Other Amps

How do I remove the amp chassis

1

Hi all, about to unload my '67 Fender Super Reverb. In order to sell it, I would like to get photos of the innards. I've read that there are deadly/leathal voltages inside the chassis and I don't really want to risk dying for a picture. 8-o

So, how do I go about doing this? It looks like there are the 2 straps along the top to remove it, but I'm not sure what else needs to be done (aside from the obvious removal of the back panel. How can I minimize my risk of killing myself? Any way to get rid of the charge? Will I need to wear rubber gloves? Bio-hazard suit? LOL!

Thanks all for any input and insight. And of course, I will give all you GDP-ers first shot! :)

Johnny

2

Disconnect the reverb cables,speaker cable and if the AC cord is attached to the inside of the cab remove that too.Take out the power tubes and then remove those straps and the chassis will slide out the back.With the power tubes removed you should be able to sit the chassis on the transformer.Dont touch anything inside and you wont get shocked.The caps that carry the dangerous voltage are under a "doghouse" on the side of the chassis where the tubes are so you cant touch them,just be aware that these attach via wire to different points inside the chassis,if you keep your hands out of it you'll be safe.

3

Haven't removed one of those in a long time, so I'll let someone else chime in on that. As long as you don't go poking around inside, you should be fine. Be sure to unplug it first, and keep your feet dry! And even unplugged, there's still plenty of juice in those caps (ask me how I know, lol).

edit: what Stokes said!

4

Q for the electronics guys- I heard somewhere that in an amp like a midsize Fender,if it's unplugged,the charge in the caps dissipates until they won't shock you. If that's true,how long would it likely take?

5

Q for the electronics guys- I heard somewhere that in an amp like a midsize Fender,if it's unplugged,the charge in the caps dissipates until they won't shock you. If that's true,how long would it likely take?

– DaveH

Q for the electronics guys- I heard somewhere that in an amp like a midsize Fender,if it's unplugged,the charge in the caps dissipates until they won't shock you. If that's true,how long would it likely take?

– DaveH

IIRC the 60s Fender amps had a 'bleeder resistor' that would drain the charge from the caps; 30 seconds should be enough.

6

The AA763 schematic (assuming that's what you have), does not have the bleed resistor over the primary filtercaps.

So unless it's been retrofitted: be very careful here: these things will hold lethal charge levels for days!

A trick that should not be done too often is:

With the power chord disconnected, put the standby switch in the 'off' position and let it sit for a couple of minutes. This will drain the primary filter caps through the tubes and passive networks, but it'll take a while.

[edit] Note that the tubes must be in the sockets for this trick to work.

7

Michiel - shouldn't that standby be in the 'on' position to drain the voltage?

9

"Drain" the caps? Sounds like a good extra safety measure.That's why I asked how you could go about doing it.

10

Thanks all for the info! I will be doing this in the coming week.

I have the AB763 chassis. Thanks for the tip to take the power tubes out and the reverb cables. I probably would have gotten the chassis loose and THEN figured out that I needed to remove them! LOL!

And, I would imagine that the Standby would be "ON"? Michiel-please confirm. THANKS!

If I never post here again, you'll know why! J/K!!!

Johnny

11

Man just list it as a 67 super reverb , and stay OUT of the thing . if someone else want to look inside , the let them .to take someone who say they know what to do can cause you to lose your LIFE !! sorry you guys thats just my thoughts !!

12

Michiel - shouldn't that standby be in the 'on' position to drain the voltage?

And, I would imagine that the Standby would be "ON"? Michiel-please confirm. THANKS!

Ah, yes, I meant, get the switch out of standby. I hardly look at the back of my amps these days; I find the switches by touch alone.;-) Sorry for the confusion, you guys got it right!

13

Standby in the "on" position,power switch in "off" position and leave the plug plugged in,it gives you a complete ground connection.That said,I wouldnt trust anything without first puttin a meter on the caps to be sure they have drained.I even check when I use my own seperate bleeder cable,a couple of alligator clips with a 470ohm resistor between them.Not saying you cant remove the chassis safely without following any or all of the safety precautions,just keep your hands out of where they dont belong,you'll be fine.

14

Yeah, I thought about just listing it without doing so, but it seems like most of the ads for the 'vintage' amps have shots of the chassis, so I wan'ted to be 'competitive' in that area. You're right though-is it worth the risk? I will probably just list it with 'normal' pictures of it. I mean, it IS pretty much bone stock except for the replacement of various caps and a 3 prong cord (all courtesy of Hal at Guitronics in SF-GREAT guy, great memory and loves to chat amps and music).

No meter to check, and I wouldn't know what do connect it to anyways.

LOL!

In any event, if it doesn't sell right off the bat, I may look into getting pics of the guts.

Thanks!

Johnny

15

"it IS pretty much bone stock except for the replacement of various caps and a 3 prong cord" That is exactly the reason people will ask for pics of the inside.You have a vintage amp that has had parts changed,any serious buyer will want to verify what is in there.

16

Yes, I know. As a buyer or a vintage piece, I too would want to see the innards.

17

It really isnt all that dangerous if you dont poke your fingers inside the chassis.

18

11/32" nuts on the bottoms of those strap screws, Philips screw on cable restraint for power cord, RCA cables to and from reverb pan. It slides out the back. Show us the photos. BZ

19

Thanks BZ-Will do!!! Will for sure post them here!


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