Recent Posts

11

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by IanB on Today at 01:54:05 pm »

what is the OPs mechanical device analogous to the LED?

This is interesting actually. The mechanical equivalent of an electrical diode is a non-return valve in hydraulics. What makes it interesting is that a non-return valve requires fluid flow to operate it (to make it open and close). For example if the valve is open and you want it to close, it requires a small amount of backflow to make it shut off--it is not instantaneous. There is a similar behavior in electrical diodes, where they do not operate until current flows through them. The amount of charge required to switch the state leads to the difference between fast signal diodes and high power diodes that switch more slowly.

12

Buy/Sell/Wanted / Re: FS: Affordable DMM Checkers: AC Reference, DC Reference, OHMS Reference, etc.

« Last post by Kosmic on Today at 01:52:30 pm »

I design 'em and build 'em and they REALLY work! 
eBay Links:
https://www.ebay.com/itm/285825801852
https://www.ebay.com/itm/285823822244
https://www.ebay.com/itm/285807578003
https://www.ebay.com/itm/285823885283
Thanx for looking! 

Also, about those "0.05% Precision Resistors" do you know the temperature coefficient ? They look like your generic metal film and could be around 200-100 ppm/C. So even, if they were selected, change in ambient temperature could easily move them outside the 0.05% you are mentioning. I don't think calling them "Precision Resistor" is really accurate.

I don't want to be overly negative but all that look a lot like a modern snake oil salesman. Of course your clients are not going to complain, they are not equipped to validate your claims. I'm not even sure you are.

13

Repair / Re: Secondary side controller SMPS don't turn on by itself.

« Last post by Huram Arvit on Today at 01:45:17 pm »

It uses a voltage divider and the 5v ref and the error amp from the IC to adjust it.

14

Repair / Re: Rohde Schwarz CMU200

« Last post by Harry_22 on Today at 01:44:41 pm »

Did you checked both CMU200 voltages? Seems that you have problem only in one CMU but somebody interchanged B68 option. That is why you have double malfunction.

15

Repair / Re: FUG HCN 14-12500, High Voltage Power Supply repair

« Last post by htm on Today at 01:43:42 pm »

Hi HighVoltage,

This topic has been quiet for a while, but, i'm interested in that tube. Can you explain what it is for?
(i came acros this post because your device was mentioned in following patent https://www.freepatentsonline.com/5048458.html )

Kind regards

16

General Technical Chat / Re: A serious (as in not troll) requestfor help w/ultrasonic transducer

« Last post by IanB on Today at 01:43:14 pm »

For anyone who wants an ASMR video to relax to, here is a complete tear down and reassembly of a watch. I can only dream of being able to do something like this. I have struggled so much even getting little tiny screws back into their holes.

You do realize of course this is like me telling Tautech how to use a scope.  Or relying on YT to explain earthing and isolation transformers.

Yes, of course. It was just, as I said, for relaxation. There is something captivating about watching such work being performed.

17

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by Sredni on Today at 01:37:39 pm »

I might start a new thread because this is so interesting -

Do you think a Vise-Grip is a hammer?

After all, I can hammer a nail with a vise-grip. If I give you two pieces of wood with driven nails - can you tell which one had the nails driven with a hammer and which one has nails driven with a vise-grip?

So I want to know if a vise-grip is in fact just another form of a hammer. Prove me wrong.

I was also thinking on mechanical lines 

... so if the electrical terms Resistance, Inductance and Capacitance have their mechanical equivalents what is the OPs mechanical device analogous to the LED? 

Not sure you can find one with the exact same characteristic, it should have to be a dashpot that opposes diminishing resistance with increasing force.
If you consider an ideal diode, well a valve opposes infinite resistance to fluidmotion due to negative flow, and zero resistance to theotion with positive flow.
An electrician's zip tie allows you to slide freely in one direction and blocks the motion in the opposite direction, so it has a friction coefficient that depends on the sign of the force you apply to one end. You can consider it a force dependent friction device.

But maybe there is not an hydraulic or a translational or rotational mechanical analog of an exponential diode.
What is the mechanical analog of a Josephson junction?

18

Repair / Ksger T12 Sudden Death

« Last post by BrokenSolder on Today at 01:37:35 pm »

Hello folks, I've had a ksger T12 for a few years not sure if it's original or not as it doesn't look the same as ones I've seen online, it was from banggood a while ago.

I'm just a hobbyist so not an expert, I use the station occasionally and have loved it, it's always worked and never had any problems before, today it's just gone dead.

The power supply appears to be working, led ons and the second board pictured is getting 24v but nothing comes on, display doesn't work and no beeps or sounds, no heat.

I swapped the tip for another one that I've used fine before, it worked I adjusted the temperature and after a few seconds the unit just made a beep and turned off and hasn't turned back on again. No smoke, under a microscope everything seems to look OK, psu seems OK is outputting 24v to the controller board, controller board just has no signs of life. Not sure where to check hope someone could possibly help me, I dont know much about these things from a visual it looks all good to me.

19

Repair / Re: TEK TPS2000 series scope fault issue

« Last post by lern01 on Today at 01:33:39 pm »

A quick exploratory look shows no specific ADG421 part, but an Altera Cyclone FPGA (EP1C4F324C7) and what appears to be associated controller (M68 SEC000PB10 L90M) and a labelled memory.  An LMS1587 LDO regulator is nearby. 

Each input channel has input circuitry that is covered, and then a differential driver AD8131 (Analog), mixer AD8343 DC-2,5GHz (Analog), and custom isolation transformer PT77172 (Datatronics), with a following AD8343 and AD8131 on the isolated side.

No obvious part damage on the top side, so at this stage I think I will just use the scope as is until some more details crop up that could assist fault-finding.

Sorry to bother you. Could you please check the U1701 chip model? Thank you very much!

20

General Technical Chat / Re: Do you think an LED is a resistor?

« Last post by MK14 on Today at 01:29:26 pm »

I am still NOT convinced.  I don't think an LED and a resistor are the same.

Apart from anything else, an LED is normally used as a light source or indicator.  Functions which a normal, non-overloaded resistor can't do.  At least in the visible spectrum.