Thanks,
any idea where I get something like that? I also wondered, how are you so sure. In what kind of application have you seen something like that before?
Thanks
What connector is this? Some type of coax...
http://th03.deviantart.net/fs70/PRE/i/2013/316/a/4/connector_by_phaedrus2401-d6u1cyp.jpg
It's just a standard male SMA connector, RP-SMA swaps the pin to the other side of the connection.
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)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.I have never seen a JFET used like that before. I wonder if they are using it as a Schottky diode.
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.
Oof! It's out of range for my Fluke 179, so beyond 50 M? - Is that indicating that there isn't a short?
This wouldn't happen to be from a Williams pinball machine would it?
Oof! It's out of range for my Fluke 179, so beyond 50 M? - Is that indicating that there isn't a short?What ac voltage do you measure on the between 0 V an 115 V terminals the output side when you put 120 Vac mains voltage on the 0 V an 115 V input terminals?
Google search 3P87 transformer takes to http://www.arcade-museum.com/manuals-videogames/P/Playchoice-Ctop.pdf in parts list. Schematic shows 'isolation transformer'.
Oof! It's out of range for my Fluke 179, so beyond 50 M? - Is that indicating that there isn't a short?It's probably a 1:1; 115 V; 1 A isolation transformer.
On the multiple voltages side only the 0 V an 115 V terminals has been soldered, same voltages as on the other side, so it has been used in 1:1 mode.
If the transformer is broken you should be able to replace it with any standard 115 V or 120 V 1:1 isolation transformer with a 115 VA (115 V * 1 A) or higher rating.
Like these two 130 VA and 135 VA examples from Mouser:
http://www2.mouser.com/ProductDetail/Triad-Magnetics/VPS230-570/?qs=%2fha2pyFaduhOD0jibV2nm8lnZ4UdaxDociGravMI74YJ9J53fBGaVA%3d%3d
http://www2.mouser.com/ProductDetail/Hammond/169TS/?qs=%2fha2pyFadug3UFJw%252bR6Egr5Hadcx0iEbk%252be6%252bvco6Ok%3d
So what is this unit doing? Cleaning/stabilizing the AC?
The parts are marked as Fairchild 1J20CB, but I cant find any reference to them anywhere.
**Package Marking Convention
Line 1:$Y (Fairchild logo)
&Z (Plant Code)
&3 (3-Digit Date Code)
&K
Line 2:FDD
Line 3:6685
Oof! It's out of range for my Fluke 179, so beyond 50 M? - Is that indicating that there isn't a short?It's probably a 1:1; 115 V; 1 A isolation transformer.
On the multiple voltages side only the 0 V an 115 V terminals has been soldered, same voltages as on the other side, so it has been used in 1:1 mode.
What ac voltage do you measure on the between 0 V an 115 V terminals the output side when you put 120 Vac mains voltage on the 0 V an 115 V input terminals?
Doesn't look like anything is wrong with this to me.
And with an intermittent fault, I really doubt this isolation transformer is what causes the fault.
But if the transformer is broken you should be able to replace it with any standard 115 V or 120 V 1:1 isolation transformer with a 115 VA (115 V * 1 A) or higher rating.
Like these two 130 VA and 135 VA examples from Mouser:
http://www2.mouser.com/ProductDetail/Triad-Magnetics/VPS230-570/?qs=%2fha2pyFaduhOD0jibV2nm8lnZ4UdaxDociGravMI74YJ9J53fBGaVA%3d%3d
http://www2.mouser.com/ProductDetail/Hammond/169TS/?qs=%2fha2pyFadug3UFJw%252bR6Egr5Hadcx0iEbk%252be6%252bvco6Ok%3d