Transistor markings

whiz115 · Jun 1, 2023

Hi

i'm trying to repair a vintage pocket tv (Casio tv-200), the owner burned it by applying more than 3V
from the DC jack. Problem is there's no schematic available and the transistor in the photo is unknown
to me. Almost everything else is identifiable e.g NJM2070 amplifier IC, M51348FP IF IC, but i have to
identify: top side IC, the SOT-89 transistor (which becomes extremely hot when powered) and also i
want to identify the component in the blue circle...is this a fuse? because certainly it's not an 100k
resistor, or diode unless if it is broken...

Can somebody help so we can fix this device?

Tony Stewart · Jun 1, 2023

There is an SMD code of "M Y" and this is usually called the SOT-223 case or 3+ tab flat.

Good luck. Most likely a 3V regulator.

https://smd.yooneed.one/code4d59.html has many but not all Mfg of this code.

whiz115 · Jun 1, 2023

Tony Stewart said:
There is an SMD code of "M Y" and this is usually called the SOT-223 case or 3+ tab flat.

Good luck. Most likely a 3V regulator.

https://smd.yooneed.one/code4d59.html has many but not all Mfg of this code.

After cleaning more the package and close checking it, i revised my post putting a more clear photo
also changing my hypothesis it could be either a transistor or regulator... you really think it's a regulator? even if it is an LDO regulator it can't regulate so close to the 3V power supply and other than that why else a regulator to exist? for noise rejection? i don't think they used a regulator just for noise
filtering

also SOT-223 is too big and different, i believe it's SOT-89

tepalia02 · Jun 1, 2023

I can see some similarities with this too: https://electronics.stackexchange.c...an-smd-voltage-regulator-chip-top-marking-15p

augustinetez · Jun 1, 2023

I get the code marking to be a 2SC2873Y, which would also appear to coincide with the age of the Sinclair device as the start of manufacture of those transistors was 1980 (and the code is "MY" without the space between letters).

whiz115 · Jun 2, 2023

augustinetez said:
I get the code marking to be a 2SC2873Y, which would also appear to coincide with the age of the Sinclair device as the start of manufacture of those transistors was 1980 (and the code is "MY" without the space between letters).

any opinions also for the other components i mentioned??

Tony Stewart · Jun 2, 2023

whiz115 said:
also SOT-223 is too big and different, i believe it's SOT-89

I agree or aka SC-62
too many stds for similar shape and too many brands with same SMD code but another possibility is https://www.mouser.com/ProductDetail/Toshiba/2SC2873-YTE12LZC?qs=B6kkDfuK7/AeXIaOyNZg%2BA==

1. MY 2SC2873-Y Toshiba SOT-89 NPN transistor GP, 30V, 1.5A, 500mW, B=90..180, 120MHz
2.

augustinetez · Jun 2, 2023

whiz115 said:
any opinions also for the other components i mentioned??

Based on it needs a 3v supply, hardly likely to be a 3v regulator.

Bit hard to tell from the photo, but it might be in some sort of voltage multiplier circuit (the 100k device circled may be an inductor).

I have a similar small tv in the shed somewhere, not sure what brand, I'll have a look in the morning and if it is a Sinclair, will whip the back off and check.

Nigel Goodwin · Jun 2, 2023

augustinetez said:
Based on it needs a 3v supply, hardly likely to be a 3v regulator.

Bit hard to tell from the photo, but it might be in some sort of voltage multiplier circuit (the 100k device circled may be an inductor).

I have a similar small tv in the shed somewhere, not sure what brand, I'll have a look in the morning and if it is a Sinclair, will whip the back off and check.

The OP's set is a Casio as mentioned in the first post.

augustinetez · Jun 2, 2023

Seniors moment - will check in the shed after I hang the washing out - back in a little bit.

augustinetez · Jun 2, 2023

My little TV is a Casio TV-410, so likely a different circuit without taking it apart and checking.

whiz115 · Jun 3, 2023

augustinetez said:
My little TV is a Casio TV-410, so likely a different circuit without taking it apart and checking.

For your pocket TV and for many other similar models, there's plenty of material available but not for
the tv-200.

anyway on this video speaking about your model at 0.58 minute shows exactly the same
component as the one i'm asking above...it's the blue one with the printed 100k on it, so
what is it? an inductor?

Probably i have found more affected components...do we know what type of transistors are the
"A6" SOT-23 type ?? is this marking common for transistors? because from what i can find seems it
can be anything between a diode to transistor.

this case needs schematic....i don't think such repairs can be done with educated guesses, especially
if the component is burned you can't even test it.

augustinetez · Jun 3, 2023

A schematic would certainly help.

A6 comes back to a variety of diodes, MOSFET's and LDO regulators, so without a schematic, it comes down to trying to trace out the circuitry around the component and seeing what might be the obvious component.

whiz115 · Jun 3, 2023

augustinetez said:
A schematic would certainly help.

A6 comes back to a variety of diodes, MOSFET's and LDO regulators, so without a schematic, it comes down to trying to trace out the circuitry around the component and seeing what might be the obvious component.

i'm not that expert...do you recommend i should leave it? although i already got a replacement
transistor for the MY. (i could try to ask for help from a repair shop, although i'm not sure it can do
better job than did since, it's an smd based device probaby using 0805 and without schematic
an experience on such devices is needed or else it makes it challenging).

by the way do we know what that 100K is on the video?

augustinetez · Jun 3, 2023

When I get a chance later today, I'll open mine up and see if I can measure that 100k component.

augustinetez · Jun 4, 2023

The item marked 100K is a 10μH inductor i.e. small coil and is part of the power supply circuit.

I would suspect there are other faulty components as well as that transistor and without a schematic I think it's going to be nearly impossible for you to repair it.

whiz115 · Jun 5, 2023

augustinetez said:
The item marked 100K is a 10μH inductor i.e. small coil and is part of the power supply circuit.

I would suspect there are other faulty components as well as that transistor and without a schematic I think it's going to be nearly impossible for you to repair it.

going e-waste probably for a couple of smd semiconductors it's not that great though...

there's a ton of inductors in there coming into various shapes, that's why i couldn't
be sure for that 100k since it's different from any other smd type they are using.
also seems there's a mix of 0603 and 0805 smds and look like hand soldered.

so..okay if nobody has nothing better to propose so it can be fixed.

augustinetez · Jun 5, 2023

Trouble is, you could be replacing semiconductors left right and center before finding any other dud's with out a schematic for guidance.

There appears to be a service manual on Sams https://www.samswebsite.com/en/photofact/search?t=model&o=0&k=TV200&submit=Search&s=Search but by the time you've paid what they want for it, you could probably pick up another TV

whiz115 · Jun 6, 2023

augustinetez said:
but by the time you've paid what they want for it, you could probably pick up another TV

i'm not trying to fix it for me and it's not for viewing purposes...you cannot watch tv on such a device
due to its size, mobile phones can offer greater experience.. and also it can't decode digital signals.

yes the link you gave seems alot of money, the total cost of repairing wont worth it...since these devices
are sold around $60 on ebay.

Transistor markings

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