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Re: BBC Model B Very Ill
Posted by Rich on Tuesday, November 19, 2002 at 17:44:34
Ian Wolstenholme wrote:

Thanks for your help - sadly I have tried all of the above without any luck. I have even tried switching on with various ICs removed one by one but no success. I thought the problem might be associated with the System 6522 VIA which drives the keyboard and sound chip amongst other things but I have replaced the 6522s with chips from a working Model B but the problem persists.

The two 6522 chips (IC3 and IC69) are very slightly different - one is an SY6522 and the other an R6522-31. These are in the opposite sockets on the ill BBC to the working one but even swapping them round does not seem to help.

Any more ideas?



Ian

The next thing that comes to mind will be the PSU. DONT fiddle with it unless you are totally confident you KNOW what you are doing as you will get one huge belt off of it.

As for the 6522's I cant see any reference to different versions of the chip in the BBC B service manual it just calls them 6522's they may be by different manufacturers.

Rich.

It could be a poor voltage on one of the lines to the board, If you know a local electronics firm they will probably be able to test it for you. If not try to source another and swap it out to see if it cures the problem.

Rich.
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