If you aren't familiar with this machine, it has 1 tone arm that goes high or low to play each side of the record with a cartridge on the top and the bottom. It uses two 51-1 cartridges. Much to my surprise, the two cartridges are wired in series. I'm planning on putting 2 new carts on it and wondering if I should put them in series or parallel. I'm surprised it works with two in series, being that they are ceramic. I forgot to look to see what the input resistor is and it's value is not on the schematic. I forgot to mention that the top and bottom cartridges are NOT wired to a switch to get a signal from only one cart at a time like Wurlitzer did. It's not the end of the world if my first attempt might not work well, but the reason behind this is boggling to me. I'll be using the Crosley cartridges as nice fitting replacements and will connect their (stereo) outputs parallel like I normally do. Not that it matters, but the machine is set to play 45's and it will stay that way. -- Tony Miklos Tony's Jukebox Repair
On 7/30/2025 8:54 PM, Tony Miklos wrote:
If you aren't familiar with this machine, it has 1 tone arm that goes high or low to play each side of the record with a cartridge on the top and the bottom.
It uses two 51-1 cartridges. Much to my surprise, the two cartridges are wired in series. I'm planning on putting 2 new carts on it and wondering if I should put them in series or parallel. I'm surprised it works with two in series, being that they are ceramic. I forgot to look to see what the input resistor is and it's value is not on the schematic.
I forgot to mention that the top and bottom cartridges are NOT wired to a switch to get a signal from only one cart at a time like Wurlitzer did.
It's not the end of the world if my first attempt might not work well, but the reason behind this is boggling to me. I'll be using the Crosley cartridges as nice fitting replacements and will connect their (stereo) outputs parallel like I normally do.
Not that it matters, but the machine is set to play 45's and it will stay that way.
Replying to myself here. I made two new cartridges fit into the tone arm and wired them in series. Works and sounds great! That's a new one to me, two ceramic cartridges in series. Now I have to figure out in what sequence you adjust the tone arm pressure. It has a big lead weight that slides back and forth, and on top is a set screw to adjust how much to lighten it up. No directions in the manual. I can adjust the tone arm for either the a or b sides but didn't figure out how to get both of them equal... yet -- Tony Miklos Tony's Jukebox Repair
On 8/1/25 14:47, Tony Miklos via Jukebox-list wrote:
Replying to myself here. I made two new cartridges fit into the tone arm and wired them in series. Works and sounds great! That's a new one to me, two ceramic cartridges in series.
A ceramic cartridge is basically a deliberately microphonic ceramic capacitor. Compared with the high impedance input of ceramic amplifier stages, the unused series cartridge is a relatively low impedance at audio frequencies. If it were in parallel it would load the circuit and the piezoelectric properties would try to move the stylus of the unused cartridge in sync with the music on the active cartridge, resulting in wasted energy and lower gain. Similarly, if you have a monaural phonograph that originally used a crystal cartridge like the little RCA 45-RPM 45-EY-2 changers and the like, it's common to use a stereo ceramic cartridge as a replacement. Wiring the two channels in series results in higher output voltage similar to that of the original crystal cartridge. -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
On 8/1/2025 6:21 PM, Jay Hennigan via Jukebox-list wrote:
On 8/1/25 14:47, Tony Miklos via Jukebox-list wrote:
Replying to myself here. I made two new cartridges fit into the tone arm and wired them in series. Works and sounds great! That's a new one to me, two ceramic cartridges in series.
A ceramic cartridge is basically a deliberately microphonic ceramic capacitor. Compared with the high impedance input of ceramic amplifier stages, the unused series cartridge is a relatively low impedance at audio frequencies. If it were in parallel it would load the circuit and the piezoelectric properties would try to move the stylus of the unused cartridge in sync with the music on the active cartridge, resulting in wasted energy and lower gain.
Similarly, if you have a monaural phonograph that originally used a crystal cartridge like the little RCA 45-RPM 45-EY-2 changers and the like, it's common to use a stereo ceramic cartridge as a replacement. Wiring the two channels in series results in higher output voltage similar to that of the original crystal cartridge.
Thanks Jay. I'll remember the two in series but who knows if I'll run across that again. -- Tony Miklos Tony's Jukebox Repair
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Tony Miklos