Panasonic obsolete Bjts replacements

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Happened to find an old maybe first generation schematic of this amp and missing the 56v zeners on the powersupply (18v supply?) and also the output trannies are sa1302 and sc3281?

So that means probably it was designed for this ones? And today Onsemi manufacture those too..
i had a paus here with this amp and starting now again. I couldn't source genuine 5171/1930 (original was 4793/1830) so wondering if Mje 115034/35 could be suitable in the psu regulator instead?
And for output trannies mjl 1302/3201 or 1943/5200 or MJL4281A/ MJL4302A or MJL21193/
MJL21194
Tough choice.
 
Happened to find an old maybe first generation schematic of this amp and missing the 56v zeners on the powersupply (18v supply?) and also the output trannies are sa1302 and sc3281?

So that means probably it was designed for this ones? And today Onsemi manufacture those too..
i had a paus here with this amp and starting now again. I couldn't source genuine 5171/1930 (original was 4793/1830) so wondering if Mje 115034/35 could be suitable in the psu regulator instead?
And for output trannies mjl 1302/3201 or 1943/5200 or MJL4281A/ MJL4302A or MJL21193/
MJL21194
Tough choice.

Use the x0302/ x281 variants. They have better gain and will sound closer to the original. the 21193's are not a bad choice, just need more bias and a robust driver to sound their best. They might work fine, but safer with the others. I'd use 21193/4/5/6 with rails in excess of +/-90vdc.
 
confirmation bias :) The 1943/4200 are form the same family as 1302/3281. All Super Beta devices. Just make sure the gain and vbe are matched on devices on same rail/ channel. These Super beta bjt's love hogging current if they are mismatched and blow when it gets warm. Initially when they came out a long time ago, papa used 0.47ohm ER's on the Forte Mode 3A to help current sharing. We now know that precision matching is better.
 
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The orginals ones were widely mismatch i think. Checked with my cheap meter and gain was all over the place, from 90-176. The new ones i couldnt get closer than 136/146 but i dont have a curvetracer though. I bought 10 extra of each to try to get them closer but this was thr best i could do.
I biased them to around 8mA (like old ones) seems to run same temp as before. In idle i have 0.81A (230v outlet) and 84w and that was same before. Plus minus 1..
 
Works for users. If this were in my service, I’d crank up the bias to 13mV per ER or 26mv across both ER’s ( same thing) as per Self’s rec for EF output stages. It further reduces distortion and I find sound is clearer. Ofcourse your heatsinks will go over 115-120F, so keep check the bias till it’s stable.

Depends how much you want to tweak this baby. :)
 
I wanna tweak for sure but i think the psu and its regulators and other elements are perhaps not up to the task although i have added some hestsinking here and there. I’m no done. Some bjt drivers ”before”
The output stage are getting seriosly hot as is (and before) These are A1478 and SC3788 and no heatsinking. When i got them bias was set at 6. I turned it up to 8 right away... thinking trying a bit higher when im done with all. I take everything step by step, dont wanna get myself into trouble hehe.. anyway thx for the suggestion. This 1943/5200 is Onsemi (not toshiba) from digikey. The old panasonics mustve been bad, one broke apart when i accidently dropped it on my workbench and one of them tested with gain of 20 so faulty i would say.
 

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