SERVICING A FENDER CHAMP 12 COMBO

Yet again, another EBay purchase and belonging to Karl who is a regular customer of mine. He brought the amp to me with a snapped-off “treble, pull-boost” control. (He knew about this when bidding for it, but it was sold as perfect in every other way!). As it is pretty impossible to stock every spare potentiometer for all brands/models of amps, I ordered the said pot from Fender. A few days later, the pot arrived and I proceeded to fit-it. After doing this, I found that there was no reverb. Further checking revealed the reverb pot was actually smashed-out of the print, but was still bolted in place…..not easily spot-able. OK, on the phone to Fender again to order this pot. (The seller must have been aware of the reverb not working!). After another few days wait, the pot duly arrived, was fitted, and yes……we now had reverb but…..very little! Checking the send and return signals confirmed every thing was OK here so, there had to be a tank (pan) problem too. I had to cut open the “cheap-tack” reverb cardboard box-tunnel and yes….a spring was off!

You only really get one chance at re-soldering one of these. The spring is trying to pull against you, the little transducer needs to be smack in the middle of the laminations and yet, keeping the soldering iron on too long melts the plastic housing! I managed to get it back about right and now we had more reverb. (There is a lot of talk on the net about users of the Fender Champ 12, changing the reverb tank for a better quality one, mounting it in the bottom of the case….highly recommended!). The reverb drive on this model is driven from the output transformer secondary (speaker) through a potential divider network. There is then a little pre-set pot for trimming this. If this pot is set too high the reverb goes into a “feedback loop”…..screaming! Talk about “cost-cutting”! This method of reverb drive is very “cheap-tack” and not too reliable or successful!