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40409 and 40410 substitutions

topgun

topgun

Active Member
Hello AK,
I’m looking at replacements for the old RCA 40409 and 40410 transistors. I’ve googled and researched all over the place and have come up with three different replacements. 1 is the same style of package which would require using the old heat sinks that are welded to the transistor shell. They are to expensive and a pain to have to go through to use them. The other two are a TO-220 and a SOT-32 package style . The TO-220 are MJE15035 and MJE15034. The SOT-32 are MJE350 and MJE340. Both are are not a problem to attach a heat sink to and are much cheaper. My question is which one of these would be the better choice as pre drivers on an old receiver I’m slowly restoring.? Thanks
 
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Those parts were also used in the old SWTPc "Tiger" amps. Worked well but a PITA to substitute. I'd go with the TO-220 and whatever heatsink you can purchase or fabricate. SOT-32 would require good PCB design to dissipate the heat. I assume they used the original part because of dissipation.
 
ConradH said:
Those parts were also used in the old SWTPc "Tiger" amps. Worked well but a PITA to substitute. I'd go with the TO-220 and whatever heatsink you can purchase or fabricate. SOT-32 would require good PCB design to dissipate the heat. I assume they used the original part because of dissipation.
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Thanks for your reply. I had a feeling that the TO-220 was the best way to go.
 
40409 and 40410 crosses to NTE128 and NTE129, respectively.

I know there's a stigma about NTE components here, but I've yet to have an issue with them.
 
rickl said:
I have a few NOS for one of them. I'll PM you to see how many you need.
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Thanks for the offer. I really do appreciate it. But I’ve already decided to go with more modern and more easily available components for this rebuild.
 
topgun said:
old heat sinks that are welded to the transistor shell.
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can you post a pic of that? I've never seen a transistor welded to the heat sink. Seems like a dumb thing to do for serviceability reasons.

also curious what you are working on here
 
They were welded for efficiency. From the RCA power transistor databook...
 

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Depending on heatsink requirements, 2N3439/2N3440/2N5416/2N5415 with cooling fins may be another pin-compatible option.
For still reasonable price (less than a dollar) to be found at Newark (for USA), or TME (in Europe), the brand will be CDIL or Multicomp (which probably is CDIL in the real), and using a fin-type of heatsink.
 
now that I see it, I remember where I've seen it. Phase Linears have one of those right in the middle of the driver board, at least the later versions do.
 
gadget73 said:
can you post a pic of that? I've never seen a transistor welded to the heat sink. Seems like a dumb thing to do for serviceability reasons.

also curious what you are working on here
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I’m working on a Heathkit AR-15 receiver. It has a weak right channel. I’ve checked all the outputs and every transistor on both amplifier boards and pre-amp board. I’ve completely rebuilt the two amplifier boards, including replacing all the resistors. Cleaned the heck out of all the switches and trim pots, replaced all the caps on the pre amp board also, and still no change. I’ve checked all the wire connections and went over all the soldering and I still haven’t found anything. My thinking is that the problem is with the outputs. They are all the same number but two different manufacturers. I have gone over all the voltages from aux input all the way to the outputs and it all seems ok. Also the hfe readings are from a low of 18 to a high of 58. So I’m just going to replace all four outputs first and see what happens. As for the driver transistors, although they test good, I may just replace those too. I know I’m crazy, but I am not giving up on this thing. My biggest excuse is that I’m still a novice, but I learn fast. I’ve already learned a ton from the few restorations I’ve already successfully completed.
 
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The original heatsink is indeed folded steel sheet, spot-welded to the TO-5 transistor package. Seemed to work ok, so long as you had plenty of airflow and didn't push them right to their limits. I changed out a LOT of these back in the day...I blame that on the disco era.

I have always used the 2N5320/2N5322 pair as replacements for the RCA 40409 & 40410. Oftentimes, going to the TO-126 or TO-220 packages just wasn't doable due to heatsink footprints.

One of these is the easiest solution;

1688062731348.png
 
gadget73 said:
ah ok, I have seen that. I was thinking these were a TO3 or something like that. Should have looked up the datasheet I guess.
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Good memory on the TO-3; the 40411 was the output transistor usually paired with those drivers.
 
Those don’t appear to be anything special. Not the exact device, but I’ve replaced those TO5 devices that are welded to those heatsinks using TO126 devices. Haven’t had a problem yet, just make sure they spec out better than the originals.

Dan
 
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