diyAB Amp The "Honey Badger" build thread

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#4,543
thompsontechs said:
Okay guys, just went back to work and my brain is cooked, need a sanity check please.


Looking at the snubber for a 115v trans with the sec at 45v. the standard .15uF cap and a R of 954.



I'm trying to make sure I have enough power rating on R954 to make sure it has a long and happy life. I think I remember Mark, or someone saying you want 2-3 times the max to ensure good life and service.



So, with those numbers I got about 47.2mA as the wattage through the resistor. Can someone check me on this... I have a 1/4 and 1/2 watt Rs and was just going to use the 1/2 to have a large margin, but not sure my addled brain has the math right.


Thnaks


JT
Click to expand...




Nobody willing to check my math? 😱
 
#4,545
thompsontechs said:
Okay guys, just went back to work and my brain is cooked, need a sanity check please.


Looking at the snubber for a 115v trans with the sec at 45v. the standard .15uF cap and a R of 954.



I'm trying to make sure I have enough power rating on R954 to make sure it has a long and happy life. I think I remember Mark, or someone saying you want 2-3 times the max to ensure good life and service.



So, with those numbers I got about 47.2mA as the wattage through the resistor. Can someone check me on this... I have a 1/4 and 1/2 watt Rs and was just going to use the 1/2 to have a large margin, but not sure my addled brain has the math right.


Thnaks


JT
Click to expand...


Paragraph 6 on page 7 of Mark's article details the selection of Rs. The question I have is, how did you arrive at 47.2mA for current through Rs? It seems a bit high - unless by R954 you mean 0.954 ohms - that would be atypically small, I think.
 
#4,549
Begging your pardon, and apologies if it's a FAQ, I have a pair of these boards that I never built up. I am curious if it's even possible to source semiconductors anymore. I know the question of substitutes has come up in this thread occasionally but I haven't tried yet to read all the posts. Has anyone published a viable BOM for 2021?

It's really quite discouraging to come back to solid-state after ten years and discover all the small-signal devices are out of stock.

Alternatively, if someone wants a pair of boards...

Thanks.

-Henry
 
#4,553
Interesting. There seem to be different documents out there. Definitely the supply of THT semiconductors is shrinking. The other day I was looking through the list of transistor options in the build guide and everything was coming up obsolete and out of stock. I will try again. Thanks.
 
#4,555
hpasternack said:
Interesting. There seem to be different documents out there. Definitely the supply of THT semiconductors is shrinking. The other day I was looking through the list of transistor options in the build guide and everything was coming up obsolete and out of stock. I will try again. Thanks.
Click to expand...

I found every transistor exept SS9014, 2SA1381 and 2SC3503 at Mouser just now. SS9014 can be substituded by MPSA18. 2SA1381 by MJE350 and 2SC3503 by MJE340.

there is also other substitudes out there.
 
#4,556
Thanks very much. I've been preoccupied with tubes for a long time, and was surprised to find how the semiconductor parts supply landscape has changed. In my mind, college doesn't seem that long ago, but I suppose it makes sense that bread-and-butter transistors from forty years ago (incredible!) are no longer in production.
 
#4,560
It looks like it's hard to get KSC1845 at the moment. RSonline do have them. But in minimum order of 200pc. And that is OnSemi. They also got KSA992 from OnSemi, with a minimum order og 50pc.

There is also a bunch of E-bay listings for these critters.
 
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