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HP 1741A oscilloscope - restoration project

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calmtron:
I have a 1742A that have/had the same problem with the grub screws. The solution that worked for me was to use high quality hex keys, not-so-gentle tapping and lots of patience. Unfortunately i used cheap hex keys (one hung low ones) first and managed to strip the heads of the screws on one of the the timebase knobs.

I don't think there's any locking compound on the screws, it just looked like a bad case of galling / oxidation. Heating the screw seems like a good idea to try.

tautech:
The timebase shaft goes through 2 plug-in PCB's and have grub screwed shaft retaining collars.
Form memory the manual describes a method to remove these PCB's that entails removing that shaft, and that will allow you to clean the dials.

tggzzz:

--- Quote from: tautech on September 03, 2014, 09:43:48 pm ---The timebase shaft goes through 2 plug-in PCB's and have grub screwed shaft retaining collars.
Form memory the manual describes a method to remove these PCB's that entails removing that shaft, and that will allow you to clean the dials.

--- End quote ---
That's the mechanism, but the grub screws holding the knob onto the shaft is the problem - the legend is "between" the two knobs and shielded/protected by transparent plastic.

tggzzz:
Thanks for all the suggestions. The problem has now been circumvented...

The original 0.050" grub screws are still as immovable as ever, despite gentle thumping/heating, WD40, gentle force. I didn't want to apply too much of any of those since the knobs were functional and I was afraid I would melt/break adjacent plastic parts of the knobs.

In the end the other two grub 1/16" screws on the delayed timebase were persuaded to turn, which allowed me to disassemble the knob and insert a replacement legend. Sure the font and colour aren't right, but at least I can read them!

SAUL BRITTO:
Tekfan I need your help! I need to know if the focus unit of 1740A is the same as the 1741A.
I bought an unit of 1741A that the seller said me that, the problem was in the focus unit and I do have a dead one 1740A.

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