Are ALPS pots supposed to be good quality?

Uncle Krunkus

I've finally tracked down a chronic problem with a Behringer guitar amp. It's a dual gang PCB mount ALPS pot which is scratchy as hell on one trace and intermittently disconnecting on the other. Even if I can get it out, I don't know if I can get the same one to replace it. It has a long shaft, and all 6 connections down one side. About 12mm across. Any suggestions? Could I dismantle it and fix it? I've done it before, but not with an ALPS. It looks very compact, so pulling it apart might make it even less reliable. Confused

fonik · Posted: Wed Oct 24, 2007 2:32 am Post subject:

they manufacture a wide range of components with different quality:

does it look like this? (medium quality, >2EUR)
Posted Image, might have been reduced in size. Click Image to view fullscreen.

or like this? (high end, >10EUR)
Posted Image, might have been reduced in size. Click Image to view fullscreen.

or like this one? (cheap, <1EUR)
Posted Image, might have been reduced in size. Click Image to view fullscreen.

bugbrand

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL

Uncle Krunkus · Posted: Wed Oct 24, 2007 5:44 am Post subject:

It's not a 90deg one, and doesn't match any of the pictures you posted Mathias. Tom, I found the same type at Farnell, but it's got a longer shaft, and only 6 terminals.
I'm thinking about doing a bit of home surgery! Twisted Evil

bugbrand

prophei · Posted: Wed Oct 24, 2007 6:22 am Post subject:

i recently bought a lot of alps pots that look like the mediums listed above, and find them to be fantastic. the travel is silky smooth, and i haven't had any fall apart at all.

bugbrand · Posted: Wed Oct 24, 2007 6:23 am Post subject:

Uncle Krunkus · Posted: Wed Oct 24, 2007 7:03 am Post subject:

Man, this job is a big number 2! Shocked

The pot has two tabs hanging off the sides which solder down for mechanical strength. Getting it off there is gonna be a bitch! I have to remove all the solder from those two tabs, and the 6 terminals, and the whole area is littered with SMD resistors! Mad

This is all just to get access to the pot which I most likely won't be able to fix.

prophei · Posted: Wed Oct 24, 2007 7:10 am Post subject:

Rykhaard · Joined: Sep 02, 2007 Posts: 1290 Location: Canada

Has anyone else been buying / using the Alpha pots from Small Bear Electronics?
I've been impressed enough with the $ when you buy 25 or more and have ordered a few piles of them.
I've been so busy building for the last few months though, I haven't yet had time to sit and actually play my synth....... so I don't know yet, their quality level.

With all of this discussion - it'd be cool if I could get feedback from anyone else with experience before I buy any more huge quantities. Shocked

Thanks for any possible bits of info. on this. Smile

Broadwave · Posted: Wed Oct 24, 2007 8:39 am Post subject:

I use the "commercial" 16mm, splined shaft Alpha pots (Futurlec, not SmallBear) - very nice smooth response.

Out of my last batch of 150 (100k Lin) 8 proved to be faulty - bad joint from the solder tag to the track, the rivit seemed a bit loose.

Of course you don't find that out until you've mounted up the pot, wired it up, powered up, listened to your VCO's frequency jumping all over the place, screamed and sworn like a trooper, calmed down enough for a nice cup of tea and a 10 minute break - I guess you know how the rest of it goes Mad

Rykhaard · Joined: Sep 02, 2007 Posts: 1290 Location: Canada

TheAncientOne · Joined: Dec 26, 2006 Posts: 144 Location: United Kingdom

Dear Uncle K

A suggestion: I have to do this every few months on a repair of some kind. ON approach is to take a fine grinding disc in your trusty Dremel and cut through the mounting pillars before desoldering the rest.

Somtimes you can snip them off and sometimes the pot can be broken up in situ, and the pins removed one art a time. I work on the theory that the pot is expendable, (usually), the board isn't .

With some modern boards i can be a real challenge to remove things like this without wrecking the board. Another non-favourite is the surface moutn power regulator chips that use a big slab of PCB copper for a heatsink. I have an antique tinsmiths electric soldering iron I use to get enough heat into the package tab.

A friend of mine had to replace a BGA package on a batch of boards at his work. Now that IS nasty.... even if you have the oven to put them back on.

Funky40 · Posted: Wed Oct 24, 2007 4:07 pm Post subject:

Alps pots:
my TC D-Two has also alps pots(looks like the cheap/small ones. btw. you get them with and without 90° angle )
TC is nown for good quality.( exept my own D-Two Wink

)

Alpha pots:
@Etaoin
in germany you get them cheaper from www.musikding.de then from Banzai ( good personal service there.)
btw.
if one is asking, you get them also as print version, and as Stereo pots
Small bear or also rapidonline in the UK has them one more time cheaper (much cheaper ! )

@Rykhaard
Dotcom uses the 24 mm alphas,
and have a look to the the Klees from Scott Stiites and State Machine Wink

.
What i see is, that most People use the Alphas ( 16mm and 24mm ) and the spectrols.
So you are right with these
I use 16mm alphas too.
I have used aprox. 80. On one module i have a fault which could be caused by a broken pot

Uncle Krunkus · Posted: Wed Oct 24, 2007 4:45 pm Post subject:

Thanks for the tip Prof,
I would love to just snip it out and break it up, but I don't know where I could get a replacement at this stage, so I'll have to keep looking.

Uncle Krunkus · Posted: Wed Oct 24, 2007 8:38 pm Post subject:

Well even I cannot believe what I just did.
I successfully, desoldered the tiny, dual trace, pot from the PCB. (popping the terminals off the body in the process) Dismantled the main body to gain access to the traces and wipers. Cleaned the traces, tweaked the wipers. Re-assembled the body. Re-attached the terminal block. Cleaned up the PCB, and re-soldered the "better than new" pot onto the board. Tested the amp, and, although it's still a little scratchy when you're changing the master volume, it's fully functional, and effectively "brought back from the dead"! Shocked

When inspecting the traces, I noticed that part of one of them had no wiper marks at all. This means it was probably quite dodgy before it even left the factory. Quite likely, because of this, only half the amp ever actually worked.
As this is not the kind of thing which is undertaken very often, I took some photos for you to all see what I'm talking about. They will follow shortly.
Some journeys take you to places you would never normally want to go.
Getting back from there leaves you feeling very good about yourself. Very Happy

Rykhaard · Joined: Sep 02, 2007 Posts: 1290 Location: Canada

Randaleem · Joined: May 17, 2007 Posts: 456 Location: Northern CA, USA

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL

jhaible · Posted: Fri Oct 26, 2007 7:36 am Post subject:

jhaible

Funky40 · Posted: Fri Oct 26, 2007 8:50 am Post subject:

sorry for more Alpha OT Wink

softfin · Posted: Fri Oct 26, 2007 10:46 am Post subject:

I've been using the split shaft Alpha pots for about a year now and have found them to be reliable and pleasurable to use (because of their small size). Futurlec is real cheap when buying a pile of pots at a time. I always order in batches of 25 (á $0.45) or 100 (á $0.40) so I get the pots duty free Smile

Really helps to keep the costs down.

etaoin · Joined: Jun 30, 2005 Posts: 761 Location: Utrecht, NL