Bourns Cermet Panel Pots?

[ruckus328]

I'm working on various projects and had planned to use Bourns 51 Series pots across the board. 

http://www.bourns.com/pdfs/50.pdf

They're really nice pots and feel great, and I've demo'd almost every pot I could get my hands on before settling on these ones.  They come in both Conductive Plastic and Cermet, but I'll admit I'm not very knowlegable or experienced on the different materials.

I had planned to use the CP versions everywhere, except today when getting ready to place some orders I realized that one of the values I need (1M) are not available in the CP, only in Cermet.  I was always under the impression Cermet pots had a very small rotational lifespan, and weren't used for applications where they would be constantly under use, but the bourns datasheet lists the rotational life at 25,000 cycles (which seems plenty acceptable to me and higher than most carbon pots I'm used to).  The CP is listed at 50,000 cycles.  For this application I would definately prefer a tighter tolerance, and the cermet's are 10% which is really nice, I just want to make sure they don't give out in 6 months and if I should trust the datasheet info.  If anyone has any experience with them (or any cermet pots), or just cermet in general it would be much appreciated.

 

[tomcat]

Afaik synth module maker MOTM (synthtech.com) is using these since years (at least for the VCO). Didnt hear negative things about cermet, except the price.

Forgot which one, but one has smaller tolerance.

 

[tomcat]

Looked into the BOMs. Paul is using cermet on other modules as well. Back then he used the Spectrol 149 series pots.

What he writes about these:

Lastly, the COARSE and FINE pots use very low drift cermet resistive material. This means when you set those front panel pots, the frequency does not drift because the resistance of the pots is changing with temperature.

 

[jsteiger]

The 51 series does go out to 1M in CP, according to the datasheet. You may not find them in stock anywhere but they will make them if you are up for a minimum.

Best, Jeff

 

[ruckus328]

Thanks guys.  Jeff - I was on the phone with Bourns all day yesterday, the 1M CP isn't even loaded in thier system, they will make them but there is a 500 piece minimal and tooling charges, and 19 week lead time (which I definately can't afford).  They wouldn't even tell me what the price is but I'm assuming somewhere around $5 each - they won't sell direct to me unless I do at least $25,000 in orders annual, so have to go through a distributor to even find ouit what the cost would be (lame).  The 1M in cermet is already available and since it's already been run there's only a 6-8 week lead time when I need more.  And I would prefer the 10% tolerance anyways and higher stability for this application, think I might just give the bourns eng department a call today to talk to them about lifespan.  If 25,000 cycles is an actual realistic number, then see no issue with this - assuming it was adjusted 10 times a day, 365 days a year, this means they'd last at least 7 years.  Seems reasonable to me.

 

[jsteiger]

Thanks guys.  Jeff - I was on the phone with Bourns all day yesterday, the 1M CP isn't even loaded in thier system, they will make them but there is a 500 piece minimal and tooling charges, and 19 week lead time (which I definately can't afford).

Ah. I had a similar thing only I needed something that does not show on the 50 series datasheet, but they do offer. Actually 2 things. 500 ohm CP cups and dual concentric shaft. Weird how they operate.

They wouldn't even tell me what the price is but I'm assuming somewhere around $5 each - they won't sell direct to me unless I do at least $25,000 in orders annual, so have to go through a distributor to even find ouit what the cost would be (lame).

Probably would be more than $5 but a moot point. FWIW, I spent nearly 2 months getting set up as a direct account with Bourns. After the worst business experience in my over two decades of running my own business(es), I found it much easier to just stay with distribution. The entire hierarchy of the way that level of buying is handled is absurd. The Midwest factory rep (who I had to deal with) was a total nightmare. I was lied to over and over about small things. The last thing was she actually told me my account was denied. When I called my contact at the factory, they had no clue what she was talking about or why she would say that! It ended with me telling the factory, if I had to deal with this rep, I wanted no part of a direct account. Sorry for the rant.    Brings back bad memories.

If I wasn't so happy with their product, I would have been long gone from them.

Make sure you talk to Paul. He is a top notch guy.

Cheers, Jeff