Those flashes are the board trying to tell you something.

It's telling you that U11 PIA chip (6821) is not functioning.

It could mean a bad 6821, or a bad socket, or corrosion of the MPU board (post some good pics, especially the bottom of the board around the battery).

Ground is TP4 upper right. Label is covered by that sticker.

It has been cut off (that's a good thing).

You can see the two stubs centered at the bottom of the board.

Nope.

Not getting the 5th flash is somehow a U11 related problem.

Looking at your pictures, I see your U11 is an AMI chip - very sucky brand. If I were a betting man, I'd say 80% chance that is your problem. AMIs are total crap.

Your HV section needs work, but that is seperate from your MPU problem above.

Slow down a little bit.

You can be 99% certain that the new Altech board will be fine, but you don't need to install it yet. You have other work to do first.

Job list:

1. Will the game off, pull out every fuse, one at a time, on the rectifier board and verify that it is the correct value. Old games will often have too large of fuses replaced and this is where you get into trouble.

Don't forget the fuse in the black fuse holder next to the transformer.

If any fuses are the wrong value, don't power up the game again until you have replaced it.

Get 5 of each value fuse on your next part order.

2. Order your flipper and sling coils (make sure you get any spring or mountings you need for the sling). Get a flipper rebuild kit while you are at it. http://www.pbresource.com/rebuildkit.html#KT-BFLIP03

Read: https://pinside.com/pinball/forum/topic/vids-guide-to-upgradingrebuilding-flippers/page/11

3. The solenoid board has the fuse out because it probably blew from a shorted component. Can you solder?

http://www.bigdaddy-enterprises.com/repairkits/bally_kits.htm#b-hvreg1

Read: https://pinside.com/pinball/forum/topic/vids-guide-quick-bally-driver-board-repair-bulletproofing

Did you notice that the diode is blown wide open on that sling coil?

You can test them with your meter, or for .01 cents each, just replace them.

You can test the coil with your meter too, in Ohm mode.

Disconnect all the connectors on your rectifier board except the 2 bottom transformer ones.

Check that your high voltage is correct.

Assuming it is, then you have enough boards to bring the game back to life.

Don't throw the old boards out, they have value to techs like me who can refurbish them.

You should be set to go then.

With connector J3 removed, TP2 on the Rectifier board can be as low as 150v.

If you want to be cautious, connect just the Solenoid board check it's test points, then add the MPU and displays.

http://www.pinballlife.com/index.php?p=catalog&parent=93&pg=1

Get your meter in DIODE mode and check each diode.

Look for solder splash from past repairs on the switches.

Most bad diodes are not blown wide open, so they need to be metered to know for sure.

Those capacitors give more time for the MPU to sense that the switch has been triggered.

They can cause problems as they get old, by falsely triggering the switch.

If a switch is phantom firing, cut one leg of the capacitor off. If that fixes the problem, replace the Cap.

Don't just leave a bad Cap off, or a switch activation will sometimes be missed.

Those switch caps are CCD-0.047uF-50V

https://www.greatplainselectronics.com/products.asp?cat=27

Some half-assed tech work there for sure.

Picture the switch matrix as an elaborate truth table.

if we lose connection, anything below that in the table can not be read.

A shorted switch or diode can cause false closures to be read by the MPU. That is why in the switch test, a switch number may be appearing that is not actually being closed.

Of course, finding one problem, does not rule out other problems existing in the same row

Usually a diode will read nothing in one direction and pass current in the other.

What coils exactly?

Give us a picture of J5 on the Solenoid Driver Board.

Make sure it is clean enough to see the wire colors.

J5 runs along the bottom.

Your pic is J2

Alltek calls it P5, it is on the bottom right side of the board.

solenoid-board.jpg

That looks OK.

J3 & J4 next.

http://www.pinrepair.com/bally/squawk.htm

The most detailed Squawk write up!

Don't mess with the jumpers unless you are changing to a different processor chip or ROMs.

Like everything else in pinball, first see if you have the correct voltage on the test points.

Then, how many flashes do you have from the sound LED?

Well, you need your chips, first and foremost.

Your board is not booting with a solid LED

Doesn't your current transformer plug into the 2 bottom plugs J5 J6?

My SpideySense™ says that the sound will be your biggest nightmare.

Someone did not just pull off all those chips because it made the card work better.

You have all those old electrolytic caps to deal with too.

Get a close up of the jumpers used on both boards.

Different processors and ROM sizes can mean different sockets and jumpers used.

See Honey? This is why I have all these clamps.

http://www.planetarypinball.com/reference/partsmanuals/BLY_Parts_1980-1/index.html#/6/zoomed

So did those terrible Firepower pop caps.....