Bridgeport Series 1 CNC

[seemackParticipant @seemack]

Yes you can run from RAM but you need to transfer it there first by putting in the code 961025. This puts you into the Markers and plc but you need a screen to go down that path.

Unlikely you have bad epproms but only way without screen is to take them out and read them.

[tomcncParticipant @tomcnc]

 

If I were to take out the eproms and read them, how would I know they were bad. I don’t have the original stuff that was programmed into them.

 

I have been going around the board with the TMS 9937 chip (a display driver). The board also contains a TMS 9995 (a

microprocessor).

The DS pin  (data strobe off the top of my head) has a signal on it but the CS (chip select  has not).

I will probe further. It’s a bit like looking for a needle in a haystack, in the dark, and not knowing what a needle looks like (for me anyways).

I have wheeled out my logic probe. It’s been a while. It is homemade. It has three lights. One lights if the pin is +5.

Another lights if the pin is 0V and the last light lights if there is a pulse on the pin.

 

Can you substitute a TNC 155B for a TNC 150B do you know. There is one on ebay at not too outrageous of a price.

https://www.ebay.co.uk/itm/327265911229 (about £350)

 

Might be better to start spending money on a more modern refit.

 

Thanks,

Tom

[seemackParticipant @seemack]

Hi Tom

It’s not giving you much joy yet, is it.

I have the same machine as you,  and it originally had a 151B on it. I have updated to the 155B due to screen issues and all connections are the same except the screen connections, which is a DB9. I would download the service manuals for both and compare both. My guess is it will be a straight swap as yours is a B model also.

That 155B looks in good condition, so it’s quite a good option to get your machine going without a lot of changes. And at that price it still makes your machine a good buy provided it is a working unit.

Not that your screen will not work on the 155B as it has a different Hsync and Vsync, but I have already posted earlier how to get a modern HDMI screen working.

[seemackParticipant @seemack]

A final check which I may have already said is the LEDs will all come on initially and stay on while it’s going through it’s check. Without the screen it’s hard to know what’s happening but if everything except the screen is OK then waiting at least 20 seconds then press the CE button at least twice (more doesn’t matter incase there are other messages on the screen you cannot see) then all LEDs should go off as you are at the MP entering prompt and your controlis good. If the LEDs stay on then you have and startup error on the screen which you cannot see.

[seemackParticipant @seemack]

How did you go @tomcnc?

[tomcncParticipant @tomcnc]

 

Not too far!

 

I got side-tracked with other matters.

Just to recap. All the red lights light and stay lit no matter how long I wait or what button is pressed. No sync. signals coming from the display plug.

I have purchased a logic analyzer, a 24 channel, el chepo, that plugs into a USB on a PC and I am waiting its arrival.

I have been going around the board that contains the display driver with a continuity meter and then an oscilloscope to see if I can trace signals (the V and H sync. for starters) back from the dislplay output D plug (centronics plug) that the display plugs into. As you trace back the lines, everything gets more and more hard to understand with everything ‘all over the place’.
There seems to be no sync. signals coming from the display driver (40 pin chip).
Is there need to have things so complicated I find myself asking? I am in no position to criticize! One of the signals I traced goes into a JK flip flop and it will not be easy to figure out ‘where it goes from there’. (that’s not even a proper way of putting it).
The signals are going through inverters, buffers,  combining with other lines through AND gates, FF’s etc.

I have not got back to it for the last fortnight.

It would be good if I could power up one board on its own simply by putting power to it when it is out of the TNC mother board. It is very hard to get wires connected to points on the board when all the boards are plugged into the mother board. There is not enough room for a 40 pin ‘clamp’ + wires. I will have to use some other method to get wires attached to chips. Perhaps solder upright pins to the pins of the chips so that I can attache spring loaded hooks. Or if you could work on a one board at a time. (Impossible I would imagine).

There are two similar processors in the TNC 150. One is on the board which has the display driver. The other one is on another board.
Which processor would start up first (if that is even a sensible question).

I would in inclined to think that one would be a slave and the other a master?

 

Cheers,

Tom

 

[tomcncParticipant @tomcnc]

 

Having thought about how I would attach connectors to the boards that are spaced close together (too close) I have decided I need to obtain some DIN 41612 Connectors and put some ribbon cable between them. I can then plug out the boards, plug the board into the connector on the ribbon cable and plug the other end of the ribbon cable into the mother board. The boards can then be put  flat on the bench and all still plugged into the mother board.

Most of the boards have two 64 pin plugs. Four plugs will be needed per board, one plug at each end of the ribbon cable.   You could leave one (or perhaps two) of the boards plugged into the mother board and still have room on them to work.

Details of plug type on mother boar attached.

I need to get cracking.

Tom

[seemackParticipant @seemack]

That’s a good idea.

Don’t forget to put your results up.

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