Guys, I have a DRRI that suddenly the red power jewell does not come on, the ONLY tube that is warming up is the rectifier and obviously there's no sound at all. The fuse is good. Has anyone seen this or have suggestions of where to start before I go to an amp tech? Thanks
John - Ohio
One of the secondaries from the power transformer provides 6.3 VAC to all tube heaters (save for the rectifier) and the pilot lamp. There's a connector in the wiring (P7/P8) that facilitates this -- if it's defective or loose it would cause the symptoms you describe.
"When injustice becomes law then rebellion becomes duty."
MUCH appreciated. You'll hate me for this, but can you tell me where P7/P8 is? I have the chassis out of the amp on my bench right now (and a show in a few hours to play) Thanks Brother.Originally Posted by phantomman
i don't have access to a DRRI chassis at the moment but you're looking for a pair of leads from the power tranny that run to the tube heaters in "daisy chain" fashion. Start at the 6V6GT tube sockets and work backwards toward the P/T until you locate the connectors, which are usually white or translucent nylex plastic. Carefully re-seat them and see if that provides a remedy. If not, you'll need to meter the leads at various points in the heater circuit to isolate the issue.
"When injustice becomes law then rebellion becomes duty."
Again, THANKS. Here's a pic of a connection labeled "P7"I note that there is also a glass fuse nearby. the fuse tests good with an ohmmeter but there is some heat discoloration at one end of this fuse. I'm not seeing any actual connectors in this area, just soldered wires. Does this pic help with any ideas or conclusions? The thing is I played a show and it forked fine, put it in the amp case for a week, then when I pulled it out of the case and plugged it in it had this problem. Thanks Buddy.
No pic visible.
"When injustice becomes law then rebellion becomes duty."
https://photos.app.goo.gl/nP8tgSCgmfniSkno8
can u try this link for me?
John
Not the area in question. Look for a pair of green wires coming from the power tranny and connected to the tube sockets.
"When injustice becomes law then rebellion becomes duty."
Well, I have made headway. The INTERNAL glass fuse is blown. Tried replacing it with the correct fuse but they blow instantly. Need to think of why this fuse is blowing now. Hmmm
Pull all tubes, except the rectifier, and try a new fuse, if it holds, replace the tubes one at a time. You may be able to isolate the shorted circuit,(I would hope for a bad tube now). The black/while wires in your pic are P7 P8, and the discolored board under the fuse may indicate a loose solder connection.
Hopefully you have a backup amp until you can sort the problem with this one!
Bill, that fuse is not shown on my schematic -- it must be something that Fender added in a later circuit revision.
"When injustice becomes law then rebellion becomes duty."
I don't find it either, on the schematics I found, just thinking the proximity to the heater wires suggests thats the function.
https://www.thetubestore.com/lib/the...-Schematic.pdf
I think you're right. And no question that the existing fuse and the fuse-holder itself are exhibiting signs of thermal overload.
"When injustice becomes law then rebellion becomes duty."
I can't find a schematic to post, but Rob's website has a 68 Custom Deluxe Reverb schematic that is similar to the board Pic, with the fuse inline with P8.
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