Star Rider PCB Repairs

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Still messing with the expander board with little to no progress. I added in this little extra board with tiny kynar attachments so I can easily measure voltages. They all seemed to be within acceptable bounds, if maybe a little low.

5V (A) ≈ 5.0V
5V (DC) ≈ 5.0V
4.7V (A) ≈ 4.65V
12V (A) ≈ 11.9V
-VR (-1.0V) ≈ -1.1V
-6V (A) ≈ -6V

So... Not power... What then would stop this from outputting video at all?
I see adjustment pots, I guess those are for RGB?

do you have any voltage at the white wire on the video plug? that should be sync. if sync is missing that will explain your no video.

this looks like a fun project
 
I see adjustment pots, I guess those are for RGB?
There are quite a few for sure.

Here's what the Star Rider Manual has to say on the subject:
And that's it. No description of what they are for. Too bad I can't call my authorized WILLIAMS distributor.

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Looking at the schematics, here's what I'm gathering:
R63 - Not entirely sure what this does. Feeds the 1458 Op Amp at IC36. Is similarly connected to all the color inputs as R67 is to the outputs. (through Q2).
R64 - Appears to be a limiter on Red Intensity In?
R65 - Appears to be a limiter on Green Intensity In?
R66 - Appears to be a limiter on Blue Intensity In?
R67- Seems to control the output voltage of the LM317 at IC56. It's not indicated in the schematics what this voltage is supposed to be. I think 7v? There's a reference to black level adjustment in the supplement booklet. I imagine this might be it as it's attached to all three color drives.
R68 - Expander Red Intensity Out
R69 - Expander Green Intensity Out
R70 - Expander Blue Intensity Out
do you have any voltage at the white wire on the video plug? that should be sync. if sync is missing that will explain your no video.
I'll double check, but should be. According to the schematics, it's a straight passthrough from input to output.

this looks like a fun project
It'll be more fun when I can get one of these expanders working and then understand how they're SUPPOSED to function!
 
1000003497.jpgWell, clearly Sync is making it through. Colors, not so much. This is with my monitor MAXED on brightness (with the TPG off, it's showing a blue screen, so these colors aren't really the TPG) but this is what I'm getting out the other end of the expander. I tried this on two expanders. Same results.
 
Additional Info for those who might know more than me. I've been going through this a bit more with @Kaworu5 and tried to eliminate a few things.

First, I tried two CPU boards and two VGG boards in three combinations. This behavior was the same across them, so I'm not sure (despite there being a whole bunch of non-working expanders) where the problem is, as none of it seems to change between any combination of boards.

Second: ALL of the inputs to the Expander board on the 5J1 connection seem to be stuck HIGH. However, the source of most of these inputs (PA0-PA7, CA2 are sourced from the PIF on the VGG) The PIF not only tests okay pit pf circuit, but none of the data lines on the bus connected to it are stuck (D0-D7) and the PIF which is also commanded through it, seems to work fine also.

The other signals which are outgoing to the expander come from the following places:

3J3 - 11 - HSYNC - Sourced from 74LS74 at IC123 and Inverted before being passed out to the expander.
3J3 - 12 - EXP CONTROL - Comes from a NOR gate (IC65) on the VGG's EXPAND DISABLE and EXPAND CONTROL Lines.

Does anyone know what the status of those control signals SHOULD be in order for the Expander to generate a color passthrough image? Or is it supposed to always?
 
So, still throwing questions at the wall here. What is the behavior of HSYNC (Disc) supposed to be when it comes to the expander board?

According to the schematics, it enters the VGG Board from the PIF pin 14 as Composite Sync

1755050329613.png


It then goes through this mess and is mixed (NAND) with the Hsync from the VGG. It's then sent out through 3J2 and NOR'ed out of 3J4 (to the Expander)

1755050400864.png

Where it then goes into this flip flop mess.


1755050470884.png

The ONLY Pin that Hsync is connected to on the Expander side is 5J11, and only that one IC - 44 (74F74).

HOWEVER

What I'm measuring right now is that if I have an expander plugged in, the HSYNC signal going to the expander ONLY is held high. What's interesting is that it has to be after that Inverter right before 3J4 right? The HSYNC going out of 3J2 is still valid and working. So, at first I suspected the Inverter (mind you, I tried this on three VGGs, and it did the same thing), but that chip on one VGG tested fine. So then I tried the 7474 on the Expander (IC54) and that tested fine out of circuit too. I also checked the harness for shorts and found none.

So. With a path that basically looks like this, how is the signal between the 74LS04 and the 74F74 getting held up?

HSYNC -> 74LS04 -> VGG 3J4-11 -> Expander 5J1-11 -> 74F74

What gives? Is this a red herring? How is this supposed to work? I don't understand how an output of a Inverter which has a pulsing input, which only goes to the input of a flip flop, is being held high when both ends and everything in the middle seems to be working.
 
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I'm still stuck on this HSYNC thing.

I don't understand it. Please someone make it make sense to me.

I tried another cable between the expander and the VGG. No change. HSYNC stuck high.
I tried removing the IC54 and leaving the cable connected. HSYNC is now pulsing again.
I tried substituting another tested good 74F74. And HSYNC is stuck high again.

I don't understand how this works.

The datasheet for the 74F74 states that pin 3 is Clock Pulse 1. And is an input. Clearly, if that signal is pulsing when the chip is removed and everything else is in place, then that chip has something to do with the stuck signal.

There are a lot of inputs to the Expander board, but only a few outputs. Literally just Video (RGB + NTSC and composite sync). The CSYNC line is a straight passthrough from the NTSC board and has NOTHING to do with the incoming HSYNC line. So... What gives? What could be feeding back or changing to stick this high? What am I missing here?

Someone with more EE wizardry... What's going on?
 
I noticed you're using the older scans of the schematics. I did a higher res scan last year and also included some extra info from the supplement manual, as well as an undocumented PCB mod discovered by Matt Ownby (that just so happens relates to HSYNC). Not sure if that will help in this situation but I figured I'd let you know just in case.

 
I noticed you're using the older scans of the schematics. I did a higher res scan last year and also included some extra info from the supplement manual, as well as an undocumented PCB mod discovered by Matt Ownby (that just so happens relates to HSYNC). Not sure if that will help in this situation but I figured I'd let you know just in case.

Oh thanks! I had no idea there was another scan. I was just using those to provide picture reference. I actually have a complete trio of booklets I've been working off of.

But.

Ladies and Gentlemen of KLOV, I must confess:
I am an Idiot.

So, it turns out I was right to be worried about that HSYNC line, but I was worried for the wrong reason. As it turns out, there is ONE connection between the boards that Williams didn't bother to provide a wire for. They expected the PCB backplane to be the ground. For WHATEVER reason. And that happens to be the REGULAR ground on the expander board. (There are two ground planes... Which are joined by the metal backplane I guess?) In any case, when measuring voltages it all looked okay because they're connected by a 500ohm(?) resistor...

I probably would have spent even longer chasing my tail on this except for I noticed this in the schematics:

1755137408234.png1755137449852.png

While the expander schematic shows ground coming in on pins 6 and 7 of 5J2, there are no actual wires populated here. Instead, it's relying on the ground plane. That's why it wasn't working. Floating ground. I've been chasing my tail for DAYS. I guess this boardset just isn't meant to be bench tested.

Anyway.

I'm real close now.

1755137530781.jpeg
 
I'm trying to identify the function of all the potentiometers on the Star Rider boardstack, because the manual sure as hell doesn't say what they do
"Call your williams serviceman..."

Here's what I've got so far:

NTSC Board Pots
VR001 - (Unknown?)
VR200 - Brightness
VR201 - Contrast
VR400 - Chroma(?)
CR400 Unknown - Hooked up to Oscillator that feeds Tint.
VR401 - Tint
VR505 - Red Drive?
VR500 - Red Cutoff?
VR705 - Blue Drive?
VR700 - Blue Cutoff?

Expander Board Pots

R63 - -6V Adjust? Black Level In?
R64 - Red In
R65 - Green In
R66 - Blue In

R67 Black Level Out
R68 - Red Out
R69 - Green Out
R70 - Blue Out

Not really sure what the input pots do. They don't seem to be able to adjust much actively on the image. It goes into DACs so I'm not sure what the purpose is.

VGG Board Pots
R58 - Blue Intensity (CG)
R59 - Blue Intensity (CG)
R60 - Green Intensity (CG)
R61 - Black Level (?) Connected to all lines, not populated on all VGGs.

Any confirmation on what the functions of NTSC VR001, CR400, VR500/5, and EXP R63 are would be awesome.

Unrelated, but
I've spent at least 12 hours nonconsecutively trying to get the colors right and I can't. Between these and the pots on the monitor, there are 34 goddamn adjustment points in this machine.
 
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I'm trying to identify the function of all the potentiometers on the Star Rider boardstack, because the manual sure as hell doesn't say what they do
"Call your williams serviceman..."

Here's what I've got so far:

NTSC Board Pots
VR001 - (Unknown?)
VR200 - Brightness
VR201 - Contrast
VR400 - Chroma(?)
CR400 Unknown - Hooked up to Oscillator that feeds Tint.
VR401 - Tint
VR505 - Red Drive?
VR500 - Red Cutoff?
VR705 - Blue Drive?
VR700 - Blue Cutoff?

Expander Board Pots

R63 - -6V Adjust? Black Level In?
R64 - Red In
R65 - Green In
R66 - Blue In

R67 Black Level Out
R68 - Red Out
R69 - Green Out
R70 - Blue Out

Not really sure what the input pots do. They don't seem to be able to adjust much actively on the image. It goes into DACs so I'm not sure what the purpose is.

VGG Board Pots
R58 - Blue Intensity (CG)
R59 - Blue Intensity (CG)
R60 - Green Intensity (CG)
R61 - Black Level (?) Connected to all lines, not populated on all VGGs.

Any confirmation on what the functions of NTSC VR001, CR400, VR500/5, and EXP R63 are would be awesome.

Unrelated, but I've spent at least 12 hours nonconsecutively trying to get the colors right and I can't. Between these and the pots on the monitor, there are 34 goddamn adjustment points in this machine.
John Newcomer had a hand in this. I'm sure he knows nothing about the hardware, but he might know someone who does. I've always wanted to talk to him just never had a reason to.
 
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