Old Wurlitzer Iron for build?

guitardude57 · 10-14-2009, 04:23 AM

Howdy,

Just got my hands on an old Wurlitzer 4100 amp that was yanked out of the organ. A couple 12AX7's, a 5U4 and a pair of 6L6's. Bummer that the chassis is unuseable for a build, but the Iron is in good shape for a 1960 year built.

The PT is huge and has 375 on each leg HT (Recto is fried) 12 volt taps, 6.3 volt taps and 5 volt taps. Seems that 750 volts is kinda high for HT even for 6L6's. Of course I did some quick probing with tubes yanked out, then with 5U4 in, didn't light.....no output obviously............

The OT is an open frame no side bells, with 5 leads in/out. Pretty sure an 8R output, but unsure of impedance.

Been looking around for some info on who made the iron and spec's for them.

Anyone know?

Deciding on what to build with this.....6L6 or EL34 something.

Suggestions/questions/comments welcome

Chuck H · 10-14-2009, 06:19 AM

Sounds like a good tranny pair for an AB763 or a Plexi build to me. The OT is probably 6600 primary. That's fine for any of the big bottles. The plate voltage under load should be around 450 with that PT and a 5u4. That's OK for most big bottles also.

Chuck

Don Moose · 10-14-2009, 07:26 PM

I've got a Wurly 4105 with 35 or so 12AX-sized tubes and a 2x6L6 power amp driving a pair of 15" speakers. If the 4100 is another tube-oscillator-and-divider design (seems likely), you have enough heater current to run any dozen preamps you care to hang on the front of this thing.

I think you can put 6.3VAC in the secondary, measure the primary VAC (it'll be HIGH) and calculate the impedance ratio - that's the number you actually care about. Exactly how to calculate that, I don't know off hand.

Hope this helps!

10-14-2009, 04:23 AM	#1
guitardude57 Junior Member Join Date: Aug 2009 Posts: 15	Old Wurlitzer Iron for build? Howdy, Just got my hands on an old Wurlitzer 4100 amp that was yanked out of the organ. A couple 12AX7's, a 5U4 and a pair of 6L6's. Bummer that the chassis is unuseable for a build, but the Iron is in good shape for a 1960 year built. The PT is huge and has 375 on each leg HT (Recto is fried) 12 volt taps, 6.3 volt taps and 5 volt taps. Seems that 750 volts is kinda high for HT even for 6L6's. Of course I did some quick probing with tubes yanked out, then with 5U4 in, didn't light.....no output obviously............ The OT is an open frame no side bells, with 5 leads in/out. Pretty sure an 8R output, but unsure of impedance. Been looking around for some info on who made the iron and spec's for them. Anyone know? Deciding on what to build with this.....6L6 or EL34 something. Suggestions/questions/comments welcome

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10-14-2009, 06:19 AM	#2
Chuck H Old Timer Join Date: May 2007 Location: pacific north west Posts: 1,482	Sounds like a good tranny pair for an AB763 or a Plexi build to me. The OT is probably 6600 primary. That's fine for any of the big bottles. The plate voltage under load should be around 450 with that PT and a 5u4. That's OK for most big bottles also. Chuck

10-14-2009, 07:26 PM	#3
Don Moose Senior Member Join Date: Jul 2007 Location: Indianapolis Posts: 676	I've got a Wurly 4105 with 35 or so 12AX-sized tubes and a 2x6L6 power amp driving a pair of 15" speakers. If the 4100 is another tube-oscillator-and-divider design (seems likely), you have enough heater current to run any dozen preamps you care to hang on the front of this thing. I think you can put 6.3VAC in the secondary, measure the primary VAC (it'll be HIGH) and calculate the impedance ratio - that's the number you actually care about. Exactly how to calculate that, I don't know off hand. Hope this helps!

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