Fabio,
The manul states the inner temp can go up to 75 degrees, i measured over 50 so
extra heating it looks not logical to me. It would be for sure more easy as
cooling.
Most important will be to get the temp stabel. A closet like joe suggested
would be an option. You could let the front come out, that will give some temp
leakage but an improvement. The meter produces enough heat to warm the closet
and if you keep that temp at for instance 35 degrees all you need is a
tempsensor and a fan ( with adjustable speed) . As long as the room temp stays
onder 35 degrees there would not be a problem. I think I will try that.
Replcing switches ect is not an option, no room. But instead of the rackmount
ears I will mount to alu profiles and mount the current inputs, Reference input
and bananabusses instead of the second input on the back. I make a small hole
in the side to lead the wirer out. On the other side I mount a profile with a
powerswitch and two bnc panel troughputs and cables to the trigger bncs.
I opened the meter and followed the checks of chapter 4.
First problem, I coul not find if i have pcb 3 or 13 and 5 or 15
40348C 70610503X D so i think it is 3
11134F 70610505Y F so i think it is 5
B11091 70610508X B is the clockboard
The meter has a date stamp 1987 so i think it is 3 and 5
The PROMs have other numbers as stated , they are toshiba TC57-256D-25 the
others are 2516-45JL from texas instruments and SP1 is closed and SP2 is open (
as for type 2764)
Allmost al solder bridges that should be open are soldered, some i can not ind
and some are there but not in the manual.
All voltages ar within specs. Tested it with a variac like the manual tells.
So this is good. But then i measured the clock voltage TP402 That is a bit low
2.7V instead of 3V (+/- 0,2) so i should adjust coil L401 but i can not find it.
This meter is ex-belgium army, so it looks like it has some mods or is a very
early model.
So this makes adjusting everything a bit tricky.
Thanks for the offer but the key I have more or less works. It is a bit
frubbling but calibrating is not something I do every day and most times i
leave the key just in the cal position.
Fred PA4TIM
Op 22 aug. 2012 om 09:58 heeft Fabio Eboli fabi...@quipo.it het volgende
geschreven:
Hello Fred,
I'm certainly not expert here, but your idea of ovenizing
the 7061 made me think aloud :)
So here are some random toughts.
My 7060 has no feet on underside and I noticed that the
unit, zeroed on 10V sitting flat on its bottom, drifted
badly if raised a pair of cm from the table, so the first
consideration I can do is that the 7060 must be calibrated
exactly in the same thermal equilibrium than in use.
The 7061 is a different beast but the internals are not too
much different from the 7060.
The top and bottom covers are thick plastic covers, so they
isolate a little the unit from the outside world but do not
spread the heat around. The front and back panels are aluminium
so probably if there is temperature difference between outside
and inside, the gradient should be maximum near the panels.
The infamous Fischer connectors (I hate them ;) should make
a very good job at maintaining no gradient between connections
of the leads, so thermocouple effects should be controlled well
by these connectors, also if there is a strong gradient on the
panel. Naturally this is just a guess from me, no mesurement
involved, this is your speciality :)
The last consideration is that if I would try to heat the 7061
I would try to avoid at any cost hot spots, so the heating should
be spread on a large surface.
As a first try I would place an aluminium plate on the underside
of the instrument, in contact with the outer side of the plastic
cover, and try to heat up this plate, for example bolting on or
gluing transistors on it in a mesh pattern.
As a second step I would try to isolate the heating plate from
the outside with foam. Later I would check the meter behaviour
and perhaps see what happens with another heat spreader-insulator
on top cover.
The problem is how to properly test it, you should have a sort
of climatic chamber, in winter it's easier, just grab a pair
of big enoug cartoons, one into the other and heat up the air
between them :)
Ok this is enough fantasy at work :)
As for the key, I can duplicate mine and send it to you,
if you want to try another key.
Fabio.
Fred Schneider pa4...@gmail.com ha scritto:
So this is normal, hmm, my shop can be over 30 degrees when it is a hot
summer and 15 degrees in a Cold winter so keeping it powered will not help
in my case ( i am just an amateur voltnut so climatize my room is no option.
But The service manual describes a test were you run it at 15 degrees, then
at 38 degrees and then adjust diodecurrent until you get the best tempco.
That would imply the thing should not react much on a few degrees.
Would it be an option to ad tempcontrol
