Re: preamp problems with the AMX
Deane D McIntyre (dmcintyr@acs.ucalgary.ca)
Wed, 29 Mar 1995 14:10:03 -0700
In message <0098E1A8.434B8DC0.1@physchem.kth.se> Peter Stilbs writes:
> During the last 1.5 years our proton preamp on the AMX-300 has broken
> down at least 10 times, as we remember. This seems to happen between
> experiments, and not during them. In 10-15 % of the cases the signal
> level is down by a factor of 256/16 or so, and in the rest of the cases
> it is completely dead, and one cannot even wobble - RG increments
> up to 4096.
>
> A repaired preamp and a modified transmitter (that would not 'ring')
> were installed this afternoon - worked fine for a few hours, and
> then the same story again ...
>
> The thing is getting annoying, although the instrument is still
> under warranty, and we get a new preamp in a few days ....
>
> Has anyone of the BUM subscribers had any similar experience, or
> knows a possible cure for this problem ??
>
We have had the same problem with the "old" style preamps in our
AM-400 and AMX-500. By "old" style I mean the box like preamps which
must be removed and replaced with a reflection bridge in order to tune
the probe. As you have a newer instrument with wobble I assume that you
have the new style preamp, and the following likely will not apply to
you.
In the old style proton preamp, there are two female BNC connectors
on the front labelled "Transmitter" and "Probehead", and two short
cables with male BNC connectors emerging from small holes in the front
of the preamp that are normally connected to the female BNC connectors.
The leads from the female connectors are soldered to the PC board in the
preamp. One on the AMX-500, and a few times on the AM-400, the proton
signal would almost disappear. Problem was due to a broken solder
joint where the leads (going to the female BNC connectors) was soldered
to the PC board, and a bit of solder solved the problem. Seems that some
people were removing the preamp by pulling on the leads at the front,
putting stress on this joint inside............
Cheers, Deane D McIntyre
dncintyr@acs.ucalgary.ca