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Hi Albert, Found the culprit. The function of Q32 is not explained in the manual. Since you pointed toward Q32 and its "strange" function, just for curiosity I pulled it out. Result: the pulse output

I now have all the latest 4041 System Controller and 4041 DDU service manuals scans available. Photos of the front page of all three manuals are in the forum photos - just search for 4041 to find my

Did you find the 0.01uF X2 mains filter cap hidden underneath the mains input socket (on the main PCB)? You have to remove the socket to see it clearly and to replace the cap. Regards, John

Hi Albert, thanks for your new photo. I've added other two photos, which shows clearly that the signal at pin "E" it deads at +15V, and so the TD was killed also. Measuring the signal on two bases of

I got a few more requests for additional scope calibration items for Tek, so added them today, along with an unusual 4 channel analog/digital Tek 2216. I bet you haven't seen one of THOSE before... I

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