Author Topic: Reconstructing schematic from two layer PCB  (Read 1792 times)

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Offline bigmacTopic starter

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Reconstructing schematic from two layer PCB
« on: January 03, 2020, 10:36:35 am »
So... i've got myself into a bit of a project.
Quick story.
I bought an electric car, a Kewet El-Jet 4 from 1995. Not working. Turned out it had the wrong type of computer installed.
So.. I sourced another El-Jet 4 in order to get the computer.

My plan is to copy the computer.

so i ripped the computer out, photographed it, documented all of the parts, desoldered, scanned, retraced in sprint layout....

but now i'm kinda stuck. I can export gerbers from Sprint layout, but to where? What would be the best route here? (pun intended) thank you
 

Offline mc172

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Re: Reconstructing schematic from two layer PCB
« Reply #1 on: January 03, 2020, 10:57:18 am »
Why do you need the schematic in order to make a copy? If you've copied the layout and know all of the component values, that's all you need.
 

Offline Rerouter

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Re: Reconstructing schematic from two layer PCB
« Reply #2 on: January 03, 2020, 11:02:21 am »
kicad can import the gerbers and allow you to edit them, and I suspect rebuild into a schematic + project, I just have not used it in this manner before,
 

Offline digsys

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Re: Reconstructing schematic from two layer PCB
« Reply #3 on: January 03, 2020, 11:54:58 am »
If you have all the board details, why not source a spare board or two off ebay / alibaba / aliexpress etc etc
I've found heaps of rare boards for various project I do, rarely failed to find one. Or do you intend to mass produce them?
Hello <tap> <tap> .. is this thing on?
 

Online mikerj

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Re: Reconstructing schematic from two layer PCB
« Reply #4 on: January 03, 2020, 12:43:21 pm »
Easy-PC can apparently do this, though it's a pretty expensive licence for a hobbyist.

Why do you need the schematic in order to make a copy? If you've copied the layout and know all of the component values, that's all you need.

If he's also reverse engineering the firmware then a schematic is going to be pretty essential to understand the operation of the board and debug it.
« Last Edit: January 03, 2020, 12:46:13 pm by mikerj »
 

Offline Yansi

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Re: Reconstructing schematic from two layer PCB
« Reply #5 on: January 03, 2020, 12:51:18 pm »
Problem is, it is not a two layer, but a four layer PCB, or you have a lot of traces missing.

Dead giveaway is the JP7 at the bottom, which is a RS232 connector, missing a GND connection from pin 5, that likely is going to an internal GND layer.
 
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Online mikerj

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Re: Reconstructing schematic from two layer PCB
« Reply #6 on: January 03, 2020, 01:07:19 pm »
Problem is, it is not a two layer, but a four layer PCB, or you have a lot of traces missing.

Dead giveaway is the JP7 at the bottom, which is a RS232 connector, missing a GND connection from pin 5, that likely is going to an internal GND layer.

Agreed, most of the bypass caps show only one pin connected, and C16 has no pins connected.  A large number of unconnected IC pins as well.
 

Offline tooki

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Re: Reconstructing schematic from two layer PCB
« Reply #7 on: January 03, 2020, 01:13:47 pm »
Besides, are the ROMs even copyable? If it uses a CPU or MPU with mask ROM or read-only EPROM, then even if you copy the board, it’d be useless.
 

Offline Prehistoricman

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Re: Reconstructing schematic from two layer PCB
« Reply #8 on: January 03, 2020, 02:43:04 pm »
Besides, are the ROMs even copyable? If it uses a CPU or MPU with mask ROM or read-only EPROM, then even if you copy the board, it’d be useless.
The current project I'm working on is exactly doing that. In fact, it's of similar vintage so maybe it's the same CPU? :o

"Is it possible to learn this power ROM?"
"Not from a Jedi mask"

Offline bigmacTopic starter

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Re: Reconstructing schematic from two layer PCB
« Reply #9 on: January 03, 2020, 03:39:46 pm »
Problem is, it is not a two layer, but a four layer PCB, or you have a lot of traces missing.

Dead giveaway is the JP7 at the bottom, which is a RS232 connector, missing a GND connection from pin 5, that likely is going to an internal GND layer.

Agreed, most of the bypass caps show only one pin connected, and C16 has no pins connected.  A large number of unconnected IC pins as well.

Ground planes on both sides. Removed for clarity. Good spotting though!
 

Offline bigmacTopic starter

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Re: Reconstructing schematic from two layer PCB
« Reply #10 on: January 03, 2020, 03:46:11 pm »
Latest gerbers uploaded. If anyone could give me a hint on how to proceed id be very thankful thanks
 

Offline ebclr

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Re: Reconstructing schematic from two layer PCB
« Reply #11 on: January 03, 2020, 10:03:05 pm »
If you are looking for a paid service those guys may help you

https://www.pcbic-reverse.com
 


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