Hameg HM207 scope
This is a very usable transistorised scope for hobbyists and small
workshops.
It has a 10 MHz vertical bandwidth and a time base with synchronisation
that works surprisingly well.
Hameg sold it either as a kit or as a factory-made unit.
The kit featured in a review in Radio Bulletin in March 1974.
This scope belongs to a friend of mine.
He said it had stopped working and I volunteered to fix it.
I greeted the opportunity to open up and examine one of these
small hobby scopes I had been reading about when I was young.
I opened the case and started to examine it.
The soldering work looked excellent so I think this scope is either a
factory-built specimen or it has been assembled by a very experienced hobbyist.
As I had no circuit diagram, I drew the circuit digram of the
vertical amplifier myself.
Interesting, much like the last DIY scopes described in the magazines
in the seventies.
Analysing the circuits of the Y amplifier by following
the wiring, I found an input stage consisting of two BF245 FETs.
At first I thought the input stage
was blown.
But after some examination, I found the input switch
(positions AC/Gnd/DC) to be interrupted.
Replacing it cured the scope and now it is working fine again.
In March 1974, an article was published in the Radio Bulletin magazine
about this nice little scope.
It contained a reviwe, gave a discussion of the assembly of the kit
and listed the specifications.
RB did not publish the circuit diagram, though.
Fortunately, I was able to fix this HM207 without the schematics.
