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1959 GA-5 with reversed polarity capacitor from factory?


BluesPretender
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I recently purchased a 1959 GA-5 (dated by 34th week of 1959 transformer codes).  The photo shows the way I received it.   I converted to a grounded cord from the original two-strand and replaced the white caps in the photo with orange drops.  I was about to replace what looks to be the original cap on the input jack at the far right in the photo.  When thinking about the orientation of the new cap, I noticed that the old one appears to be reversed.  Am I right?  Does this look to be the original wiring and thus represent a production error?  What effect would this have? 

GA-5_circuit.jpg.1552da1094ff3c1756c6b6c26d75cb77.jpg

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Good eye!  That's reversed, alright.  And it does look original.  When you do the three prong plug, make sure you run the hot (black) wire from the new cord to the tip of the fuse, then from the side of the fuse to the switch, and then to the transformer and back to the white wire on the new cord.  That's to make sure the fuse is on the hot wire instead of on the neutral wire, like they used to do with the two prong plugs.

The blue filter cap isn't original.  I can't make sense of the wiring, but it looks a little sketchy.  The hot leads should be shielded.

 

I'm not sure if there is an artificial ground on the filament wiring.  I don't see one.  If not, you might want to put a pair of 100 ohm resistors - one from each lead on the pilot light, to ground.  That will help with hum.

Good luck!

Edited by badbluesplayer
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I appreciate the advice.  I have a copy of that schematic; however, I'm not skilled in reading it.  I've done a good bit of building and modifying from wiring diagrams, but I'm still pretty ignorant of electronics (although I'm acutely aware of the dangers of amps.)  My initial wiring for power is in the image below - using a European coded power cord scavenged from a defunct water pump.  Although the original plug wasn't polarized, I followed the original wiring with the switch on the neutral side of the transformer.  I have read that best practice places the switch on the hot side, which I gather is what you're advising.  To confirm, I should take the transformer wire off the side of the fuse and the blue, neutral wire from the switch and splice them together.  Then I should connect the side of the fuse to the switch at the lug that currently holds the blue wire.  Correct?

Then, you also advise installing 100 ohm resisters from each lead on the lamp on the right in the photo to ground to control noise.  Correct?

Meanwhile, I'll also shield the hot sides of the caps as you suggest.  Even in its earlier configuration, it's a great sounding amp.  Do you have a sense of the impact of the original inverted cap?

 

ga-5_power.jpg.51e1d31e98e08dbe1dd0b39d8398e706.jpg

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