9 minutes of TE fun with Marco Reps on Keithley 2001 repair

[Cliff Matthews]

I had a good laugh, but I've never seen this kind of turn-on circuit either. Is this considered best practice for a turn-on delay?
Also, with 1.2v chopped away from the mains voltage at crossover, wouldn't these spikes travel right through the transformer?

As is usual with this guy, I missed his editing humor at 48 sec. the first time viewing..    Enjoy!

[lundmar]

Thanks for sharing. I liked the guys humor and use of subtle graphical effects

[HighVoltage]

Yes, that guy is funny.
Isn't he a member here on eevblog?
 

[lundmar]

Yes, that guy is funny.
Isn't he a member here on eevblog?

He must be, all electronics guys with good humor find their way to this forum

[saturnin]

Cable detector Btw. have you noticed an extra board on the top of the ADC board? Perhaps some workaround from factory?

[rt]

I have two pieces of test gear that came to mind at this point in the video ( https://youtu.be/HVDQeJTEHFI?t=174 ).  Can't look at them without a grin now!

... and Dave obviously missed a trick by not including the Cable Detector in the GW121.

rt

[Cliff Matthews]

Yes, that guy is funny.
Isn't he a member here on eevblog?

baltersice seems to be a new member, but new fame may not give him much time on EEVblog (his channel adds +100 new subscriptions per day).

[macboy]

I had a good laugh, but I've never seen this kind of turn-on circuit either. Is this considered best practice for a turn-on delay?
Also, with 1.2v chopped away from the mains voltage at crossover, wouldn't these spikes travel right through the transformer?

It isn't a turn on delay or soft start, it is a pre-regulator. During normal operation, the MOSFET is continuously being turned on and off, either shunting the resistor or not, in order to keep certain secondary voltages at exactly the desired level. This allows for use over a broad range of input voltages, while minimizing the associated change in the power dissipation of the linear regulators. That in turn minimizes the change in thermal (and thermal EMF) gradients across that big analog board. Those are the kind of hoops that need to be jumped through to achieve 7.5 digits.

[baltersice]

A new member, huh, Mr. February 2015?

board on the top of the ADC board

Here's a close-up of that:

No idea what a TIF222 is, but since it just plugs into the 4 pins of the usual crystal osc there, I would bet that it just mimics the behavior of one?

[Kleinstein]

I Don't know what the TIF222 stands for, but HCU04 looks familiar - like 74HCU04, which would be an obvious choice for a crystal.
Still odd they could not us an of the shelf oscillator in a can.

[rsjsouza]

Mehdi from ElectroBOOM spoiled bridge rectifiers for me - when the bridge rectifiers were shown, all I could think was that it was a FULL Bridge Rectifier!

That was a very enjoyable video!

[saturnin]

Thanks baltersice,

Indeed, it is a workaround instead of single can oscillator (Y800). They must have been desperate 

[doktor pyta]

baltersice,

please put a link on EEVblog any time You make test equipment- related video.
It's always nice to watch !

[baltersice]

Will try, doktor pyta. Btw I got lost clicking around on your website and saw for the first time a Keithley 640 "vibrating capacitor electrometer" ... another item for the shopping list