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Replacement pots for a '50s Magnatone lap steel guitar Electric Guitar
Old 5 days ago
  #1
Here for the gear
Replacement pots for a '50s Magnatone lap steel guitar

Hello, everyone. I won an auction on eBay for a '50s Magnatone lap steel guitar. A really cool guitar in superb condition that even came in its original cardboard case. The case had some minor damage, but a friend returned it to nearly as new condition. The only other thing that needs attention is the pots. At first they were very sticky and unreliable. Basically all they did was completely cutting the signal at any position of the pot. You might move it a little bit and you had no sound, and move it again a little bit and you'd get full volume. After cleaning them with G22 contact cleaner, they work very smoothly but again they do nothing but completely cut the signal when turned to zero and let it all out in any other position. I guess I have to replace them and so I ordered a pair of 500K Emerson Pro CTS pots from StewMac that are on their way to my house now. Then I wondered if maybe someone out there who knows better about old Magnatone guitars might advice some other option, which is why I send this post. Thanks everyone in advance for any ideas you may give me.
Old 4 days ago
  #2
Here for the gear
I send some pictures taken from the eBay listing so you can see the condition the guitar is in and the condition the case was in when I received it. You can also notice the tuners are in such good shape that I doubt they are original.
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Old 3 days ago
  #3
Gear Addict
 

You will need to open it up and have a look - hopefully the pots will have an OHM spec on it's casing. You probably won't go wrong placing a 500K pot in it - but it may a different original spec. It will probably have a single P-90 style pick-up - in which case - many early P-90's style pick-ups used 300 K pots. The 500K pots may make it sounds a little brighter - according to Internet legend.
Old 3 days ago
  #4
Quote:
Originally Posted by RBHan View Post
It will probably have a single P-90 style pick-up - in which case - many early P-90's style pick-ups used 300 K pots. The 500K pots may make it sounds a little brighter - according to Internet legend.

It's more than legend....

The less you load an inductive pickup, the more HF amplitude you get.



-tINY

Old 2 days ago
  #5
Lives for gear
 

Either the pots will have a resistance stamped on them like 250, 300, or 500K or you'll need to measure them with an ohm meter.
You can pretty much bet, if it uses a single coil pickup, its likely to have 250 or 300K pots. If it uses a humbucker (unlikely) it might be as high as 500K.

The pots in guitar are typically Audio taper. Linear taper typically drops all the volume within 25% of the pot turn. Audio has a curved response which is better for the way our ears perceive loudness. You'll hear a 50% volume cut with the volume turned down half way and it will seem to be even to your ears.

If the pots you currently have in there drop in volume all of a sudden then either the wrong pots were installed at one point or the rotors have worn through the resistive pads so there is no resistance to ground the pickups in the center of the turn. Wrong types of cleaners can do this too. The ONLY cleaners you want to use are designed for pots and either contain silicone or mineral oil to lubricate the pots. There are also some audio pots packed with conductive grease to give the pots a smooth feel which should never be cleaned. Old Tapco gear used them. The grease gives then a harder then normal smooth feel when turning. Problem is when that grease dries up it acts like glue. Cleaners make the problem even worse so replacement is the only option.

Most lap steels I've seen are copies of the Fender which all use single coils and 250K pots. Cant tell you if something like a Tele pot would work or not without seeing it. There are a few different shaft types and lengths. You'd obviously want the knobs to fit so you want to measuer the shaft diameter, check and see if its a split splined or solid shaft too.
Old 2 days ago
  #6
Lives for gear
 
Mikhael's Avatar
 

Quote:
Originally Posted by wrgkmc View Post
Wrong types of cleaners can do this too. The ONLY cleaners you want to use are designed for pots and either contain silicone or mineral oil to lubricate the pots.
I'll have to disagree with this. I'll NEVER use a cleaner that has lubrication - unnecessary, and that goop collects dust and stuff over time, which will screw it up even worse.
Old 22 hours ago
  #7
Quote:
Originally Posted by wrgkmc View Post

If the pots you currently have in there drop in volume all of a sudden then either the wrong pots were installed at one point or the rotors have worn through the resistive pads so there is no resistance to ground the pickups in the center of the turn. Wrong types of cleaners can do this too. The ONLY cleaners you want to use are designed for pots and either contain silicone or mineral oil to lubricate the pots.
Some lubricated cleaners attract dust which eventually makes them noisier than they started before cleaning. If you MUST use a lubricated cleaner use it VERY sparingly. Many techs will use a little bit and then spray it out with a non-lubed cleaner.

Quote:
There are also some audio pots packed with conductive grease to give the pots a smooth feel which should never be cleaned. Old Tapco gear used them. The grease gives then a harder then normal smooth feel when turning. Problem is when that grease dries up it acts like glue. Cleaners make the problem even worse so replacement is the only option.
That stuff you find in old Tapco mixers and other pots from that era is NOT a factory lubricant, it's an aftermarket product called "Blue Stuff". It worked great at first but after a couple of years it dried out and caused severe problems, eventually hardening and gluing the pots so they couldn't turn. It was eventually withdrawn from the market after causing big problems for many repair facilities.

Quote:
Most lap steels I've seen are copies of the Fender which all use single coils and 250K pots.
Magnatones aren't copies of anything. Their better instruments were more expensive than the Fenders.

A lot of old steel guitars have pots that are significantly lower resistance than those used on regular guitars. This was an intentional design feature intended to create that "mellow" steel guitar tone.
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