HP 9915A failed 8048

[Curious Marc]

Awesome! Congrats to everyone involved!
Marc

> On Mar 28, 2022, at 12:24 PM, js--- via cctalk <cctalk at classiccmp.org> wrote:
> 
> 
>> On 2022-02-25 16:09, js--- via cctalk wrote:
>> 
>> Hi, folks.
>> 
>>   I've a HP 9915A computer with an interesting problem.   The motherboard utilizes a ceramic Intel D8048 chip.   The problem is that this 8048 has a crack right across the top middle of it, and half of the top of the chip has begun to separate.
>> 
>>  Powering up the machine as-is unsurprisingly results in no activity.   HOWEVER, if I push firmly on the cracked area with my finger the machine starts to operate normally.   All appearances are that clamping down the separating piece of the chip re-establishes any broken wire connections within the chip.
>> 
>>   I've obtained a replacement P8048AH.   My question is: do these chips simply swap like a CPU, or -- as I fear -- is the 8048 a pre-programmed piece?    More simply put, is this a repairable problem?  Or am I SOL?
>> 
>>   Any thoughts welcomed.
>> 
>> - John Singleton
>> 
> 
> 
> Hi, folks.   With the help of the extremely talented people here, the far less talented me was able to repair this seemingly impossible problem and get the 9915 functional.
> 
> The process was to:
> 
> 1) burn a new 8748 CPU with the 9915's 8048 ROM code.
>   I used a Data I/O 2900 for this purpose.
> 
> 2) remove the remnants of the original 8048 CPU
> 
> 3) install a new milled 40 pin socket
> 
> 4) install the 8748 into that socket and power-on test.
> 
> 
> Thanks to Paul Berger, Will Cooke, and Wayne S for their useful suggestions.
> 
> A very special thanks to Tony Duell for offering to go to great lengths to help.
> 
> A very, very special thanks to Dave McGuire for having done all the hard work in retrieving the 8048's code to begin with (which he had done already for someone else), then providing the 8048 ROM code to me in hex format, plus guidance on how to fix the problem all the way through.
> 
> - John S.