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Hoffman Amps Forum image Author Topic: Help finding bias pot  (Read 3012 times)

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Offline dude

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Help finding bias pot
« on: October 13, 2021, 08:55:40 pm »
Can’t seem to find a small, 16 or 17 mm diameter 50kl, 1/4” diameter thread with a screw slot. A locking nut would be great.
Someone posted a vender that sells locking bias pots but l lost the link. I tried Mouser, Digikey but no luck
« Last Edit: October 13, 2021, 09:14:09 pm by dude »
If it ain't broke, don't fix it.

Offline acheld

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Re: Help finding bias pot
« Reply #1 on: October 13, 2021, 09:11:01 pm »
I have not seen those for sale anywhere.

I use Bourns 3296 -- they can be inconvenient due to their legs/connections, but they are very robust and do not lose their setting.   

Yeah, I know those are not what you want . . .

Offline sluckey

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Re: Help finding bias pot
« Reply #2 on: October 13, 2021, 09:17:55 pm »
Well, Weber designed that amp. Did you look there???

     https://www.tedweber.com/wp503l-slot/

Or do you mean these that require a 1/4" mounting hole? Look at the last two pics...

     http://sluckeyamps.com/sunn/sunn.htm

A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline Willabe

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Re: Help finding bias pot
« Reply #3 on: October 13, 2021, 09:52:47 pm »
I think I bought mine at Mouser or Digikey? I think their Precision Electronics, but others make them too.

Do a search for; mil. spec, 2w, wire wound, locking nut.

They are small body.

 

Offline dude

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Re: Help finding bias pot
« Reply #4 on: October 13, 2021, 09:54:36 pm »
Or do you mean these that require a 1/4" mounting hole? Look at the last two pics...

     http://sluckeyamps.com/sunn/sunn.htm
Yes, Weber’s design. Yes, looked at Weber they no longer carry 1/4”, saw the 3/8” hole 50kl but the back face plate is drilled for 1/4”, if l drill it out, takes the lettering with it.
Your last picture, the two pots would work. I decide to not use pin jacks and just keep the stereo jack. As long as the pots aren’t extremely big bucks they would work, available?
But did find a 1/4” hole 50kl, with a slotted thin shaft, but it’s 25kl. I thought of raising the 39k R supply before the diode, then maybe use a 27k to ground off the bias pot but …, not sure that would give me the range. Probably better to use a pot like your Sunn pic, if it’s available in 50kl
If it ain't broke, don't fix it.

Offline dude

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Re: Help finding bias pot
« Reply #5 on: October 13, 2021, 10:00:01 pm »
Do a search for; mil. spec, 2w, wire wound, locking nut.

They are small body.
I try again using your filters, thanks l think l did see those 2 watts, expensive..?
If it ain't broke, don't fix it.

Offline dude

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Re: Help finding bias pot
« Reply #6 on: October 13, 2021, 10:03:58 pm »
What l did for my Plexi’s was use a reg solid shaft, cut it shorter and cut a screw slot. Seems to stay out of the way from accidental turning, l think available in 16mm, 50kl, 6.5mm hole
If it ain't broke, don't fix it.

Offline sluckey

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Re: Help finding bias pot
« Reply #7 on: October 13, 2021, 10:05:08 pm »
These pots are called RV6 blah-blah-blah. Lot's of them in military and FAA equipment. Here you go. Buy two so they will match. Won't be a better price...

     https://www.ebay.com/itm/202145285373?hash=item2f10cc44fd:g:CJkAAOSw3ZtaL1CM

BTW, the bias pots in my Plexi6V6 and Phoenix are both 50K RV6.

     http://sluckeyamps.com/6v6plexi/P-6V6_05_big.jpg
     http://sluckeyamps.com/phoenix/p12_big.jpg
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline dude

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Re: Help finding bias pot
« Reply #8 on: October 13, 2021, 10:54:27 pm »
Thanks,
If it ain't broke, don't fix it.

Offline dude

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Re: Help finding bias pot
« Reply #9 on: October 16, 2021, 03:30:05 pm »
These pots are called RV6 blah-blah-blah. Lot's of them in military and FAA equipment. Here you go. Buy two so they will match. Won't be a better price...

     https://www.ebay.com/itm/202145285373?hash=item2f10cc44fd:g:CJkAAOSw3ZtaL1CM

BTW, the bias pots in my Plexi6V6 and Phoenix are both 50K RV6.

     http://sluckeyamps.com/6v6plexi/P-6V6_05_big.jpg
     http://sluckeyamps.com/phoenix/p12_big.jpg
I just got the pec pots from the link you provide above. I cannot thank you enough, they are about as small as a pin jack in length, extremely accurate. I opened the link from eBay the next  morning to order and they raised the price a dollar, l guess they had so much action… :icon_biggrin: .
Thank you again!
If it ain't broke, don't fix it.

Offline sluckey

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Re: Help finding bias pot
« Reply #10 on: October 16, 2021, 03:46:47 pm »
They add a touch of class to your projects.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline Blooze

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Re: Help finding bias pot
« Reply #11 on: October 20, 2021, 10:43:41 pm »
I’ve been looking at bias pots as well. So I’m assuming the RV4LAY is just the larger 2W version?

https://www.digikey.com/en/products/detail/nte-electronics-inc/501-0060/11646225

 


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