Recent Posts

21

Beginners / Re: buying a oscilloscoop

« Last post by tggzzz on Today at 11:02:41 am »

If you are working on Tube radios, the power supplies are likely several hundred volts.  A high-voltage probe from a reputable source may be needed if you are poking around those with a scope. 

A little excessive.  Most standard passive probes are rated to 600V.  That and a little care should be fine for 99.9% of tube radios.  Most 100X probes I've seen are rated over 1KV.

... and not rated at 600V at "high" frequency.

Always check the V-vs-f derating curve.
Always remember that the highest frequency in a signal does not depend on the signal's period. It depends only on the signal's risetime.

22

Beginners / Re: buying a oscilloscoop

« Last post by rsjsouza on Today at 10:58:35 am »

Since you stated to have no knowledge on using a scope, I would advice to at first get some experience with low voltage signals before diving into devices with high voltages. A big risk lies in using the wrong point to connect your ground lead and then have your scope be at a high voltage on points you can touch. Or blow out things because your scope itself is properly grounded.

Indeed this is good advice. One suggestion that I can give regarding the choice of oscilloscope that mitigates this issue is a fully portable unit, which is isolated from anything else. I have one of these newer portable oscilloscopes from Zoyi/Zotek (ZT-702S) that allows troubleshooting several minor issues common in computers such as power supply ripple, RTC clocks, activivity on data or control lines, monitor reset lines, etc. Naturally, you might find yourself wanting for a better unit later in time, but these units are a great starter.

if any one has a schematic or knows where what kind of replacement i could buy please let me know     

I suspect you might find some good help with the schematic or tips to troubleshoot your 8514/A in the VCF forums
https://forum.vcfed.org/index.php

23

Test Equipment / Re: Lecroy Wavesurfer 44MX vs WS3054

« Last post by Martin72 on Today at 10:57:19 am »

For heaven's sake, hands off a WS3000 without Z....
Very slow, at least two nasty bugs still present, absolutely not recommended.
We had the WS3024, but it has since been replaced by a WS3024Z, which is much faster and doesn't have the bugs.

24

Projects, Designs, and Technical Stuff / Looking for a sensor to detect burning "smell" of coal and wood

« Last post by Miyuki on Today at 10:56:09 am »

Hi folks,

I'm trying to find the best way to detect "smell", not one particular but basically from all burning of coal and wood.
The main purpose is to detect when clean air can be draught into the house.

I do not think particular matter alone will do the trick as there are probably many volatile compounds that are annoying even in small quantities.

25

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

« Last post by tggzzz on Today at 10:55:21 am »

I would say not ...  while i salute the projects,  they can not compare to well designed lm399  and ltz1000  ones or the AD xxx series too

to check 6.5 digits meters you need more ...

Resistors references   are weak ... say ordinary

"You might think that. I couldn't possibly comment"
https://villains.fandom.com/wiki/Francis_Urquhart

26

Beginners / Re: Switching a 3KW (240V) immersion heater: Solid state or mechanical relays?

« Last post by Siwastaja on Today at 10:54:57 am »

Resurrecting an ancient thread that Google directed me to, since reputable-brand 25 and 40A SSRs from the likes of Digikey are now a few tens of dollars I've been looking at using one to turn power to a hot water cylinder off during peak-rate times, so it'll heat off cheap off-peak power rather than whenever the thermostat tells it to including at maximum rates, in effect emulating the old ripple control that hasn't been used for years.  This means it'll only switch on and off once a day, and be carrying 2-3kW of load for brief periods while heating.  Is an SSR still the best option for this sort of usage?

Just use mechanical relay. They are much cheaper, more resilient against grid overvoltage transients, and do not have massive leakage current like SSRs. Switching a few times per day, mechanical relay lasts forever. SSRs are useful for process control heating etc. where you have to switch hundreds if not thousands a time per day.

27

Metrology / Re: DIY 0.1 to 10Hz Noise Amplifier

« Last post by andrewtaylor on Today at 10:54:24 am »

Hi Richard,

great project, congratulations!
Is it possible you add the PCB layout files (I think you might have orderd your pcb from JLCPCB) on your project homepage later?

would appreciate this.

28

Other Equipment & Products / Which 3M static shielded bag

« Last post by Shock on Today at 10:54:11 am »

Looking for static shielded bags for 3.5" HDDs. I'd prefer 3M and resealable, has anyone got a part number that fits well? Experiences?

29

General Technical Chat / Re: What happened to 9-axis IMUs?

« Last post by Berni on Today at 10:52:32 am »

The magnetometers are often actually a separate die inside the package. So it is also a cost thing of having to combine multiple dies and wire bond them together. Some pretend like it is the same chip, some don't even bother and it is just multiple chips on the same I2C pins.

So at some point it is easier to just put the magnetometer in a separate package.

30

Other Equipment & Products / Re: Ring light for microscope

« Last post by artag on Today at 10:52:23 am »

LED ring is inherently going to be lower peak brightness because you don't want a massive fan and heatsink on the end of the microscope. Thats the advantage of the fiber optics, you take the weight/noise/heat somewhere else. But of course its not cheap, even just for the fiber parts.
You could look at replacement LED automotive bulbs, they are insanely powerful, though I don't know how good spectrum is.

I already have the fibre optic, so perhaps the best bet is to replace the halogen bulb but to go beyond what's commonly available in the MR16 package. Automotive is something I hadn't thought of, and there's also the high power COB devices.