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View Full Version : Deluxe Reverb rectifier query

Clearspider
07-16-2007, 01:13 PM
I have a '76 Deluxe Reverb that was bought "blackfaced."
When I got it over a year ago, I replaced the 5U4 with a GZ34 (groove tubes (i know)) because I thought that should go in it and I didn't know any better.
After reading something on here about 5U4's being installed stock in the 70's I put it back and rebiased.
Now, after opening her up over the weekend I realized it's not as "blackfaced" as I thought, and even some of the electrolytics had not been replaced.
I just read Mike's link to the KCA rectifier guide, so I'm kind of worried that running the wrong rectifier, GZ34 at 2ma, instead of the right one, 5U4 at 3ma, could have stressed some components, mainly the power transformer.
Is there anything in particular to check for damage or is it cool as long as it still works?

Incidentally, the work I did (remove oscillation-dampening wire wrap, clip bright cap, and reverse the filaments on the power tubes) it is louder, beefier and more responsive. Go figure!
Blue Strat
07-16-2007, 01:16 PM
If the GZ34 did any damage you'd have blown up electrolytic caps. The GZ34 is actually safer (2 amp heater load) than a 5U4 (3amp heater load) for the transformer, but less safe for the power supply caps and power tube. Since the amp/transformer was designed for a 5U4 you're better of with that one.
phsyconoodler
07-16-2007, 01:22 PM
The B+ is the key here.The 5AR4 is not an issue and many DR's sound better with the 5AR4.If the B+ is below 450v and the first filter cap is at least 500v there will be no probelms other than bias.Check the B+ and the rating on that filter cap.
Blue Strat
07-16-2007, 01:37 PM
The B+ is the key here.The 5AR4 is not an issue and many DR's sound better with the 5AR4.If the B+ is below 450v and the first filter cap is at least 500v there will be no probelms other than bias.Check the B+ and the rating on that filter cap.

..except that you may ALSO be in danger with some 6V6GTs (which have a published max plate voltage rating of 350).
Clearspider
07-16-2007, 03:17 PM
Cool. Thanks guys.
The 6V6s are old RCA smokey glass. They seem to perform fine and I don't bias very warm at all.
Clearspider
07-16-2007, 03:19 PM
What's preferred method for checking plate voltage?
roknfnrol
07-16-2007, 03:26 PM
I clipped the bright cap on my Deluxe and it made some loud crazy noises and I smelled burning... It's at the shop now :(
Clearspider
07-16-2007, 03:29 PM
That sucks. I'm really lucky I haven't screwed anything up, besides touching the soldering tip to innocent nearby wiring :)
phsyconoodler
07-16-2007, 04:54 PM
If you have little experience inside an amp,I would suggest getting a Biasrite or other toll for checking bias.It plugs into a tube socket and the tube plugs back into it.You can check the bias and plate voltage this way safely.If you are comfortable inside the chassis,check the plate voltage at pin #3 of the power tubes or B+ at pin #8 of the rectifier tube.
soulohio
07-16-2007, 05:21 PM
what do you do if you have like 4 tubes in an OR 120? the Biasrite won't work. I got a voltmeter but the damn thing don't seem to work as good as the $3600 dollar machine the tech hooked up...
Clearspider
07-16-2007, 07:09 PM
I have a bias probe. I only know the voltage range for 6V6s and 6L6s.
Blue Strat
07-16-2007, 07:14 PM
what do you do if you have like 4 tubes in an OR 120? the Biasrite won't work. I got a voltmeter but the damn thing don't seem to work as good as the $3600 dollar machine the tech hooked up...


Why do you say the Biasrite won't work?