Unidentified SMD transistor - anyone knows 6TL???

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Khron said:
I don't suppose you can be bothered to trace out what it's connected to..?
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Dear "Khron Cave"-man! What kind of question it's? Or rather judgement than question... Are you some forum troll? Did i do something to you or something else is matter here? Of course i traced the circuit, but this is just some kind of buffer (don't know how to properly name it in english), in 5V regulation circuit. It can be anything but it looks like PNP BJT, like i described this in main converter topic. Collector placement (assuming it is PNP) is proper (grounded), base and emitter also. Manufacturer described it as "Q" on PCB (like multiple other transistors). It isn't PNP, because alredy checked this, it isn't NPN also, assuming it could be FET - and there's question - which one? There's no problem to substitute BJT, with FET this is not so simple.
This is why i started separated topic for only this single SMD part. Maybe someone here knows it, had problem with such part or anything else possible. I searched multiple smd based units i have at home (also in the rest of the swissonic circuit) for "6TL" and didn't found anything.
Tried to replace it with multiple different transistors, BJT and FET.
So simply answering your question (judgement), yes i "bothered".
 
Now-now, there's no reason to resort to name-calling.

Would you be willing to share with us some sketch of that part of the circuit? Just to try to avoid language barriers etc. And perhaps a (well-lit, well-focused) photo of that part?
 
As wrote before in Swissonic topic, my english is rather autistic, so if i understood something wrong, then sorry.
I'm currently out of home for over a month, so for now, have no option. When i will back (and change broken phone) then i'll be able to draw schematic and do its picture, same like pcb picture.
 
deedee said:
Are you sure it's a transistor? Not a voltage regulator?
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Yes, i'm sure, all the voltage regulators and voltage detectors from that list are different smd package, mostly 5pin components. Swissonic marked voltage regulators as "V" or "U" (don't remember exactly, have no unit with me), this one is marked "Q" like all other transistors. This section have regulation based on transistors and mainly on that big 4pin diode, which is near electrolytic caps.
 
Based on the TO92 next to it, it seems pinned backwards, as normally it would be EBC, but the Emitter seems to go to the SOT23 Collector. May be one of those older ones that's backwards.
 
FIX said:
Based on the TO92 next to it, it seems pinned backwards, as normally it would be EBC, but the Emitter seems to go to the SOT23 Collector. May be one of those older ones that's backwards.
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Hmmm, fact, that there were rarely backwarded SOT23, this could explain why they used two different BJT in the same section. THT pinout don't explain anything since multiple THT BJT have different pinout, but it could explain NPN (then Emitter would be grounded) in SMD, which i suspected, but possibly testing i could connect THT NPN wrong way. Damn, probably you are right, but i will test it in a month to check. Thanks man a lot!
 
Per the (slightly fuzzy) picture it is hard to tell if the PCB uses a U designator for the voltage regulator. If so then there is a very high probability Q2 is a transistor and not an IC. The fact that it possibly connects to an adjustable inductor makes me wonder if it is not some sort of oscillator. Might make sense to pop the part off the board and put it on one of those $25 Asian part identifier/testers just to see what it deciphers.
 
Hubbub said:
Per the (slightly fuzzy) picture it is hard to tell if the PCB uses a U designator for the voltage regulator. If so then there is a very high probability Q2 is a transistor and not an IC. The fact that it possibly connects to an adjustable inductor makes me wonder if it is not some sort of oscillator. Might make sense to pop the part off the board and put it on one of those $25 Asian part identifier/testers just to see what it deciphers.
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For the parts description on PCB - this i'm sure 100%, regulators are marked U or V, here's Q like other transistors, as stated before.
This is voltage step-down circuit, 12V to 5V converter. One of two 5V sections for logic circuits. Second one is made just with 7805 regulator, this one, i believe, had to be ultra low noise or stable or other reason which designer had in mind. Yes, it is adjustable inductor marked L11, there is L12 fixed inductor at the output too. I tried to adjust L11, but stuck, i'm not sure isn't glued after factory setup.
This section is source of noise, i checked this with oscilloscope.

Here's what i wrote in other thread, checking it with multimeter (not sure it is good as 25$, this one cost something like 250$ ;) ):

Checking Base and Emitter it give the constant beeping sound, so it shows that this part of the circuit is shorted. Base and Emitter works as the same node.
Between these nodes and Colector there's reading as for PNP transitor.
B/E red probe, C black probe - shows nothing.
B/E black probe, C red probe - shows reading
Summary - testing was made out of the PCB, it acts like broken PNP transistor, this is the only part in the whole circuit which have strange reading (yes i checked every capacitor, diode, transistor, IC, inductor, regulator and everything else), it's part of the noisy section, so i did my lessons in most aspects of circuit diagnose, in theory and practice. Of course testing burnt parts can show wrong reading, everything says for now it's PNP, but it doesn't have to be. Yesterday Paul "FIX" push me to think that this could be NPN with reversed (non standard) pinout in SOT23, or second option is that this is FET (seen in similar circuits also). If this would be generic PNP, then Q1 and Q2 both rather would be same type PNP SOT23, to cut the costs. Don't see any reason to use two different PNP transistor in such circuit.
 
ADaddy said:
Yes, this one, but it isn't marked v7805 as you think about 5V regulator, but V7005, which is varicap diode:

https://www.web-bcs.com/diode/dv/ma/MV7005.php
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And what exactly would that be doing in a device like this? Especially if it's marked "Q" as a transistor.

ADaddy said:
Checking Base and Emitter it give the constant beeping sound
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The continuity indicator on multimeters beeps if the resistance measured is less than whatever threshold they decided when designing it. Some bench metes allow you to select that threshold. What actual resistance are you measuring there? Could that inductor be connected between the apparently shorted base & emitter?

That's what reverse-engineering that piece of circuit would help reveal...
 
Khron said:
And what exactly would that be doing in a device like this? Especially if it's marked "Q" as a transistor.



The continuity indicator on multimeters beeps if the resistance measured is less than whatever threshold they decided when designing it. Some bench metes allow you to select that threshold. What actual resistance are you measuring there? Could that inductor be connected between the apparently shorted base & emitter?

That's what reverse-engineering that piece of circuit would help reveal...
Click to expand...
I'm sure here what i'm writing, you have also THT footprints for 2 and 3pin diode as a substitute. This picture from web is low resolution, so you may see "Q" but in fact it is marked "D" like rest of the diodes. Motorla V7005 also is proper part, which fits datasheet correctly. Besides that, this part isn't issue here at all, so i would skip all considerations around it.
I measured transistor out of the circuit, for separate resistance measurements, i have written them on a paper at home, so when i will back i can share it, but it don't tell you anything.
 

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