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SMD SMT surface mount replacement or equivalent for 2SC992 KSA992 2SC1845 KSC1845 BC549 BC550 BC559 BC560 low noise BJT transistors

I've ordered a mini hot plate from Aliexpress. When it arrives, I'll do a video comparing hand soldering, then hot air, and finally hot plate for these tiny adapter boards. I've done the hand soldering already and know how much more difficult it is than through hole work. I've got a cheap hot air gun from some gift long ago. For $20 I'll have a cheap-but-works test bed for hot plate. Stay tuned.
 
dlucy said:
I've ordered a mini hot plate from Aliexpress. When it arrives, I'll do a video comparing hand soldering, then hot air, and finally hot plate for these tiny adapter boards. I've done the hand soldering already and know how much more difficult it is than through hole work. I've got a cheap hot air gun from some gift long ago. For $20 I'll have a cheap-but-works test bed for hot plate. Stay tuned.
Click to expand...

I've shared the results of using the micro hot plate in a different thread:

How to mount a SMD device on one of these tiny adapter boards https://audiokarma.org/forums/index...apters-for-through-hole-replacements.1079170/
 
Richard P said:
I already have the soldering paste and hot air station, so I'll probably pre-mount them on the boards so I can do them all at once. It does take some practice and i've blown my share of tiny capacitors and resistors off of boards while I was removing ICs and other components but I have it down pretty well now. A single SOT-23 should be simple. Kaptan tape is useful to protect plastic connectors and other components you don't want to disturb.
Click to expand...
When you try this, will you share the results (how to use a hot air gun for SMD replacement transistors) in this other thread?
How to mount a SMD device on one of these tiny adapter boards is covered in a different thread: https://audiokarma.org/forums/index...apters-for-through-hole-replacements.1079170/
 
I did just come across a situation where an SMD part on an adapter might not work.

The Yamaha AX-890 amp that I just finished uses a 2SD1915F in each channel of the power amp section to do thermal tracking in the idle current section. It is mounted flat (aka horizontal) on the top of a tab of the main pcb.

When the main heatsink is mounted it presses down on the transistor+tab. I can see that this pushes the tab downward slightly. The 2SD1915 measures 2mm thick. A 2SD2704K mounted to an adapter board measures 2.75mm thick.

So my concern is if the tab on the pcb will be overstressed, and if the contact geometry will change in a way that the transistor is not making full contact with the heat sink. Thermal paste can only do so much.

This may in fact be a non issue, but I thought that it might be worth bringing up.

:beerchug:
James
 
Is there opinions about the:
2SC869 NPN, Pc 0.2W, Ucb 160v, Uce 40v, Ueb 5v, Ic 0.03A, TJ 125°C, ft 75MHz, hfe 35
Very hard to find the replacement. From what is really to find now is 2N5551 (very similar but a little bit better in everything), but it's not SMD. And as I can understand it's not very linear. Popular KSC1845 is worse, KSC2310YBU is not available in my country; good sounding (accordingly to reviews) SMD 2sc2713-BL is worse by voltages. The 2SC2310 is low vlotage.

2SA628 PNP, Pc 0.15W, Ucb 30v, Uce 25v, Ueb 4v, Ic 0.1A, ft 50Mhz, hfe 55
?
 
What kind of n adapter do I need to replace the sk97 by the and version f the Lsk 389 in my Sansui au 717 and if possible a link to where I could purchase one. Thank you for your help.
 
Unfortunately, I bought 10 of them in the smd package and hence the question. I will probably have to purchase the to-78 version now. Thank you
 
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