[Test-Equipment] PHILIPS PM5100/06 LF GENERATOR INFO , SCHEMATIC WANTED

[John Byers]

The PHILIPS PM5100/06 is a vacuum valve (tube) instrument of quite small
dimensions covering 15Hz to 150kHz, though the dial extends to cover more
on each side  It is variable capacitance tuned with a very well shielded and
well made
air speced variable dual capacitor for noise free output when rotated
I have two of these instruments which I was sure I would have to repair
and refurbish, but you can imagine my surprise to find that both of them
were still working well and close to original specs, with very low
distortion
figures (HP334A agreeing with Tek A501A dist analyzers, less tham 0.18%
unadjusted)
and very stable, low frequency and amplitude drift characteristics after
30min warmup
Further, when opening up, both still had the ORIGINAL 'VALVO' VALVES (TUBES)
FITTED which all were inside specs for their gm !!!
I dont have a manual or schematic but I believe these may have been produced
by Philips in the early 70's
I thought I would have to replace at least the electro caps, but I found the
HT smoothing caps not only in good health but had BETTER ESR than brand new
low ESR types I had
bought for replacement !!  (measured at 100Hz, 1kHz and 10kHz)

Does anyone have a schematic of the 5100/06 or at least can satisfy my
curiosity on at least one adjustment?
There is an access hole on the side of the cabinet for a wire wound rheostat
which is
in series with the filament supply to the twin triode oscillator(E182CC)
What is the purpose of this and how is it set up?  I can think of only two
answers 1. To prolong the life of the valve by slightly underrunning the
filament
        2. To increase the input impedance of the (Wein?) triode oscillator
Can anyone tell me the actual reason?
Ime going to keep the 5100/06 as it has 2 sets of output terminals, one at
600 ohm
and the other at 15 ohm. The unit can place more than 10v across each at low
distortion.
which is difficult to do with solid state generators
This is a well designed, fine little instrument
A schematic would be really appreciated together with setting up details for
internal adjustments
A search of the web was negative
Anyone?
Thanks
John