M470A pan pot replacement
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Bill Sallak
May 18, 2021, 7:45:32 PM5/18/21
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I was able to get the L2042 console into my storage/shop area today, and one of the M470A pan pots just spins around and around. Does anyone have the actual Bourns replacement part number?
The schematic shows this to be a multi-gang 5k pot, and the part is listed as Bourns. When I search Mouser and Digikey, it looks like a Bourns PTD-908-something at 5k would be the right thing, but I'd like to confirm. (Hoping I'm wrong, since the Bourns PTD-908's are non-stock parts with a minimum order quantity over 300.)
Thanks always,
Bill
Bill Sallak
May 18, 2021, 9:15:28 PM5/18/21
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Update: found a vendor for small quantities of Bourns PTD-908 at 5k, but any confirmation that this is the right part would be really helpful.
Cheers,
B
Bill Sallak
May 19, 2021, 7:43:37 PM5/19/21
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If the Bourns inventory website is correct, the only >=4-gang 5kΩ pots in North America are here: https://www.arrow.com/en/products/ptd908-1020f-b502/bourns
B
Anthony Kuzub
May 22, 2021, 6:40:34 AM5/22/21
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It's a custom wbs part. You'll never source a NOS one. I may have a few, let me look
Anthony
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Anthony Kuzub
May 22, 2021, 6:40:34 AM5/22/21
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Anthony Kuzub
May 22, 2021, 11:36:39 AM5/22/21
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Found one...
Inside this module is the pan pot you desire
Anthony
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Bill Sallak
May 22, 2021, 11:37:58 AM5/22/21
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Thanks so much!
B
Anthony Kuzub
May 22, 2021, 11:40:40 AM5/22/21
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Confirmed. 10-017 inside
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Anthony Kuzub
May 24, 2021, 9:36:06 AM5/24/21
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I have a loose one. $50 including shipping
Anthony
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John Maizels
May 24, 2021, 9:54:48 AM5/24/21
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Just wondering - the value is 5k, but what is law of the pot? EG:
is it four gangs of linear, or half log/half antilog, or something
else?
John
At 23:35 24/05/2021, Anthony Kuzub wrote:
John
At 23:35 24/05/2021, Anthony Kuzub wrote:
I have a loose one. $50 including shippingÂ
AnthonyÂ
On Tue., May 18, 2021, 9:15 p.m. Bill Sallak, <bills...@gmail.com> wrote:
- Update: found a vendor for small quantities of Bourns PTD-908 at 5k, but any confirmation that this is the right part would be really helpful.
- Cheers,
- B
- On Tuesday, May 18, 2021 at 6:45:32 PM UTC-5 Bill Sallak wrote:
- I was able to get the L2042 console into my storage/shop area today, and one of the M470A pan pots just spins around and around. Does anyone have the actual Bourns replacement part number?
- The schematic shows this to be a multi-gang 5k pot, and the part is listed as Bourns. When I search Mouser and Digikey, it looks like a Bourns PTD-908-something at 5k would be the right thing, but I'd like to confirm. (Hoping I'm wrong, since the Bourns PTD-908's are non-stock parts with a minimum order quantity over 300.)
- Thanks always,
- Bill
- --
- The WBSps.ca is run by Canadians who appreciate Well Built Stuff
- Photos:
- https://drive.google.com/drive/u/2/folders/0B0yR0b5T78SKd2JnQzlrckY2bWM
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Manuals: https://drive.google.com/drive/u/2/folders/0B0yR0b5T78SKczBIcDgzZkstUjQ
Photos:
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Anthony Kuzub
May 24, 2021, 10:17:37 AM5/24/21
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Great question.
I think it's called a sine cosine pan pot.
So two elements are one taper and two the other way around
In other words, the most expensive way to do it. Thus the rareness of it all
I don't see any slugging on the drawings and that to me that it's not linear. You only see slugging on linear pan pots.
Thanks for asking!
Antjony
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John Maizels
May 24, 2021, 10:49:31 AM5/24/21
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And is the switch in the circuit part of the pot, or a separate
item? I ask because the switch looks to be not part of the pot in
the picture.
It's possible to fake a reasonable approximation of a log pot by connecting a suitable resistor from the wiper to the ground side. If the pot is R, then a good value for the resistor is R/4, and this produces a useful law which gives about 4dB/10% rotation at the extremes and 1.5dB/10% rotation in the middle. Constructing a log/antilog pair this way creates a control with somewhat finer adjustment in the middle, and coarser adjustment at the extremes. Works for me.
So while a quad/dual log-antilog pot would be a very special item, a quad linear pot with four resistors might be easier to locate and fabricate into what's needed.
j
It's possible to fake a reasonable approximation of a log pot by connecting a suitable resistor from the wiper to the ground side. If the pot is R, then a good value for the resistor is R/4, and this produces a useful law which gives about 4dB/10% rotation at the extremes and 1.5dB/10% rotation in the middle. Constructing a log/antilog pair this way creates a control with somewhat finer adjustment in the middle, and coarser adjustment at the extremes. Works for me.
So while a quad/dual log-antilog pot would be a very special item, a quad linear pot with four resistors might be easier to locate and fabricate into what's needed.
j
At 00:17 25/05/2021, Anthony Kuzub wrote:
Great question.
I think it's called a sine cosine pan pot. Â
So two elements are one taper and two the other way around
In other words, the most expensive way to do it. Thus the rareness of it allÂ
I don't see any slugging on the drawings and that to me that it's not linear.  You only see slugging on linear pan pots.
Thanks for asking!
Antjony
On Mon., May 24, 2021, 9:54 a.m. John Maizels, < john.m...@conzealand.nz> wrote:
- Just wondering - the value is 5k, but what is law of the pot? EG: is it four gangs of linear, or half log/half antilog, or something else?
- John
- At 23:35 24/05/2021, Anthony Kuzub wrote:
- I have a loose one. $50 including shippingÂ
- AnthonyÂ
- On Tue., May 18, 2021, 9:15 p.m. Bill Sallak, <bills...@gmail.com> wrote:
- Update: found a vendor for small quantities of Bourns PTD-908 at 5k, but any confirmation that this is the right part would be really helpful.
- Cheers,
- B
- On Tuesday, May 18, 2021 at 6:45:32 PM UTC-5 Bill Sallak wrote:
- I was able to get the L2042 console into my storage/shop area today, and one of the M470A pan pots just spins around and around. Does anyone have the actual Bourns replacement part number?
- The schematic shows this to be a multi-gang 5k pot, and the part is listed as Bourns. When I search Mouser and Digikey, it looks like a Bourns PTD-908-something at 5k would be the right thing, but I'd like to confirm. (Hoping I'm wrong, since the Bourns PTD-908's are non-stock parts with a minimum order quantity over 300.)
- Thanks always,
- Bill
- --
- The WBSps.ca is run by Canadians who appreciate Well Built Stuff
- Photos:
- https://drive.google.com/drive/u/2/folders/0B0yR0b5T78SKd2JnQzlrckY2bWM
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Anthony Kuzub
May 24, 2021, 11:06:20 AM5/24/21
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Well $50 is about 20 min of engineering time.
But who am I to tell you how to use your time.
So by the time you factor in this investment you are in the hole hundreds to replace one pot.
It can be done. All things can be done.
My experience: not worth it... Especially if someone like me comes along with parts...
The switch brings the pan pot in. Not a part of switch. External resistors match the loss when the pan pot is in. The resistors make it drop when in the pot is not engaged... I think if you pan all the way one way it's 6dB if it were middle.
The best way to pan hard left and hard right it to use the assignment switches...
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Anthony Kuzub
May 24, 2021, 11:22:45 AM5/24/21
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Related and kinda inspired by this I made a tutorial video on how the knob caps are sometimes stubborn and people use the back stop of the pot to torque the knob off...
Bill Sallak
May 24, 2021, 11:43:31 AM5/24/21
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Thanks for all of this—the knob cap video and the new switch cleaning video are both really helpful.
Anthony, I think I'm gonna buy a couple of those 490F's and scavenge the pot, but if that falls through for some reason I'll hit you up for yours.
B
Anthony Kuzub
May 24, 2021, 11:47:19 AM5/24/21
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Cheers
That's the proper thing to do. That's what I would do... That's what I've done for decades to get them functional in a production environment.
You get fader parts in the process... And other wink caps... And loads of 201 op amps...
There is method to my madness... Ask around
Anthony
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John Maizels
May 26, 2021, 7:14:15 AM5/26/21
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Hey, Anthony - I wasn't suggesting that faking a panpot is my preference, just saying that there are cool and appropriate DIY solutions available if the real parts turn out to be made of unobtanium. The challenge with specialised components is that they do disappear rather sooner than generic parts. The log/antilog pot trick is not well known, but easy to do.
Anthony Kuzub
May 26, 2021, 8:16:33 AM5/26/21
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All groovy man
I'll waive the warning warning danger danger flag sometimes when I see a path I've gone down that ended in disappointment.
This is one of them
There is a great web resource called the secret life of pots:
Anthony
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warren beck
May 26, 2021, 3:38:15 PM5/26/21
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Hello!!
FWIW I am approaching a manufacturer this fall to have new pan pots made for me in the blue Clarostat with detent style for my consoles. I am having about 40 units made for my personal inventory. Please drop me a note later in the year if you are interested
in any of my olde pots, or having a few new pots.
Regards,
Warren
From: wb...@googlegroups.com <wb...@googlegroups.com> on behalf of Anthony Kuzub <44...@apkaudio.com>
Sent: May 26, 2021 8:16 AM
To: WBSps - Ward-Beck Systems Preservation Society <WB...@googlegroups.com>
Subject: Re: [WBS] ps.ca- Re: M470A pan pot replacement
Sent: May 26, 2021 8:16 AM
To: WBSps - Ward-Beck Systems Preservation Society <WB...@googlegroups.com>
Subject: Re: [WBS] ps.ca- Re: M470A pan pot replacement
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Anthony Kuzub
May 26, 2021, 4:12:18 PM5/26/21
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Speaking of doing it the right way.... Thanks Warren
What's the minimum order? Group buys are the only way
Sometimes 120 cost what 500 do...
But you know that :)
Anthony
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warren beck
May 26, 2021, 4:54:37 PM5/26/21
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Hi!!
All to well.
Set-up is $100 plus pot. when I know if anyone is interested, and they have ash in hand, I'll get a qty price and go from there.
Regards,
Wb!
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Sent: May 26, 2021 4:12 PM
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Bill Sallak
May 26, 2021, 10:00:15 PM5/26/21
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I'm happy to go in for some of those new pots. Will keep my eyes open for next steps.
Now, to try to figure out whatever wrench/tool is meant to remove the odd jam nut that secures the pot to the panel face...
Anthony Kuzub
May 26, 2021, 10:12:27 PM5/26/21
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No moq of 500?
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Bill Sallak
May 26, 2021, 10:40:46 PM5/26/21
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At the risk of seeming pedantic, is this wrench easily obtainable?
Anthony Kuzub
May 26, 2021, 11:05:54 PM5/26/21
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Bill Sallak
May 26, 2021, 11:18:23 PM5/26/21
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Figured it was something like that. Guess I'll have to shred them on removal and replace them with hex jam/panel nuts.
Anthony Kuzub
May 28, 2021, 10:01:36 AM5/28/21
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There is another option
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