Here's some softcore Tek pern for ya....
I'm about to dig into this 475 vertical calibration, find and replace the faulty ceramic trimmers, then calibrate the vertical and adjust the other circuits as needed.
Today is my last day off for the next two weeks so I'm hoping to get it finished up today.
That’s begs a question: what’s a group of tektronix scopes called? Herd, gaggle, flock?
That’s begs a question: what’s a group of tektronix scopes called? Herd, gaggle, flock?
Here's the B&K 3010 Function Generator pron. It powered up fine and was working for about 5 minutes then it quit. No smoke...just quit. So I'll have to get a schematic and figure out what took a dump.
And the case.....it's the same shitty beige as the Fluke cases. It's gonna get painted.
That’s begs a question: what’s a group of tektronix scopes called? Herd, gaggle, flock?
That’s begs a question: what’s a group of tektronix scopes called? Herd, gaggle, flock?A struggle.
That’s begs a question: what’s a group of tektronix scopes called? Herd, gaggle, flock?
Acronyms - the brown paper bags for Americans for nasty expressions.Surf around on that Urban Dictionary website if you want to get the full scope of the nastiness from the nastiest of the nasty yankees!!
This late SN 475's transient response is looking pretty scruffy..
(pulse from 106 through tunnel diode pulser)
Interesting. Looks like there's frequency compensation present on the CC and CV opamps. The design is a little weird though as the entire thing is referenced to the adjustable rail after current sampling rather than a low impedance ground. I'd start by trying to slow the driver transistor down T1/T101 with a bit of miller capacitance and see it that responds.
Edit: Previous attempts to design power supplies myself have always resulted in a monumental effort on stability! Diagnostics usually involve fecking around for hours measuring sampling vs control voltage phase shifts and trying to get that loop stable at all frequencies. LTspice only gets you 80% of the way there. One I did which was a simple diff amp with a couple of 2n3904's was only stable when it was a warm day. Fixed with a bit of heatshrink over the two transistors! Makes you appreciate the effort HP put into their linear supplies over the years even if they did feck up a bit with the E36xx
Edit 2: actually a mini rant. You see loads of crappy power supplies described all over the internet and in electronics magazines. They worked for the author, precisely once under one set of load conditions.
Remember when mnem was going to send me a B&K function generator and frequency counter? Well today the box showed up. MUCH bigger and heavier than I had anticipated. And no wonder. Look what was inside. I guess he wanted to lighten the load to Canada.
Among the assorted parts and odd stuff we have:
B&K 3010 Function Generator
B&K 1801 Frequency Counter
Heath IM-1202 2.5 digit DMM
Heath SG-5240 Color Bar Generator
Texas Instruments TI-95 Procalc (I think that's gonna result in being disowned by Nixiefreqq. )
Thanks pal....I'm somewhat dumbfounded at the moment.
Interesting. Looks like there's frequency compensation present on the CC and CV opamps. The design is a little weird though as the entire thing is referenced to the adjustable rail after current sampling rather than a low impedance ground. I'd start by trying to slow the driver transistor down T1/T101 with a bit of miller capacitance and see it that responds.
Edit: Previous attempts to design power supplies myself have always resulted in a monumental effort on stability! Diagnostics usually involve fecking around for hours measuring sampling vs control voltage phase shifts and trying to get that loop stable at all frequencies. LTspice only gets you 80% of the way there. One I did which was a simple diff amp with a couple of 2n3904's was only stable when it was a warm day. Fixed with a bit of heatshrink over the two transistors! Makes you appreciate the effort HP put into their linear supplies over the years even if they did feck up a bit with the E36xx
Edit 2: actually a mini rant. You see loads of crappy power supplies described all over the internet and in electronics magazines. They worked for the author, precisely once under one set of load conditions.
Here is a screenshot of the oscillation.
The PSU was set as follows:
- output voltage set to 2V
- current limit around 500mA
- output shortened with a DMM
This was measured at Pin 1 of IC 101.
Here are the schematics as I have them in Eagle:
I'll try the Miller caps on the weekend.
Would it be helpful to increase the values of C3 / C103?
Ooh nasty. That may help but that’s one crazy oscillation that is banging the rails hard. What happens if you shove 1000uF across output?
Next thing is probe the input pins for IC101A and see if one or the other is triggering this. That will determine if it’s the reference or the sample circuit that is going crazy.
was actually looking for one with the dot led display.
but am impressed with this guys honesty.