|
Several months ago, I picked up a beat up early '50's Webcor "one tube wonder" record player at the flea market. This model used a selenium rectifier with the 25L6 tube filament wired in series with the 90V turntable motor. This seems to be a very common design among these types of players. The cartridge was a flat metal high output type with a 2 mil. "all speed" needle.
Of course, the old cartridge was dead. I had a Pfanstiehl P188 ceramic cartridge that I salvaged from a junk '90's stereo. From my research, this cartridge puts out .3 volts output and I installed it in the "one tube wonder" just to see what would happen. It actually gave moderate volume on some 45's. The results were not as good with an LP.
So, I stripped the chassis, drilled a hole for a 7 pin miniature tube socket, rounded up the needed parts, and added a 6AV6 preamp stage. Now, this record player has plenty of volume. There was no tone capacitor across the output transformer in the original amp; but, I added a .047 cap to the modified amp. The high frequency response was way too pronounced for my taste. With the cap, the tonal quality is much better. I will likely be doing this preamp modification to the other "one tube wonder" phonographs that I restore. This modification will allow me to use a modern ceramic cartridge that will be less likely to destroy a record and I won't have to worry about finding a NOS 3 volt cartridge that may not be much better than the dead one that was in the player.
|