Products > Test Equipment

HP 1741A oscilloscope - restoration project

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bilko:
It looks like the scope may have been stored in a damp basement. Good look with the restoration and its great to see the progress shots.

tekfan:
More progress.

The vertical preamplifier board removed. One custom HP hybrid can be seen in the middle of the board.


Gold plating has to be cleaned on the vertical attenuator contacts.


Attenuator cam switch gold plated fingers. These move up and down in a certain sequence when turning the volts/div knob and
route the signal trough attenuators and compensation networks.


Bare frame without any circuit boards ready for assembly.


Front panel being cleaned. Looks nice without too many scratches ;D.


The things that go around the buttons being cleaned. The LEDs are probably going to be replaced because they are now 30 years old and quite dim.

tekfan:
Now the scope is assembled. Knobs still have to be put on.


All the tools and crap leftover after assembly


Ready for a power up without the CRT. A few knobs are still missing because I had to drill out the screws because they rusted and couldn't be removed normally. The knobs will be tapped and a slightly larger screw will be used.


First power up. The transformer makes a terrible buzzing noise. The problem was a shorted rectifier.


No rectifier available. What now? Four diodes of course! It looks ugly but it works. Four 1N4007 diodes were used. The reverse breakdown voltage and current is higher than the original rectifier so they should work nicely. After that the scope turns on and all the power supply voltages are present and nicely regulated.


I connected the output amplifiers that originally connect to the deflection plates to another oscilloscope in XY mode with differential inputs.


Here I'm feeding a sine wave into channel 1 input and YAY!!! The amplifiers work and I get a display on the external scope.


Scope in a scope. This is what I would see if the CRT were in the scope. Now I just have to be patient and wait for the CRT to come from America Hope it doesn't break on the way here :'(


Should I do the calibration procedure as well?




alm:
The service manual may give give more details, but I would at least expect that you have to go through geometry and storage circuit adjustments after a CRT replacement. If you have the equipment, you might as well do a full calibration for peace of mind.

slburris:
Very nice!  Of course while I'm staring at the photos, I can't help but notice
the Datron 1072 multimeter in the background.  What's that, a 7 1/2 digit
meter?

I'm about to try for a scope repair myself, on a Tektronix 2246.  It works,
but the trace is noisy, even when the input is grounded, so I'm suspecting
high ripple in the power supplies.  Probably at least a nice recapping job
ahead of me.

Scott

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