Concert Bass head

[Todd]

Hey all,

I got a concert bass head awhile back, and for some reason I'm getting a little fuzziness in the sound. It's more like a white noise fuzz than an overdriven/distortion type of noise. The amp is from '74 (it's as old as me!) - is there anything that I should check out - something that might commonly wear out - capacitors or anything? I know my way around a multimeter, and could call in some more experienced help if necessary.

Any ideas? I've got a Rick 4001 in front of the Concert Bass, and am going into a Bag End 2x10 that  I bought new, si I know everything's ok with the cab, and I don't get the fuzzy sound through my Laney combo amp.

While I'm poking around in there, are there any modify-able parts to the Concert Bass head - to increase the power output or anything?

Thanks in advance for the advice,

Todd.
.

[Joe]

: Hey all,

: I got a concert bass head awhile back, and for some reason I'm getting a little fuzziness in the sound. It's more like a white noise fuzz than an overdriven/distortion type of noise. The amp is from '74 (it's as old as me!) - is there anything that I should check out - something that might commonly wear out - capacitors or anything?

I know exactly the kind of noise/fuzz you mean.  The common cause is a loose/intermittent type connection.

Check the jacks... the ones that internally connect the preamp/poweramp together and give you a power amp in, preamp out on the back of the head.  Some crud could have built up on the switching contact.  A couple swipes with emery cloth on both sides of the contact.

Play your bass plugged into the power amp in jack.  The output will be lower, but you should be able to hear if you still have the fizz.  If not then the problem is isolated to the preamp board.

These amps use wire contacts instead of soldered joints and any one of them could have dirt or corrosion.  Pull each one off (one at a time, so you don't lose track of where they go) checking for a firm contact.  

Finally, a transistor could have worked itself lose in a socket.  These amps are really neat for using sockets for all the transistors.  Press each one lightly with a finger and wiggle it.  Don't take one out unless you are confident you'll be able to get it back correctly.

If all else fails, take it to a tech with a scope.  These types of problems really need a scope for signal tracking.

Hope this helps!

[c pardus]

I also have had the same problem with my concert bass head.  My problem was two-fold.  First off there is a noise filter transistor that went bad.  Secondly one of my power transistors on the rear external panel were bad.  

Finding the noise filter transistor was easy enough once i got a schematic and a plysical layout diagram from Fender.  They only cost me a couple of bucks and were well worth the money.  The power transistors on back come out with two small screws without haveing to tear the whole head apart. Evidently these were expected to go bad occassionally, thus the ease of access.  Oddly enough, I was able to get replacements at Radio Shack.  They are covered by black plastic pointed oval covers (on mine anyway).  Hopefully it's something that simple, I haven't had a problem with mine for 8 or 9 years now.  Good luck!

[Joe]

:
: I also have had the same problem with my concert bass head.  My problem was two-fold.  First off there is a noise filter transistor that went bad.  Secondly one of my power transistors on the rear external panel were bad.  

: Finding the noise filter transistor was easy enough once i got a schematic and a plysical layout diagram from Fender.  They only cost me a couple of bucks and were well worth the money.  The power transistors on back come out with two small screws without haveing to tear the whole head apart. Evidently these were expected to go bad occassionally, thus the ease of access.  Oddly enough, I was able to get replacements at Radio Shack.  They are covered by black plastic pointed oval covers (on mine anyway).  Hopefully it's something that simple, I haven't had a problem with mine for 8 or 9 years now.  Good luck!

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Hi... could you give me the transistor number off the schematic ("Q" something or another) of what you are calling the "noise filter transistor"?

Thanks!