Magnavox Automatic 400 cartridge wires

Hi, I'm putting a new cartridge into a pretty decent Magnavox Automatic 400. The universal replacement cartridge is a (P191D) 4 prong, to replace the 3 prong ((Astatic Mod 195 d) that was in there. The 3 wires on the record player arm that go to the cartridge are grey, brown, and black. I read on the net that the center 2 posts on the new cartridge are for grounding, requiring a solder connection, but I haven't found a wiring diagram for knowing how to connect the remaining wires. What side does the grey go on, the brown go on? Plus I'm not sure if black is ground or not. I'd appreciate any tips/assistance with this fix. Thanks, Rick new member tonight, 8/18/2014

Rick,
First--caution --Do NOT "Solder" to any cartridge--they can not take the heat--use "slip-on lugs".
You will need to figure out which is the "ground" and jump that to both ground terminals on the new cart. Once that's done, it won't make any difference which way the other two are connected. Ron Rich

Thanks Ron, Yeah, I was hoping for an easy r/r, but the posts are round on the new cartridge and the original connectors are flat slip-ons. Some new round connection ends came with the cartridge so, I'll solder them on the wires. When I do that, I can bridge the ground posts, before connecting them to the cartridge. I'm guessing that ground would be the wire without any voltage on a voltmeter test??? Thanks, good to know the others are interchangeable. Cheers, Rick

Robert,
Just guessing, but it would seem to me that if you measured ohms, on all of the wires, against one another, and found two wires that read "nothing", they would be the two "hot" wires. The one that measured "something" to both others, would be ground. Ron Rich

Black is common ground - the other two are L/R signals.
Retrofitting another cartridge is not an easy task with these changers.
Custom fitting of new mounts is required.
The re-balancing of the tonearms etc. is needed in order for them to track correctly.
This requires a stylus pressure gauge and proper service documentation.

I'm currently servicing an RCA Victor RP218-C12 out of a console that someone messed up - melted cartridge, superglued function levers, etc.
I wish people would leave serving these things to us experienced techs - this mess just increases the costs involved.

I have done this many times.

Usually the correct clips for the new cartridge are included with it. The pinout of the new cartridge should be in the instructions that came with the cartridge.

I do all of the soldering with the cartridge removed from the tonearm, so the hot soldering iron never comes near the cartridge.

The colors are:
- Black or bare = common ground
- Gray - left
- Brown - right

There are two pins on most cartridges for the left channel, and two pins for the right channel. They are connected directly to the coil or the piezo element for that channel. One pin is marked + and the other is marked - . The - pins are the ground pins. Older Magnavox cartridges have a common ground pin (hence only 3 wires).

Actually, I lucked out on my own unit. The solder ends of the new clips fit perfectly into the old flat clips that came with the arm. I used a short jumper wire to solder two of the new clips together for the two ground terminals. Then I just pushed the ends of the new clips into the old clips. They have been that way since 1974, and I have never had a bad connection.

On other units, I soldered both the black wire and a short piece of jumper wire to one of the new clips. Then I put another new clip on the other end of the jumper. Then I soldered one new clip to the brown wire and one new clip to the gray wire.

Some units have tiny shielded cables in the arm. The center conductors (gray and brown) are the + wires, and the shields are the - wires.

Once the new clips are connected to the wires, push the clips onto the correct pins on the new cartridge.

Because the new cartridge will probably weigh more or less than the old cartridge, you will need a tracking force gage to set the correct tracking force to match the specifications of the new cartridge (found in the instructions). Unmodified, the Collaro/Magnavox arm will work down to about 2 to 3 grams equivalent force.

Do not guess at stylus force. Too much force will wear out both records and needles fast. Too little force will cause the stylus to not follow the groove correctly, causing distortion and even faster record wear.

Note that if you are replacing a ceramic cartridge with a magnetic cartridge, you need to insert a stereo magnetic preamp between the record changer and the amplifier phono input.