Hi Max,
Those pictures helped me a lot to understand what you previously said in words!
Just for comparison I added an annotated picture to your album (and somewhat destroyed the order).
You said R90 was almost CCW. But that produces almost the lowest arming current. When there is no output pulse in period 8 I would turn R90 CW, not CCW.
It struck me that at higher "+15V" there is something wrong in the output level. Only during the reset periods 3-6 and 9 should the output be true zero. In the "unused" remaining periods there should be some positive level as shown in your pictures up to 14.5 V. That's due to current via R97+R98. I suspect a state fault in comparator Q86/Q88. The zero output voltage also appears in period 7 at higher "+15V", probably due to the same fault.
Albert
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On Wed, Jul 1, 2020 at 11:21 PM, unclebanjoman wrote:
Hi Albert,
sorry for the late reply but during the week I work hardly and in the evening
I am too tired to take care of my Teks and I want to avoid mistakes.
Anyway I took just now some photos of the pulser while operating, varying the
positive supply between 13.5 V and 15.5 V, in 0.5 V intervals.
I've created a new photo album, you can see it at the following link:
/g/TekScopes/album?id=249667
NOTE: The TD is the original one, carefully reassembled .
The optimal voltage seems to be around 14.5V. The pulse are stable and
clean.NOTE: The TD is the original one, carefully reassembled .
You can see, at 15V the impulse disappears and only the impulse of pre-bias
with the ramp remains.
The pot R90 (trig level) is almost fully counterclockwise (it's in the
original position when I bought the thing).
At 15V ,turning it completely ccw I do not get appreciable effects anyway
I think the resistors, one or more, changed their values,
In the weekend I will check carefully their values.
I can confirm that the couple of 2.7 ohm resistors in parallel give me a
reading of 2.8 ohm and not 1.4 as it should be ...
Max
