Recent Posts

21

Repair / Re: unknown DC-DC chip of SI-9110 differential probe

« Last post by teatime on Today at 01:08:06 am »

After remove the chip, then I draw this schematic, it's right.
The chip MAX743 is the chip I needed.

22

Repair / Re: unknown DC-DC chip of SI-9110 differential probe

« Last post by teatime on Today at 01:05:16 am »

After compare with the datesheet, MAX743 is the right chip.
Thanks alot for your great help!
 

23

Metrology / Re: reading Keysight 3458A serial number

« Last post by analogRF on Today at 12:55:03 am »

Still I would like to do the short term A3 drift test (as per service note 18A) using the CAL? 72 but I cannot keep the unit running 24/7 for 7-10 days.
I can run it for like 5-6 hours per day.

Is it ok to run it say 6 hours a day and get the temp and cal?72 after an ACAL at the end of each day and then turn it off and repeat the next day to
gather enough data?
or is it mandatory to run the unit 24/7?

24

Metrology / Re: reading Keysight 3458A serial number

« Last post by analogRF on Today at 12:53:15 am »

Worth checking if is stored in the calibration string. CALSTR? from GPIB or keypad

BRILLIANT  THANKS

YES the calstr? has the S/N at the end of it and it is 2823Axxxxx 

25

Repair / Re: Heathkit EC-1 Analog Computer repair

« Last post by vintcomp2 on Today at 12:47:36 am »

I spent a little time this morning  on possible EC-1 failures ...

Thank you for the detailed feedback on some failure modes.

If attempting to power this up, repair and when using it, I would use a 120:120V isolation transformer with a grounded interwinding screen, and leave the EC-1 chassis floating. That would reduce the possibility of a grounded user receiving shock, except if he was touching the chassis at same time.

I was able to find a really good article https://www.nutsvolts.com/magazine/article/May2016_Heathkit_Restoration on Nuts&Volts, where an absolute pro rebuilt one. Although he made other parts upgrades to the unit (he didn't worry about keeping it completely stock) - he also left the unit with the two wire plug.

And the analog computer that I learned on, was a EAI, fairly new in 1969. It had transistorized op-amps as plug in modules.
 
 Hope this info helps

The information definitely helps. The National Cryptography museum in DC has an EAI Pace on display for anyone out there who wants to see one up close. That machine is a real beauty.

26

Projects, Designs, and Technical Stuff / Re: Why transistor Vbe drops when is in active region? BC547 ib=constant

« Last post by moffy on Today at 12:44:01 am »

I think the Ic vs Vbe traces are the same as the Ic vs Vce except that Vbe replaces Vce. If that's the case then you have constant base input current and stepped Vce voltage for a number of different base currents. If you notice the first trace you will see that for higher currents the Vce voltage cuts short earlier, that is because BJT breakdown voltage is current dependent, and when the tester detects this problem it ceases that test. For the Vbe vs Ic you have the same condition except it is a bit more pronounced. There is special overcurrent protection built into the tester it might be a side effect of that.

27

Metrology / Re: reading Keysight 3458A serial number

« Last post by manupthehills on Today at 12:39:24 am »

Worth checking if is stored in the calibration string. CALSTR? from GPIB or keypad

28

Other Equipment & Products / Re: Helping picking quality flush-cutters (Knipex vs Ideal-Tek) ; Steel vs Carbide?

« Last post by connectTek on Today at 12:00:06 am »

Lindstrom

29

Thermal Imaging / Re: Infiray T2S Plus or Infiray P2 Pro with Macro lens

« Last post by zus on Yesterday at 11:59:37 pm »

Thank you for your reply. The pc software xtherm 2.0.7 works in my case.

30

Metrology / Re: Hioki DM7276-01 Precision DC Voltmeter (9 PPM)

« Last post by Alex Nikitin on Yesterday at 11:49:46 pm »

Well, I've purchased the DM7275-03 for my home lab. So far I am quite happy with what this small unit does. I like that it is completely quiet, seems to be very stable and as arrived did differ about -3ppm from my usual standards (which I count as about 10ppm accuracy in any case). The input current measures about -20pA and seems to be stable and not noisy. The temperature measurement feature is very handy and useful. I am already getting some good data on the low frequency noise of my HP3245A and other sources, with the passive filter the baseline noise is about 600nV p-p in 0.1-10Hz range at 1NPLC.

I have a question though - does anybody knows a calibration company in the UK which would calibrate this unit with traceability, data and uncertainties (to my surprise, the unit came without any calibration data from the manufacturer).

My next home project now could be to build a universal shunt box for the Hioki and the HP3456A, to measure DC currents from about 100uA FS to 1A FS. I have good 10K and 1R0 references but it would be much more convenient to have a box with proper range switching and fuses.

Cheers

Alex