Re: Repairing my Tektronix 454 oscilloscope need some advice

Albert Otten

I would first of all test the waveforms at terminals 7, 9 and 10 and check that the amplitudes have more or less the same ratios to each other (and perhaps to the 1 V pp) as in my case. Your 52 V is really to low, so check it against the (negative) peak voltage at terminal 9. The secondary waveforms may show a slightly flat negative peak because of diode conduction, but only slightly. At terminal 9 the negative "flat" peak was about 5 V smaller than the "round" positive peak.
Can you measure the primary current? Perhaps your generator can show the current drawn?
For test HV diodes see the message by Chuck Harris or see message #163125).


On Thu, Feb 20, 2020 at 09:42 PM, Victor wrote:

This afternoon, I was reviewing the measurement done yesterday and found a
problem (intermittent connection) with the cable connecting the wave generator
to the Q1430 collector. After repair it I test again my 454 and now with a
1Vpp on the collector of the Q1430, I get 52V at the HV test point.So, with
this result I believe my HV transformer is Ok. I have a doubt about the HV
diodes... what do you think ? By the way how do you test HV diode,I understand
you cannot do it with a regular tester.Tomorrow before made the test that you
recommend today. I would like to review the HV CRT circuit to see if any
resistor or capacitor are out of specs (transistors have been test and look
Thank you,Victor

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