Your video shows you are actually getting 7 LED flashes.
When you power on you get the initial LED flicker.
Then you get one LED flash, then a bit of a pause then a further six LED flashes (7 flashes in total).

At this point, the MPU board has completed the power on self test. It should then enable interrupts and go into attract mode.
If you connect the J1 connector to the MPU board do the playfield lamps flash?

What electronic equipment/skills do you have?

The ROM board is connected to the MPU board on the upper J5 connector. Is that J5 connector clean and making good contact?
It looks like your MPU board is stalling / crashing as it enters attract mode which is likely interrupt related.
If you have a logic probe / oscilloscope check that you get pulsing activity on pin 18 of U10 (100Hz) and pin 40 of U11 (320-420Hz)

Oops, double post.

Multimeters aren't really suitable for diagnosing digital/logic circuits.
Do you have access to a logic probe?
Do you have an EPROM progammer? Because I would remove the ROM adapter and just use two 2732 EPROMs at U2 and U6 to run the game. The ROM adapter is an extra point of failure.

With your multi-meter what voltage do you measure at:
U10 pin 18
U11 pin 40
U11 pin 38

Can you post some clear high resolution pictures of the MPU board? Best if you can take pictures outside in daylight.

I measure:
U10 pin 18: = 0.328 VDC
U11 pin 40: = 4.45 VDC
U11 pin 38: = 4.83 VDC

But my readings are from a 6 digit game so my U11 readings will be a bit different to yours. For the moment let's assume your readings are ok.

Before you buy an oscilloscope, I see you have a Chinese counterfeit PCD5101 chip at U8 and we have seen those cause some strange problems. Do you have any spares you can change it with?

BTW, the capacitor at C16 near the U12 chip, you must change it to a polyester type. The ceramic types are temperature unstable and will cause the 555 U12 timer chip output frequency to vary.

Hi, try any other of your same 5101 chips. Some of them may be ok. Lets see if things change.

These are the last lot of PCD5101P I bought from China one year ago which were original Philips parts:
https://www.aliexpress.com/item/33015720318.html

But there is no guarantee they will send you original parts anymore because the fake ones are now common in China. The one shown in the picture with the white print marking is genuine. Any you see with dark etched brown marking are fake.

As you may be aware, Space Hawks is a bootleg of Ballys "Cybernaut". Bell copied the Cybernaut ROM but made small changes, including disabling the ROM test!
So right now your ROM test is being skipped on power-up meaning you have no idea if the ROM is actually good or bad. Or it could be a problem with the ROM board, or J5 connector or maybe something totally different.

Can you post some very clear pictures of the ROM EX3 board both back and front. If you can take the pictures outdoors in daylight the pictures will be much clearer.

I need to closer inspect the ROM board pictures so will come back later.

At the moment I can only see your problem happening for one of two reasons.

1) After the power on tests, the software enables hardware interrupts which are normally used to flash playfield lights and show numbers on the displays. So the CPU at U9 might not be seeing these interrupts. This is pin 4 of U9 but it maybe hard to measure with the ROM board covering the CPU.

2) After the power on tests, the software jumps from one part of the ROM to the other part of the ROM using address line A14 at pin 33 of connector J5. So there could be a problem with this pin or the EPROM maybe corrupt.

If you are able, measure the voltage on:
CPU U9 chip pin 4 (Interrupt request signal at the CPU)
ROM board EPROM chip pin 23 (Address line A14)

Hi,
You measured this 0.9V at U9 pin 4 with the ROM board installed right?
If you measured this voltage during the power on test, then please remeasure it after the 7th LED flash.
If you already measured it after the 7th LED flash, then note: you previously measured 3.67V at U11 pin 38. This signal goes to U10 pin 38 and then to the CPU at U9 pin 4 which you now measured at 0.9V
These three pins must all measure the same since they are the same signal. If they don't equal you have an open circuit maybe at the U9 socket where pin 4 is.

Sorry I wasn't clear on this, I need to know the voltage on pin 23 of the actual 28 pin EPROM chip on the ROM board. See below: Please measure its voltage during the power on LED flashing, and after the last 7th LED flash. Report both voltage measurements.

Bell_Games_MEM_EX-3_(2)_front_pin23.jpg

2.2V seems rather low.
If possible can you measure this pin while the machine is booting (performing the LED flashes) and another measurement after the 7th LED flash?

Same story with pin 23 of the EPROM, one voltage measurement during boot-up and another measurement after the 7th LED flash.

Need to understand what the voltage on these two signals is doing during power on test boot, and after the 7th LED flash to see if they change.

As you see this is a complex problem.
Have you tried the easy things of replacing all the socketed chips (6800, 6810, 2x 6821) with good ones?

Checked my game to look at the interrupt signal voltage from power-on til after the 3rd LED flash then after the 7th LED flash:
Power-on --> 3rd LED flash --> 7th LED flash:
U11 Pin38: 4.9V --> 0.06V --> 4.83V

Are you still expecting to receive an EPROM programmer? Will it come with a UV eraser and some spare 2732 EPROMs?

Do you have a spare -35 MPU board?

Hi,
Do you mean another -35 MPU board shows the same fault?
Are you sure the U7: 6810, U9: 6800, U10: 6810 and U11: 6810 are all good?

This all depends on the problem. Does U11 pin 38 show 5 volts when you power-up until the 3rd LED flash?

When you say "another mpu", do you mean with another 6800 CPU chip installed on this MPU board, or do you mean another complete original Bally MPU board? If you mean another Bally MPU board, does it have all the original chips on it?

Ok, so since the problem happens with two MPU boards then they are not the problem. I guess the problem is likely with the ROM "MEM EX3" board connected to J5.
If you purchased an EPROM programmer and some blank 2732 EPROMs, you can use them direct on the MPU board at U2 and U6 and this will allow you to discard the ROM MEM EX3 board. I can even fix the Space Hawk ROM code so the ROM test is not skipped anymore.

Did you check the important test point voltages on the MPU board?
TP2 should be around 14VDC
TP5 should be around 5.1VDC
TP3 should be around 21VDC

Check your local ebay for 2732.
When will your new EPROM programmer arrive? You can use the programmer to test the EPROM on the MEM EX3 ROM board.

BTW those MPU board voltage measurements are good.

This is a little complicated because these EPROMs are old technology no longer manufactured and new EPROM programmers do not support them well.

Many 2732 EPROMs need 21 VDC to be programmed.

The TL866II Plus EPROM programmer only supports maximum of 18 VDC. This means it has trouble programming 21V EPROMs.

There are some 2732 EPROM which can be programmed at 12.75 VDC and these are the 2732 you should look for. Here is an example in Europe ebay:
ebay.com link: itm
You can see on the chip in the first picture it is marked "PGM=12.75V". This is a National Semiconductor chip.
BUT, this seller also may send ST brand 21V program parts. You must ask him if he has the "National Semiconductors NMC27C32BQ200" parts in stock before ordering.

Basically:
2732 needs 25V programming
2732A needs 21V programming
2732B needs 12.75V programming

This seller also shows pictures of some National Semiconductor 2732 and 2732B parts, but you must first ask if he has the 12.75V PGM parts in stock.
ebay.com link: itm
From his pictures:
NMC27C32Q-45 needs 25V programming
NMC27C32Q-35 needs 25V programming
NMC27C32BQ-200 needs 12.75V programming <-- Good for your programmer
NMC27C32BQ-150 needs 12.75V programming <-- Good for your programmer

The "D2732A D2732 EPROM 4K x 8 IC Intel Corporation CDIP - 24" need 21V for programming. They are not good for your EPROM programmer.

Yes, the point was to eliminate the MEM EX3 board and use standard 2732 on the MPU board at U2 and U6 like all other Bally.

Alessio88 if you have received your TL866II+ programmer, can you please read the 2764 EPROM from the MEM EX3 board and post the data somewhere for us to check if it's good? Be careful to insert the 2764 correctly in the programmer.

Hi,
The ROM has some corruption. There are some bits stuck high.
Do you have an EPROM eraser?
An empty EPROM has all data bits high. When you program it, the bits are programmed low.

If you do not have an EPROM programmer, you can try to reprogram that 2764 chip to fix those incorrect high bits. You will need to disable blank check in the MiniPro software to do this.

If you do have an EPROM programmer then better if you erase the your 2764 and perform a full reprogram.

Here you can find the Space Hawks 2764 EPROM data you need:

https://www.sendspace.com/file/kytvkk

The file is downloading ok for me and my friend.

Anyway I have also uploaded it to a different web server. Try this one:
https://www.mediafire.com/file/tbrq39ehww262y0/SpaceHawks_2764.zip/file

Your 2764 likely has some programmed bits that have become weak over many years. Try to refresh them - you have nothing to lose.

Start the MiniPro EPROM programmer software
Select M2764 EPROM
Load the ROM file I sent you
Untick the "Blank Check" box in the bottom lower corner of the MiniPro software so blank check is disabled.
Perform the Program function

If you are lucky this will fix the weak data bits in your 2764. If you are unlucky and it verifies bad after the program, your 2764 may be faulty.

Hope you are feeling much better.

Which kind of EPROMs did you program? 2732 or 2764?
Did you perform any verification in your programmer to make sure the data was written properly to the chip?

Can you read the newly programmed EPROM and tell us what the ChkSum is reported by the programmer software? The ChkSum is shown around the middle top area of the programmer software.

The EPROM read is good.
You have some other new problem now.

Re-install the 2764 EPROM and remove/reconnect the EX-3 adapter back on the MPU board just in case it was offset by one pin.

I still think it would be better to use two 2732 EPROM on the MPU board and discard the EX-3 adapter - this adapter is providing no value, just an extra point of failure. But anyway..

Great!

All the displays have three test points. Check the voltages on one of the displays. Use test point TP3 on the display as the ground for your multi-meter.
Measure TP1, it should read 5VDC
Measure TP2, it should read 190VDC (I think this voltage is probably ok because I can see the glow under the digits on the displays).

Did you find any logic probes yet?

These wires all come from the J3 connector on the MPU board. Just in case there is a short circuit at those wires, disconnect the J3 connector from the MPU and see if there is any improvement.

Ok, you have a logic problem.

1) If you go to the display test and wait 30 seconds, do you eventually see the 888888 and 999999 numbers show (while all other numbers seem blank)?

2) MPU connector J1 pin 10 has the display blanking signal which goes to all the displays on their pin 10 connector. Can you check if the wire is making good contact at both ends?

This is high for 5V logic power.
How much voltage do you measure at TP5 on the MPU board and also TP1 on the solenoid driver board?

Ed, this whole machine is a counterfeit of a Bally game. The counterfeit parts just add to the character

You didn't show enough of the displays in your video, but from the little I do see they seem to have the glow under the digits. This indicates the U12 display interrupt generator and also the 6821 at U11 on the MPU board are driving the display digit enable signals ok.

Check the voltages on the MPU board marked with the red arrows below (click the image to zoom in). Also measure the voltages on all the outputs of the U20 chip.

Display_Data_Voltages.png

It's a rethemed Cybernaut which uses the Cheap Squeak board.

Alessio88 built the MPU board from a blank PCB I believe. Can't tell if U14 is a "B" or "UB" version chip but I don't notice any lamp flickering in the videos.

Yes, there is one wire signal from the MPU board at J1 pin 5 that goes to all displays at pin 8 which controls that digit. So you possible have a bad connection at the MPU board connector J1 pin 5.
Try to swap the J1 pin 5 wire with the J1 pin 4 wire to see if the problem follows the wire.

MPU_J1_Disp_Digit_Conn.png

This ^^^

BTW I will be working on updating Space Hawks code with freeplay this week. Let me know if you're interested.