enclosure mounted trimmers

[lopsided]

Hey,

did anyone ever thought of a way how to mount trimmers, so that they could be accessed externally?
I have came to a couple of Tesla OC75 transistors which sound pretty good in a Fuzz Face and I am thinking of an external bias control which would be safe from accidental readjusting which happens to pots.
From what I have heard Ge transistors are more sensitive to temperature and I am thinking of a possibility to readjust them with a small screwdriver before the show/practice without the annoyance of opening the enclosure.

Any thoughts?

Jakub

[crane]

trimmer mounted on pcb and a hole drilled directly on drimmer. or else you should find a really good shape factor trimmer which is hard to do.

[Jdansti]

trimmer mounted on pcb and a hole drilled directly on drimmer. or else you should find a really good shape factor trimmer which is hard to do.

+1 But watch out for accidentally shorting something on the circuit board if you use a metal screw driver for adjustments. The other thing to watch for is trimmers where the bottom of the plastic screwdriver slot is open and there's a piece of metal under it. I've shorted these out when the shaft of a metal screwdriver touches the enlclosure and the metal under the slot. 

Use one of these:

http://www.mouser.com/Search/m_ProductDetail.aspx?Vishay-Spectrol/ACCTRITOB308-T005/&qs=sGAEpiMZZMtArvHj40ttL2wxM2qTOy%252bv3ujHBNDXmQs=

[R O Tiree]

The first snag that occurs to me is that trimmers typically aren't designed for repetetive... trimming. Some are good for only a few hundred cycles, whereas pots are OK for thousands. Worn trimmers will behave just like worn pots = scratchy noises.

The second snag is that a hole in the face of your pedal is just inviting rain, the drummer's spilled rum and coke, dust, fluff, biscuit crumbs, whatever, into your finely made pedal.

How about just using a pot and marking on the case where the pointer needs to be for "typical" operation. You know (or figure out) which way it needs to go for warm and cold environments and you're good to go. I'm thinking that, if you set it up at the sound check (before the show) then your lights might warm it a bit between then and the gig... or the ambient temperature might drop (afternoon into evening)... setting it up some time before might therefore do no good at all.

[John Lyons]

Always thought this was an elegant way to do it.

[snarblinge]

I was looking for a system like this for a while, to make stage use pedals which can't be easily knocked. In the family Sound gear there are these old 50w amps we use for testing and they have panel mount gain adjust, I searched everywhere for these to no avail.

carefully cut down  a pot. mark a notch sorted... could do a much better job if you dismantle the pot prep and reassemble, but i always ruin pots when I do that.

that blackstone option seems a lot more sensible

[LucifersTrip]

for easy access & covering:

1) put some type of "door" or "hatch" above the hole to the trim so you can get to the inside quickly....maybe even something like those clip on battery covers

2) you can cover the hole to the trim with a small piece of metal that rotates, anchored on one edge with a screw and slide it in a circular motion

so you can't accidentally "bump" an external pot:

3) you can use an external pot with a push or pull "switch", like some treble or bass controls in car radios...a switch that you have to push down or pull up to activate and then push down or pull up to deactivate...if you can find one

[Jdansti]

for easy access & covering:

2) you can cover the hole to the trim with a small piece of metal that rotates, anchored on one edge with a screw and slide it in a circular motion

Use a pick with a hole for the screw.

[Paul Marossy]

Always thought this was an elegant way to do it.

When I first saw that pedal, I didn't like that idea. But now I think it's a cool idea because once you set them the only way they will ever get changed is deliberately with a screwdriver (or a pick if that'll work on those controls).

[defaced]

Keystone electronics makes mounting hardware that I have used for this.  There are straight (link: http://www.keyelco.com/products/specs/spec186-metric.asp) and right angle versions of these.  The pins go in the PCB, the screw through the chassis, and presto, suspended board perfect for mounting trimmers to an enclosure.  They have a really good catalog of all their stuff, well worth the download and perusal. 

[glops]

Always thought this was an elegant way to do it.

When I first saw that pedal, I didn't like that idea. But now I think it's a cool idea because once you set them the only way they will ever get changed is deliberately with a screwdriver (or a pick if that'll work on those controls).

I really like that method. I wonder where to find those?  I would really love to have pedals with less knobs....

[davent]

How about just cutting the shaft off a regular pot then slotting in what's left of the shaft, then some sort of tool is necessary for adjustment.

bias controls

dave

[Mac Walker]

How about just cutting the shaft off a regular pot then slotting in what's left of the shaft, then some sort of tool is necessary for adjustment.


dave

You can buy pots already set up with this type of arrangement, I bought a bunch of these, only problem might be finding the exact value you need without paying an arm and a leg (these are technically surplus)....

http://www.allelectronics.com/make-a-store/item/LTP-100K/100K-SCREWDRIVER-ADJUST/1.html

[davent]

^I got the idea from seeing PEC pots but didn't want to spend the premium dollars to buy them so improvised  (some, i'm sure i've seen as being muti-turn as well) ,  those you linked to are a bargain.
dave