Vanguard to Nibbler?

dungeonmastr

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Howdy! So I just came across a very well worn Vanguard boardset that needs some work. Is it possible to convert one of these to a Nibbler boardset? They're labeled SK4 and SK5 whereas a Nibbler should be labeled SK7 and SK8. Are there enough similarities between these to convert from one to another, or is this just chasing my tail?
 
Howdy! So I just came across a very well worn Vanguard boardset that needs some work. Is it possible to convert one of these to a Nibbler boardset? They're labeled SK4 and SK5 whereas a Nibbler should be labeled SK7 and SK8. Are there enough similarities between these to convert from one to another, or is this just chasing my tail?

The only thing really interchangeable with Vanguard & Nibbler is the bottom board (and that still requires a modification to work 100% for Nibbler).

The top board would require a number of modifications, for starters you are short a rom socket.
 
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It's possible, but probably not by you :)

They hardware is pretty close, but it's certainly not just a ROM swap.

Trust me - I know it's beyond me. ;) Just was curious if there was some weight to what what the guy I bought it from said (see below). The board I picked up has seen better days, and is missing some socketed ICs, but struck me as interesting for two reasons:

  1. The old operator said it was a Nibbler conversion, and
  2. It has a handful of bodges and a stacked 9th ROM.
For $15, I figured, eh, what the heck; it was about as low risk an investment as they come. Worst case scenario? I have a potential Vanguard after some repairs (with no voice module :()
 
The only thing really interchangeable with Vanguard & Nibbler is the bottom board (and that still requires a modification to work 100% for Nibbler).

I have it with me at work at the moment; I'll snap pics of the front and back in a few. Both boards have modifications, but some of the bodges have come loose over time.
 
I have it with me at work at the moment; I'll snap pics of the front and back in a few. Both boards have modifications, but some of the bodges have come loose over time.

The stacked 9th ROM is certainly interesting, you would need that for Nibbler. Take a picture of the solder side of the bottom board, zoomed to the end opposite the ribbon connectors.

Makes me wonder though back in the day why anyone would have been that desperate for Nibbler that they would convert a Vanguard! ;)
 
Trust me - I know it's beyond me. ;) Just was curious if there was some weight to what what the guy I bought it from said (see below). The board I picked up has seen better days, and is missing some socketed ICs, but struck me as interesting for two reasons:

  1. The old operator said it was a Nibbler conversion, and
  2. It has a handful of bodges and a stacked 9th ROM.
For $15, I figured, eh, what the heck; it was about as low risk an investment as they come. Worst case scenario? I have a potential Vanguard after some repairs (with no voice module :()

Sounds like it's potentially already been converted to Nibbler... heh.
 
Here's the back:

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And the front:

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ROM5 on the front board is the double-stacked IC. The bodge that goes off to the lower-left on the back board is disconnected, but it looks like it went to pin 2 on IC12 (the leftmost IC with a pre-exisiting bodge).
 

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I don't have my Vanguard boards in front of me, but the jump wires on the bottom board look standard.

What type of rom is on top of the "double-stacked" socket? Hard to read, but looks like a 2732.

Something else that just occurred to me is there is no sound rom @ IC53 on Vanguard (instead a second SN76477). For Nibbler, that sound rom just provides the coin-up sound effects (there are 7 of them that rotate with each credit given). Your top board also has a rom installed @ IC51, which for Nibbler would play whatever music is on that rom during the first ~ 14 waves. Maybe it is Vanguard music, can't imagine what that would sound like.
 
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Definitely looks like it was modded for Nibbler (or Fantasy). Pin3 of IC6 has a jump wire that goes to the top rom of the double stack. That pin on IC6 is the chip select for $3000-3FFF, which is the missing address range that Vanguard doesn't implement. Nibbler and Fantasy both have game code at $3000-3FFF.
 
Definitely looks like it was modded for Nibbler (or Fantasy). Pin3 of IC6 has a jump wire that goes to the top rom of the double stack. That pin on IC6 is the chip select for $3000-3FFF, which is the missing address range that Vanguard doesn't implement. Nibbler and Fantasy both have game code at $3000-3FFF.

On this board, it looks like it was set to pin 4 on IC6 (the wire came loose at some point, but in the photos of the board faces it does look like it's on pin 3 - sorry about that). Looking at the Vanguard schematics, it's kind of hard for me to tell how they've numbered the pins, so I'm a bit confused. Should it tie to pin 3 and they had it in the wrong place?

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Whoops yes it it should be pin 4, I mis-read the schematic. You can still see the extra solder on the chip leg.

Gotcha! I'll look for a pinout for that 154 - I'm curious how it works! Most of my work in this hobby has been carpentry and graphic design; I really want to start branching out into logic and electronics over the next year or two.

I guess what I'm most curious about at this point is, surely that's not all that's required for massaging a Vanguard into a Nibbler, right?
 
Gotcha! I'll look for a pinout for that 154 - I'm curious how it works! Most of my work in this hobby has been carpentry and graphic design; I really want to start branching out into logic and electronics over the next year or two.

I guess what I'm most curious about at this point is, surely that's not all that's required for massaging a Vanguard into a Nibbler, right?

Off the top of my head no, but you'll have to post a photo of the underside of the top board to show additional jumper/trace mods.

The CRT controller & I/O ports on Vanguard are mapped to $3xxx, so that mapping would have to be switched to $2xxx.
 
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The CPU board is immediately below; for reference, the bodge at the far right is pin 3 of IC6 and it leads off to a bridge to a pin on CN2; I am unsure of how the pins on CN2 are numbered, but it is boxed in red in the picture. The three ICs on the left are 40, 41, and 42 (42 being the topmost). Pin 4 on IC42 is bodged to pin 3 of IC40, and pin 2 of IC41 is bodged to pin 4 of IC40.

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Back board:

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Those jumpers on the back are normal... just do composite sync.

The hack on the back of the cpu board prob swaps the 0x2000 and 0x3000 address space for the I/O.

The stacked ROM takes care of the extra socket, but you'd still need to populate all of the rest.
 
The mods near the edge connectors on the underside of the top board are consistent with what I have seen on some Nibbler/Fantasy boards. There are 7 & 8 series top boards that I'm not 100% sure the difference between.

The other jump wires for the top board look to be partly for the sound section (IC41), which is a little different than Nibbler/Fantasy.

PS - IC73 on the bottom board looks a little trashed, not sure what happened to it.
 
Those jumpers on the back are normal... just do composite sync.

The hack on the back of the cpu board prob swaps the 0x2000 and 0x3000 address space for the I/O.

The stacked ROM takes care of the extra socket, but you'd still need to populate all of the rest.

Traced the jumpers in the schematic and it looks like, yep, they lead to the CSYNC output pin on the card edge. Taking care of the rest of the empty sockets shouldn't be too huge a problem - won't be able to address them for a few weeks, though. As for the hack on the back of the top board, I traced around and went through the schematic and it looks like it heads off into the sound system (see below). Not sure which direction to head in with adjusting the address space. :(

The mods near the edge connectors on the underside of the top board are consistent with what I have seen on some Nibbler/Fantasy boards. There are 7 & 8 series top boards that I'm not 100% sure the difference between.

The other jump wires for the top board look to be partly for the sound section (IC41), which is a little different than Nibbler/Fantasy.

PS - IC73 on the bottom board looks a little trashed, not sure what happened to it.

IC73 looks like someone tried to pull it while it was still soldered in place - it'll get replaced as well. As for the rest of the jumpers, I know Mark said he thought they might be for the address space swap, but it looks like they do actually flow into the sound system. This Vanguard PCB has two 76477s, one of which is where a Nibbler sound ROM looks like it should go (IC53) on some Nibbler boards. There are two ROMs (IC51 and IC52) labelled NA and NB on this PCB where some Nibbler boards have one and some have two ROMs (the Olympia boardset looks like it only uses one). Any thoughts?

Aside from sound, and because I'm still trying to understand TTL logic on a large scale like this, where would be the place to start looking on this PCB for swapping the address space? Once I start trying to seriously abstract myself from basic logic, I start getting lost. :( Any input or advice would be tremendously appreciated; thanks to you both for the guidance!
 
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