but a LED, if actually blinking

But it's not an LED it's a normal diode!

 

I admire your perseverance, but I would ask you to take a step back and consider the task difficulty.

In the past years, i've been trying to fix this really old (and very hard to find) phone

So, this obsolete telephone answering machine broke and you have been trying to fix it for a while.

While trying to fix it recently, you reversed the polarity on the power input...

its not the multimeter that makes the diode flash, it's connecting the power supply that does, first time I tried it was with the correct polarity (negative on bottom pad and positive to top pad, the one closer to the edge of the board)
and the diode started flashing, then I tried reversing the polarity, and it still blinks, I realize I may of have done more damage

By your own admission...

i dont really have any experience in electronics or repair

It was broken before you started, a diode (but not an LED) is lighting up in a fun sparky sort of a way and you have also reversed the polarity of the power input.

You are basically trying to identify components and replace them and there are a lot of components.

I am the last to discourage education, but given what you are up against, would it not be better to leave this one as a simple spare land line phone (since it still works as that) and move on to a more systematic electronics education plan? Or is there something particularly special about this one?

 

Yes, probably something like that.

With no schematic we are flying nearly blind.

 

The TS could use the boards for salvaging components and learning how to test them.

 

Sorry for the late reply everyone, I get that trying to fix that thing will be rather difficult, but i've spent this much time, i'll spent more and will not give up on it unless I really run out of options, for now I ordered a replacement diode and see how it goes from there

There are so some SMD resistors (around 2 or 3 of them) on the bottom of the board, there is no continuty across them (then again im not sure if you are supposed to test them like that) but most of the other ones do have continuty, I wonder if those are problematic or something

 

Can you read numbers on the resistirs?

 

Can you read numbers on the resistirs?

I can, I just use a nice resistor code calculator on the Internet and just look 'em up by ohm rating on eBay

 

Oh by the way, does anyone know if I can still buy this IC online somewhere?

This IC handles the phone's keypad, but some keys do not work, I checked to make sure that the wiring signal makes it to the IC pins and it does, but some keys just don't work, so the IC must be half-dead? It was working but the ribbon cable snapped because it was glued instead of being soldered even though there were pads, good job GE, anyway that sorted a bunch of wires together in the keypad, if im correct doesn't that simulate alot of keys being pressed at once? Can ICs even 'half-die'?

I removed the bad cable and rewired every single thing back manually, I made sure that wires do not touch each other and that its wired exactly as it was before with the correct orientation, and again, some keys work as they are supposed to but some others dont.

Whatever the case, it seems I can find it by looking up 'OKI M6263-01' and they do come up in certain stores but the bottom number '6112Z09' is the only number that does not match, would it still be okay to use? and uh, im not sure how to say this, would the IC pins be the same as the one I have now? Or would I have to figure out wiring to match the new IC?

 

The bottom number is probably a date code/batch number and doesn't mean that the chip is different.

 

Oh by the way, does anyone know if I can still buy this IC online somewhere?

This IC handles the phone's keypad, but some keys do not work, I checked to make sure that the wiring signal makes it to the IC pins and it does, but some keys just don't work, so the IC must be half-dead? It was working but the ribbon cable snapped because it was glued instead of being soldered even though there were pads, good job GE, anyway that sorted a bunch of wires together in the keypad, if im correct doesn't that simulate alot of keys being pressed at once? Can ICs even 'half-die'?

I removed the bad cable and rewired every single thing back manually, I made sure that wires do not touch each other and that its wired exactly as it was before with the correct orientation, and again, some keys work as they are supposed to but some others dont.

Whatever the case, it seems I can find it by looking up 'OKI M6263-01' and they do come up in certain stores but the bottom number '6112Z09' is the only number that does not match, would it still be okay to use? and uh, im not sure how to say this, would the IC pins be the same as the one I have now? Or would I have to figure out wiring to match the new IC?

Likely a proprietary chip. You are not going to be able to buy it.

I have seen those "stores" you mentioned. None of them are well known stores. My guess is they are ripoffs. I have seen them pop up on other searches too.


It is time for a new phone. some things are just not worth the trouble.

 

but the bottom number '6112Z09'

Likely denoting week 12 from year 1961. Many companies used/use that system. The rest could be a code to denote the factory where it was actually encapsulated.

 

Hello, sorry for late response

Replacement diodes have arrived..! I removed the original blinking one and it was definately bad, it literally fell apart in two pieces, also the board below it was black, likely from it blowing up? im not sure

I installed a new one but unfortunately nothing, it does seem like the phone reacts a bit differently, I can hear a pop sound from the front speaker but thats about it im afraid, those resistors with no continuty are my next target, after that im not sure what else I could go after

 

There are a few IC's (integrated circuits) on the board. They do not respond to reversed polarity with alacrity. That is, a very short period will likely destroy them.

 

There are a few IC's (integrated circuits) on the board. They do not respond to reversed polarity with alacrity. That is, a very short period will likely destroy them.

Are you saying that reverse polarity has killed my ICs? If so thats when im really helpless, is there a way to test them somehow? I always manage to throw reverse polarity at ICs somehow (because im an idiot XD) and they always survive it, well that said I know not every IC can survive it, since the board is old there may not be as much protection, also you can tell they are old ICs just by how thick they are

 

Are you saying that reverse polarity has killed my ICs? If so thats when im really helpless, is there a way to test them somehow?

Yes, I meant it likely killed the IC's, as there was no protective circuitry.

I always manage to throw reverse polarity at ICs somehow (because im an idiot XD) and they always survive it,...

Apparently you need more practice.

 

Yes, I meant it likely killed the IC's, as there was no protective circuitry.



Apparently you need more practice.

Yep you are probably right, ive only actually done it 4 or 5 times, most was on a EPROM IC for my PC (the bios chip) which I inserted in with the wrong orientation and it got REALLY hot, in fact it burned my finger! but it still survived somehow

There is also a humming noise now, that lasts for about 4 seconds before it fades, how weird

Oh i've also thought about measuring voltage across the board, not too sure how to do that actually but i've thought of sticking my negative multimeter probe on negative power input pad and then just touch positive ends on wherever i want to measure voltage on the board, is that how it works or..?

Im also kinda scared to leave it on power for too long, who knows what'll happen? But maybe I can also identify a short somewhere if I do that, find out where the board gets really hot, dont really have any thermal cameras, but I can drench the board on Isopropyl Alcohol and see the spot where it evaporates faster

I wish I could do the same thing on the cassette mechanism but I dont think it's
too good of an idea to pour liquid on there:

It's also very surprising that the cassette belt hasnt degraded, they can literally turn into paint after a few years

I know that this point the problem is a bad IC, but there are still a few possibilities left like the resistors and a possible short somewhere,

 

Oh my god I have new information, I left it to power on for a few seconds to see what what'll happen, then removed it from power and touched the board to see if anything got really hot

And it did, what looks like a transistor was so hot that my mind pulled my finger instantly, could that be the culprit?!?!

Here it is:

Kinda worried how it's marked as IC22, is that an IC ? Please dont tell me its proprietary

Its hard to make out whats written on it but it says KIA 780SPI 6K

Update: It actually says KIA 7805PI 6K, sorry its kind of hard to read!

 

7805 is a standard 5 volt regulator.

 

7805 is a standard 5 volt regulator.

So then, I can definately replace it! I found this, which is a similar one, it says KEC KIA 7805PI but the bottom writing is 4E instead of 6K, does that matter?

P.S. you can click on highlighted words, they are links!

 

Hello,

The 4E and 6K could be production codes. It will have no influence on the actual function of the part.

Bertus