JR-20 amp

[bootchman]

Anybody know where I can get an amp for a JR-20 tone cabinet? Mine has burnt up and I need to replace it.
Thanks,
Roy

[fredy2]

Re: JR-20 amp

Burned up? How about repairing it.

[toasterDude]

Re: JR-20 amp



You might be able to find a replacement on Ebay, but no guarantees the "new" one would be much better off than yours. So I agree with Fredy2 - yours should be repairable. These old amps are really pretty simple, and replacement parts are cheap. </P>


The difficult thing would be if you toasted the transformer. So: what happened when it died? Unless there was a big puff of smoke from the transformer, it should be fixable. You probably don't want to put too much money into it, though -JR20s can be had for free or maybe up to $50 if you look around. Or you could consider a nice PR40 as a replacement. Lots of people consider the PR40 Hammond's best tone cabinet. anyway good luck-</P>


Scott</P>

[bootchman]

Re: JR-20 amp

The socket for the rectifier, anyway the first tube from the left, (V6) 5u4 is all broken up, and I don't know how to go about replacing a tube socket. I am willing to try, though.
Thanks,
Roy

[johnny b3]

Re: JR-20 amp



If its held in by rivets you'll need to drill it out. I would first mark each wire with tape and number them, in order of their correct position on the socket. From the "key" (blank space (or notch) between the first and last pin), the pins go clockwise when viewing the underside of the socket from inside the chassis (Therefore, counter clockwise when viewing from the top if the amp is right-side up). Then unsolder the wires.
</p>

Make sure there is clearance for the drill to fall through when the rivet(s) gives up. </p>

Be sure to do a clean job when you re-connect the wires, they should be exposed only at the pin. Make sure any portion leading to the pin is insulated and that there is zero chance of contact between the exposed areas. When in doubt, call a tech or solder-able friend. I wouldn't be complete surprised if these wires were brittle and their sheilding deteriorating if you move them too much so just be aware of that. May not be a bad idea to replace their entire length if you happen to crack them badly. Use your discretion and stay safe.
</p>

[bootchman]

Re: JR-20 amp

Thanks johnny b3. You're right, the socket is riveted - that's why I didn't know how to proceed.

I found a site on-line that tells how to retension the socket -- it may be that the plug is just loose -- I'll check tonight.

Thanks, everybody.

[johnny b3]

Re: JR-20 amp

But you mentioned something is "broken up". The glass tube? or the actual socket?

[toasterDude]

Re: JR-20 amp



[quote user="bootchman"] I found a site on-line that tells how to retension the socket.[/quote]</P>


Hey, would you mind sharing a link to that? The rectifier tube on my A101's power amp is so loose it won't work at all if it gets bumped even a little.</P>


thanks-</P>


TD</P>

[bootchman]

Re: JR-20 amp

Toaster Dude. Here is the link. Refer to Tip #4

http://kbapps.com/tubeamptips.html

[fredy2]

Re: JR-20 amp



Once a tube socket has arced, often the carbonizing of the insulation causes conduction. </P>


Replace the socket. Drill out the rivets and use small screws to install new socket. The sockets are available.</P>


Once the socket pins have been hot, they lose the temper so re-tensioning is NOT usually successful long term.</P>


The burning of the insulation though is the real reason the socket must be replaced. </P>


If you have trouble finding a new socket, let us know as we can find one for you.</P>

[TheAdmiral]

Re: JR-20 amp

And go with a ceramic socket.

[fredy2]

Re: JR-20 amp



Here is a link to a supplier:</P>


http://www.tubesandmore.com/</P>


Go with a ceramic as the other poster said.</P>


Part # P-ST8-807 cost all of $1.76</P>

[bootchman]

Re: JR-20 amp

Thanks, Fred.