need to understand how a diode (current limit?)..I have seen in some older
gear,..a diode glowing,...not an LED,...thought maybe being driven in inverse?...

thanx

 

It probably wasn't a diode but a neon lamp if it was for current limiting? Aren't neon lamps used for that at times, or were?

 

I've seen some LEDs like that. They look like an ordinary small signal diode, similar in style to a 1N4148, but are actually LEDs. They were being used as status LEDs on a PCB to aid in trouble shooting.

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Inside every little problem, is a big problem trying to get out.

 

A neon lamp can be used to generate a constant voltage but not current. The only two terminal devices that are current limiting are some called constant-current diodes, but they usually consist of a JFET with the gate connected to the source to provide the constant current function.

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Carl
Curmudgeon Elektroniker

 

no,...I don't think so...
the diode appears in a clock circuit,near a large cap,...does not appear
as a neon,....(flickering...),...but as a constant glow (red)...equipment is an
older JVC stereo VHS....

and thanx for the replies..

 

A neon lamp will normally give off a constant orange glow (which can look red with a red filter). They usually only flicker when they get old, after many hours of operation.

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Carl
Curmudgeon Elektroniker

 

Just before everybody tries to solve a riddle how about two photos?
(one with the device glowing and one off)

A picture says more than thousand words.

Boncuk

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Proper Planning Prevents Piss Poor Performance

 

have yet to post either pics schm,..or other
do not have camera for my beast here..
that's why I tried to present my delema as I did..

also, while wr're it it,..could anyone provide a sch for keyboard or pad
endcoder...and an example of hard-wired diode mem?

thanx again..

 

It's probably a status LED used for troubleshooting. If it's near a large cap, that could be part of the power supply circuit, maybe an indicator that the power is on.

If it looks like a diode but it glows, it's an LED in a diode-type housing. I too have seen these on some older boards, as status or troubleshooting indicators.

 

Many years ago they made current-limiting "diodes" (that had two leads like a diode) from a Jfet with its gate connected to its source.

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Uncle $crooge