Thank you I will definitely check that.?
The rubber feet inside on the bottom boards all dissolved into goo, which I¡¯m seeing more often. I fear many older plastic items will meet this fate over time. I cleaned up and should check operation, maybe the goo affected a high impedance circuit like a reset line. BTW if this happens to you I found that some acetone and a brush with paper towels to catch the runoff make quick work of cleanup and leaves the board looking like it just came from the factory.?
These things play out in slow motion for me as I only have a short time each evening to play.?
Peter
toggle quoted message
Show quoted text
On Oct 10, 2018, at 2:55 PM, Pete Manfre <
pmanfre@...> wrote:
CHeck for a bad bleader resistor on the reset line.? I have seen
that same thing before.? Once it charges it keeps the processor in
reset.
Pete
On 10/10/2018 2:51 PM, Peter Gottlieb
wrote:
No I¡¯m happy enough just amazed! ?And I will end up learning a
bunch more about these instruments as well as ending up with a
better capability unit.?
Of course it would be even better to end up with *two*
working units, right?
While I wasn¡¯t able to find a direct replacement YTO for the
first unit, I did retrofit a different model but it doesn¡¯t seem
as stable as I imagine it should be. Maybe I¡¯m expecting too
much from an open loop? ?
The YTOs in these units are mounted in a mu-metal shield but
the replacement it physically too large for that and I even had
to make a new mounting bracket.?
Once I clean up the second unit and dig in and get running I
may have more questions from the operational side but for now
it¡¯s just some time on the bench.?
The unit did fire up when I first powered it on but gave an
error (maybe 80?) so I hooked up a noise source to see if that
was the issue and hit instrument preset but then it stopped
responding and further attempts to start it showed a locked up
display. Thus my initial guesses at the controller or power
supply or mechanical connection.?
I know the theory of NF measurement just never used an
instrument to play with it on the bench.?
On Oct 10, 2018, at 2:38 PM, Pete Manfre <
pmanfre@...>
wrote:
BTW¡ if not happy I can take it back.?
P
On Wed, Oct 10, 2018, 2:27 PM Peter
Gottlieb <
hpnpilot@...>
wrote:
A
while ago I bought a 8970B noise figure meter but never
got it running due to a bad YTO. Recently, thinking it
would be interesting to play with, I bought another for
parts, figuring I would make one good one.
To my surprise, internally they are quite different!?
The YTO in the second one is completely different, with
an entirely different frequency range. Hmmm, that¡¯s
interesting...
It turns out that the second unit has option 20, meaning
it can go to 2 GHz. I am amazed how different these
units are internally!
In any case the initial problem in the second unit
appears to be in the controller which usually doesn¡¯t
run at all. Or maybe power supply, I haven¡¯t dug into
it. The unit was dropped hard at one point in its life
as the back panel where the transformer is mounted is
bent so I¡¯m going to look for a mechanical cause for the
problems and instead of looking to fix the first unit
concentrate on the option 20 one. Hopefully the YTO
wasn¡¯t damaged in the drop.
It is just interesting to me that the slight increase in
the top end frequency required such massive RF system
changes.
Peter
