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I think one of the subsequent modifications that Tek put out, which was the replacement of Q247, a 2N3739, to a more robust 2N4240 transistor, helped control some of these 'A Supply' power aberrations

Hello-- I'm offering FREE FOR POSTAGE plus the price of a cuppa coffee: one only 515/515A manual in good condition (plastic spiral binder chipped, front cover missing small piece). There's no serial

The vintageTEK Museum has this part available. Contact the Museum directly to pursue this. -- Bob Haas

Hi Christophe, HO display most likely looks at the pot being in all the CW position but the display of HO doesn't necessarily mean B-ends-A is active or not. They are two loosely connected functions

Ok, 9 volts is good.? What do you mean "alters the voltage on pin 2"?? The voltages on pin 2 and pin 3 ought to be exact within a few microvolts.? I am willing to bet that the voltage on pin 1 is

Hi Ozan, Let let me see what I can access tomorrow when removing the screw with the proper 1/16" allen key. I've checked the hold-off pots at the analog level (on the MUX input) and the dc voltage

Hi Ozan, Too bad I did not see these pictures in advance, they surely make sense now and I shouldn't have tried to pull the knobs at the first place. No, unfortunately, I can't glue the broken know

------- +140V is not in current limit based on voltage across R1716. As others commented probably +65V is affecting it. Do you have another scope? If you look at "+" side of C1723 and C1722 you will

Hi Christophe, My comments are based on 2467B but I think 2465 is similar enough. You will see that A/B switch is a separate slide switch. There is a plastic arm that controls it. Assuming there is no

----- Hi Christophe, My preferred way is not to pull the small knobs at all. Take a look at the photo album: /g/TekScopes/album?id=259435 You can slide off the knobs from shafts, when

Ozan, thanks for this comment as well. Any recommendation for cleaning the timebase switch? Christophe

If pin 2 of U1724A is at close to 9V when the nominal +65V line is at 43V then something is amiss with the divider chain R1735, R1736, R1737, or possibly U1724 is defective. You probably need to lift

Hi Jared , thank you for your response . I have tried looking for any posts from anyone that has actually done it for a very early TDS744 . Mine seems to be late in the production or has been

Hi Siggi, I just re-run exer 01 and it seems that the digital code affected to the hold-off pot is stuck at 6FFF whatever position I make it. The two digits BB and CC nicely change as I turn the

It may be possible to use TDS744A firmware on the TDS744. I have a TDS744A processor board here in my stock of spare parts that looks identical to the pictures I can find online of the TDS744. If you

----- B-ends-A is also a switch at Row7/Col1, pot is not used for determining B-ends-A. I agree that switch also needs to be looked at. Ozan

[email protected]> wrote: Note that I came to this conclusion by reproducing the "anomalous" display you had on one of your videos by setting my scope to B-ends-A and fiddling with the delay time.

Barry, I have a 7B80 I am looking at while typing this post, if that will help you. If you have not already cleaned the switches and sockets for the active devices, do so. That may make a difference.

Hey Christophe, I believe that the only problem with the scope is that the front panel is not read correctly. Check the holdoff pot, I believe you'll find that it's set to B-ends-A, e.g. all the way

Dear all, I ran many experiments and dc/ac bias controls on the board this WE but still could not trace some of the observed weird signals to any particular origin. I actually overlooked Mark's