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Vintage Computing / Re: What was you first computer?
« Last post by djos on Today at 03:44:48 PM »
Apple II clone

It's kind amazing to me that the II was cloned by so many companies given they would have needed the copyrighted ROM images to do so. I dont ever recall seeing Apple II clones in Aus but I was only 5 1980.
General Chat / Re: Breadboard installation for $87 US
« Last post by rstofer on Today at 03:40:38 PM »
Your link heads toward a permanent prototype breadboard...  $87 ?

I could be way off but I think these boards are made for solder.  In fact, they look a lot like PCBs and that's pretty much what the description says.  They seem very suitable to a 'permanent' breadboard.
I haven't looked at the schematics, but that board has an edge connector on each side. I'd also suspect that it's for options other than the eighth digit. BCD output sounds good. I suppose some kind of option to display values might be another although I don't know what that might be since you already have the voltmeter.

That would be my guess.  Additional options for the unit included: Opt 002 - Remote Programming (all controls but sep/com switch, fast/norm mode, input attenuator and AC/DC coupling); Opt 003 - Digital Output (numerals and polarity only); and Opt 004 - Remote Programming (including all BUT fast/norm mode).

I'd expect those to tie in to the 'mystery' edge connectors on the display board.

Keysight has a scan of the manual online, but it's not the greatest quality.

Repair / Re: HP 54501A troubleshooting - repair
« Last post by tinkertokyo on Today at 03:38:05 PM »
Just in case it's of any interest to someone, I posted a video of me replacing the NVRAM on my 54501A.

Buy/Sell/Wanted / Can you help identify this Schematic Capture Program?
« Last post by TurboSam on Today at 03:36:58 PM »
http://So I was looking around for circuits to help me learn a few thing and try them on my new DS-1054Z, and I came across a YouTube video that creates a circuit and tests it with an oscilloscope on line that looked pretty interesting--a least to me.  I have no idea if the program is a professional/corporate program or something suited to a hobbyist (like me), and I have searched hi and lo for what it is.

I am reluctant to post a link to the video since I don't want to be accused of driving traffic to a video that, at this point, has ~1000 hits, 4 likes, 2 dislikes, and no comments.

This is a screen of the program, so I am hoping someone can help me identify it:

Just catching up on the thread now as I have been traveling for work.  As an update I too ended up getting a bad unit again with BA serial number.

I returned it to amazon and didn't bother with a third unit - took a refund. Not sure what I will do now in terms of another vendor or see what Siglent does.


Beginners / Re: Recommendations for educational materials
« Last post by Shock on Today at 03:35:10 PM »
Start with something like this circuit:

Order the parts if you don't have them (get multiples in case you kill a few and for building)
Save or download a datasheets (especially the 555) in a folder for the project
Breadboard it
Use your multimeter to confirm voltages and continuity.
Follow the datasheet see the pins you are using and look at the examples
Redraw the schematic from left to right.
Add suitably sized fuse protection
Add a power source like a voltage regulator to power from 9V
Add an AC supply to power from mains.
(can be as simple as a small AC wall wart, you don't need to expose yourself to mains transformer voltages).
Include a system to switch from DC to AC when it's connected and to power it off.
Look into making a simple modification so you can easily adjust the output frequency.
Layout on a prototype pcb.
Build it.

For the next project you could look at making a small amplifier that allows you to amplify or attenuate the signal, or monitor it through a speaker. Or improve on the power supply design efficiency, add a rechargeable battery and charging circuit.
General Chat / Breadboard installation for $87 US
« Last post by ez24 on Today at 03:33:46 PM »
First time I have come across an installation for a breadboard.  If I had an extra $87, I would find out what a breadboard installation consists of.

Any guesses ?

The breadboard has round holes.  Does this mean it is better?
Test Equipment / Re: Keithley 614 electrometer
« Last post by Octane on Today at 03:25:26 PM »

Has anybody the schematic and the PCB component locations drawing?
It seems that it should be in the manual, but there are only lists, no drawings in the 48 pages.

I have good results with my regulator experiment, with both voltage and current regulation.
 Using a faster op-amp made it easier to get good performance.
The bottom trace shows an output short circuit with the CC set to 3 amps . The top trace shows the output on the CC op-amp, U2, rapidly slewing down because the integrator capacitor, C1, isn't connected to the op-amp's output yet. When U2 does take control of the MOSFET's Gate, Q1 gets turned on, putting C1 into U2's feedback path. The regulator then goes into stable current regulation.
 I'm thinking about going further with the design and etching a PCB for it. Ill add a better reference, a TL431 likely.

Extra: the bottom trace is the voltage across the current shunt resistor.
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