Tempest PCB: corrupt vectors, otherwise game plays.

Jeff F

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Tempest PCB: corrupt vectors, otherwise game plays.

Just started doing a little troubleshooting and figured I'd take a video to show just what is going on. The video shows the output on a scope which when the monitor is connected shows the same thing. The scope leads are connected to the XY test points. BTW, X=~18Vpp and Y=~14Vpp.

http://www.youtube.com/watch?v=fPkHgzc1U3A

As you can hear in the video(sound starts at the 12s mark), the game appears to be playing fine there is just garbage on the screen.

So far I've rebuilt the A/R II(just because), re-soldered the interconnect pins, cleaned all socketed chip pins, checked the ROMs, put in a new 6502(shot gun attempt), replaced one POKEY(had no sound before replacing), and replaced D/E12, D/E13, and C12.

The reasoning behind replacing the TL082CPs was I read that the IO of the DAC(pin 18) should be zero and when it's not, it's a sign that the related TL082CP is shot. Replacing both didn't seem to change the XY output or the IO signal.

The reasoning being replacing the 1495 was more out of curiosity... I've read that these go bad semi-often and just took a shot in the dark. Needless to say nothing changed. ;)


I've looked at the inputs to the DACs on the scope and they seem to be fluttering away. I looked at all of the X DAC inputs and most of the Y DAC inputs and none were stuck high or low.

Next on the list is research. I just want to read more and look at the schematics to try and come up with a game plan. I posted this "just in case" someone else has run into this or has any ideas.

-Jeff :beerchug:
 
I don't know what you're talking about... that screen looks good to me!
It might be easier to investigate if you put it in test mode to get the cross-hatch, regular pattern.

not much help... but then again, if I knew how to fix it... :D

cheers
/Tim

p.s. Its pretty easy to see the "center"ing going on (like we were talking about on your BZ).
 
The test screen only show a rectangle around the outside boarder of the screen... nothing inside. I'll try to get a picture or video tomorrow night.


For some reason(non-technical, just gut feeling) I keep thinking it's trying to draw a SUPER-SIZED play field in a small window. Like trying to draw an actual size 18-wheeler on a 19" screen... you only get bits and pieces.


At any rate, thanks again Tim! :beerchug:
 
Does playing with the various video adjustment pots on the board have any affect at all?

Exactly... You need to try to adjust the size down. The scope looks like most everything is off screen due to a size issue. Also, since you don't get the blanking on your scope it makes it harder to see what is good vs. bad. You might try flipping the scope into persistence mode or increase the delay before it clears the trace.

Anyway, adjust the the pots on the game board per the manual and see how well that goes. The pots on the game board can go bad too and may need to be replaced. There could be other game board issues, but start with the pots since it is easy to see what impact they have.

-VJ
 
Jeff,

Do you have an eprom burner and which rom set is the board strapped for?
a) twelve 2716
b) six 2532?
 
Does playing with the various video adjustment pots on the board have any affect at all?

Before I changed the 1495, the X-size pot didn't appear to do anything. Now changing the three X and three Y pots moves the video like you'd expect. The X and Y BIP adjustments seem to move the vectors... but it's really hard to tell because of the garbage.

Anyway, adjust the the pots on the game board per the manual and see how well that goes. The pots on the game board can go bad too and may need to be replaced. There could be other game board issues, but start with the pots since it is easy to see what impact they have.

Like I said, things do move when I adjust all the pots, but I'm not sold on them all working 100% correctly so I'm going to replace them.

And I'll take a quick video of the monitor to show what is actually being drawn... it's really close to the scope. I don't want to leave the monitor on long though because I'm thinking it can't be good to slam 100% left, right, up, and down like that.

Do you have an eprom burner and which rom set is the board strapped for?
a) twelve 2716
b) six 2532?

This board uses the twelve 2716 EPROMs. I did pull all of them to clean the legs and check to make sure they weren't corrupt. I did re-burn one just because leg looked fubared.

Any idea what I should look for in regards to strapping? I haven't run across what you actually do to the board to make it use 2532 EPROMs but my other Tempest is strapped for those and I like the idea of only having 6 EPROMs instead of 12.


Great ideas guys! Keep 'em coming. I don't know if I'll be able to work on the game today as I have a friend in from out of town, but Friday I have off of work so I'm hoping to "get into" the game then. ;)

Thanks again everyone! :beerchug:
 
Geeze... after reading your post Tim I went to the schematics and it dawned on me that I'm mixing up my Battlezone troubleshooting and this Tempest troubleshooting. :(

Looks like the two TL082CPs I referred to as possible problems when the voltage coming out of the IO pin on the DACs is large aren't D/E12 & D/E13 but A11 & D11. Seems like D/E12 & D/E13 just amplify the final XY output while A11 & D11 act as current-to-voltage converters that actually help create the XY signals.

And I think I see why you're saying to take a look at A/B12 & A/B13... if they are putting out bad correction data then that could completely screw up the XY signals also.

Soo much to look at... wish I was sitting in front, I mean behind the game right now. Work sucks! :D
 
New video... this time it's the monitor and I step through the self-test.
http://www.youtube.com/watch?v=Q1oaRJfcI8w

As you can see... there is a strange graphic in the lower-right that changes as you turn the spinner. Really strange. Didn't really notice it before because I had the brightness turned *WAY* down.

This graphic will move up/down and left/right when you adjust the Xbit and Ybit pots.
 
Hmmm. I think the graphic that responds to the spinner is the radar you see on some revisions. Wish I could help you more than that, but this one is beyond me.
 
New video... this time it's the monitor and I step through the self-test.
http://www.youtube.com/watch?v=Q1oaRJfcI8w

As you can see... there is a strange graphic in the lower-right that changes as you turn the spinner. Really strange. Didn't really notice it before because I had the brightness turned *WAY* down.

This graphic will move up/down and left/right when you adjust the Xbit and Ybit pots.

One think in that video that was very interesting.... The sound steps in the self test where it changes tones was way too slow. It is as if your board is running at 1/3rd or 1/4th the speed. At least based on the sound. I wonder if it was running slow if that would explain the vector garbage.
 
Hmmm. I think the graphic that responds to the spinner is the radar you see on some revisions. Wish I could help you more than that, but this one is beyond me.

Yeah, this one is odd. It's a fun one to look into for sure, but there's a part of me that has already admitted defeat... I'm just too stupid to recognize it. :) Thanks for the help here and on the other Tempest! :beerchug:

One thing in that video that was very interesting.... The sound steps in the self test where it changes tones was way too slow. It is as if your board is running at 1/3rd or 1/4th the speed. At least based on the sound. I wonder if it was running slow if that would explain the vector garbage.

Hmmm... I'll have to look into that tonight. I'll put the cabaret in test mode and compare the two. I have to be honest, I haven't wanted to use the cabaret in a "stare and compare" way because I don't want to do anything stupid and kill it. :) But I think you're right... listening to that on the video it seems to take an aweful long time between tones...

Pretty sure I looked at the 6MHz and 3MHz test points but I'll check all that tonight for sure.

Another odd thing I noticed after I posted last night... both the X and Y outputs really look "digital" still... there aren't slowly changing signals that float between the min/max values... they basically look like square waves slamming between min/max. I have a few new DACs coming in(needed one for Battlezone) soon so I think I may change one out to see if that IO and the output changes.

Does anyone know for sure if the IO(pin18) on the DACs should measure around 0v? I've read that a few times in the Vector List archives but I'm not sure why it is? I am definitely NOT measuring zero there and I've changed the components recommended to change and it's still not measuring zero(thus my thoughts on trying to swap out the DAC).

Thanks again guys! :beerchug:
 
Yeah, this one is odd. It's a fun one to look into for sure, but there's a part of me that has already admitted defeat... I'm just too stupid to recognize it. :) Thanks for the help here and on the other Tempest! :beerchug:



Hmmm... I'll have to look into that tonight. I'll put the cabaret in test mode and compare the two. I have to be honest, I haven't wanted to use the cabaret in a "stare and compare" way because I don't want to do anything stupid and kill it. :) But I think you're right... listening to that on the video it seems to take an aweful long time between tones...

Pretty sure I looked at the 6MHz and 3MHz test points but I'll check all that tonight for sure.

Another odd thing I noticed after I posted last night... both the X and Y outputs really look "digital" still... there aren't slowly changing signals that float between the min/max values... they basically look like square waves slamming between min/max. I have a few new DACs coming in(needed one for Battlezone) soon so I think I may change one out to see if that IO and the output changes.

Does anyone know for sure if the IO(pin18) on the DACs should measure around 0v? I've read that a few times in the Vector List archives but I'm not sure why it is? I am definitely NOT measuring zero there and I've changed the components recommended to change and it's still not measuring zero(thus my thoughts on trying to swap out the DAC).

Thanks again guys! :beerchug:

To be honest, I have been in test mode on my Space Duel more than my Tempest. So, maybe those are different, but it did sound lethargic in your video.
 
The Pokey self-test sounded the same in my other Tempest so I guess it's just different between Space Duel and Tempest.

The crystal looked good on the scope too.

Replaced both X & Y DACs and even the DAC08 for giggles :) and it's exactly the same.

Also received a logic probe today and played around with the DAC inputs and all of them are cooking away.

Not sure where to go from here so it's looking like more research is needed.
 
The spinner self test on Rev A. ROMs will readout in Hex, that almost looks like that weird graphic in the lower right hand corner.

From looking at your borders, it looks like severe wrap-around on the left hand side and a general lack of geometry too.

Have you adjusted all the pots on the board? How about reflowing the header pins on the interconnect cable between the two boards?
 
Yep, all the pots can be adjusted and I took two of them out to test and they were fine. I have replacement pots from Bob Roberts here but I have yet to put them it.

The header pins looked re-flowed when I got the game but I ended up removing the solder and re-soldering them myself just in case. I also tested the cable and the aux. board in my other Tempest and they worked just fine.

It's funny, that wrap around is there on some test screens, and not in others. I may poke around some more today to see if anything is stuck high/low. And I should replace the pots just so I know they are good.
 
Pretty sure I looked at the 6MHz and 3MHz test points but I'll check all that tonight for sure.

Jeff,


The AVG uses 12, 6 and 3 and 1.5 mhz. Have you verified the correct frequencies are present?

Did you ever look at the opamp in the output section after "confusing them with battlezone"?

Have you tried this board in a different cab with a known good power supply, ARII (yes, i know you rebuilt this one) and known good monitor? Have you tried swapping in a good tempest board to validate this cab and monitor are good?

Can you post a pic from this PCB on a scope?

The fact the drawn line wraps back is disturbing...
 
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