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8032-SK Restoration

daver2

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Yep, always safer to use pull-up resistors. +5V directly can kill (semiconductors) if you get something wrong!

Dave
 

ScottishColin

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I would show you a photo of mine, but I'm a bit embarrassed by it. I found it a bit tricky/fiddly to be honest to make it, but it came in handy.

Colin.
 

Gary C

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:)

At £4 its hard to think of any reason not to get one of these NOP Generator

As an aside, has anyone tried a 6845 in place of the 6545. I believe they are 'almost' identical ?
 

Gary C

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I do note that it uses the big round pins and would bugger up a PET socket, so I will have to use an intermediate thin pin 40 way socket to stop it damaging the socket on the board.
 

ScottishColin

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I do note that it uses the big round pins and would bugger up a PET socket, so I will have to use an intermediate thin pin 40 way socket to stop it damaging the socket on the board.

Just to let you know it arrived today and has normal pins, not turned pins so it doesn't have the issue above.

Colin.
 

Gary C

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Oh good :)

We have another 8032 with the tynemouth board and that wouldn't work because the board with its big turned pins had destroyed the socket and the picture looked like this was similar.

No need to worry then.
 

ScottishColin

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Oh good :)

We have another 8032 with the tynemouth board and that wouldn't work because the board with its big turned pins had destroyed the socket and the picture looked like this was similar.

No need to worry then.

I have one of them but due to a faulty socket, I had already removed and replaced the 6502 socket with a turned pin one anyway. I have still added an extra socket on top in an attempt to protect the turned pin one I soldered in because I don't fancy ever having to get it out.....

Anyway - good luck with this one; I will watch from a distance.

Colin.
 

Gary C

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Right

NOP generator installed.

I am not seeing consistent waveforms on AB12 and above. There are long and short ones which I did not expect. I'm not getting any activity on RDY, NMI or IRQ. Don't think anything else on the board should be grabbing the address bus at the CPU pins ?

Should I just get solid 50-50 square waves like I expected ?

Pin 25 (AB15) looks like this

NOP pin25 (2).jpg

and detail of the pulses down

NOP pin25.jpg

odd
 
Last edited:

daver2

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Like you say, odd...

They should follow the logical progression of AB0 through AB11 - with each higher address line being half the frequency of the previous one.

There is a 'grey area' where one address changes into another of course - but that is quite a small time frame in comparison to the overall cycle.

Dave
 

Gary C

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Grrrr

I decided to buy a NOP as it was only £4 and has LED's for NMI, IRQ,RST but !!!!!!!!!!!!!!!

They forgot to cut off the data pins, so while the resistors were connected, the data pins were also connected to the motherboard !!!!!!!!!!!!!!!!

Pins cut and now I have nice wave forms

Laser Business systems ROP generator more like :)
 

Gary C

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Picture on their website shows the pins cut off :)

Anyway, all addresses look good through the buffers and at the crtc the select line is being pulled down along with the ba0 and ba2 lines. Br/w isn't active of course but it's looking like the crtc itself
 

Gary C

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Step by step. I have no video signal at J7 pin 1 or at UC2 pin 9. Seems to be at pin 1 of UD4 but doesn't come out at pin 12. Pin 1,2 & 13 have signals, but never seem to be high at the same time, which means pin 12 will always be high.

Really need a three channel scope :)
 

daver2

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NO ROW comes from the CRTC via UD1 so should be relative simple to debug this line

Ditto with DISP ENA - that also comes directly from the CRTC.

Dave
 

Gary C

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I believe the 6845 is a substitute for the 6545 in the PET application but I suppose its just possible there is a conflict there.

Anyone tried one in an 8032 PET ?

Might just buy a 6545 anyway to keep it as near to original as possible.
 

dave_m

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I believe the 6845 is a substitute for the 6545 in the PET application but I suppose its just possible there is a conflict there.
There is a minor difference, but in the mode that the PET uses, they are compatible.

Before I would replace the CRTC, check the NOR gate UD1 pin 1, 2, and 3. Pin 1 should be high during the first eight horizontal scans of each character line with pin 2 and 3 low.

http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/univ2/8032087-10.gif
 
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