Hello,

In the past years, i've been trying to fix this really old (and very hard to find) phone, i dont really have any experience in electronics or repair (but have learned a few things when I was researching in attempts to find the problem) and today I discovered something interesting, whenever I apply power to it, a diode blinks...? I don't think they are supposed to blink? Did I get polarity wrong or something? The diode is directly connected to one of the power pins of the jack

What could this mean? Thank you

 

The brand, model and a picture would be good to have.

Otherwise someone could try this:

 

Hello,

In the past years, i've been trying to fix this really old (and very hard to find) phone, i dont really have any experience in electronics or repair (but have learned a few things when I was researching in attempts to find the problem) and today I discovered something interesting, whenever I apply power to it, a diode blinks...? I don't think they are supposed to blink? Did I get polarity wrong or something? The diode is directly connected to one of the power pins of the jack

What could this mean? Thank you

It could mean the phone isn't really all that old and has a blinking LED built into it. It could mean you're having a stroke. Hard to tell without more details!

 

Thanks for the reply everyone, I should of have given you a model number you are right, but the problem is that phone is extremely rare and has no information online, its an old GE combination of a landline phone and cassette answering machine. But the part that is blinking isn't an LED, its seriously a diode (I know hard to believe) and everytime it blinks a pop sound is heard through the speaker, I can tell that its a diode because it looks like one and is marked as such in the board

Phone Model Number (Though I doubt you can do anything with it):

And the component that blinks:

I can clearly see that it blinks every around a second or so, i doubt thats normal and ive never ever heard of diodes blinking

 

Can you darken the room and video it? Catch it on video, before anything else. This is a good one. Do you know anything about electronics? Do you posses the skill to remove and test the diode? But only after the video. Do you have any test equipment?

I would love to see that diode blink.

 

Can you darken the room and video it? Catch it on video, before anything else. This is a good one. Do you know anything about electronics? Do you posses the skill to remove and test the diode? But only after the video. Do you have any test equipment?

I would love to see that diode blink.

Will video it tommorrow because it's getting kind of late here, I have a fair amount of soldering experience and a multimeter that can do volt measurements, continuty, ampere measuring and ohm measuring, so I can remove and test the diode, and replace it if need be. As for experience, i'm self taught, ive been trying to fix this for a very long time and ive doing research on component level repair in the hopes of figuring the problem out, so I dont really know alot about things like tracking problems in a circuit boards apart from basic continuty tests, that said in willing to do alot in hopes of fixing that phone, and maybe that diode is finally a clue as to what the problem is

 

From that very blurry image it looks like burn marks. The phone is toast (literally). Toss it.

 

From that very blurry image it looks like burn marks. The phone is toast (literally). Toss it.

No not really, that black mark was created when a solder pad fell off as I was removing the power jack, that solder pad was connected to nowhere looking at the tracks at the bottom of the board, it was for that third pin of the power jack which the board made no use off, it's also exclusive to that pad and there isn't one anywhere else on the board, in short, the board looks fine and so does every component (which makes it very difficult to pinpoint the problem)

 

A blinking diode is most certainy an indication that you have a bad diode.

And that is probably not the only thing that is broken.

Do you have a DVM with which ti test the diode (as a double check).

 

Since someone here asked, here is a video that shows the blinking diode, also the only testing equipment that I have is this cheap multimeter:

Since this diode is most likely bad, i'll have to replace it, but how would I find an appropriate diode if I don't have a schematic of the board...?

 

Do bad diodes blink? That must be a physical spark, as the physics of ordinary silicon and germanium diodes would not allow them to act as LED's.

Edit: Looks like a spark maybe from a very high reverse bias?

 

Do bad diodes blink? That must be a physical spark, as the physics of silicon and germanium diodes (not doped) would not allow it.

Whatever causes this to happen, it's still strange so chances are it's bad, but i haven't the slightest clue as to what replacement diode to get, I don't even know the correct polarity for the power input pads, at one point I went screw it and flipped the power wires, but it still behaved the same, the blinking diode. a schematic would be nice but there isn't one I can find

 

Oh and before anyone suggests that I check the marking on the casing to find out polarity, it's no good, it's just this

does not say whether it's center positive or not, so yeah im out of luck, not knowing polarity makes it even more difficult, unless this mark means something else I don't know

 

Is that a dark band or shadow in your picture. If a dark band, then that is the negative end (cathode, lower potential end). Otherwise, remove it and see whether it conducts differently depending on polarity of your meter probes.

Center positive is more common. You can test between the sleeve/barrel and an obvious common/ground on the board. Then test the pin. I would do those tests with the diode removed and not replaced, since we know it is bad.

Electrolytic capacitors will likely have their negative side attached to ground/common.

 

A blinking diode is most certainy an indication that you have a bad diode.

And that is probably not the only thing that is broken.

Do you have a DVM with which ti test the diode (as a double check).

In that kind of diode is there a piece of relatively thin wire from one electrode to the semiconductor on the other electrode?
If that's the case then maybe there is a high current pulse making that wire glow.

 

A pulse came to mind as well, but im not sure what could be causing it, maybe that big red capacitor charging and discharging...? i dont know

Here is the board, maybe someone could figure out polarity as well based on clues on how everything is wired?

Top of the board:

Bottom of the board (ignore horrible soldering, its temporary):

As I mentioned, that black pad doesnt seem to be connected anywhere, so im not worried about it

 

Spark v. glow? Wonder whether a decent radio would pick up the spark if nearby?

 

Since someone here asked, here is a video that shows the blinking diode, also the only testing equipment that I have is this cheap multimeter:

Since this diode is most likely bad, i'll have to replace it, but how would I find an appropriate diode if I don't have a schematic of the board...?

Looks like a static image of your DMM to me.

 

Looks like a static image of your DMM to me.

Im not sure what you mean, the video is a little staticy (because I needed the room to be dark to catch the blink, and phone cameras dont do well on dark, so much for the S9 camera samsung keeps bragging about)

I dont know what you meam by DMM, except maybe Digital MultiMeter? the picture of it is fine

 

Looks like a static image of your DMM to me.

The underlined word 'here' in that message (post #10) is a link to the video which does indeed show a blinking diode.