Racal 9903 / 9904 counter timer repair

[Martin Whybrow]

As mentioned in a previous post, I have a Racal 9903 counter timer that I'm
trying to repair; I found a manual that, unfortunately, has a vital section
of the schematic missing due to a bad scan, but I have determined that the
LSI device IC5 is probably at fault. The IC in question is, of course, a
custom part, a Ferranti manufactured 22-4601. Anyone have any idea where I
might get one? Not holding out much hope as it's a 30 year old device, but
you never know.
Martin

 

[N Cook]

As mentioned in a previous post, I have a Racal 9903 counter timer that I'm
trying to repair; I found a manual that, unfortunately, has a vital section
of the schematic missing due to a bad scan, but I have determined that the
LSI device IC5 is probably at fault. The IC in question is, of course, a
custom part, a Ferranti manufactured 22-4601. Anyone have any idea where I
might get one? Not holding out much hope as it's a 30 year old device, but
you never know.
Martin

What is the fuction of the IC in block function terms ?

 

[N Cook]

As mentioned in a previous post, I have a Racal 9903 counter timer that I'm
trying to repair; I found a manual that, unfortunately, has a vital section
of the schematic missing due to a bad scan, but I have determined that the
LSI device IC5 is probably at fault. The IC in question is, of course, a
custom part, a Ferranti manufactured 22-4601. Anyone have any idea where I
might get one? Not holding out much hope as it's a 30 year old device, but
you never know.
Martin

that is a Racal part number it is the same LSI in my 9913 manual.
Looks possible to workaround with a multiplexer plus divider TTL etc

 

[Martin Whybrow]

that is a Racal part number it is the same LSI in my 9913 manual.
Looks possible to workaround with a multiplexer plus divider TTL etc

The manual I found has a missing section right down the centre where IC5 is
located so I can't see all the interconnections; the circuit description
indicates it acts as a counter, multiplexer and display control logic so
there's a good chance it could be replaced with some TTL. I'll contact you
by email about the manual as I see you have a 9911 manual on your list,
hopefully it's fairly similar.
Martin