my 1998 Chet Atkins is giving me problems

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my 1998 Chet Atkins is giving me problems

Postby bobbydino88 » Sun Jun 15, 2014 2:09 pm

for some reason the volume is very low even when I crank it all the way up I check the battery I took it to a technician they don't know what is the problem please someone help me
bobbydino88
 
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Re: my 1998 Chet Atkins is giving me problems

Postby Terry Tolley » Mon Jun 16, 2014 10:15 pm

I have a 1999 CEC which had a similar problem. I have spent a long career in electronics, so I tackled this issue with my guitar and 2 others who had one of these models made around the same year as mine. The problem with all three of the ones I worked on (mine included) was the impedance matching stages that directly follow the piezo pickups. Gibson used a device called a J-FET (junction field-effect transistor) of the type 2N3821. There are two of these units, usually the one that is connected to the volume controls is the one that usually fails, causing the symptom you described. I doubt that a guitar tech could fix this, unless they are used to doing work on devices like the small amplifier board that the Gibson guitar uses. You really need an electronics tech. Replacing these transistors involves miniature electronic soldering techniques. One other issue is finding replacements for these transistors! They are no longer manufactured. All the ones I have bought were NOS (New, old stock). The last time I bought any was in 2002, but I did a quick search, and there are still sellers who have some in stock. Some are in England, Russia, and other countries and most of them sell on EBay. The cost of the transistors is trivial when compared to actually finding them for sale. I have read of replacement string pickups with companion amplifier assemblies, but these solutions are considerably more expensive than replacing the transistors mentioned here. If you do find some transistors and can get someone near you to replace them, it would be VERY advisable to replace both of the transistors of the 2N3821 transistors (this is what I did on mine). I've been using the guitar since I repaired it 15 years ago, and it continues to work fine.

Some of the later CE's and CEC's use a different board that uses an integrated circuit that is more robust than the board used in our vintage. Of course, it is also hard to find, and it is NOT cheap! There are some aftermarket solutions to this issue where pickup assemblies made by someone other than Gibson are available...but they are also not as cheap as a single transistor!

Whether you opt to replace the electronics package or repair the one you currently have....precautions have to be taken to avoid damage to the static sensitive components on the circuit board, like the two 2N3821 transistors on the amplifier of your unit. The other version that Gibson used also had a static sensitive issue, so anti-static handling is a major concern no matter what solution is used.

As you might guess, Gibson customer service leaves a lot to be desired. They left us CE and CEC users high and dry. I wasted many weeks trying to get help from Gibson when my problem first occurred!

Good luck to you with your guitar, as it is a very good instrument outside of this design shortcoming.
Terry Tolley
 
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