So I am replacing the original phono cartridge with a replacement from VOM. Vom emailed me supporting info(pdf file). The 2 leads from the phono cartridge go directly to the impedance matching transformer mounted in the bottom of the cabinet.
I assume I don’t need the transformer and I can connect directly to the chassis. In the enclosed pdf file he says he connected to the phono/radio switch. Pb 1 is power to the phono and FS4 is the front knob selector. My question is do i go to FS4 -7 and what is the advantage? Or to the female RCA plug (phono input)? Also the cartridge has two leads at the phono arm, red and black, does the black go directly to gnd? The little round plug at the transformer has 3pins, the red , black and shield. Any help is greatly appreciated.[
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Not exactly the answer to your question, but you have not said if the cartridge was EM or Piezo. In case of the former you do need the transformer. In case of the latter no.
PS. I had exactly this, a piezo cartrridge in VOM player with Philco 4812, and I could not get rid of hum.
This the cartridge from VOM
P51-3 Ceramic mono cartridge with 3 mil sapphire needle for 78 rpm records Astatic 5
I’m thinking of just connecting it back to the impedance matching transformer. Because I’m not sure where to connect it in the chassis minus the impedance matching transformer. Any help out there please feel free to comment. Thank you.
Does the wiring going to the cartridge have two connections and a shield that is grounded?
Yes radioroslyn , a black and red wire.
Ok and does the matching transformer plug into the radio chassis thru a RCA connector?
Yes, RCA out of impedance matching transformer to chassis
OK, 1st cartridge pictured is the replacement Astatic ceramic unit? The 2nd one pictured looks like a variable reluctance unit. That one would require a matching transformer (likely a step up one at that. Unfortunately, that one looks a little gnarley.
Connect the black and shield to the body of the RCA, connect the red wire to the pin. Ensure that the shield is grounded only at one end. Hopefully, that will solve the hum. Consider replacing the lead wire with one with outside insulation. This is a transformer powered set. Make sure that the turntable is grounded to the chassis through another wire, not one carrying or shielding the signal.
When mounting the cartridge try to match the geometry of the original cartridge, both in how far the cartridge protrudes from the tone arm and location of the needle in the shell relative to the original needle. It appears that you used pieces of metal. This may provide too much stylus pressure on the record. Getting this to track between 2 - 5 gram tracking pressure would be ideal, but try to get it under 10 gram.
Hope that helps.
Thank you Mr. fix, yes, the original cartridge was smashed. I replaced it with the Astatic cartridge from VOM. Had to manufacture a bracket for the replacement cartridge it actually has less weight than the original, thinking about adding some small pieces of lead in the shell to compensate for the reduction in weight from the original. Does it matter which color red or black goes to the pins at the back of the new cartridge? Otherwise I’m going to use the same configuration and do what you had recommended wiring to the RCA. So basically, these two connectors tied together, one black to shield and the yellow wire to the red wire, correct? Thanks again
Ps how would I measure the force at the needle in grams?
Hi RStokes, The RCA Jack goes to the chassis, right? What is that 3 hole receptacle?
Yeah, the the black to the shield at the plug. Red goes to the center pin of the plug. That will connect to the yellow wire when the plug is inserted into the jack. Do take some emery cloth to the mating surface on that socket for the plug shell. If you are replacing the shielded cable with new 2 wire w/ shield and insulated jacket (recommended) wire the same way.
They used to sell scales for measuring tracking pressure. You can likely find one on eBuy.
Yes , theRCA plug goes directly to the chassis. The three hole receptacle is coming from the tonearm/ cartridge . It’s black, red and shield plugs into the the matching transformer. The transformer has a male pigtail that plugs into the female RCA I.. hope I’m not too confusing.