a few diodes,if you please

[NATY]

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

 

[smanches]

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?

 

[kchriste]

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.

 

[crutschow]

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.

 

[NATY]

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..

 

[crutschow]

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...

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.

 

[Boncuk]

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

 

[NATY]

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..

 

[kpatz]

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..

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.

 

[audioguru]

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.