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Post subject: 1983 Proreverb Chassis removal
Posted: Sun Jun 05, 2011 8:57 am
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Location: Montreal. Quebec.
Hello,
I have to change the power switch on my 83 Proreverb :( As I have never pulled the chassis before, perhaps someone can run me through the best way of doing this.
I see two chrome straps on top of the case and some screws on the base of the chassis. I suspect that inverting the amp onto padded blocks might be neccesary.
Anyway if someone feels like clueing me in I would appreciate it.
Regards.
David. :mrgreen:


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Post subject: Re: 1983 Proreverb Chassis removal
Posted: Sun Jun 05, 2011 9:42 am
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Unpluge the amp. Leave stby switch for several minutes to drain the filter caps.
Leave the amp upright. Remove top back panel. You can remove the tubes if you want to play it safe. Or at least the power and rectifer tubes. Unplug the reverb or footswitch cables taking note of positions. Unplug speaker cable. Remove cable clamps for the power cord. The fours screws on top have nuts on the other end under the chassis. Reach your hand under there hold the nut and unscrew the from the top. Should loosen pretty easily then spin the nut off with your hand. Remove all four and lift he screws with the straps up. The chassis will sit on the inner frame. Gently push the chassis out from the front to the back. Grab one of the transformers for support and pull while you push. May require a little jiggling. If its stuck it could be haning up on the RF screen/shield on the under side of the top of the cab. If so run a putty knife or spackle blade to allow the chassis to slip past the shield.[b] Should come out pretty easy.
[b]Be really careful if you decide to functionally check it after you change the switch. Read up on safety and bleeding the filter caps.
[/b][/b]


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Post subject: Re: 1983 Proreverb Chassis removal
Posted: Sun Jun 05, 2011 10:55 am
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Thanks for your reply MXVIN,
Actualy this model does not seem to have nuts on the ends of the two chrome strap screws. Perhaps they now have a location point inside the chassis. As i said there is also three phillips head screws located on the chassis lip screwed directly into the cabinet. I am also not 100% on the make up of the chassis guts. As this is an 83 it may be a PC board set up. I will only no that when i get it apart. the reason I had talked about inverting the cab was, not knowing how heavy the chassis was I did not want to get caught between a rock and a hard place without enough arms to support the whole thing.
Regards.
David.


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Post subject: Re: 1983 Proreverb Chassis removal
Posted: Sun Jun 05, 2011 10:59 am
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+1 to the procedure detailed by mxvin!

I'd add that if the power switch is toast due to age-related deterioration, the standby switch is likely hosed as well -- replace them both. Be sure to use switches of similar voltage and current ratings to the originals.

Best of luck, be careful, and HTH

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: 1983 Proreverb Chassis removal
Posted: Sun Jun 05, 2011 4:25 pm
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Be carefull, filter capacitors won't drain by this way ( re ; mxvin)


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Post subject: Re: 1983 Proreverb Chassis removal
Posted: Sun Jun 05, 2011 4:48 pm
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Stratele52 is prolly correct. I'm guessing you have the last of the the silverfaced Pro Reverbs. To properly drain the main filter caps:

1.) Turn off and diconnected amp from wall outlet.

2.) Leave Standby in the on (or play) position.

3.) I use a 150-ohm, 5 watt sandbox resistor with around 4 inch leads and alligator clips at each end (red and black). The clips DO NOT have to be red & black. Now, carefully open the cap can lid on the top of the chassis.

4.) Connect one end of the drain resistor to the (+) side of any of the big electrolytic caps. Connnect the other end to the chassis.

5.) I usually keep the drain wire connected while doing work. To drain out any residual charge left by the trannies' field collapsing.

6.) REMEMBER to remove the drain wire before buttoning up the chassis and firing it up.

Good luck with your amp!

http://www.ampwares.com/schematics/pro_ ... aa1069.pdf


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Post subject: Re: 1983 Proreverb Chassis removal
Posted: Sun Jun 05, 2011 5:01 pm
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Thanks for all the info guys.
Regards.
David.


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Post subject: Re: 1983 Proreverb Chassis removal
Posted: Mon Jun 06, 2011 2:01 am
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++1 BMW, very good advice

As you know BMW, an information for people don't know about resistor and in case if your local electronic store don't have a 150 ohms resistor, almost any resistor value between 150 ohms and 1500 ohms is good for this purpuse.


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Post subject: Re: 1983 Proreverb Chassis removal
Posted: Mon Jun 06, 2011 5:49 am
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also if you do fire it up with the chassi out be wary of the A/C voltage that will be live on the exposed lugs of the power and stby switches.....that is a definite gotcha!!
I usually run a strip of duct tape over that part of the chassis since I am an airhead and tend to forget there is juice present there...:)


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Post subject: Re: 1983 Proreverb Chassis removal
Posted: Mon Jun 06, 2011 6:31 am
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+1 mxvin


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