Author Topic: What's this please? (Component Advice) (Read 1320743 times)

Mechatrommer · « **Reply #25 on:** March 15, 2011, 05:59:07 pm »

thanx guys! i thought the J is Joule

Time · « **Reply #26 on:** March 15, 2011, 08:52:18 pm »

j means jiggawatt

NiHaoMike · « **Reply #27 on:** March 16, 2011, 04:11:58 am »

Quote from: Hero999 on March 12, 2011, 05:27:23 pm

Quote from: NiHaoMike on March 10, 2011, 08:31:28 pm
In every CRT monitor or TV I have taken apart, there was this odd inductor that has a permanent magnet glued to it. Is that to offset the magnetic field generated by a DC bias current so a cheaper core can be used?
Yes, that's what it's for, the permanent magnet biases the inductor to oppose the DC current so a smaller, cheaper core can be used.

So why isn't that technique used in a lot more applications where there is a significant DC bias current?

Zero999 · « **Reply #28 on:** March 16, 2011, 09:16:33 pm »

Good point, the only place I've seen it is inside CRTs. I would think it would also be handy for inductors used in SMPSes which also have a high DC current.

Mechatrommer · « **Reply #29 on:** March 26, 2011, 07:28:47 pm »

what is this? A78374 HP 8555A Spectrum Analyzer-RF Section .01-18 Ghz. i know the name alright, what it does? i'm serious, i'm not joking.

oPossum · « **Reply #30 on:** March 26, 2011, 07:49:09 pm »

That is one of the two modules that can be installed in a 141T frame to make a spectrum analyzer.

It converts the high frequency RF to a lower frequency that is fed to the lower module. Sort of a tuner.

Late 60s vintage.

tekfan · « **Reply #31 on:** March 30, 2011, 07:13:00 pm »

Anyone know what the FET labelled E401 is (second schematic). It's in the peak detector circuit and it looks like the drain and source are shorted together.
Is it maybe used as a variable resistance device? Anyone know a substitute or part number?

BTW This is a very nice voltmeter with plenty of rectification options and bandpass filter selections. Perfect for audio work really (or anything to 500 KHz).

Though it's built with standard components, this ac voltmeter contains many features not typi-cally found in commercial meters; the most unusual is a selection of rectification modes. The meter responses available include true RMS ('fRMS), average, RMS-calibrated average responding, positive peak, negative peak, positive-peak hold, and negative-peak hold.

High- and low-pass filters (S1 and S6, respectively) allow the -3-dB-passband to be varied from as little as 10 Hz to 200 Hz, to as wide as dc to 500 kHz. The low-pass filter also is effective in the 100x amplifier mode, where the input equivalent noise level is only 0.3 pV, with 10-kHz roll-off.

(NOT WRITTEN BY ME)

Time · « **Reply #32 on:** March 30, 2011, 08:06:59 pm »

Thats a strange symbol for a fet. might not even be one.

Zero999 · « **Reply #33 on:** March 30, 2011, 08:15:15 pm »

The symbol is standard, the configuration is not.

VIPR · « **Reply #34 on:** March 31, 2011, 01:45:17 am »

Looks like a standard N-channel JFET being used as a diode for clip detection. If you tie the drain and source together the JFET also works similar to a diode, except you have one P-region and two N-regions.

What I find interesting is that the part number is not called out while every other part on both schematics is clearly labeled as to what the specific part number is or at least the value. Instead, for that part they apparently used the PCB part identifier label. That seems rather odd and possible a clue as well.

Zad · « **Reply #35 on:** April 02, 2011, 01:59:17 am »

I have never seen a JFET used like that before. I wonder if they are using it as a Schottky diode.

Rufus · « **Reply #36 on:** April 14, 2011, 08:40:52 pm »

Quote from: tekfan on March 30, 2011, 07:13:00 pm

Anyone know what the FET labelled E401 is (second schematic).

Well I guess it is an E401. Maybe at the time it was a good choice for use as a low leakage diode, maybe it or a similar JFET still is.

I found LS841 listed as an equivalent. Searching will turn up a datasheet for that, strangely it is a dual n-channel JFET.

If you are trying to re-create this circuit you just need a low leakage diode or JFET used as one. The LS841 gate leakage is specified at 50pA max, 25C and 20v so that's a target to match.

tekfan · « **Reply #37 on:** April 21, 2011, 07:42:31 pm »

Quote from: Rufus on April 14, 2011, 08:40:52 pm

Quote from: tekfan on March 30, 2011, 07:13:00 pm
Anyone know what the FET labelled E401 is (second schematic).

Well I guess it is an E401. Maybe at the time it was a good choice for use as a low leakage diode, maybe it or a similar JFET still is.

I found LS841 listed as an equivalent. Searching will turn up a datasheet for that, strangely it is a dual n-channel JFET.

If you are trying to re-create this circuit you just need a low leakage diode or JFET used as one. The LS841 gate leakage is specified at 50pA max, 25C and 20v so that's a target to match.

Thanks very much for the explanation

Psi · « **Reply #38 on:** May 03, 2011, 11:54:28 am »

Anyone have any idea what part number this diode is?

I've tried searching on SGS / E1274 / 525 and cant find any info
edit: Its actually E 1271

The DMM says it's forward voltage is 0.5v

tekfan · « **Reply #39 on:** May 03, 2011, 12:36:10 pm »

I've seen many older (from 70's and 80's) varicap diodes packaged in black. Exactly like that one. It may also be a zener diode. Try measuring the voltage drop in both ways.

Where did you get it? How old do you think it is?

Psi · « **Reply #40 on:** May 03, 2011, 03:06:49 pm »

i've tired one up to 40v, it's not a zener, well, not unless it's over 40v

It could be old, i was just given a whole bunch of electronics and i have bag of those diodes.
I'm trying to decide if i should keep or throw away.

Unless i can find a datasheet there not really of any use to me.

tekfan · « **Reply #41 on:** May 03, 2011, 04:22:11 pm »

I would guess the 1274 is the date code. It seems to be about right since SGS (Italy) was formed in 1972. So 525 must be the part number.

You say you've got more? Do all of them have 1274 written?

If you want to check if it's a varicap you caan build this simple circuit. http://www.hanssummers.com/varicap/varicaporig.html

Psi · « **Reply #42 on:** May 04, 2011, 12:29:47 pm »

Just noticed its E 1271 not E 1274
Still no luck finding any info though

The SGS and E 1271 is always the same.
The 525 part varies a little 424 / 510 / 525 with lots of duplicates

vk6zgo · « **Reply #43 on:** May 09, 2011, 03:03:01 am »

I think it's just an ordinary silicon signal diode like a 1N914 or the like.

I seem to remember them in various boards I either fixed or stripped for parts,& yes, they are quite old.

Why not keep them & use them in non-critical applications?

VK6ZGO

Psi · « **Reply #44 on:** May 09, 2011, 07:53:12 am »

Quote from: vk6zgo on May 09, 2011, 03:03:01 am

Why not keep them & use them in non-critical applications?

I think id rather solder in a diode which i know the specs of.

Without knowing the max voltage and current of that diode i wouldn't want to use it.

vk6zgo · « **Reply #45 on:** May 09, 2011, 08:49:47 am »

I did say "non-critical"!

In "hobby" type low power applications there are many circuits where the actual specs of the diode are

fairly unimportant----just a "signal diode".

In fact,you could build up a simple circuit,using a known spec diode,then substitute the E1271 & see

what the effect is.

If the circuit operates in the same manner,it gives you a clue to the characteristics of the E1271.

You could even measure the characteristics using a fairly simple test setup,which you could find on the Internet.

Then again,diodes are dirt cheap,so you could throw them away,but you wouldn't learn anything.

VK6ZGO

Psi · « **Reply #46 on:** May 09, 2011, 12:34:44 pm »

normally when ya build stuff, even for hobby use, enough things go wrong that you dont really want to be adding to problem by using components of unknown specs

i was mainly interested in finding info about the diode incase it turned out to be something special that might be of use. Like ultra fast etc.
I've got a few 100 normal signal diodes and about the same quantity of 1n4007's already.

Excavatoree · « **Reply #47 on:** May 12, 2011, 02:47:01 am »

Just a quick ID question - can anyone identify:

Diode: Marked 62T02 and GI9774 (both on one diode, two lines) Google is no help. About the size of a 1N4002

unknown device in TO-220 package: IR9502 International Rectifier's website doesn't recognize it.

vk6zgo · « **Reply #48 on:** May 12, 2011, 06:36:47 am »

Quote from: Excavatoree on May 12, 2011, 02:47:01 am

Just a quick ID question - can anyone identify:

Diode: Marked 62T02 and GI9774 (both on one diode, two lines) Google is no help. About the size of a 1N4002

unknown device in TO-220 package: IR9502 International Rectifier's website doesn't recognize it.

Are they just loose components,or are they in a piece of equipment?

If the latter,you can probably work out what they do,& find something similar to compare

with.

VK6ZGO

Excavatoree · « **Reply #49 on:** May 12, 2011, 04:19:24 pm »

That's the problem - these are "grab bag" components. I suspect the diodes are house-numbered, but I can't explain why I can find no info about the IR parts.

I did a bit of testing on the diode - I reverse biased it up to about 200 V (limit of my curve tracer) with no breakdown.

It must be a garden variety rectifier with a house number or a number from some defunct manufacturer or something.


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Author Topic: What's this please? (Component Advice) (Read 1320743 times)

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