seeking transitor replacement for 2SC2705 - Page 1
Forum section: electronics / beginners

author: mjrpainless
author_rank: Contributor
timestamp: December 24, 2013, 05:07:34 am
content: New to the forum so if this is the wrong place, or the wrong forum, let me know.I am currently seeking a replacement transistor for 2sc2705, as they are end of life.the only thing that i have been able to find is one of these: KTC3206 But they are also not available, aside from on ebay. And frankly i don't want to end up with fakes.Q708 is the one that is blown, and I'm looking at replacing both Q708/Q707 at the same time.

author: mrkev
author_rank: Regular Contributor
timestamp: December 24, 2013, 07:38:52 am
content: Well, it's just a basic current mirror and by the quick look (really have to go) at the voltage, about 12mA is running through, so you could probably use almost anything...

author: SeanB
author_rank: Super Contributor
timestamp: December 24, 2013, 07:50:47 am
content: MPSA42 will probably work there, not exactly a demanding application aside from the possibly high voltage. Gain is a little lower but there you do not really need much, more just handling the voltage, so a 300V part will do. 40c each at Digikey as well, so do both channels at the same time. 10 will be cheaper. Order new capacitors for the amp at the same time, the originals probably are getting elderly.

author: JOERGG
author_rank: Contributor
timestamp: December 24, 2013, 08:41:57 am
content: Out of this comparison tablehttp://www.eca.de/xtshop/product_info.php/language/en/info/p73_vrt-Vergleichstabelle-Band-1-Ausgabe-2010-2011.html/XTCsid/uob605nd8p3i1cee9c31h4dp062SC2705 Si-N =2SC2704:0,8W Comparision Types: BF 297...299, BF422(A), 2SC3467...69, ++

author: kripton2035
author_rank: Super Contributor
timestamp: December 24, 2013, 08:42:51 am
content: here is a list you can use :http://alltransistors.com/crsearch.php?mat=Si&struct=NPN&pc=0.8&ucb=150&uce=0&ueb=5&ic=0.05&tj=150&ft=200&cc=1.8&hfe=80&caps=TO92Cross-reference Search Result (Equivalent Transistors)Mat Struct Pc Ucb Ueb Ic Tj Ft Cc, pF Hfe Caps1. 2SC2705 Si NPN 0.8 150 5 0.05 150 200 1.8 80 TO922. 2SC2705-O Si NPN 0.8 150 5 0.05 150 200 1.8 80 TO923. 2SC2705-Y Si NPN 0.8 150 5 0.05 150 200 1.8 120 TO924. 2SC6132 Si NPN 0 0 0 1 100 TO925. 2SD2213 Si NPN 0.9 150 8 1.5 150 1000 TO92MOD6. ECG2341 Si NPN 0.8 0 0 1 150 2000 TO927. HIT468 Si NPN 0.8 0 0 1 85 TO92Mod8. HIT667 Si NPN 0.9 0 0 1 140 TO92Mod9. KTC1006 Si NPN 1 0 0 0.8 175 100 TO9210. KTC1026 Si NPN 1 0 0 0.1 175 120 TO9211. KTC1027 Si NPN 1 0 0 0.8 175 80 TO9212. KTC3205 Si NPN 1 0 0 2 175 100 TO9213. KTD1145 Si NPN 1 0 0 5 175 140 TO9214. SM2284 Si NPN 1 0 0 1.2 200 220 800 TO9215. STL73D Si NPN 0 700 0 1.5 0 TO9216. STSA1805 Si NPN 0 150 0 5 150 TO9217. STSA851 Si NPN 0 150 0 5 85 TO9218. STX616 Si NPN 0 980 0 1.5 0 TO92

author: mjrpainless
author_rank: Contributor
timestamp: December 24, 2013, 06:08:48 pm
content: Thanks for all the responses!So the small output capacitance for 2sc2705 has no real effect on this particular circuit?Also i am a little worried about the power dissipation because all around this particular area it is very burnt, see the picture attached. Would some heat sinks be a good idea?The problem area is in the bottom right hand side.

author: SeanB
author_rank: Super Contributor
timestamp: December 24, 2013, 06:39:35 pm
content: You might want to order around 20 clip on TO92 heatsinks then, and place the new transistors in with full lead length with clip on heatsinks on all the devices there. Probably most is from hot power resistors, but cool transistors will help as well. U91 definitely would benefit from a heatsink on it, do not know what it is but it runs hot.

author: mjrpainless
author_rank: Contributor
timestamp: December 24, 2013, 07:21:17 pm
content: Awesome! Thats what I was thinking. U91 is just a jumper, but Q701 is a K389 a dual channel JFET. Can you get heat sinks for the K389's?

author: SeanB
author_rank: Super Contributor
timestamp: December 24, 2013, 07:28:24 pm
content: Probably a clip on TO220 heatsink will fit it, or you will have to modify a clip on one to fit.