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2sc1451 sub for Pioneer (Can I use 2SC3467C ?)

sean sweeney

sean sweeney

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I have a receiver, SA-9100, and am a local tech of many different things here in STL... I have a pack of 2SC3467C transistors and was thinking they look like they could replace the 2SC1451's.... because they are obviously noisy and triggering the protect... I just got the amp in here and adjusted the amp and all the levels, idle current, balance of voltages, and offset are pretty stellar... there is a crackle and I hear the protect come in... the crackle sounds like the infamous 1451 in the amp driver... I would probably bet money on it! lol. I guess I want to know if that transistor and I guess I should use it for all the ones in the amp... otherwise I'll have to order some and have the amp here longer and this guy has a music store and needs this amp quick... not sure WHY... but he says he does... So I guess if anyone can pipe in, I really really appreciate it. Thanks a million!
 
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I see that it shows up on some searches as a similar... so maybe I'll give it a spin with the old dim bulb...
 
well it's 200v 0.1a 1w 150Mhz 40-320Hfe video drive transistor
but the case looks like a to-92L on steroids. hard to heat sink....
they do get warm, which is why I specified a TO-126 cased transistor that handles 1 watt bare and 7 watts heat sunk.

i'd try it for troubleshooting and watch it's temperature like a hawk.

having the amp QUICK, then having it blow out during a hard run (likely in a store) would be counter productive...
 
markthefixer said:
well it's 200v 0.1a 1w 150Mhz 40-320Hfe video drive transistor
but the case looks like a to-92L on steroids. hard to heat sink....
they do get warm, which is why I specified a TO-126 cased transistor that handles 1 watt bare and 7 watts heat sunk.

i'd try it for troubleshooting and watch it's temperature like a hawk.

having the amp QUICK, then having it blow out during a hard run (likely in a store) would be counter productive...
Click to expand...
thank you! I will... I bought a heat sensing camera and it's come in very handy for a lot of things like this... I didn't mean to be glib in my last post... I wasn't expecting instant responses... I just have this guy breathing down my neck... so you're saying... dim bulb it, watch for temp, then maybe try it and watch for heat... and if it works ok then maybe it's a fix?
 
I was thinking with its size it may dissipate heat better... but you're thinking a heat sink would be necessary... I can make that work... I just found a couple instances of them being suggested out there... so I guess it's been pondered before... I'll give it a go... and the amp driver on this is JUST the 1451's correct? as far as the gain stage.
 
so far it's working well... temperature is actually hovering at 100 when idle... that's about 10-20 degrees cooler than the 1451's...
 
PSX_20220215_150928.jpg PSX_20220215_150843.jpg I've got program running through the channel I swapped. The amp modules are inverted where left is right output, right? In which case it sounds fine. The protect comes on just right, abd here's some pics of levels up 2/3 with speakers hooked up... temp readings of the two transistors, sans heat sink...
 
So that worked, and it's doing ok, but the static is coming back at very random intervals... there are more 1451's in there... would they be causing that, or am I to keep looking at the amp board... I haven't been able to trace the static to one side, it's just too random and at long intervals apart... but similar to the initial sound that was much more constant...
 
Lots of other bad transistors in there too. Realistically anything other than the outputs and drivers should be replaced in the entire amp.
 
Ok, I was mistaken... I thought there were a few more in there, but, yeah, replaced all the 1451's in the amp... and there's still a little static about once every hour and a half... it goes into protect and then starts a minute or so later.... so I'm thinking there are some other steps up to the 1451... and I believe they're likely in the amp driver section, since it goes into protect. oook... so... if anyone knows the likely culprit next in the amp drivers... I don't think this guy wants to replace them all... he kind of balked at the stuff I've already done... but he's strangely clueless about audio, for owning a record shop! lol
 
Ok. I found some posts on here where the guy used 992's and 1845's to replace the other transistors in the gain stage before the 1451's... so I think I have those already in stock... so gonna do a little more work and hope that does it! lol
 
what did you do to q1 and q2 in the protect, no less the caps C1 & C2?

sometimes the amp is blameless and the protect circuit jumpy...
 
I had a SA-9500 on the bench with a similar problem, and the protection circuit is almost a clone of the 9100. Mark is spot-on (as usual) in that replacing the 2SC869s w/ KSC1845s can help. I also replaced C1/C2 on the protection board with Nichicon 0.22μF/50V for the 9500.

Also, @EastPoint offers some good advice in that the rest of the unit has a lot of suspicious devices as part of the design - A726s, C869s, C1312s, and C1451s are scattered through it.
 
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