Recent Posts

1

Beginners / Re: LC filtering for combined Vref/VDD of ADC

« Last post by strawberry on Today at 09:59:43 pm »

separate linear regulator may help to reduce ripple up to some ~1MHz
above 1MHz ferrite bead ,
 inductor saturation current and parasitic capacitance will limit filtering effect

2

Repair / Re: Tek FG502 fails at high frequency end of dial - help needed!

« Last post by BlownUpCapacitor on Today at 09:58:50 pm »

the collector voltage at Q292 which switches the ramp voltage on and off measured low (30-140mV depending on the multiplier settings)

That seems about right. Pulldown for Q175 changes with the multiplier setting, changing the flow of current through CR170.

to measuring -3V when the oscillator stopped.

Whoa, I think you got something!

Looks like the oscillator is locking itself in the negative cycle it seems.

But the problem is still evasive.

Maybe check the voltage across R155 during failure, and working? A negative voltage at the collector of Q292 indicates current flowing through it. Q292 is controlled through Q230A.

Check the circuit pictured below.

Also try removing CR204. Take it out of the circuit and see what happens. Earlier versions didn't have it.

Frankly I'm out of good ideas. Maybe someone else on the forum can help?

3

Manufacturing & Assembly / Re: Vacuum Pick-Up Tool for Rework (Includes video of my own design)

« Last post by thm_w on Today at 09:58:32 pm »

I don't have the Auyue 932 but likely either the tubing is glued on or they used a barbed fitting which can make it hard to remove. Cutting it inline should work for you? Or put the valve inside the unit if there is space.

The foot switch you linked is 120V, you want to be switching the 12V. It can still work fine of course, assuming you cut off the 120V plug part of it.

4

Thermal Imaging / Re: My decent in to Infrared abyss (IR microscopy and telescopy, on the cheap)

« Last post by Bill W on Today at 09:57:12 pm »

If I can be forgiven the self promotional links, my attempts at connecting a FLIR-One dongle TIC to some BIG lenses, like a 150mm f/1.


Basic setup:
http://www.fire-tics.co.uk/project4/index.htm

Then the BIG lenses:
http://www.fire-tics.co.uk/project4/lenses.htm



Bill

5

Other Equipment & Products / Re: Filter advice please on home made fume extractor

« Last post by shabaz on Today at 09:55:08 pm »

I used 120mm fans (since I had a load of them) and had to use 4 of them I think, to work through that filter!). A larger filter and different (and larger fan) topology for that sounds very sensible.

Also you're right on the noise (I was hoping to put it under the desk with just the ingress hose exposed, but it's still unnecessary sound that could be solved by better design). Also needed a soft-start (I used extremely crude series resistors shorted out by MOSFET delayed by RC circuit) since the fans have so much demand on start-up. I definitely would scale it up and do things differently if I were to do it again.

6

Test Equipment / Re: New 2ch pocket DSO+SG - Zeeweii DSO2512G

« Last post by Aldo22 on Today at 09:54:32 pm »

What sources do you use for AC and DC calibration?

With what I had at hand.
I took my FY3224s and verified the voltage with the multimeter. This for all voltage ranges, but only at 1kHz.
Here is a photo of it: https://www.eevblog.com/forum/testgear/new-2ch-pocket-dsosg-sigpeak-dso2512g/msg5086450/#msg5086450

Today I might do it with my second scope.
But you shouldn't exaggerate, it's not a high precision device. 

7

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by Martin72 on Today at 09:48:40 pm »

What was the topic again?
Question for a friend...

8

Test Equipment / Re: New Hantek DSO2X1X models?

« Last post by Pin240 on Today at 09:46:10 pm »

I would start by searching "Hz", "KHz", "MHz" strings in the binary and finding where they're being used.

I found them in Phoenix and in some xml files.

9

Other Equipment & Products / Re: Filter advice please on home made fume extractor

« Last post by thm_w on Today at 09:43:53 pm »

Do you think this will be OK?

£16.50 for 2.5 kg

Looks good

Some vacuum-cleaner filters are a decent size, I gave it a shot a while back too, I can't say I was entirely happy with it all (it was a bit experimental; it would probably need a rebuild, with more air-tightness around the fans). I didn't complete : ( But I was happy with some aspects of it, it needed better execution. For the ingress end, I used a 3D-printed oval-shaped funnel, connected to a short length of conductive plastic hose (from eBay).

Tooki beat me to it. Your construction looks very good but, the vacuum these filters are from is probably using a 500W+ centrifugal motor. Those 3 axial fans you have most likely aren't powerful enough in comparison. You could 10x the surface area of that HEPA filter and greatly decrease the pressure needed, which might make those fans usable (depends on their static pressure rating, if its from a PC they are probably no good).

Also that mesh carbon filter is near useless. Get some granulated media in a mesh bag if you can.

10

Projects, Designs, and Technical Stuff / Re: digital RGB LED question

« Last post by glenenglish on Today at 09:37:25 pm »

harmonics maybe might have made EMI worse, it depends on their amplitude, which might depend on the cable characteristics, the driver characteristics, the load characteristics...

problem 1-
the lack of sharp edges mean the link is unreliable (those chips need square waves). long periods in the transition region  leads to (even poorer)  RF immunity
problem 2-
signals in the broadcast band on unshielded cables are radiators and likely cannot meet CISPR25 etc emission requirements, and are likely to cause harmful interference to you and your neighbour's listening of the radio.