4k ROM ICs

[Delta]

I checked the voltages on the video RAM. Neither the 5V nor the 12V is present but the - 5V is. 

The question seems to be, what is causing the +5V and +12V to be reduced when connecting the PSU board to the system board?

[+arcadeshopper]

2 minutes ago, Delta said:

I checked the voltages on the video RAM. Neither the 5V nor the 12V is present but the - 5V is. 

The question seems to be, what is causing the +5V and +12V to be reduced when connecting the PSU board to the system board?

short somewhere

bad capacitor

broken wire

broken bus bar

bad connector

 

I'd take a meter and continuity test 12v to ground (with power off)  and see if they are connected somewhere then start tracing out from the power connector to find it.. if you are up to this if not I sell working boards in my store

 

[Duewester]

Hey @arcadeshopper, while you're here. I just installed the new MK1 F18a, Absolutely wonderful video. How do I get Audio out. I've tried 4 and 8 ohm speakers (that work to varying degree via the audio out on the 5 pin din). Do I need an amplified speaker setup?

[Delta]

I am finally making some progress! 

The voltages going to the board are now correct as are the voltages at the video RAM. 

However, I now have a high pitched whine which is constant and no display. I have tried both VDPs. 

[Duewester]

@Delta, now we're getting somewhere. What did you do? Is this the same for both boards?

 

[Delta]

9 minutes ago, Duewester said:

@Delta, now we're getting somewhere. What did you do? Is this the same for both boards?

 

I noticed the white connector strip had come away from it's solder points on both boards...I therefore resoldered it. 

On board A, the voltages are now correct on the board, the video RAM and I have 5V on the processor, but have the loud noise with no display. 

On board B, the voltages still not correct. Display as before. 

[+arcadeshopper]

4 hours ago, Duewester said:

Hey @arcadeshopper, while you're here. I just installed the new MK1 F18a, Absolutely wonderful video. How do I get Audio out. I've tried 4 and 8 ohm speakers (that work to varying degree via the audio out on the 5 pin din). Do I need an amplified speaker setup?

it's the same line level as the console video port was, you need an amp

[Duewester]

@Delta,Those white strips seem so resilient to me, it's hard (for me) to imagine them coming away from the board. However, it happens.

The high pitch whine is the board not getting reset. You can do away with the annoyance while troubleshooting by removing the sound chip.

@arcadeshopper, thank you. I hooked up a set of powered speakers and I got the initial reset sound but nothing else. I've got some sound amplifier breakout boards from Adafruit. I'll try that next. In the meantime I have a 4ohm, 3 watt speaker hooked up to audio in the din connector. Doesn't sound too bad actually. Now, where to get 3v-5v from...🤔

[+arcadeshopper]

52 minutes ago, Duewester said:

@Delta,Those white strips seem so resilient to me, it's hard (for me) to imagine them coming away from the board. However, it happens.

The high pitch whine is the board not getting reset. You can do away with the annoyance while troubleshooting by removing the sound chip.

@arcadeshopper, thank you. I hooked up a set of powered speakers and I got the initial reset sound but nothing else. I've got some sound amplifier breakout boards from Adafruit. I'll try that next. In the meantime I have a 4ohm, 3 watt speaker hooked up to audio in the din connector. Doesn't sound too bad actually. Now, where to get 3v-5v from...🤔

there's 12v on the same connector

[Duewester]

1 hour ago, arcadeshopper said:

there's 12v on the same connector

@arcadeshopper Yea, thought of that. Got a buck converter around here somewhere...

[Stuart]

21 hours ago, Delta said:

I noticed the white connector strip had come away from it's solder points on both boards...I therefore resoldered it. 

On board A, the voltages are now correct on the board, the video RAM and I have 5V on the processor, but have the loud noise with no display. 

On board B, the voltages still not correct. Display as before. 

If the strips have been bashed about enough to come away from the board, they may be more damaged than they appear. There's actually 3 separate strips in one at least of them, distributing several voltages + Gnd. They may be the source of your earlier short. Might be worth checking the 3 voltages on the video RAMs to make sure they're all getting through.

[Delta]

32 minutes ago, Stuart said:

If the strips have been bashed about enough to come away from the board, they may be more damaged than they appear. There's actually 3 separate strips in one at least of them, distributing several voltages + Gnd. They may be the source of your earlier short. Might be worth checking the 3 voltages on the video RAMs to make sure they're all getting through.

Thank you for that! It might explain why my +5V has disappeared. 

When the strip broke off, I improvised a solution using several wires to make a connection between all the points - I believe there are 6 in that strip. But if there are different voltages, my wires are incorrect, at least partially. I must now try and solder the original strip back on or determine which voltages are between which points. 

[Delta]

I managed to put the original strip back on...and all the voltages at the system board connection are now correct but the video RAM has the +5V missing. 

 

So both of my boards are in a better albeit non working state. 

The first seems to have all the correct voltages but that dreaded continous beep and no display. 

The second has no beep, no display and the video RAM voltage is not correct. 

I am using the same VDP, Clock IC and ROMs in both. 

[GDMike]

Swap the socketed sound Chip, and groms??

Edited April 28, 2023 by GDMike

[Delta]

There has been a development, but not a good one 😒

I managed to acquire another Ti which was working...I wanted to test the other ICs...however, this Ti only had a socketed VDP so I was initially only able to test the other 2 VDPs...at least that was a start. 

I then realized I would have to desolder one of the ROMs to introduce a socket...so I very carefully desoldered the ROM to the right of the processor and soldered the socket. I then inserted the ROM to do a quick check before testing the other ROMs. I switched the new Ti on and to my horror...no display and only the infernal high pitched sound! I have managed to break my newly acquired working Ti! 

I feverishly checked my soldering to ensure there were no shorts or dry joints... Nothing. 

I now have 3 non working boards with 2 showing the same symptoms. 

 

[Duewester]

@Delta first, make sure you have the chip installed in the correct orientation. Make sue all pins are actually in their sockets. I have more than once installed a chip with a pin bent in or out and not in the socket. Look out for possible lifted trace or pad(s). These old boards can easily be damaged by lifting a pad.

Me personally, based on past experience, would have started with the 6810P chips. If you botch them up, they are more easily replaced (no eeprom stuff to deal with), just install new 6810P. I got pretty lucky on my massive chip adventure and by the time I got around - read scared to death - to the 8249 and 8250 chips (which were not 49 and 50 chips but a TI chip and a mystery chip - same make as 49 but different numbers completely) I was pretty proficient at socketing my chips and getting the pins in the sockets.

If you're like me, some form of board swap with @arcadeshopper (the easy way out) just isn't in your DNA.

[GDMike]

On 4/29/2023 at 2:40 PM, Delta said:

There has been a development, but not a good one 😒

I managed to acquire another Ti which was working...I wanted to test the other ICs...however, this Ti only had a socketed VDP so I was initially only able to test the other 2 VDPs...at least that was a start. 

I then realized I would have to desolder one of the ROMs to introduce a socket...so I very carefully desoldered the ROM to the right of the processor and soldered the socket. I then inserted the ROM to do a quick check before testing the other ROMs. I switched the new Ti on and to my horror...no display and only the infernal high pitched sound! I have managed to break my newly acquired working Ti! 

I feverishly checked my soldering to ensure there were no shorts or dry joints... Nothing. 

I now have 3 non working boards with 2 showing the same symptoms. 

 

That happened to me once. I had a board with a bad vdp. And so I pulled a VDP out of another board because the console was dented but the VDP worked. So I pulled it out and put it into the other board and that VDP went out of me well I had another VDP that was good on another console that had a bad keyboard so I pulled it out and I put it in that same computer and that VDP went out on me. All three really sucked. I acquired an f-18a popped it in everything worked.

Edited April 30, 2023 by GDMike

[Delta]

8 hours ago, Duewester said:

@Delta first, make sure you have the chip installed in the correct orientation. Make sue all pins are actually in their sockets. I have more than once installed a chip with a pin bent in or out and not in the socket. Look out for possible lifted trace or pad(s). These old boards can easily be damaged by lifting a pad.

Me personally, based on past experience, would have started with the 6810P chips. If you botch them up, they are more easily replaced (no eeprom stuff to deal with), just install new 6810P. I got pretty lucky on my massive chip adventure and by the time I got around - read scared to death - to the 8249 and 8250 chips (which were not 49 and 50 chips but a TI chip and a mystery chip - same make as 49 but different numbers completely) I was pretty proficient at socketing my chips and getting the pins in the sockets.

If you're like me, some form of board swap with @arcadeshopper (the easy way out) just isn't in your DNA.

The ROM is definitely in the correct way and I have checked the pads. It does appear to be ok. However, short of desoldering the socket and putting the ROM back in, I am not sure what else I can do. Have a look at the pictures and see if you can spot anything. 

[Delta]

7 hours ago, GDMike said:

That happened to me once. I had a board with a bad vdp. And so I pulled a VDP out of another board because the console was dented but the VDP worked. So I pulled it out and put it into the other board and that VDP went out of me well I had another VDP that was good on another console that had a bad keyboard so I pulled it out and I put it in that same computer and that VDP went out on me. All three really sucked. I acquired an f-18a popped it in everything worked.

When you say "I acquired an f-18a popped it in", do you mean the VDP? 

That being the fourth VDP you tested which did work? 

[HOME AUTOMATION]

maybe it's just the light... or the angle... but...

[Delta]

I'm afraid it's just the light or the angle. I have checked for both shorts to the tracks on either side and for continuity along the track. 

I have noticed pictures often make the solder points look much worse than they actually are. 

[Stuart]

Tried reflowing the pin connections, just to be sure?

[Delta]

1 hour ago, Stuart said:

Tried reflowing the pin connections, just to be sure?

Just done it...no difference. Probably did a better job this time too! 

[GDMike]

Yeah, it needed verification... but the hunt is still on.

[Delta]

38 minutes ago, GDMike said:

Yeah, it needed verification... but the hunt is still on.

I need a few more straws, however short! 

I don't have any more VDPs to test with and despite what happened with you is it really just a coincidence that the problem occurred after I desoldered the ROM and/or soldered the socket? 

I would say that both boards which exhibit the no display and continous beep show correct voltages on the video RAM and processor. However, they both show 0V on the bottom right pin of the ROM - it was 3.3V when it was working. However, the top left pin shows 5V.