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Buy/Sell/Wanted / Re: FS [CAN / US] Fluke PM6680B frequency counter / timer
« Last post by fenugrec on Today at 01:38:21 am »Bump, summer price 400 CAD
Recent Posts
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Test Equipment / Re: SDS800X HD Wanted Features
« Last post by electronics hobbyist on Today at 01:38:11 am »I wonder how many use these buttons (see picture). You can move the fields by simply dragging them, so i would say these buttons are redundant. They would cover a field that you could otherwise click without moving the fields at all.
Dragging is implicit, while arrows are explicit, I think this is the main reason for retaining the arrow.For first-time users or users of the mouse, this arrow is necessary.
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Projects, Designs, and Technical Stuff / Re: HP 3478A ROM Dump
« Last post by fenugrec on Today at 01:32:29 am »The second has an internal ROM. I don't know if its readable with a programmer.
Yes, the analog-side 8049 has been dumped and is available from ko4bb.
+1 to comments by pqass and Kleinstein.
Without the ASIC magic , the rest of the hp3478a is non remarkable and IMO a waste of time to try and duplicate. You also do not want to be looking at, let alone writing, 8039/8049 firmware in 2024. I speak from experience
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General Technical Chat / Re: Is LinkedIn worth keeping?
« Last post by Halcyon on Today at 01:31:19 am »I tried to add Dave as a connection, very long time ago. But it's only famous celebrities that are "on the list" lol. Didn't make it.
I'm not even connected to Dave! My invite ended up expiring because he never uses it.
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Beginners / Re: 555 driver and Transformer questions
« Last post by Andy Chee on Today at 01:23:34 am »This context is most helpful and would’ve been appreciated in your first post!
So just to confirm, you’re seeking to build a replacement HT supply for a car valve radio operating from 6V system?
In other words, you’re not attempting to use this power supply to run a different HV device like a Tesla coil, taser gun, electric fence, or other?
So extra questions, are you just trying to replace the vibrator unit? Or the entire HV power supply?
So just to confirm, you’re seeking to build a replacement HT supply for a car valve radio operating from 6V system?
In other words, you’re not attempting to use this power supply to run a different HV device like a Tesla coil, taser gun, electric fence, or other?
So extra questions, are you just trying to replace the vibrator unit? Or the entire HV power supply?
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Manufacturing & Assembly / Re: Fellow LPKF equipment users?
« Last post by rsaxvc on Today at 01:16:16 am »I've noticed the local harbor freight tools carries 20-pack of what appear to be compatible 38mm carbide drill bits, up to 1.1mm diameter, $7. No testing yet.
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RF, Microwave, Ham Radio / Re: fake MPF102s from AliExpress
« Last post by radiolistener on Today at 01:09:51 am »almost all transistors on aliexpress are fake. It can be branded but remarked other type, old repackaged, or just custom made with unknown parameters.
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Projects, Designs, and Technical Stuff / Re: Vacuum Fluorescent Display Driver
« Last post by bostonman on Today at 01:04:10 am »All the solder connections on the VFD looked good, however, I re-flowed them anyway including the ribbon cable.
FL1 and FL2 to ground is high impedance, 9.7ohms across the two pins FL pins, and approximately 1.3ohms across the two FL pins when the ribbon cable is connected to the unit. All other pins on the VFD to ground was (I believe) 4xx k. Not sure if these are good, but seems correct based on the FL lines being AC (most likely this is the resistance of the output transformer).
I found a previous message that states the DC/DC pins are off by one which makes sense when compared to the schematic.
Tomorrow I'll measure the SEG lines to see if they are going to approx. 38V, but what should the AC voltage be?
As for measuring the new HV518, obviously the VFD needs to be removed again, and this eliminates measuring voltages under a load since the VFD isn't connected. The other thing I'm keeping in mind is the start up sequence.
FL1 and FL2 to ground is high impedance, 9.7ohms across the two pins FL pins, and approximately 1.3ohms across the two FL pins when the ribbon cable is connected to the unit. All other pins on the VFD to ground was (I believe) 4xx k. Not sure if these are good, but seems correct based on the FL lines being AC (most likely this is the resistance of the output transformer).
I found a previous message that states the DC/DC pins are off by one which makes sense when compared to the schematic.
Tomorrow I'll measure the SEG lines to see if they are going to approx. 38V, but what should the AC voltage be?
As for measuring the new HV518, obviously the VFD needs to be removed again, and this eliminates measuring voltages under a load since the VFD isn't connected. The other thing I'm keeping in mind is the start up sequence.
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Projects, Designs, and Technical Stuff / Re: Accurate sine wave in terms of amplitude
« Last post by PCB.Wiz on Today at 01:01:49 am »But I do know today that I am iterating options how to generate sine wave - as clarified in the initial message including an example circuit.
Quadrature oscillator might be "the fresh idea I was looking for". Just that none of the first examples I tried to simulate on LTspice didn't work. Like this one:
Probably a simulation related issue - I need to analyze it further...
Whilst that circuit has two waveform at 90', it also has 3 RC elements, so it is less suited to a knob controlled oscillator.
When simulating such oscillators, you need to adjust the idealized gain, to account for real opamp effects.
You then find a trade off between oscillator startup time and clipping of one node when stable.
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RF, Microwave, Ham Radio / ROHDE & SCHWARZ SMDU and SMDU Z1 test set owners!
« Last post by py1dkw@yahoo.com on Today at 12:51:33 am »I had worked with this nice test set from 1984 to 1999 and now I could get the same unit here in Brazil. The R & S Support gave the available manuals, but my SMDU is changing its frequency in RF generator mode fast, but only in the lower band, the upper bands are ok and not out of lock. Does any owner of SMDU knows where I could start looking for the defective part? I had the SMDU Z1 unit restored and works fine. Many thanks, 73s Sam Rocha, PY1 DKW