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Whilst looking through my test equipment inventory a bit of trivia came to mind regarding a unit that I had acquired back in the late 90s off of surplus. It is still tucked away in storage and I had

O.K Albert, . I've found theDennis' documents you mentioned on how to build a complete dummy supply load for the 7104/7854 SMPS. I will buy the necessary resistors... :-/ BUT the document only

My Tek485 has been sidelined for some months with a power supply issue - the inverter keeps cycling on/off. I've fixed similar issues a few times but this one has me foxed. Balance node shows a short

In cases where you need to measure a transistor (or other device) at extremely low currents, electrical noise or hum pickup and inter-electrode capacitance can become so great it completely swamps the

Hi Dennis, Thanks for the feedback. Any ideas regarding the 5114 - D14 mainframe; why that number was skipped or who'd be the designers or subject matter expert(s) regarding that line of equipment?

Hi, The 5000 series mainframes were, in part, designed to be low cost products. As such they were very attractive to other manufacturers as the display portion of the product they developed. Often,

More. You can check diodes by making differential measurements across the diode. I found two bad power diodes this way. You can do this measurement while the unit is in tic mode. I found the diodes

You need a load of about 50W, possibly equally shared between positive and negative outputs. Either on the raw voltages or after the regulator board. You need to check all caps and diodes on the

Hi Max, Well, I didn't say that the load MUST be distributed. For me reasons to do so were that I could use available 5 W and 10 W resistors and that I wasn't always sure about the maximum current an

To G?ran: OK, shorted pin 13 to ground. Still same result: the SMPS refuses to starts and ticks herratically. I've checked the signal across A and K of Q30 (the PUT): it fires up every 20 msec (I

In the archive there is another document "7k_PS_currents" describing typical loads, also scanned by Zenith. In my case the total load was 50W. I connected a number of power resistors to the various LV

Hi Max, From my own experiments with a 7704A SMPS I remember that it needed a much heavier load for proper operation. I tried with loads on the HV outputs and also with loads on the raw rectified

Thanks for the tip!

That’s what mine looks like.

In the archive there is a document scanned by Zenith, a specification 155-0067-02, pdf. For pin 13 there shall be two conditions: Logic "0": 0.0 - 0.05 V Logic "1": 0.85 - 10 V Well, if you dare you

The "filter on" position is useless except for very low sweep speeds or manual scanning - not normal operation. I found the same sort of thing when I was refurbishing the switches (Deoxit-treatment)

Following the Goran suggestion, I've shorted to ground pin 2 (FAULT SENSE). The behavior was the same: random burst interspersed with single pulses. Probing with an oscilloscope the pin 13 (Current

Hi all, Interestingly, after acquiring the Pacific Measurements 1038 system, I found the Tekwiki had a reference regarding using the D10 and D11 mainframes. I noticed the D14 which I had wasn't noted

/g/TekScopes/album?id=89780&p=Created,,,20,2,0,0 This is what the display filter does to my screen

I've gotten this 7L5 worked over to where it is mechanically squared up and fits properly in the mainframe. It took a lot of blacksmithing and modifications, but it now looks good, and is apparently