# Old Gibson GA20RVT Woes....



## Gene Machine (Sep 22, 2007)

Hi all, some advice is requested:

I have a 1967 Gibson GA20RVT, and the reverb died. I managed to track it down to a bad tube socket, which I am in the process of replacing.

BUT, I noticed that the capacitor on the power switch (.022ufF) was broken off, and in fact the lug was snapped right off the switch.

This switch is wired for reverse polarity selection. And is a pretty wierd looking switch, not sure if i can find another one easily.

So, how necessary is it that I have polarity reversal anyway? provided I have the plug wired in correctly, I should be good. Besides, there is no indicatin of which way is correct so I could be taking a chance at electricuting myself 1/2 the time anywayy.

Any suggestios or advice?

thanks in advance


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## Ripper (Jul 1, 2006)

You don't need the reverse polarity, that comes from the old days of strictly two prong plugs and non grounded electrical circuits. Put a regular switch in and install a three prong plug to ground it. That cap is what is referred to as the "death cap"(probably an old black sprague with red lettering?). If you do a search on the net you can find alot of info on death caps and on installing three prong plugs in amps.

This one is in reference to a GA-8 
http://www.tdpri.com/forum/amp-central-station/110189-death-cap-what-cap.html

This one shows a pretty good picture of the cap in a GA-6
http://www.netads.com/~meo/Guitar/Amps/Gibson/GA6/photos.html


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## Wild Bill (May 3, 2006)

Ripper said:


> You don't need the reverse polarity, that comes from the old days of strictly two prong plugs and non grounded electrical circuits. Put a regular switch in and install a three prong plug to ground it. That cap is what is referred to as the "death cap"(probably an old black sprague with red lettering?). If you do a search on the net you can find alot of info on death caps and on installing three prong plugs in amps.


Yep! If you have a 3-wire cord properly installed you don't need a ground switch or a "death cap" at all.

Which usually leaves you a perfectly good switch sitting there which you can wire for some neat mod function...:smile:

:food-smiley-004:


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## Gene Machine (Sep 22, 2007)

*phase 1*

So another thing this thing has is a fuse on the neutral, which is wrong. It also has a 3 prong, but the ground wire was never connected inside the amp. Also had a broken neon indicator lamp.

So last night I rewired the whole input power section.

first, removed the old switch, removed all the old connections and cleaned the old gunky solder from the existing lugs. I re-used old switch, but only as SPST. all the fancy reverse polarity removed.

Then I wired it up as follows:

hot from plug ->fuse->switch->transformer

transformer neutral -> plug neutral

I placed the new neon lamp in parallel with transformer on the load side.

Next step Phase 2: attaching the ground, reseating the cable grommet, fixing all the reverb tank cables, prepping to replace tube socket.

yeah I know I should probably take some pictures. But you've all seen the inside guts of an amp before. "hey look, here's a solder lug on a switch. here it is with a wire attached...."

I'm hoping to have this thing functional for my gig in Trenton on 19 July. Anyone around can come listen.


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## Ripper (Jul 1, 2006)

Sounds like you've been busy, but it will be worth it in the long run. Keep us posted on the progress


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## Gene Machine (Sep 22, 2007)

*wow, frustrating day*

So I started off by making better/shorter cables for the reverb tank and attaching the ground wire. pretty strait forward.

Then I started to take the wires off the old tube socket. I labelled masking tape 1-9 so i could mark the old wires for the new socket. I heated up pin 1 and gently tugged on the wire. Then i tugged a little harder. then i got out my dental pic and started fiddling, then I realized...

The guy that soldered all the wires wrapped them through and around the lug before soldering them. So, I had to cut them all off. 

hopefuully what is left is long enough to reach, but I don't know how i'll strip the damn things, they are inside the chassis. I will likely have to make new wires and wire them into the turret board.

I'm no amp professional, but i've never wrapped wire around a lug to solder it on. Just a little dab on the lug, tin the wire, slip it through the hole and touch up the dab if required, minimal solder use.

So I went to go mount the tube socket in the chassis, and couldn't find the fasteners I bought. Oh I found the bag, but somewhere along the way the fasteners fell out...

ARRRRRRRRRAYYYYYYYYAARHHHHHHGGGG!
Insert Cursing Here

My darling heard me "working" and brought me down a beer, told me to take a break. 

phase three.... starts tomorrow....


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## Ripper (Jul 1, 2006)

Wrapping the wire once through the hole, then soldering is the way it was done. It was the way it was taught. When I took my training, that was the way they taught it and they taught different methods for the wrapping as well. 

If you are using a soldering iron and a dental pick you should be able to heat it and lift the wrap and slide it out of the eye hole.

As for stripping, just hold the wire really tight with your one hand and use a small set of strippers to peel back what you need.


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## Gene Machine (Sep 22, 2007)

*hmmm*

really? I never soldered a tube socket before. I've done lots of potentiometers & components, but never wrapped the wire through/around the hole.

Yeah I tried to bend it with the dental pick, but it was on there tight. Plus 40 years old solder goo. Cutting it was the only way I could get the wire off without melting all the insulator off the wires, or melting the tube socket.

I'll go back at it this week with less frustration. 

I have to rewire/assemble a pedal board for a gig next week. I'm downsizing, trying to get smaller & lighter.


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## Ripper (Jul 1, 2006)

Gene Machine said:


> really? I never soldered a tube socket before. I've done lots of potentiometers & components, but never wrapped the wire through/around the hole.
> 
> Yeah I tried to bend it with the dental pick, but it was on there tight. Plus 40 years old solder goo. Cutting it was the only way I could get the wire off without melting all the insulator off the wires, or melting the tube socket.



Do you use a solder sucker or braid? Sometimes a small set of needle nose will help alot too. One thing you can try, is just snipping the loop where it starts to wrap, you should still have some exposed wire left and still be able to pull it out.


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## Gene Machine (Sep 22, 2007)

*braid*



Ripper said:


> Do you use a solder sucker or braid? Sometimes a small set of needle nose will help alot too. One thing you can try, is just snipping the loop where it starts to wrap, you should still have some exposed wire left and still be able to pull it out.



i always use braid, hate solder suckers.

with the sockets inside the amp, it is difficult to really work down in there, so not much dexterity. and there are lots of wires there for me to melt when i'm not paying enough attention 

but good idea, i'll try that next time: desolder with braid and try to lift or snip the loop.


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