Atari System 2 PCB Repair - Paperboy
- Thread starter Purity
- Start date
I setup my Paperboy test rig today to see if I can actually get a picture out of it.
I had confirmed that the boards at least gave something on screen at RGP's - thanks James
So I was very pleased to see the game playing, although I've got work to do as there are graphics issues.
A few really important things I was able to confirm today, and is probably very useful to other folk:
1) I had two working T11 CPU's
2) I had two working Paperboy slapstics
* 3) The most important one for other folks - The T11 clone CPU "KR1807VM1" works! *
4) It is possible to output a medium res game to one of those EGA converters - I had spoken to RGP about this and he said he never got one working
5) The board needs +-15v or it will not boot
Purity2018-09-15 19:18:18
I had confirmed that the boards at least gave something on screen at RGP's - thanks James
So I was very pleased to see the game playing, although I've got work to do as there are graphics issues.
A few really important things I was able to confirm today, and is probably very useful to other folk:
1) I had two working T11 CPU's
2) I had two working Paperboy slapstics
* 3) The most important one for other folks - The T11 clone CPU "KR1807VM1" works! *
4) It is possible to output a medium res game to one of those EGA converters - I had spoken to RGP about this and he said he never got one working
5) The board needs +-15v or it will not boot
Purity2018-09-15 19:18:18
John Bennett
Senior Member
I thought lots of folk used those converters with Sega Model 1/2/3, which is also medium res, when they downgrade to widescreen LCDs.
I don’t know much about DEC chips, but are those clones easier to find?
I don’t know much about DEC chips, but are those clones easier to find?
Nice setup
people have been using those converters for years for sega medium stuff like John said. There are at least three revisions of the converter and certain mods that need doing depending on the input. Like resistors on the sync line, a certain cap that gets changed and people even add copper tape to clean up the interference.
Progress is good
SUPERSPRINT
Active member
Pretty sure retroclinic repairs system 2
SUPERSPRINT
Active member
Yeah, I’m sure he would give you a few tips.
There seems to be a conflict of opinion with regards the voltages required. I've read on Klov that if the +-15v is not present on the PCB, it will not boot. So 12v is not good enough
The other voltage required is 10.3v DC for the Power OK.
The rest of the voltages are standard - +5v
I have seen this being booted on a test setup with a variable power supply, supplying the the +15v only.
However I have not been able to achieve this myself yet - i.e. removing the new for the Atari brick and AR3
It needs looking into and documenting.
I have tried substituting the +15v with +12v and 10.3v with 12v.
The PCB booted but I could not get a stable screen and lots of video was missing when I did see a picture
Purity2018-10-31 13:03:27
The other voltage required is 10.3v DC for the Power OK.
The rest of the voltages are standard - +5v
I have seen this being booted on a test setup with a variable power supply, supplying the the +15v only.
However I have not been able to achieve this myself yet - i.e. removing the new for the Atari brick and AR3
It needs looking into and documenting.
I have tried substituting the +15v with +12v and 10.3v with 12v.
The PCB booted but I could not get a stable screen and lots of video was missing when I did see a picture
Purity2018-10-31 13:03:27
I've repaired (or tried/in the process of) about a dozen boards in the last few years. They can be quite tricky mainly due to the number of devices sharing the different buses. I've used the exact same EGA board as you, and whilst it works well, it's rather fragile. It seems to have no input protection whatsoever, so they're quite easy to kill with cable/induction spikes above 5.5v. I'm on my third one, and that has lasted a while with a seperate board I've made that has clamping diodes on each input.
I added a seperate toroidal transformer on my rig that does the 15v/22v for Atari games, because of issues like these, it worked out fairly low cost:
I'm sure we discussed a similar topic a while back with RGP, and my memory is a little hazy, so this is what I remember from memory (please correct me if I'm wrong).
- The system 2 POR/"Power okay" requires 15v, 12v probably won't do. The reason is that it goes into a potential divider (~2/3) and into an opamp with a - of 5v. Meaning it outputs the differential of ~10v and 5v (TTL high). If you apply 12v, it then compares ~7.7v to 5v, outputing 2.7v and after the following circuitry may not be enough to create the required logic high.
- I think we also discussed how not having quite +-15v might result in the wrong colours due to the video amplifier voltage changes, but that's not a problem for testing.
- The -15v creates the -5v for certain things on the CPU board, something to do with the audio from memory, but it won't stop the game from running.
The CPU boards seem to be quite reliable, most of the issues seem to be with the lower boards, usually the I/O buffers, but thankfully you can narrow it down somewhat with the onboard test program. Thank god the schematics are good!
Andy
I added a seperate toroidal transformer on my rig that does the 15v/22v for Atari games, because of issues like these, it worked out fairly low cost:
I'm sure we discussed a similar topic a while back with RGP, and my memory is a little hazy, so this is what I remember from memory (please correct me if I'm wrong).
- The system 2 POR/"Power okay" requires 15v, 12v probably won't do. The reason is that it goes into a potential divider (~2/3) and into an opamp with a - of 5v. Meaning it outputs the differential of ~10v and 5v (TTL high). If you apply 12v, it then compares ~7.7v to 5v, outputing 2.7v and after the following circuitry may not be enough to create the required logic high.
- I think we also discussed how not having quite +-15v might result in the wrong colours due to the video amplifier voltage changes, but that's not a problem for testing.
- The -15v creates the -5v for certain things on the CPU board, something to do with the audio from memory, but it won't stop the game from running.
The CPU boards seem to be quite reliable, most of the issues seem to be with the lower boards, usually the I/O buffers, but thankfully you can narrow it down somewhat with the onboard test program. Thank god the schematics are good!
Andy
I'm assuming it's a misprint in the paperboy manual, as both CS/SS state that it should be connected to 15v and not 10.3. I can't see how the Power Okay would work reliably connected through the unregulated 10.3vDC (essentially still positive AC) to a TTL IC. Could you use your scope on pin 11 of 5k, just to ensure the signal is stable and above 3v, just so we can confirm I'm wrong here?
How are you generating the -5v required for the sound processing? You would need at least -8v, as it's fed into a 7905 regulator (on the CPU board, not the AR3), so if you just provided -5v for example the regulator wouldn't function properly and it would output -5v minus the forward voltage drop of the regulator as it wouldn't be able to regulate itself. So the next port of call would be to use your MM to read the -5v at a point, for example at R159 which controls the Sound Reset, which might explain your sound issues.
All of the LM324 op-amps require dual supplies. So if you're feeding them with 12v (instead of 15v), that should work okay, apart from a slight change in colours/audio as mentioned before, but you will also need to supply them with -12v as well. The op-amps will function perfectly fine as long as they have a small amount of voltage headroom above/below the input levels.
Andy
How are you generating the -5v required for the sound processing? You would need at least -8v, as it's fed into a 7905 regulator (on the CPU board, not the AR3), so if you just provided -5v for example the regulator wouldn't function properly and it would output -5v minus the forward voltage drop of the regulator as it wouldn't be able to regulate itself. So the next port of call would be to use your MM to read the -5v at a point, for example at R159 which controls the Sound Reset, which might explain your sound issues.
All of the LM324 op-amps require dual supplies. So if you're feeding them with 12v (instead of 15v), that should work okay, apart from a slight change in colours/audio as mentioned before, but you will also need to supply them with -12v as well. The op-amps will function perfectly fine as long as they have a small amount of voltage headroom above/below the input levels.
Andy
RaveN said:
Immediate thoughts:
I know I ran a 720 pcb off +- 12v from either (1)a pc power supply or (2)one of those odd hantarex psus that included an isolation transformer for the monitor. However, maybe I just got lucky with the logic levels.
The -5v is almost certainly used for the TMS5220 speech chip.
Ah right. What kind of current does the pcb take I wonder? Just thinking if it's possible to use one of those small step up converters on eBay that gives you 15v from 12v. If so then with the above way of stepping 12v down to 10.3 maybe you could run from one jamma supply (or two at the most). Same for boosting the -5v up a little to compensate for voltage drop.tb20002018-11-01 09:21:18Purity said:
This is incredibly confusing!
I have wired up my AR3 and brick exactly to the CPU and Video board as illustrated in the Paperboy manual.
However I can see that in the CS manual it definitely has +15v as Power OK instead of 10.3V DC so I agree with that
Where is the -5 volt connected? It mentions nothing about this on the wiring diagrams, but I can obviously see -5 being referred to at the 7905 as already mentioned. I currently do not have a -5 volt connected.
This is probably why my speech doesn't work etc!
What I've wired up to power is:
Video PCB:
P13
Pins 1,4 Ground
Pins 5,8 +5
Pins 9 +sense
Pins 11 -sense
Pin7 +15v
CPU PCB:
P15
Pins 1 Ground
Pins 2 +15v
Pins 3 -15v
Pins 4 10.3v
P20
Pins 1 -sense
Pins 2 +sense
Pins 3,5 Ground
Pins 6,8,9 +5
I have wired up my AR3 and brick exactly to the CPU and Video board as illustrated in the Paperboy manual.
However I can see that in the CS manual it definitely has +15v as Power OK instead of 10.3V DC so I agree with that
Where is the -5 volt connected? It mentions nothing about this on the wiring diagrams, but I can obviously see -5 being referred to at the 7905 as already mentioned. I currently do not have a -5 volt connected.
This is probably why my speech doesn't work etc!
What I've wired up to power is:
Video PCB:
P13
Pins 1,4 Ground
Pins 5,8 +5
Pins 9 +sense
Pins 11 -sense
Pin7 +15v
CPU PCB:
P15
Pins 1 Ground
Pins 2 +15v
Pins 3 -15v
Pins 4 10.3v
P20
Pins 1 -sense
Pins 2 +sense
Pins 3,5 Ground
Pins 6,8,9 +5
Looking at the 720 schematics page 4a (which are most convenient for me to locate) it looks to make -5v from the -15v input.
I have dug out my test loom, which I haven't used in years (and very nasty it is too) unless a wire has dropped off the loom I only have connections for gnd, +5 and +15v (sub labelled by me as +12v). I was originally testing for a non booting CPU so probably never needed/cared about -5v for speech. I might find the time to plug it in to a variable PSU and see if it actually works on +12v or only +15v rather than me idly speculating about what voltage I stuffed down it. It's been a looong time since I used it.
I have dug out my test loom, which I haven't used in years (and very nasty it is too) unless a wire has dropped off the loom I only have connections for gnd, +5 and +15v (sub labelled by me as +12v). I was originally testing for a non booting CPU so probably never needed/cared about -5v for speech. I might find the time to plug it in to a variable PSU and see if it actually works on +12v or only +15v rather than me idly speculating about what voltage I stuffed down it. It's been a looong time since I used it.