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JOLT replica

Here's the front side so far, thanks to snuci's timely help.

This is still pretty rough - I want to make an effort to get the traces as close to the original as possible, including curves, and I have to add the lettering. There are also a few places where the photocopy snuci provided AND the available pictures are hard to make out details on. Coming along though!
 

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daver2 said:
Did you enter the schematic first?

If you did, the PCB tool can identify missing tracks.

Dave
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Unfortunately the schematic does not, as of this moment, exist anywhere. I did write Ray Holt asking about it but no response as of yet. So I'm just treating this as a 'connect and pray' situation for now.
 
Question.. does anyone know if there was a specific 'font' PCB layouts tended to use? I note many boards look pretty similar. It's hard to tell in photos, it does look like they're not 100% consistent.

So far I've resorted to tracing them in KiCad and then copy and pasting around.. but if the actual font exists somewhere it'd be great to try using that instead.
 

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falter said:
Unfortunately the schematic does not, as of this moment, exist anywhere. I did write Ray Holt asking about it but no response as of yet. So I'm just treating this as a 'connect and pray' situation for now.
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The best way is to create / recreate the schematic first, then create a PCB layout. If done that way, everyone gains more knowledge. If one just re-creates a PCB without the schematic, one has just created a new piece of artwork, which may or may not work.
 
tingo said:
The best way is to create / recreate the schematic first, then create a PCB layout. If done that way, everyone gains more knowledge. If one just re-creates a PCB without the schematic, one has just created a new piece of artwork, which may or may not work.
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I think the best I can hope for is to try and reverse engineer what I have into a schematic and then turn that over to people who know more than I do to check and correct. Not having a schematic to start with makes the task really difficult for me.
 
I have either seen the schematic for the Jolt somewhere, or seen the schematic for the TIM 6530-004 - which is what the Jolt will be based upon...

I will boot my laptop up tomorrow and have a look. This may save you some work.

The Jolt appears to have an extra 6820 (when compared to the TIM reference design) and U6 and U12 appear to be on the Jolt but not on the TIM reference design.

I assume these account for the slightly different address decoding between the two.

Probably much less reverse engineering required to generate the schematic...

 Dave
 
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It appears there is more than one verison of the original JOLT also. I just noticed this pic of one and it has a single large chip on the left (can't make out part number) vs the three that are there in the revision I'm working on, which I assume is the first one. Or maybe mine is the second since the original ad shows the one with the single big chip.
 
daver2 said:
Correct. I noticed the same. The large chip is a 74154 4 to 16 decoder. I think this is an early version of the address decoder that was replaced by the subsequent chips on the board you are cloning.
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It seems like a lot of early 6502 designs loved the 74154. The Commodore PET also uses it.

(The giveaway signature that a machine uses the 74154 is a memory map divided into 4K chunks, which at first glance seems to apply to the Jolt.)

@falter, what does your machine have instead? A common sub for the '154 is a pair of 74138s.
 
falter said:
I think the best I can hope for is to try and reverse engineer what I have into a schematic and then turn that over to people who know more than I do to check and correct. Not having a schematic to start with makes the task really difficult for me.
Click to expand...
Yes - that was what I was trying to say here: reverse engineer the pcb into a schematic, then share it to get more eyes on it.
 
I have to wrap my head around how to organize and reverse engineer a schematic. Just the 'how to place and follow things in a logical way' so I don't get lost or confused. I've traced out parts of a machine or board into a schematic of sorts but the bigger it gets the more confused I get
 
As I said, use the existing schematics from the SuperJolt and the 6530-004 TIM manual as a reference - and trace those on the reference board layout (not the one you are developing).

Copious use of a red pen (to highlight differences) and a yellow highlighter pen (to identify pins and interconnection already checked) is a must - otherwise you will get lost...

Dave
 
I also print out the two sides of the PCB images (to the same scale) and staple them back-to-back (just like the PCB looks). This makes it mentally easier to follow the tracks on the reference image without going mad(er)...

Dave
 
I'm surprised there isn't a AI way to trace this stuff mostly automagically. The 21st century continues to disappoint.. :)
 
Generally, as you can see, the quality of some of the documentation is pretty poor...

My experience with auto recognising text from document scans is not very good...

Dave
 
falter said:
I have to wrap my head around how to organize and reverse engineer a schematic. Just the 'how to place and follow things in a logical way' so I don't get lost or confused. I've traced out parts of a machine or board into a schematic of sorts but the bigger it gets the more confused I get
Click to expand...
The way I do it, I use photographs of the PCB (no surprise there), which I annotate on the solder side with drawings of the components. Based on that I draw a first version of the schematic, this is more like a ratsnest than anything else, no division of circuits into logical blocks etc. When I am reasonable sure that it is correct, I start to organize the schematic into logical subcircuits and so on.

I keep everything in a git repository. Generally, the "master" or "main" branch is the ratsnest, and a different branch (for example "reorg") is my attempt at giving a better organization to the schematic. This way, I can go back to the ratsnest and correct mistakes when I find them.
 
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