Re-Capping the Gibson GA5-T Skylark Amp

The Gibson is a killer little harp amp. Probably not a giggable amp, but awesome for playing at home and probably good for a garage jam.

Mine is absolutely perfect. Just like it left the factory. Unfortunately, that means it had all its original capacitors. That also meant it had a pretty substantial hum. Not a good thing....

I talked via email with Greg Heumann. He's the accepted expert on Kalamazoo amps, and since that is the direct cousin of my amp, I figured he'd be the right guy to ask. He confirmed that the caps in my amp were probably dead. Guessing that they are all 48 years old, I think he was/is right.

I found a good tutorial on my exact amp including a suggested set of caps to replace mine with and placed an order.

Link to the how to - http://www.paleoelectronics.com/2012/02/replacing-the-cap-can/

Link to the caps I used - https://www.tubesandmore.com/products/C-SA

The Skylark takes 2- 10mf x 500v and 1- 20mf x 500v capacitors to replace the Sprague 'cap can' which is really a 3 in 1 capacitor mounted on the chassis in the amp.

First off--- Safety first!!!! I discharged all the existing capacitors to ground using appropriate procedures and checked them all with my multimeter. If you don't know how to do this, don't touch your amp!!!!

To do this, I drilled out the rivet which held the clamp and slid the cap can out. Then I desoldered the old cap can connections. Next up, I soldered each of the new caps in at their positive locations. Finally I brought all of them to ground at the original grounding location. The paleoelectronics site mentioned the idea of re-grounding the caps, but I figured the old design worked and I am not really capable of improving upon it.

The results are pretty awesome. Quiet amp. Without a cord plugged in, it is dead quiet. With a poor quality cable plugged in, I begin to get a 60 cycle hum, but that is not the amp's issue IMO, that is poor quality gear plugged in.

Before

 

After

 

One other thing I've done to the amp to improve it. A known failure point of the amp is chassis flex which allows the upper chassis to flex, and then the connections inside to eventually flex and break. I designed a small aluminum brace which connects the upper corner of the chassis to the lower mounting point and eliminates this flex. The rivet head is not visible in normal use. The result is a solid chassis and no future breakage!