themselves? the common braid that services all the switched lamps, measure DC from the braid to the metal frame of the game. It should be 6.3vDC at all the switched lamps.
Do not confuse the switched bus with the GI, (lamps on all the time), that is a separate bus and should be 6.3 v AC.

Finally, you report TP5 on the rectifier board is measuring only 24v?? That should be 43vDC. If the game is playing and the coils are working that should not be the case as the game needs 43vDC on that circuit so you may want to double check your readings.

Good luck with your tests. Report back what you find.

For your voltage measurements, you can put the negative (black) lead to a test point labeled ground or attach it under the ground braid at the base of the head.

Also, there’s a ground junction point in the base of the head. There’s one braid that goes from one side to the other, and another braid that comes up through the hole that the cables from the play field come up from and attach to the circuit boards. Make sure that junction is tight.

You mentioned the machine is imported from England. Is your house power the same as in England? Likely not a problem, but just something else to check.

Also, how do the connectors look at the rectifier board? Maybe post a pic so we can see.

I still lean toward connector issues since there’s a Altek board, and the machine has been in storage.

Glad you saw the fuse on the side. I would look at the contacts in the connectors off with a flash light. With battery leakage they could be broken (contacts).

OK. Lets go back to start. First lets not confuse the rectifier board, (the one with all the fuses) With the PS/SD board, (the one with the power supplies and coil transistors)

Post a picture of each board. Are the connectors burned on the rectifier board? They usually are.
You may be looking at rebuilding the connectors on the rectifier board or possibly replacing it all together. Lets see pictures and a list of current voltage. readings.

I would definitely start by replacing the female connectors to the rectifier board and re-flowing solder to the male header pins (or replacing the header pins, which is what i usually do). Without good voltages you can get stuck chasing down all kinds of weird and/or intermittent problems. Also replace both big capacitors on solenoid driver board.

On the rectifier board, verify the fuse clips have decent tension. Bally made their own clips and they tend to fail.

I only say this because you got lights, etc. when you touched (flexed) something on that board. That should not happen.

Your pictures are a big help, please take more! Lets start with the rectifier board: I always check the fuses to make sure correct, & like said apply some tension on the fuse holder ends before installing fuse. That 20 pin surface displacement harness is not factory, I replace with salvaged display one & new contacts (trifurcon where needed (GI, etc)). Usually you sand the pins to clean them (that pin got a lot of moisture). You can use the ground on J2 with probe from meter, & other to test points. I had a wire on the transformer cold soldered, that through off readings at times.

Sand the pins on your mpu, & maybe reflow new solder on the end pins. Check the .100 contacts like I said with a flash light inside harness. I just had a poor Supersonic with broken .156 contacts on bottom of driver board.

Ask around your area. I always have a spare power supply to test. Or some one local may be willing to look at yours. If you get into classic Bally pins you can make a simple power cord with power, neutral, ground into a J2 plug. I have a few & this was suggested by a now dead tech. I have 20+ years working on hundreds of these classic pins. Space Invaders was a weird power supply (KISS), you can use a mass produced one from the other titles (3 varo bridges the same).

6 flash could also be playfield fuse blown. In North America 1 amp slow blow for 2 flipper, 1.5 for 3 flipper, & 2 for 4 flipper. this is what I was told years ago by old techs. If there is no sticker, mark the value by fuse holder. Also Bally used cheap ass cardboard fuse holder, replace with a good quality one. Gottlieb or vids, plastic body ones.

For some weird reason this pin title seems to cause the most service calls & work. Paragon, Hot Doggin, & Future Spa seem to have less problems with power supply.

Most likely you've gently blown fuse F4 on the rectifier board: The manual lists it as a 5 amp fast blow fuse, not 10 amp slow blow which is what's currently there. The MPU board uses the voltage from this fuse for game timing and tests its validity for the 7th LED flash. Failure of this fuse is a common reason for only getting 6 MPU LED flashes on power up.

SpaceInvadersRectifierFuseA (resized).jpg

Might be an idea to clean all the debris off that board to prevent something shorting/burning.
Highlighting what others have said, the upper fuse clip on the very left fuse (F1) is poorly mating with the fuse. Pull that fuse out and fix the clip so the fuse fits in tight.

SpaceInvadersRectifierA (resized).jpg

The playfield fuse is wired after the flippers. The flippers are fused by F4 on the rectifier board.
Somewhere in 1981 the Bally manuals (Centaur, Elektra, etc) generically started stating F4 as 5A but noted "All games with 4 or more flippers use 7A".

That rectifier board, and the cabinet in general looks bad. Was the game under water?
You might consider just replacing it. Replacement rectifier boards are not very expensive and will save you a lot of time.
As usual Quench is right on top of things. Bad fuse holders and fuses abound!
Lets get the rectifier up and working to spec before moving on.

Order a SD/ power supply rebuild kit while you are at it. That will be next.

Ground braid is for safety. It should be repaired/replaced where broken, but is not required to make the game operate. The signal ground is transferred between boards on the connectors. Best bet is to use a test point ground, or find ground on the connectors for the board in question.

Fast blow glass tube 3/16 amp (0.187 amp) AGX or 8AG style 250 volt (6.3x25mm)
https://www.marcospecialties.com/pinball-parts/F8AG-0.187

Any tinned copper 1/4" flat braid is fine, from whatever cheapest source.

Wayout440 -

Please clarify your comment about the ground braid. If the braid that comes up through the neck is not connected to the ground braid that runs horizontal across the neck, the machine will not operate.

I had a machine that I could not get any voltage, and ultimately, the reason was because someone had removed the ground braid that comes up through the neck. Had it not been for Vid1900, that machine would probably still be frustrating me.

Signal ground is handled by the returns in the harnesses. The ground braid that runs to the rails, the coinbox, and other metal parts is to protect against hazardous electrocution. Many times you'll find an old game with the ground pin sheared off the mains plug, then you have no safety, but the game still operates. Often the braids are snapped at the backbox because of folding the head down - and the game still operates. I'm not sure what your specific situation was, this is what I find in the games I have owned and repaired.

Pin will still run with out the head braid attached, same with a ground prong removed from plug. You should fix these. A new rectifier board will have 3 BR's.

The wiring to your old rectifier board looks decent. I have seen some real hack jobs. Verify the wiring on the transformer solder lugs are ok. I had one that was cold soldered, intermittent readings. When you get the new board, only transfer a wire at a time so you do not screw it up. If you have not soldered before, get a experienced person to perform the job!

Correct board, follow GreatwichJohn's advice. Also, before starting, take lots of pictures. Nothing worse than getting in the middle of a transfer and then question your memory.

The pictures you have of the transformer looks like it is poor or questionable. Yellow goop near #7 lug, & discoloured wrapper. Over heating of the windings in the past (transformer)? Out of the hundreds I have thrown out 5 transformers that were serious bad or questionable like yours. If it was me I would search out a good used transformer & rectifier board that is verified OK. Save the new board for the future. Look for the mass produced Bally head mounted ones.

Your past post on testing points. Be cautious with the test probe leads to your meter.

Those transformers were built to last forever so I would not worry about replacing it as long as the game was booting. Take care in moving the wires from the back of the old board to the new. Move them one at a time double and triple checking the transformer wire is soldered to the correct location on the new board.
Pay close attention to the hack on J3. You will need to undoo that with the new board.

Transformers should last, but they do fail. Had 3 newer 1981-1982 ones fail also. Same with pins from the 1990's. People on pinside always looking for them.

Yes it could be that little fuse on the SDB.

Do you have [CAUTION!] high voltage on the rectifier Test Point?