BT Cheetah similar to LO3000 - Repairing.

[M1ECY]

Hi Patrick,

Yes, I hope the same.

It will be interesting to see if the CPU cards in the Lo3000 are the same as in the Cheetah.

I might be able to source a replacement processor, but I am hesitant to order parts until I have a better idea of what is going on.

Do you know if there were extender cards made for the Lo3000, to allow tests to be carried out on the boards?

Sean

[Patrick]

Hi Sean,
I'm not aware of any extender cards. Would be helpful to build one to get better access to measure. The connectors are standard parts which should be easily available. Which supplier do you have in the UK (except RS) ?
Patrick

[M1ECY]

Yes, I think I can source the connectors - will take a look, and make a set of extenders up.

Think there may be an order with Richelt about to happen - they are better value than RS!

[M1ECY]

Connectors ordered - will make up a pair of extender cards.

Now on the hunt for a processor - this one is dead.

Sean

[M1ECY]

I have now made the extender cards, this will make checking the boards in circuit so much easier.

Luckily, there was a good supply of Eurocard connectors on eBay UK.

I have found a UK source of spare processors, so one is on order.

[M1ECY]

A couple so pics of the story so far

[M1ECY]

Work carries on slowly.

I have replaced the processor on the CPU board, now the green status LED is illuminating again.

I also traced a bad 74s04 chip on the smaller board that sits behind the CPU - this was replaced with a 74LS04 that I had laying in stock.

A couple of times this evening the bell sounded in the machine, and the screen rubbish changed, but nothing else has happened.

Awaiting a logic probe to have a look around the CPU to find out what is going on.

[Patrick]

Hi Sean
attached is the content of the M2716 EPROM on the CPU board for testing, hope this helps for the start (it also contains the telex number). I think that's the CDP (customer data prom) and there is not much in it. Changes are programmed into this eprom as well (using a configuration plug). I've never tried it before but it is an old loudspeaker connector as we have used them many years ago.

Regards
Patrick

[M1ECY]

Thanks Patrick, I will get a new eprom blown, and see if this helps the machine to do something.