Replacing Tektronix 465 range bulb

Boris Mohar wrote in news: snipped-for-privacy@4ax.com:

you have to remove the vertical preamp board and attenuators to access those TWO lamps,a PITA. I definitely would consider LEDs and resistor in place of the lamps.I think you could get away with one resistor for both LEDs.

the original lamps had 50K hour lifetimes.

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Jim Yanik
jyanik
at
kua.net

I think that you talked me out of it. Thanks.

BTW I just finished repairing the 307 modules.

At first I thought that it was the socket but it turned out that the pins become intermittent at the ceramic substrate solder junction. The gain and the frequency response was all over the place. I unplugged them, removed the lids and resoldered the pins from inside. I used some rather aggressive water soluble flux because rosin flux just would not work wit those pins. Washed them out with lots of water. It is rock steady now.

-- Boris

Boris Mohar wrote in news: snipped-for-privacy@4ax.com:

I got pretty good at it while at TEK. I got to know what screws and shields to remove,and had a flex nutdriver for the nuts bolting the attenuator frame to the front casting. Of course,I didn't have the option of skipping the job... 8-)

Amazing that you could solder them at all,the plating/tinning on those ceramic substrates always seemed to vaporize under soldering heat. did you use ordinary solder,63/37?

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Jim Yanik
jyanik
at
kua.net

I used 0.015" Kester 63/37 that contains organic water soluble flux. The flux is more aggressive that rosin flux. It is also conductive so everything has to be washed thoroughly. Having a Metcal soldering iron wit a tiny tip and stereo microscope made things rather easy. Time will tell.

-- Boris