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Hi Christian, Rollyn is absolutely right about the 2N3055. The original hometaxial process was switched to an epitaxial process. Unfortunately the side effects of this change were not considered

Looking for a Tek SC-501 scope part of the TM-500 system Thank you Jose Orgnero

Tom: Just for reference, you might show that I do have a copy of the Tektronix TS-4353/U Distortion Analyzer manual. I sold a dozen or so of these sets many years ago while owner of DiLette

Hi Max, For comparison I added a photo of the waveform at timing pin E to your album. Because of both the "+15V" effect and the temperature effect also Q32 might be suspect. As far as I can see Q32

It's been fifty years so I don't remember what current setting we used on the 575 to check the Hfe of the 0140's. This had to do with the HV osc in the 611 during B Phase in Plant 2 and Building 50.

Hi Max, At the more negative level Pin E resets the output to true zero in periods 3-6 and 9, by switching the pair Q86/Q88 such that Q86 conducts and Q88 is off. Pin E is the only Timer board output

I peaked into this HV circuit and its push-pull oscillator. It seems quite simple, primitive, It appears that before the negative HV appears there is plenty of current to the bases of the two

The timing board A1 rolled to revision -01 at s/n B080000, then to revision -02 at s/n B091450. R12 changed from 4.3K to 3K at s/n B091450. R26 changed from 15K to 13K at s/n B080000. R27 changed from

Thanks Rollyn for the trick. Will check that. As for your beta range, I suppose it is meant at its specific operation current within the 7603? Christian

Just discovered that R27 on the schematic is 510 ohm: on the board there a 2.0 kohm is mounted instead. My timing board has the code number 670-1320-02 so I don't have the latest schematic. I bought

Probably to decrease parasitic inductance on the power and ground pins.? Wirebonds make great inductors, and as the edge speeds increased, ground and power bounce became a problem.? V = L*di/dt.? I

74L series of chips should be checked for pin compatibility with anything else.? Not sure why they did that, but that's been a design problem for any number of years when substituting. Also, not all

That is true for other 74 series.? Should always check pinout.? Example, 74L,LS,W: 95, 85, 78, 72, 74 and maybe others. Carl Hallberg (W9CJH)

While checking the circuit I just discover that SN74L93 and SN74LS93 are NOT pin-to-pin compatible! I was using the "classical" 7493 datasheet from Texas Instruments datasheet and wondering how it

Work still in progress. Yesterday I put a normal metal film resistor in parallel with the other two (R65/R68). Measured total resistance now is 1,33 ohm. OK. Behavior is almost unchanged. With +15 V

It isn't that they were selected, the 2N3055 devices at the time were all homotaxial and had low beta compared to more modern versions. Even with this in play some HV circuits were cranky and wouldn't

I'm against it. We've got the curated (and excellent) Tekwiki. Marketing campaigns don't belong on any of the wikis.

Hi Bert OK it means in my case t906. Do you have the schematic for 2230 so that we can confirm the transformer. Thanks.

No, I mean the HV supply, the one that runs off the input AC and supplies the +40V. Shorted turns make it draw too much current.

Hi Bert Thanks for your concern and suggestion. But it operates normally with external power supply (in my case I used 38v dc across tp950 and tp940). Saroj