I own the Route 66 and think it is time to get new tubes. I want to purchase a device like the Weber Bias Rite to do the adjustments myself.
I think I know how to get at the bias pots (Turn amp face down, loosen 4 bolts holding chasis to cabinet. Remove chasis, look underneath) but maybe I am wrong.
I would then remove old powertubes and rectifier, replace rectifier, place bias rites in amp and tubes in bias rite. Follow Bias Rite instructions turning the bias adjusters on the Route 66. I just have not seen the adjusters myself. Are they easy to spot and access?
I guess I just want to know if this is something I can do for the first time by myself or whether I should pay to have someone show me.
Are there any pictures of this available out there so I can judge whether to try this myself?
Last Edit: Jun 25, 2007 10:24:45 GMT -7 by edoetsch
I change tubes and bias my Route 66 all the time, it's not a big deal if you're comfortable enough to do so and know what to do and what not to do.
1) I don't like placing the amp on it's face, I put it on the edge of the table and remove the screws from below one side at the time, then I pull the chassis out horizontally. 2) remove the tubes, insert Weber BR probes into tube slots, insert tubes on top. When done, remove the tubes first by holding the Weber BR probes down, then remove the probes. Always use gentle circular motion to remove both the tubes and probes. 3) you don't want to rest the amp on the tubes or the transformer ... I use a small block of wood under the transformer and prop the amp on it's side being careful not to knock it down. This way I have easy access to the underside of the chassis where the circuit and the bias pot is. 4) connect the speaker or resistive dummy load (like a Hot Plate set to load), turn the amp on, let warm up, take the amp off standby 5) with volume all the way down, turn the Weber BR on and read the plate voltage and bias current, bias to specs, the bias pot is the only trim pot inside the amp, can't miss it, it's blue. 6) at this point I usually plug the guitar in and play the amp making sure it sounds good regardless of the bias setting, adjusting it within the spec'd range to see what it sounds like. I like leaving the amp on for at least 5 min because I find that the bias seems to drift a bit after a few minutes, some more knowledgeable folk can explain it better then me. Once happy with the bias and sound, turn amp off, wait for tubes to cool off, remember which tube was in which slot and re-insert accordingly. Put the chassis back in the head case ... plug, play, enjoy. 7) DO NOT TOUCH ANYTHING INSIDE THE AMP WITH BARE HANDS OR A CONDUCTIVE OBJECT EVEN IF THE AMP IS OFF AND UNPLUGGED. The voltages stored inside a tube amp will either seriously hurt you or kill you. Bias with one hand, in case you do touch something inside, the current will (hopefully) not go through your heart as it would if you were holding the amp with the other hand.
One pot for both tubes, so you'll need a matched pair. Some amps have pot for each tube, not sure what the pros/cons are for that setup, experts could chime in with more detail.
Since the matched tubes should be within 5 mA (if not, take them back to the store and ask for a better matched pair) adjust the bias so the "hotter" one is at the top of desired bias range. That's what i do anyway.
Yes, the picture of Z-28 shows the pot on the right side of the board, similar placement as in Route 66.