6L6 vs 6V6 in Leilani by Gourley (Probably really by Dickerson)

[Resonator Guy]

Is there a way to tell, internally, if an amp should have a 6L6 output tube opposed to a 6V6? I have been working on this now and then for about a year and a half. My exhaustive online research (where everything you read is true) has found one very similar example that has an original 6L6 output tube rather than a 6V6.

This amp has always been very anaemic. I have replaced just about all the caps and resistors in it after replacing the bias cell with a cap and resistor. The only other major change was adding an on/off toggle. It had none and no volume control either. I believe the speaker has been replaced also. It has good tone but no balls whatsoever. So I began wondering about the output tube. After reading extensively I tried a 6L6 for a very short time and it sounded great.

Using a bias tester the 6V6s I have tried run at about 58 ma. A NOS JAN one rapidly developed a lovely blue glow at the base and went all distorted.

The PT has the following numbers 391647 and 5567 but I can't read the faded name on it. The OT is a Thermador, as near as I can read with no visible numbers

How can I accurately determine what the tube should be?

[Jazz P Bass]

What value is the B+ voltage ?

[g1]

For your research try adding magnatone or magna electronics. From what I can tell all the single ended ones used 6V6. The three tubes being either 12SL7/50L6/35Z5 or 6SJ7/6V6/5Y3.

[Resonator Guy]

Jazz, if this makes any sense, with a 6L6g it is 223 volts, with a 6V6g it is 255 volts.

g-one, I have tried about every search variation and can find only the one mention of tube types in a Gourley, 6L6:
The Steel Guitar Forum :: View topic - Valco? vintage Ray Gourley-branded amp not working

I also found one picture with no details at all. Looks just like mine in a nicer colour.

[Resonator Guy]

I have convinced myself that this must be a 6V6 amp, although the 6L6 does sound better. Every 6L6 I tried has too big a bottle and comes way too close to the back panel which is covered with MOT that I believe is highly flammable.k
I found this schem on Schematic Heaven and, although it is a Dickerson with a volume control, the tube set and many of the cap and resistor values are similar to mine. The fellow that drew it seems to have had similar problems to mine, going by his notes and the mod he suggests.
I am going to study it carefully, do some more reading and see what changes could be made.
I don't wish to get the site in trouble with SOPA but here is the schem. I would appreciate anyone's comments on it.dickerson_mots_1946.pdf

[Jazz P Bass]

Jazz, if this makes any sense, with a 6L6g it is 223 volts, with a 6V6g it is 255 volts.

The fact that the 6L6 is dropping the B+ tells me that the bias is different from the 6L6 to the 6V6.
Did you check idle voltage at the cathode?

[g1]

Please, before you make any changes, draw out the schematic. You have one that is close, use it as a template, change the values to the ones you find in your amp.

I have convinced myself that this must be a 6V6 amp, although the 6L6 does sound better. Every 6L6 I tried has too big a bottle and comes way too close to the back

I'm assuming a coke bottle 6L6 would be even worse. I agree this is probably a 6V6 amp, the earlier version used a 50L6 which is even less power than 6V6 : Leilani Amplifier Magna Electronics Corp; Inglewood, CA, bui

The fact that the 6L6 is dropping the B+ tells me that the bias is different from the 6L6 to the 6V6.
Did you check idle voltage at the cathode?

Can you tell us the cathode voltage with 6V6 and 6L6, and what is the value of the cathode resistor?

In another thread you mentioned the bias cell at the input. Is it working and what is the voltage? (should it die I have read you can put them in boiling water, then reseal the seam. Some have had luck rejuvenating them this way).

[Resonator Guy]

Definitely not a 50L6 amp. It has a power transformer. The B+ readings I gave were off the cathode at idle. I don't have the amp at hand right now, it's at home, I will get the cathode resistor value later.
I am not going to change anything without a careful comparison to that schem I posted. I will use it as a template to draw another.
I have replaced the bias cell with a cap and resistor. I don't remember their values but I used values from another 6sj7/6v6 amp.

[g1]

I realize it is not a 50L6 amp, my point was a 6V6 in the new version would already be an upgrade, just further speculation that it's probably not a 6L6 amp.
Those B+ readings would have been on the plates, cathode voltage readings will help figure out where the 2 tube types are biasing for comparison.

[Resonator Guy]

g-one, I think I am trying to do too many things at once these days. Yes, the B+ readings were on the plates. However your earlier q about the cathode resistor may do it. I was going to tell you a .05 uf 600 v, but I figured I had better check. I used, in error, a 472, not a 473 so it is a .005uf. Now that might mess things up with the bias, Jazz? I am going to change it tomorrow and take some readings and do some listening. The print on a lot of things is getting too small for me.
Tonight I am not touching anything with more voltage then the PVR remote.

[g1]

Tonight I am not touching anything with more voltage then the PVR remote.

I know that feeling, sometimes it's good to take a break and get a fresh start another day.
The cathode resistor in question would be connected to pin 8 of the power tube. In the schematic you attached, it is shown as 390 ohm. Let us know the value of yours, and what the voltage is from pin 8 to ground with the 6V6 and with the 6L6.

[Resonator Guy]

All right, I think I have it right this time. I only did it with a 6V6 because I am convinced that is the right tube, but after these results, I will try it with a 6L6 if you like. I got a reading, on three separate tries, of 11 volts.
The resistor is a 200 ohm wire wound one.
The amp has great tone but almost no volume. The perfect attenuated bedroom amp if you don't talk too loud.

[Jazz P Bass]

So the real question is "why does the 6L6 sound better?"
Is the 200 ohm resistor bypassed?

[Resonator Guy]

No, there is no cap bypassing the 200 ohm resistor.

[Jazz P Bass]

Well when you finally decide on which tube you want in it, afterwards you can try a bypass cap.
It usually helps give the signal some punch.