Old Wurlitzer amp?

[Ritchie200]

I was just given a "Model P" Wurlitzer tube amp, minus tubes unfortunately.  Someone had penciled in tube designations underneath.  (1) 6SL7, (2) 6J5, (2) 6L6, and a 5U4.  I have seen schematics for Model P-XXX, but none look like what I have.  I have searched the internet for a "Model P" with no luck.  I just wanted to see what the specs were, as I would like to strip the iron.  Which brings me to my next question...  There are some nice looking potted transformers on this thing.  The PT is huge, but surprisingly the OT is the same size as the choke - very small.  If I am not mistaken, it has just an 8ohm and a field coil out - but this looks like a Champ tranny!  Anybody know anything about these things?  Makes me wonder what records had been played through this thing over the years.  If only that OT could talk!

Jim

[theundeadelvis]

Can you post some pictures? They might help with determining what you have.

[Willabe]

Ritchie200,

Are you talking about the amp from a juke box? If so werent some/most of them stereo? Maybe your missing  the other chan. which would have another OT on a 2nd chassis? Might answer why the PT is so large and OT is so small. PT feeding both sides, OT (you have) only feeding one side of the stereo? Is there some kind of jack/plug connector (like on a Hammond/Leslie) to hook up a 2nd chan? Just a thought.

   Brad 

[stingray_65]

Jim,

I've done a few "conversion amps" and in general, they sound OK. in all but 1 I've ended up gutting the chassis, using the Iron and sockets and built a guitar amp in them and those sound GREAT.

Just my opinion here, these HiFi, Organ and Juke box amps were made to give LOTS of clean sound.

Most Guitar amps get dirty

Gut it, measure your Iron  find your HT, reverse engineer your current max, find your OT impedance, and guestimate by your HT and tube type plus physical size of the ot to determine wattage.

Find a suitable proven design to  plug in.

The Iron is always the most expensive part in a scratch build. resistors and caps are cheap.

you've got +50% of the costs of an amp there in your lap.

My guess would be that you have the right platform to build a single input, all octal, 5E3.

If you're looking to restore it to it's former glory, just test its components individually and replace everything  thats out of spec. Again, no schematic necessary.

Ray

[stingray_65]

 If I am not mistaken, it has just an 8ohm and a field coil out - but this looks like a Champ tranny!  Anybody know anything about these things?  Makes me wonder what records had been played through this thing over the years.  If only that OT could talk!

Jim

I've only dealt with a couple amps that had field coil speakers. in both the field coil acted as the choke for the PS.

This may not be the case for you, but it may be worth checking out again.

[jojokeo]

I've done a few "conversion amps" and in general, they sound OK. in all but 1 I've ended up gutting the chassis, using the Iron and sockets and built a guitar amp in them and those sound GREAT.

The Iron is always the most expensive part in a scratch build. resistors and caps are cheap, you've got +50% of the costs of an amp there in your lap.

My sentiments exactly Ray! I always gut them out and like to create something fun for personal exploration.

[rdrgtr]

I am with stingray.  Gutting the insides and leaving the iron and sockets takes a huge step out of buiding one from scratch.  I have built a fender deluxe type amp from an old organ chassis (2 6v6) and a 50w 6L6 type fender amp with a brownface (3 knob-bass treble volume) pre, and they both sound good enough to carry to a gig.  These old chassis are great for converting.  I think you can also get the 9 pin to octal adaptors for the preamp tubes so no special modifications required.

[softwarejanitor]

I've got a pair of similar Wurlitzer amps, but the ones I have use a 6SN7, 2x 6L6 & 5U4.  I've had trouble finding a schematic.  My plans when I get around to these (got lots of other projects to finish first) are basically to do what has been suggested -- use the iron and sockets to build an amp based on a vintage Fender design.  In my case probably a 5F4 Super.  That one is particularly easy because I can buy a pre-made tag board (even available pre-populated) which would save a lot of effort.

[Willabe]

Hi All,

Wait a second, if it has a choke, why would it also have a field coil out on the OT? They used to use the field coil for 2X duty as choke and instead/inplace of permanent mag. on the speaker. So why a second choke?

   Thanks,   Brad

[Tiny_Daddy]

More chokes = smaller filter capacitors, which was an issue in those days.

[jojokeo]

Hi Jim,
Too bad you can't use the iron for nice protein skimmer pump or halide light? 
(just got done w/ the monthly maintenance)