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Another TO-3 ➡ TO-3P output conversion

Karl vd Berg

Karl vd Berg

Super Member
Another TO-3 ➡ TO-3P conversion

I received this Sansui 317-II, which has the right channel dead. The owner said he uses Alesis passive monitors at 4 ohms. This version accepts minimum 8 ohms or higher.
Also, the unit was wired for old 220V operation and had 2 blown 8A 60V (!!) fuses. Checked drivers and pre-drivers, all good, but I replaced the four 82 ohms fusistors, prior to turn it on later.

I don't have any TO-3 devices "suitable" for this unit, so I decided to make a conversion using some TO-3P of similar specs - 2SA1104 / 2SC2579 that I have from another
unused unit laying around - to replace the 2SA981 / 2SC2261. I could have ordered 2 pairs of the MJ21193 / MJ21194 and sing the midnight song, but I wanted to try a
conversion with all the available material I already have. A bit of DIY is also reward and we are not lazy.

2SA981 / 2SC2261: 120Vceo / 8A / 80W / 30~180 hFE / fT 20MHz
2SA1104 / 2SC2579: 120Vceo / 8A / 80W / 50~180 hFE / fT 20MHz

Amp is alive again, no other issues so far. DC offset was 1.2mV and bias was 3mV, before re-adjusting back to specs.

Following some pictures...

































 
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Skywatcher said:
TO-3P were made to directly replace TO-3. The same goes for TO-220 being developed as a direct replacement for TO-66. That is why the lead dimensions are what they are, to match those sockets.
Click to expand...
Yes, and there's a few threads showing these conversions. It's pretty convenient when you're looking for some TO-3 and/or TO-66 devices with a mid-to-very high fT, for example, and you want to match as close as possible their original characteristics.

https://audiokarma.org/forums/index.php?threads/to-66-to-220.398227/

http://www.diyaudio.com.hr/viewtopic.php?f=8&t=706&hilit=standardne
 
May I ask what you used as under the collector connection? Thank you! I will start a thread on mine when i get to it but I pulled it off a shelf today after reading this. Nice thing is I tested the ouputs correctly this time and found them good. This thread is pretty bad assed though! Always kept this thing around and wife wants this and some jbl l26's in the bedroom.
 
I believe I used an M3 nylon washer type under first, and another regular nylon ring on top of it.
Ring crimps were M3 too, but for these M4 can also be used if the top washer is larger.

m3.jpg
 
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