RCA Berkshire Phono Cartridge Help

[Bob G]

I've been working on an 1948 RCA Berkshire Breakfront unit (see pic below) for several years now and am finally getting to the point where I can begin to reassemble it. It's been a long hard battle, but mostly successful. I have a question for you phonograph cartridge experts.

Originally the system was equipped with a Thorens CD-40 78rpm record changer and a GE VR cartridge. Somewhere along the line the cartridge was replaced with a more modern ceramic type, and the preamp was removed. Several years ago I acquired a GE VR cartridge...but there's no model number on it (see pics below). I'm wondering if this would have been the cartridge that came with this unit? Also....I have a GE UPX-003 preamp, would this be the correct one to use with this cartridge? If the cartridge pictured below is not a 1948 vintage VR cartridge, what would be the appropriate one?

Finally....I did connect this cartridge up to the preamp (using alligator clips) and there was a lot of high frequency noise. I understand that I was not running it through a shielded cable, and was expecting possibly some hum, but not the high frequency hash I was hearing. I tried the cartridge on a modern solid state preamp, and got the same kind of high frequency noise. I was able to get some signal from it, but the noise is quite loud. Is the cartridge defective? I checked the DC resistance and it was about 460 ohms, so it's not open. Any suggestions...ideas??? Thanks. Bob

 

[maxhifi]

That hash is probably ambient noise from switch mode power supplies in your house like cell phone chargers, etc. Try it with shielded wire

 

[gadget73]

I think thats actually an RPX, but they more or less stand in for one another. There are also two main variants of those, the single play like you have and the triple play that had a knob to flip the needle from LP to 78. If your tonearm has a hole through the top where it looks like something went, you had a triple play originally.

 

[Bob G]

The tone arm on the Thorens doesn't have a hole in the top to rotate the needle assembly. Since the turntable is exclusively 78 RPM, it wouldn't have needed a cartridge with a stylus capable of playing an LP record. Thanks for the info.

 

[Sandstrom]

That is an original RPX, both this and the original triple play were called the RPX. These were subsequently superseded by the VRII. These are easy to identify as they don't have the channel running all the way down the bottom of the cartridge to accommodate the flip around stylus holder. If you look at the top you will see a small hole that you can push the stylus assembly out with a paper clip or similar. These have extremely low compliance and are only really suitable (and are quite popular for) 78s. You can find LP size styli for them but I wouldn't use them myself, believe they track around 8 grams.

 

[Bob G]

That hash is probably ambient noise from switch mode power supplies in your house like cell phone chargers, etc. Try it with shielded wire

I'll check it out...thanks.

 

[Bob G]

That is an original RPX, both this and the original triple play were called the RPX. These were subsequently superseded by the VRII. These are easy to identify as they don't have the channel running all the way down the bottom of the cartridge to accommodate the flip around stylus holder. If you look at the top you will see a small hole that you can push the stylus assembly out with a paper clip or similar. These have extremely low compliance and are only really suitable (and are quite popular for) 78s. You can find LP size styli for them but I wouldn't use them myself, believe they track around 8 grams.

Since the turntable is only 78 RPM, that's all the cartridge will be used to play, 78 RPM records. So then this is the cartridge that RCA would have originally used in this unit in 1948, correct?

 

[maxhifi]

I'll check it out...thanks.

My guess is the same alligator clips connected to nothing will pick up similar noise as connected to the cartridge

 

[Sandstrom]

Since the turntable is only 78 RPM, that's all the cartridge will be used to play, 78 RPM records. So then this is the cartridge that RCA would have originally used in this unit in 1948, correct?

yes late 40s early 50s would be the time period of that cartridge body, when equipped with the 3 mil stylus for 78 play it was called the RPX-040. Replacement styli can be a bit challenging to find but they are out there. These actually play pretty nicely into a standard MM phono stage, your GE stand alone stage should be perfect for your cartridge as they were made for one another. To recall, these Variable Reluctance cartridges put out about 10mv.

 

[Sandstrom]

As for the noise you were getting, did you have the cartridge mounted in the arm? Is the arm metal? If you ensure the cartridge is grounded to arm and arm to preamp you should be ok. That resistance reading sounds right to me.

 

[Bob G]

The cartridge was not mounted in the arm. I had it sitting on my workbench and used alligator clips to connect it to the preamp. By using a shielded cable from the cartridge to the preamp, the noise is gone. I should have known better. I'm glad this is the appropriate cartridge (and preamp) for this application. Thanks for all of the help and information. Bob