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PostPosted: Sun Mar 30, 2014 9:43 am 
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Joined: Wed Nov 19, 2003 4:58 am
Posts: 925
Location: Southern Indiana
You should be reading this if you have an Electra MPC guitar and the pickups sound muddy or flat on it. This is not normal for the guitar and most people like the original pickups fairly well. But there is a known problem with a batch of Electras. Electra had a sizeable number of MPC guitars that shipped with the wrong value pots in the volume and tone position. Any typical pickup put into those guitars when there are 50K pots in the volume and tone position instead of the normal 500K will sound muddy and dull. The 50K pots attenuate and dull the output of the guitar. The result can be that people think it is the pickups and change them out and it still sounds like junk. You can easily overlook the real problem and needlessly spend a lot of money trying to fix it as a result (and still not fix the problem). The real FIX it turns out is really cheap and easy.

It does not happen to Electras only! I learned this first the hard way in that I had another guitar that happened with and I put in at least three sets of pickups and it turned out to be the pots! This was a premium American-made guitar too with CTS pots in it from the factory - so Electras are not the only ones this happened to. I have since estimate maybe 5-15% of the MPCs had this problem. That is a guess, but it really is not that uncommon. Some were clearly caught and fixed before the customer got the guitars. Some people bought the guitars with the "super charger" stickers already on the volume and tone knobs. But Electra had a number of these escape to the dealers and get to the customers with this problem - in fact they even had the "super charger" kit they issued to fix this problem back in the day. The kit itself does very little as far as wiring goes - it installs some resistors to help reduce some "pop" when switching on the MPC effects - not really recognized as a real problem to most (the only difference in the wiring). What the kit did do is put the correct value pots in place, and that is not mentioned in the kit instructions! Today it is easily fixed by a couple of full-size cheap import alpha or bournes 500K pots (most prefer Audio taper pots, but you can use either depending on your preference). Import pots are the same size as the ones in there and will generally fit the knobs and nuts, washers, and holes in the electra. US pots are not recommended as they may require different knobs, larger holes in the guitar, and other nuts/washers. The "super charger" wiring changes talked about won't really help because the problem isn't the wiring but 500K pots Electra included with the "Super Charger" kit. The kit doesn't state this at all (I put those values in the picture I posted online of the super charger kit). Take a mistake and make it into an upgrade! That was some creative SPIN put on the situation. Someone at Electra must have had an excellent career in politics or in Hollywood!

Tech Tip!
Fixing the wiring in these is not hard because all you have to do is wire them the same way as the originals - so you can take a digital photo of it before and just look at the picture. Everyone has a digital camera now or one in their phone. Use it to take a closeup of any wiring before you mess with anything, so you can always get back to where you started! I do this all the time. I used to have to draw hand diagrams, but the digital camera takes care of all of that. Technology is good thing if you use it.

Another good tid-bit!
If you are lucky enough to stumble upon one of these guitars, they frequently are in better cosmetic condition. The reason is, they really don't sound good - they sound dull and muffled. So they usually got put away in a closet and didn't get played all that much. Not good for the original Electra customer and I am sure it didn't help with people's opinion of these guitars - they didn't play them because they didn't sound good. So sometimes they are in much better condition than the ones that had the heck played out of them because they sounded fantastic. They may have been sold at a sizeable discount too originally. Stuff like that happens today if a product does not sound right frequently the problem isn't caught and corrected, it is just blown out the doors at a sizable discount. Electras normally really do sound pretty good - certainly a lot better than these 50K quality control mistakes. Again, this has happened many times from the factory on any number of guitars. I regularly check the pot values if it does not sound like it should - sometimes parts are not what they are marked as well! It happens. Experienced electra collectors found this out too, sometimes reporting this particular MPC guitar they collected didn't sound as good as the others - well - they went back and looked to find it had the wrong value pots in it and that it actually sounds fantastic now.

About local guitar techs!
Some techs are great, but frankly most I would not trust many with my guitar! Many I run into are not good. So don't assume they are good and take a little effort to know with whom you are dealing. Don't ever let a tech talk you into changing the two 150K pots (on an Electra MPC) - because if he (or she) does they do not know what they are doing! Lots of people out there really don't have a clue, so be careful. Even guys that do know what is going on may not have seen one of these MPCs because they came out 30+ years or so ago. I have seen some really butchered Electras done by "techs" and have had to try to fix their mess. Most don't have a clue unless they look here first! Hey, I DID myself a LONG TIME AGO - that is how I first got in contact with these guys on this page. Just because they work for a music store it does not mean anything. Many music stores will hand over tech duties to anyone that is willing to pick up a soldering iron and dig in whether they know any more than you do or not. I liken it to calling anyone a mechanic that has access to a set of tools - it isn't so. Many will try to change pots even if you had 500K pots in there already, so don't let them change those out. These original pots seldom go bad. They can even be frozen stiff and if you use the right cleaner (caig deoxit) you'll be able to free them up with a little bit of effort and patience. My first X330 had EVERY POT frozen in it, and I cleaned them out with deoxit, and worked them little by little until they freed up. Originality will always be worth more if you to a collector. The only exception is if the orignal pots are the wrong value and you replace them with the right value. This is generally considered a required fix. If it bothers the collector, they can hold onto the 50K pots to show the originals are included with the guitar.

How do I check the POTS?
I don't know how to use a Meter
If you don't own an electronic multi-meter, you need to get one! You don't need an expensive one. They are cheap, widely available and really easy to use. You can get a cheap multi-meter from Walmart, Radio Shack, Harbor Freight, or any cheap tool place. A very inexpensive one will do, frequently in the $5 range - sometimes even less. Harbor Freight sometimes has coupons and gives them away for free! Once you know the basics you will have lots of uses for it around the house.

Checking pots are VERY easy even if you don't have experience using a multi-meter. Make sure your black and red probes are plugged into the right sockets. The black one should go into the "COM" one - short for "Common" or ground. The red probe should plug into one that says "V ohms mA" or similar. You don't have to disconnect anything on the guitar. Open up the back of the guitar. Set the meter to the correct resistance range - usually 2M for suspected 500K or 250K pots, or 200K for anything 200K or less. Below I did a drawing of the back of a pot with three terminals on it. Then on the back of the pot you will see three terminals. Touch one probe the the left one, and the other to the right one - don't touch the middle terminal or the body of the pot. It would be like the touching the ones with the Xs below, and the middle one being the "O" and not touched:

(Pot)
(Back)
X O X

It won't likely read exactly the correct value, so a 500K pot may read 436K or 532K - usually somewhere close within 10-20%. Start at the 2M resistance range on your meter and if you don't get a reading, you switch to the next lower value range (usually 200K on the meter) until you do get a reading. So if it reads 45 to 55K or so - that would likely be a 50K pot - and an incorrect value. Generally that will be either the 2K or 200K range - the range is the maximum value it will read. If yours is an auto-ranging meter you don't have to worry about any of this, but they are usually about $30 or more instead of the cheap $5 meters. If you have one good, but a cheap $5 meter is fine for occasional work around the house. If you happen to break or mess up a $5 meter, you just buy another one! Sometimes the 9V battery can cost more than the meter!

So, mine has 50K pots, now what do I do?

You change them out - usually with 500K Audio alpha (or similar import) pots! These are the first two pots - the Volume and Tone - in MPC guitars, not the 2 rear/bottom ones that go with the MPC/flapper switches. Those MPC pots should read 150K (or close) so leave those alone.

Take a good clear digital picture of the wiring you are removing on the back of the pot prior to removing anything. If you can't tell wire from wire, then label them 1, 2 and 3 and take a picture of them that way. If you screw up we do have schematics here if you can read them. But don't screw it up!

You will need a 35W-60W soldering iron and some electronics solder. You can even use a cheap one from Radio Shack, but if you are going to do a lot of it a better brand name one is worth it. Radio Shack or Walmart brands will do if you only use them occasionally. I use an import temperature controlled soldering station, but I use it a lot! I use the 60/40 solder electronics solder. Don't use a soldering GUN - way too much power and heat and it will fry things. Likewise don't use "pipe solder" either. I use a needle-nosed pliers for holding the wires. I don't tell you how to solder, so look for a tutorial online if you want to know how to do that.

Pre-heat the soldering iron and melt some solder to "tin" (coat) the tip with solder.

Desolder the 50K volume and tone pot and position and replace each (one by one) with the new pots.

Solder them in (again, one by one) using your digital picture as a guide.

There you go - doesn't get much easier than that.


Are there other problems that can cause this?
Certainly, but they are not as common. You can have bad pickups, bad switch contacts, a bad part, a wrong tone capacitor value. It is just these problems are much less common or likely. You should clean your pots and switches first with a quality cleaner (caig deoxit) and that usually fixes most problems. I have had a LOT of electras and only had a couple bad pickups in the whole bunch. You may need to set your pickups closer to the strings if they are set very far back, but it is assumed you have checked that first too. You still may want aftermarket pickups, but I think most people are happy with the originals. The biggest complaint with some of the pickups is that they are microphonic, and this can generally be taken care of by potting them (you can read how to do that online). These are always more valuable with the original pickups to collectors. So best to at least give them a fair shot.

Good luck!

:up:

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