Weber 6A40 issues...

[rmj134]

Anybody have a chance to check out my voltage readings?

[ahamay79]

How does the amp sound if you play through the regular channel?

Plus, have you tried pulling the vibrato tube?

[ahamay79]

Are you absolutely sure that all of you resistors in that section are the correct value? Have they all been checked with a meter?

[rmj134]

The regular channel and the vibrato sound very similar. No noticeable difference. Even with pulling the vibrato tube all together, still no noticeable difference.

I'm pretty sure the values are correct, but I will go through with a meter and make sure.

Based off the PDF, are there any stand-out values that could point to a problem?

[Five_E35]

I didn't see anything unusual. You can also test the AC operating voltages shown on the Fender schematic for the reissue version. They're usually close enough and that will show any stages or tubes that aren't pulling their weight.

http://www.fender.com/support/amp_sc..._Schematic.pdf

You need a dummy load resistor(50 watts @ whatever impedance the amp needs), and a meter that can read AC signal voltages(or scope). If you don't have a signal generator, there are some sample 1K sine waves online in MP3 format you can download and use - just loop them. See the instructions on the schematic for the test procedure.

It may just be a case of the real thing vs. a clone, but did you happen to notice what kind of tubes the original had - if it was loaded with RCA's, Sylvania's, and GE's that would make a big difference too, especially preamp tubes and a real tube rectifier.

[ahamay79]

What you posted is for a Super Reverb Reissue, not an AB763 like the guy built.

Double check the filter caps and resistors under the cap pan, too. Make sure they're hooked up correctly... check polarity.

[TD_Madden]

Don't forget that the plate voltage changes as you adjust the bias...that's why I use two meters at the same time when doing this, one for the plate-voltage and the other for the bias ma..

Just keep a calculator handy.

[Diablo]

I would work on the vibrato circuit first, because that's where your voltages are screwy. Trace back each resistor and capacitor and check values and voltages. It could be miswired too.

[rmj134]

You guys have been a big help. I feel like I'm really close.

The tubes in the original that I played were just your basic Groove Tubes. It did use a tube rectifier though, and mine is the Weber "Copper Cap" solid-state rectifier replacement (came with the kit). Do you think this could be the culprit? Also, I have no idea what the amp was biased at.

I will try and track down the problem in the vibrato circuit. Is there any way to "remove" this from the overall circuit as a quick way to see if it changes the tone of the amp, or is the amp's tone dependent on the vibrato circuit? Also, being a bit of a newb, how can I use my mulitmeter to check the values of the resistors AND the caps individually to insure they are all correct?

[MWJB]

"Clearly, there is something wrong with my vibrato, but I have no idea what it is, and if it would impact the sound of amp either way (turned off / on)." There should be a 220K resistor between B+ supply and the vibrato tube plate 1, as you are only dropping 2v accross whatever resistor is there, its either much less than 220K or your cathode resistor at pin 3 is open?

It's a bit odd that your heater voltages seem to drop as you get nearer the preamp and that you have odd voltages at each leg? Should be constant wherever you measure.

If you played through 10 vintage Super Reverbs all 10 would sound a little different. But you seem to be describing a significant difference in tone. Do you have any pics of the circuit?

[bnwitt]

The tubes in the original that I played were just your basic Groove Tubes. It did use a tube rectifier though, and mine is the Weber "Copper Cap" solid-state rectifier replacement (came with the kit). Do you think this could be the culprit?

Yes indeed. Your complaint was a lack of compression. Lack of a tube rectifier would certainly deliver that effect.

[MWJB]

"I will try and track down the problem in the vibrato circuit. Is there any way to "remove" this from the overall circuit as a quick way to see if it changes the tone of the amp, or is the amp's tone dependent on the vibrato circuit? Also, being a bit of a newb, how can I use my mulitmeter to check the values of the resistors AND the caps individually to insure they are all correct?"

Pull out the vibrato tube altogether...it has no effect on basic tone anyway, just works the wobble.

Many of the resistors in the circuit are in parallel with other components (which will affect your reading), few of them will read their real value, the voltage check you did was more useful than trying this.

[rmj134]

So I did a little research on tube rectifier vs. solid-state rectifier. I knew that the rectifier was responsible for AC to DC conversion, but I never really heard the term "sag" before. It sounds exactly like what I am describing as the tonal difference between mine and the vintage counterparts I have been playing. I am going to order one today, and I will let everyone know how it works out. Are there any suggestions?

Also, although it doesn't sound like the vibrato is contributing to the tone of the amp, I would like to resolve that issue as well. I believe the 220k on Pin 1 is there (even though the Weber schematic says 22k and the layout says 220k). I will check to make sure the cap on Pin 3 is making a good connection.

Thanks again, you guys have been awesome!

[Diablo]

So I did a little research on tube rectifier vs. solid-state rectifier. I knew that the rectifier was responsible for AC to DC conversion, but I never really heard the term "sag" before. It sounds exactly like what I am describing as the tonal difference between mine and the vintage counterparts I have been playing. I am going to order one today, and I will let everyone know how it works out. Are there any suggestions?

Make sure you wired up the rectifier socket correctly to use a tube - see Ted Weber's schematic/layout for directions. If you want to get a "good" tube, try a NOS 5U4GB for the rectifier. They're widely available for around $20, and more reliable than current production. Any US brand will do fine. The 5U4GB will drop the voltage a little and give you some compression.

[Daedalus]

What kind of 6l6s are you using? The chinese ax7 and at7s that come with those kits are pretty good, not so sure about the 6l6s.