Falcon doesn't initialize blank screen

[sdisla]

@Badwolf

Data lines alongside AS

My interpretation:

I think you need to work on interpreting these.

Remember, you're looking at the voltage at the end of the AS cycle (ie. the point it goes high).

I haven't gone through and done the analysis yet, but perhaps have another go and then try to convert them to hex. This will help you with debugging further if the GAL isn't the answer, so it's worth practicing.

BW

NB. There are nothing wrong with your images, it's just the translating them to binary I'm suggesting you try again.

@Badwolf

" The only way to learn is by doing. "

The new reading is a match, see below.

Code: Select all

D0 0000
D1 1000
D2 1100
D3 1000

D4 0001
D5 1011
D6 0010
D7 0010

D8 0000
D9 0000
D10 0100
D11 0000

D12 0000
D13 1000
D14 1000
D15 0000

Assorting them and converting to hex.

Code: Select all

0110 0000 0010 1110  ===> 602E
0000 0100 0000 0100 ===> 0404
0000 0000 1110 0000 ===> 00E0
0000 0000 0011 0000 ===> 0030 

It must be the GAL U62 or at least part of the problem.

Thank you for all your help so far.

[Badwolf]

Assorting them and converting to hex.

Code: Select all

0110 0000 0010 1110  ===> 602E
0000 0100 0000 0100 ===> 0404
0000 0000 1110 0000 ===> 00E0
0000 0000 0011 0000 ===> 0030 

It must be the GAL U62 or at least part of the problem.

Thank you for all your help so far.

Well that's really good news. Well done.

Yes, it certainly looks like U62 might be to blame, or perhaps one of the other chips that feeds into it and is causing issues.

You've got a machine that's running code and now able to get data out of the ROM correctly. Hopefully you're not now far away from a booting device. :)

BW

[sdisla]

Assorting them and converting to hex.

Code: Select all

0110 0000 0010 1110  ===> 602E
0000 0100 0000 0100 ===> 0404
0000 0000 1110 0000 ===> 00E0
0000 0000 0011 0000 ===> 0030 

It must be the GAL U62 or at least part of the problem.

Thank you for all your help so far.

Well that's really good news. Well done.

Yes, it certainly looks like U62 might be to blame, or perhaps one of the other chips that feeds into it and is causing issues.

You've got a machine that's running code and now able to get data out of the ROM correctly. Hopefully you're not now far away from a booting device. :)

BW

@Badwolf

I wanted to give you a quick update on my efforts troubleshooting the GAL chip in question. I tried using three different programmers (T48 TL866-3G / GQ-4X4 / BPM Microsystems) to read and re write, but unfortunately, none of them support the chip according to their profiles. As a result, I've decided not to invest more effort and wait for a replacement. Once I get them, I will let you know the results. Let's hope it works and if not at least one step closer to get the Falcon fully functional again.

Thank you for your support.

[sdisla]

Assorting them and converting to hex.

Code: Select all

0110 0000 0010 1110  ===> 602E
0000 0100 0000 0100 ===> 0404
0000 0000 1110 0000 ===> 00E0
0000 0000 0011 0000 ===> 0030 

It must be the GAL U62 or at least part of the problem.

Thank you for all your help so far.

Well that's really good news. Well done.

Yes, it certainly looks like U62 might be to blame, or perhaps one of the other chips that feeds into it and is causing issues.

You've got a machine that's running code and now able to get data out of the ROM correctly. Hopefully you're not now far away from a booting device. :)

BW

@Badwolf

Finally got the GALs replaced but still the same condition.

You mentioned on your last comment that perhaps may be another IC that feeds U62. Which ones in specific you were referring?

I will search on the schematics to see if I can correlate some of the names from the pins that goes into them.

Thank you,

[sdisla]

Assorting them and converting to hex.

Code: Select all

0110 0000 0010 1110  ===> 602E
0000 0100 0000 0100 ===> 0404
0000 0000 1110 0000 ===> 00E0
0000 0000 0011 0000 ===> 0030 

It must be the GAL U62 or at least part of the problem.

Thank you for all your help so far.

Well that's really good news. Well done.

Yes, it certainly looks like U62 might be to blame, or perhaps one of the other chips that feeds into it and is causing issues.

You've got a machine that's running code and now able to get data out of the ROM correctly. Hopefully you're not now far away from a booting device. :)

BW

@Badwolf

I did the recap, almost 70% of the board, missing just the DSP circuit.

After powering up the Falcon still the same, no changes.

I left the Falcon ON for one hour then check all the voltages on each of the components one more time.

Noticed that U30 VCCs one of two that goes to (AVCC1 & AVCC2) the voltage drop is just 4.1 volts.

Also, the component is running a little warm than the others, not sure if that is normal.

I will focus on the GALs inputs now.

Keep you posted,

[Badwolf]

Finally got the GALs replaced but still the same condition.

You mentioned on your last comment that perhaps may be another IC that feeds U62. Which ones in specific you were referring?

I don't remember off the top of my head, but IIRC most of the inputs to U62 come from another GAL.

Did you replace only U62 or all of them?

If all of them, you may need to chase the chain further up, or see if you can spot any shorts/broken traces going into U62 that would cause erroneous output.

It does feel that there may be something floating.

BW

[frank.lukas]

... why don't you just remake all GAL chips new using Lattice 16V8-15ns GAL chips ?

[sdisla]

Finally got the GALs replaced but still the same condition.

You mentioned on your last comment that perhaps may be another IC that feeds U62. Which ones in specific you were referring?

I don't remember off the top of my head, but IIRC most of the inputs to U62 come from another GAL.

Did you replace only U62 or all of them?

If all of them, you may need to chase the chain further up, or see if you can spot any shorts/broken traces going into U62 that would cause erroneous output.

It does feel that there may be something floating.

BW

@Badwolf

I replaced only four U63 U62 U67 U68, still waiting for U44 the one near the DSP side of the board.

! will keep looking, keep you posted, thank you for your support.

[sdisla]

... why don't you just remake all GAL chips new using Lattice 16V8-15ns GAL chips ?

@frank.lukas

Lesson learned, next time.

Getting the originals, "blanks" is a big challenge (hard to get) specially here in the USA.

Thank you.

[Badwolf]

I replaced only four U63 U62 U67 U68, still waiting for U44 the one near the DSP side of the board.

! will keep looking, keep you posted, thank you for your support.

No worries. Keep looking. Check pins around the affected GAL for intermediate voltages or drift, etc. Check removing the GAL still resolves the problem.

Try to keep a written record. It will help as you'll have hundreds of things to check.

Good luck & keep going. You're getting closer, I'm sure.

BW