Zen trimming pots a big no no ?? - diyAudio
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Old 27th January 2003, 05:44 PM   #1
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Default Zen trimming pots a big no no ??

I have a friend who knows much more than me about electronics and he keeps warning me that the trim pots in the zen amp are seeing DC and will inevitably fail sooner than later.

Anyone care to comment ?

Shoog
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Old 27th January 2003, 08:32 PM   #2
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Sometime before the universe experiences heat death
the pots will fail.

None have failed yet, and if they do, put another one in.
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Old 27th January 2003, 09:06 PM   #3
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Default Trim pots - Very usefull items.

Trim pots are extremely useful devices and when properly used and rated will have a long life and allow optimization of some circuit parameters that would be very difficult to do by other means. It does not make much difference whether the trim pot adjust DC or AC parameters, or a combination thereof.

Modern trim pots are very stable and no one should be scared to use them in any circuit that may require some adjustment after being constructed. Consideration should be given as to the location within a circuit for any trim pot. Some locations are just more suitable than others.

I agree fully with Mr. Pass. Like any part when it fails, replace it. Donít hesitate to use these very useful parts.


John Fassotte
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Old 28th January 2003, 05:11 PM   #4
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Default Thanks !!

Thanks for putting my mind to rest. i wasnt very worried but its nice to get confirmation.

Shoog
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Old 28th January 2003, 05:24 PM   #5
miguel2 is offline miguel2  Portugal
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Just my 2cts: I wish that trimpot had some more resolution as it can be tricky to adjust the 23V voltage.

Anyway, are these 23V important as bias is directly related, or around that is ok?
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Old 28th January 2003, 06:07 PM   #6
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On the lower side of the original Zen (32 volt rail) I replace the pot for comodity with a 5500 ohm resistor
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Old 30th January 2003, 05:24 PM   #7
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Default tweak tweak tweak

If I had a device without trimpots, just how could I justify the "tweaker" that's always in my pocket?

My brother was a nuke ET and nuclear power instructor in the US Navy. He told me one day that he was proud to see that his brother wearing his tweaker. A tweaker is a small flat blade screwdriver, usually with a wee pocket clip- a necessity aboard ship- used to adjust the trimpots of various gear.

This is the difference between engineers, my father told me years ago: if one has only pens in his pocket, he is a theoretician. The guys who understand what a device will do when things go wrong, who have the hands-on edge, wear their tweakers! This was of the utmost importance when working with instrumentation.

The trimming of your devices can save many times the price of the trimpots, in terms of device life! Nelson is right!

Keep those pots in the circuit!

Bob
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Old 30th January 2003, 06:24 PM   #8
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Default keeping trimpots from failing

You have to first "parametrize" what you want to trim -- get to about where you are going with a pair of metal film resistors on each arm of the trimpot and just use the value of the pot for a small portion of the total resistance. This way the R*(I^2) generated in the pot won't exceed its rating.

With respect to precision, you can buy 10, 15 and 25 turn trimpots from Bourns (among others).
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