W61 Countertop Cartridge Conversion

[mauro]

My model 61 always had beautiful sound with the original cartridge but I hardly ever used it because of the tracking weight on the records, so I decided to do the cartridge conversion to an Astatic 51 cartridge. (Its an Original 51-3 I have been keeping)
Completed it last night with the usual volume box conversion using a 1 meg pot, 22k resistor, 0.047 and 0.0068 capacitor, that I have used on many 40's Wurlitzer.
The tone arm is impossible to get just right now but that's not my issue.
I was expecting an improvement is sound but instead have much lower volume.
Is there anyone who knows if this volume box should be treated differently than other 40's Wurlitzer?
Would the cartridge wiring cause this if the ground and signal are reversed? Haven't tried that yet but imagine there would be no sound at all?

[jukeboxmarty]

Are you sure the cartridge is good? Just because it hasn't been used doesn't mean it hasn't failed.

[mauro]

I suppose that is a possibility.
I'll have to find another and test it out.
Is there a way to test the output of the cartridge with a voltmeter or a scope?
I imagine you should see something on a scope?

[robnyc]

Mauro, connect any DVM to the output from the car and use the low-AC scale. You should see 1/2 to 1 volt -maybe higher given these are 78s.

If that cart is "original" 50-60+ years old it is probably shot.

RobNYC

[mauro]

Thanks Rob,
That's what I figured, just never tried it before?
Seems weird to me that the cart would actually create a voltage.
Unfortunately I won't be able to get back on any machines for a while as I underwent shoulder surgery yesterday.
Left handed typing sucks!
Mauro

[Ron Rich]

Hi Mauro,
I hate to tell you this--I have also had shoulder surgery-- there's one thing worse-er-ER !, then typing with your left hand, if you are right handed, and your RH is dis-abled----

[Startgroove]

The table model Wurlitzer amplifiers are different from the floor model amplifiers, they have a different input impedance and drive a speaker which is not very bass responsive.  I've never been a fan of gutting the volume unit and replacing the guts with a potentiometer which eliminates the tone compensation, and does nothing to boost the low end frequencies (which a crystal or ceramic cartridge lack).  

The best method of conversion is to install a Kit 87, (or equivalent such as a Jacobs), and not gut the volume unit (leave all the factory parts in place).  That is the way the factory upgraded in the late 1940's and early 1950's.  The part is a bit hard to find, but if you are a good techie, you can build one.  If you want a schematic, I can send you one.  I build them in a small metal box, less than 2X3X4 inches.  This method retains the tone compensation systems, boosts the bass to a more pleasant sounding level, and properly matches the high impedance of the cartridge to the lower impedance input of the sound system.  If all is working correctly, you'll have more than enough volume and tone to drive that little speaker.  Russie

[mauro]

Hi Russie,
Thanks, I'd like to get more info on this as I will attempt it again at some point.
Is this something you can scan and sent to me via email?

[Startgroove]

Yes, I can scan it for you. Just need your email address. OR, if you have a copy of "Wurlitzer Sound System & Remote Control Schematics" it is in there about 3/4 of the way in. I've found the Kit 87 preamp is sometimes a little too hot, so to drop the volume some, I add a 200K or higher resistor in series with the grid (pin 5) of the 6J5. To get a little more bass, I increase C-1 to .1 uf or larger (this doesn't always seem apparent, as many pre-war recordings simply do not have enough bass there to begin with). To work best, all the original components in the volume control unit must be in place and check out good. The pre-amp is designed to get its power from one of the 6L6 sockets on a 851, 854, 700, 800, 501 and 503 amplifier. On your 61 the power take off place would be pin 3 of either of the 41 tubes, or any other point where 250 to 300 vdc is available. Cheers, Russie

[mauro]

Hi Russie,

Thanks for the info,
Mauro

[Startgroove]

That email keeps coming back to me as undeliverable. Wish I could post it here. Russie

[Ron Rich]

Russie,
Why can't you post it here ?
Ron Rich

[mauro]

Oops, sorry thought that would work.
Try this one:
[e-mail]

[Startgroove]

Here you go:

[mauro]

Thanks a ton!!
Much appreciated.