Recent Posts

1

Projects, Designs, and Technical Stuff / Re: Corrosion on DIP pins

« Last post by edavid on Today at 02:52:51 pm »

Just an additional annoyance: MOSTEK is known nowadays to have a relatively high incidence of memory rot, which renders the IC unusable due to internal degradation even on ICs that are physically in good shape.

That's a problem with mask ROMs.  Aren't the ICs in the photo DRAMs?

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Test Equipment / Which Arbitrary function Generator Can Hold after generate Arbitrary waveform

« Last post by ElectronicABC on Today at 02:49:07 pm »

For Rigol DG1062Z,output  Arbitrary waveform in *.raf then cycle again，but how to hold after the latest point?

and I test the Burst mode ,but there is 1ms zero voltage Pulse before it go to Idle (as set ) level.

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Projects, Designs, and Technical Stuff / Re: Accurate sine wave in terms of amplitude

« Last post by mawyatt on Today at 02:40:53 pm »

Generating a precise & stable amplitude (and frequency) square-wave isn't difficult, see below.

https://www.eevblog.com/forum/testgear/ac-rms-dmm-tests/

However extracting a precise & stable sine-wave from this square-wave may be more difficult than expected.

Since a waveform's rms value is the sum of all the individual components that make up the waveform, extracting the fundamental from a squarewave requires removing all the harmonics to a level sufficient to guarantee the "precision" of the leftover sinusoidal like waveform relative to a pure sine-wave.

Removing these harmonics entails utilizing a Low Pass filter, which must attenuate the harmonics to sufficient levels to meet the desired precision and stability of the desired resultant waveform but not attenuate the fundamental to effect the desired result.

This may become a tall task if one seeks a high level of precision, and even more so if one demands temperature and time stability. Sure one can "calibrate" the LPF and squarewave but then the circuitry must maintain an acceptable level of temp and time stability after calibration. As shown in the link above, creating a precise low frequency squarewave that is stable in frequency and amplitude over temp and time isn't difficult, converting to an acceptable precision sinusoidal waveform may be another story!!

Best,   

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Projects, Designs, and Technical Stuff / Re: Accurate sine wave in terms of amplitude

« Last post by Alex Nikitin on Today at 02:38:18 pm »

Have a look at how it is done in the Fluke 510A AC Reference circuit, it compares the amplitude to the level of a DC reference (easily set with a good DC voltmeter) and provides a ppm-level of amplitude accuracy and stability on AC.

Cheers

Alex

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Beginners / Is it safe to store CMOS devices in the AideTek ESD Boxes

« Last post by watchmaker on Today at 02:31:19 pm »

I now have some CMOS devices in ESD tubes and envelopes.  I would like to develop a rational storage system. Are the AideTek ESD boxes safe or do I still need the black foam?  The Learning Art of Electronics offer I purchased made this an issue much sooner than I was ready for.

Also, since I tend to order by 5s (at least) from DigiKey, what are the storage strategies for tubes?

I am thinking of categorizing by logic chips, op amps, regulators, etc. and then call number.

Regards,

Dewey

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Manufacturing & Assembly / Re: Brief review of the Zhengbang ZB2520HL reflow oven (T-962A alternative)

« Last post by MR on Today at 02:27:58 pm »

Cheap IR heater ... no thanks. might be okay for some easy PCBs without special requirements. And no one can convince me that unshielded IR will be good (or good at all for components).
Conventional is much less troublesome, the next level of that seems to be Vapor Phase Soldering.

One of those IR modules probably costs around 5-7$ (just that you know what the engine of that IR heater costs). Multiply it with 4 and that's it the rest is enclosure and the controller.

7

Test Equipment / Re: Fun With Low Leakage/Bias Current: Femtompere, Electrometer, Keithley 617

« Last post by Alex Nikitin on Today at 02:24:42 pm »

After put back the original BNC connector, I recorded the offset. Is it normal or not?  thanks

If that is the drift when switching on from cold, it might be normal. According to the manual, the warm up time to rated accuracy is 2 hours. There are two trimmers on the input board, one to adjust the DC offset (in the Voltage measuring mode) and the second is to compensate the input current (in the Current measuring mode), so it can be adjusted to zero. Both are not easy adjustments, mostly because you need to keep the top cover on to get the temperature stable and correct, than open the cover (thus upsetting the thermal equilibrium) to do the adjustments, only to close it quickly and see if you hit the spot after the temperature settles again  . Both the offset and the input current will drift noticeably when you open/close the cover however by several iterations it is possible to get a reasonable result.

Cheers

Alex

8

Beginners / Re: What function generator, that does a bit more than just a simple signal

« Last post by radiolistener on Today at 02:23:18 pm »

Have you used the programming feature? The manual is not so good to explain things here. Also i wonder if there are limitations when using some more complex function on one channel, for example using sweep or FM/AM/... : The other channel can be used what ever you want to do with it? Is it possible to use AM/FM/... on one channel, and sweep (with fm) on the other?

If you're talking about JDS2800, I don't have it so I can't say. I have PSG9080.

Both are manufactured by the same manufacturer and has similar display interface.
So I think my tool designed for PSG9080 can be compatible with JDS2800 either. Needs to test it.

Regarding to PSG9080, it has nice front panel with large contrast display. The performance is comparable with the same class generators like FY6800, may be a little bit less noise but harmonics may be a little bit higher. I would not expect something special, this is just a signal generator. It has sweep and modulation, but these functions are limited and has not a good quality. If you want some more functions or better quality sweep and modulation, it's better to look for something more higher class. Like Siglent SDG2048X.

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Projects, Designs, and Technical Stuff / Re: Vacuum Fluorescent Display Driver

« Last post by bostonman on Today at 02:11:46 pm »

I thought the DC-DC output AC to the filaments?

At the time I only had schematics handy and saw it's a "DC-DC" convertor, so I assumed it was DC out, however, I should have included that I measured the AC as well, it was approximately 600mV; but I measured this with respect to ground and maybe needed to measure across.

The datasheet specifies pins 5 and 7 are AC, but doesn't give a voltage. The schematic shows FL1 and FL2 are on pins 4 and 6, so that's a bit confusing.

Later today or tomorrow (hopefully) I'll take the steps you suggested. Usually I start with the obvious such as do I have voltage(s). My personal rule is first figure out what happened between when something worked and when it didn't. Since the only anomaly in that process was me replacing the chip, seems the obvious route is to start with soldering issues.

My other thought is the replacement IC takes more current and damaged the convertor. My somewhat focus is on the fact the display was working until I recycled power. As you suggested, a power up sequence failure, shorted pins, etc... so I'll look and report what I find.

Update: just for reference, this is the chip I ordered and installed    HV518PJ-G (DigiKey part number: HV518PJ-G-ND)

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PCB/EDA/CAD / Re: JLCPCB alters soldermask without any notice

« Last post by xvr on Today at 02:09:10 pm »

> They don't have strict rules for layer extension ".xxx" at JCL.

They have preferable naming (and it described on its site). If your files match it there is should be no problems. Otherwise they will do their best, but not always right

Very strange that they won't come back to you for approve