Wurlitzer amplifier needs help

Original Burnedfingers · 9th May 2006, 10:47 PM

I will try to include a poorly drawn schematic for your suggestions.
This is a 6l6GC PP amplifier with a 6SN7 for input and driver tube.
This is a 1940's vintage animal and is missing the field coil so I don't really know what voltage to run it at.

The output transformer measures 375 ohms across the plate winding out of circuit.

Any suggestions?

Original Burnedfingers · 9th May 2006, 10:51 PM

Maybe this will work.

Original Burnedfingers · 9th May 2006, 11:00 PM

Final one

Enzo · 10th May 2006, 03:50 AM

What model is the Jukebox? Does the amp itself have a model/serial plate on it? if so, what model is the amplifier itself?

Original Burnedfingers · 10th May 2006, 11:03 AM

Please excuse me for not being clear. Its a organ amplifier and I believe the model number is 6420.

I am needing the correct B+ voltages to run the 6sn7 on and the correct 6l6gc plate and screen voltages in order to obtain maximum output. Right now the maximum I can get from it is about 22 watts into a 8 ohm load.

With a spare transformer sitting on the bench un terminated from the chassis I tried to figure the turns ratio and input impedance of the output transformer. I input a 400HZ signal at 10 volts into the transformer and loaded the output with a 150 ohm resistor.
(all I had handy)

The black lead from the transformer is terminated to the 2.2K feedback resistor so I'm going to guess its 16 ohm?

The yellow lead goes to ground from the transformer. There is a green lead I'm guessing is 8 ohm?

Voltage readings were .339 across the 150 ohm resistor (yellow to black. Yellow to green across the 150 ohm resistor was .471

Still haven't figured out what I have.

Any help would be appreciated.

The schematic is as wired so any suggestions for modifications would be appreeciated.

Thanks

Original Burnedfingers · 10th May 2006, 11:23 AM

If you want to see what the amplifier looks like there is an ebay auction # 6629018297 that someone has listed that shows a 6420 amplifier. The picture shows two amplifiers. The tube compliment is 5U4, (2)6L6GC, 6SN7

Trout · 10th May 2006, 11:52 AM

Quote:

Originally posted by burnedfingers
If you want to see what the amplifier looks like there is an ebay auction # 6629018297 that someone has listed that shows a 6420 amplifier. The picture shows two amplifiers. The tube compliment is 5U4, (2)6L6GC, 6SN7

Ohhh its a leslie unit by wurlitzer.
I have gutted about 12 wurlies here as the factory was 10 miles from where I now live.

If memory serves, Every unit I have salvaged was 22W output. That leslie unit is pretty nice on ebay, A lott of them contain 2 power amps!
Trout

Original Burnedfingers · 10th May 2006, 11:57 AM

Don't happen to have a factory schematic do you?

Trout · 10th May 2006, 12:08 PM

Quote:

Originally posted by burnedfingers
Don't happen to have a factory schematic do you?

Nope, Sorry, those are nearly impossible to find. The Leslie units often had them stapeled inside the cabinet, Both of the ones I got had already been removed

Trout

Original Burnedfingers · 10th May 2006, 09:28 PM

Quote:

Both of the ones I got had already been removed

Do you still have them? If so could I twist your arm to tell me the plate voltages on the 6L6 and 6SN7?

9th May 2006, 10:47 PM	#1
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Wurlitzer amplifier needs help I will try to include a poorly drawn schematic for your suggestions. This is a 6l6GC PP amplifier with a 6SN7 for input and driver tube. This is a 1940's vintage animal and is missing the field coil so I don't really know what voltage to run it at. The output transformer measures 375 ohms across the plate winding out of circuit. Any suggestions?

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10th May 2006, 03:50 AM	#4
Enzo diyAudio Member Join Date: Sep 2004 Location: Lansing, Michigan	What model is the Jukebox? Does the amp itself have a model/serial plate on it? if so, what model is the amplifier itself?

10th May 2006, 11:03 AM	#5
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Please excuse me for not being clear. Its a organ amplifier and I believe the model number is 6420. I am needing the correct B+ voltages to run the 6sn7 on and the correct 6l6gc plate and screen voltages in order to obtain maximum output. Right now the maximum I can get from it is about 22 watts into a 8 ohm load. With a spare transformer sitting on the bench un terminated from the chassis I tried to figure the turns ratio and input impedance of the output transformer. I input a 400HZ signal at 10 volts into the transformer and loaded the output with a 150 ohm resistor. (all I had handy) The black lead from the transformer is terminated to the 2.2K feedback resistor so I'm going to guess its 16 ohm? The yellow lead goes to ground from the transformer. There is a green lead I'm guessing is 8 ohm? Voltage readings were .339 across the 150 ohm resistor (yellow to black. Yellow to green across the 150 ohm resistor was .471 Still haven't figured out what I have. Any help would be appreciated. The schematic is as wired so any suggestions for modifications would be appreeciated. Thanks

10th May 2006, 11:23 AM	#6
Original Burnedfingers diyAudio Member Join Date: Nov 2002	If you want to see what the amplifier looks like there is an ebay auction # 6629018297 that someone has listed that shows a 6420 amplifier. The picture shows two amplifiers. The tube compliment is 5U4, (2)6L6GC, 6SN7

10th May 2006, 11:57 AM	#8
Original Burnedfingers diyAudio Member Join Date: Nov 2002	Don't happen to have a factory schematic do you?