Channel identification and phase test

[Michael Lafont]

I'm trying to make a Sumiko Blue Point Special work. Got it all hooked up, tracking fine, etc. So now I've moved on to the test record. The Hi-Fi News test LP. First track is channel identification. The voice should come only from the left and then only from the right. (or vis versa) But that is not what I am getting. Sounds very nearly mono. So, then I played the next track, the in phase and out of phase track. In phase sounds fine. sounds like mono. But out of phase has no sound at all.
My question is; possible wiring incorrect or is there a real cartridge issue?
I've tried this cartridge on two different tables and gotten the same results. I've verified the wiring all the way through. (cartridge pin colors match the headshell wire colors and are correctly soldered to the interconnect block) I've also mounted other cartridges to verify and they ID and phase correctly. Which they do. So no problem further up stream.(I have a few cartridges mounted to swapable headshells for easy testing.)
Any thoughts? Sure seems to me the wire attachments to the back of the cartridge would be wrong, but I am not color blind. Any experts out there have suggestions as to which wires to swap to test a different ID and phase outcome? I can't think of anything else to check.

[steve195527]

If you have your amp in mono the out of phase signal should be like that:-each channel is cancelling the other out,the right and left signals should come out of the correct speaker if its in stereo,are you sure you haven't inadvertently switched your amp to mono or have a tape loop running in mono from it:-that can cause all other inputs to run in mono on some amps

[Michael Lafont]

Thanks for the idea Steve, but its not that. Preamp is in stereo mode. I'm confident that the down stream system is correct because all I am doing now is swaping out cartridge/headshell combinations. The two other cartridge/headshell combinations I have play those tracks as they should. It's just this BPS that is giving me problems. All I am doing is swaping headshells and setting the traching force.
Is it possible that the cartridge internals share a common ground or something like that?
Anyone out there with a BPS or a Blackbird that can confirm these tests?

[josephazannieri]

Yo Michael Lafont:

You say that the other cartridges work just fine in this setup, but the $umiko cartridge shows up out of phase and in mono, rather than stereo, when using your test record. Frankly, I'd go back to the dealer and tell him or her about the problem. I am assuming that your speakers are correctly wired and that you are following the color code for the cartridge wires. If your amp or your speakers were wired incorrectly, the same problem woud show up with other carts and other turntables. But I would check one thing. Compare a good headshell with the Sumiko headshell and be sure that the color code and the pins on that shell are identical with the color code and pins on the good shells. I would also take a close look at the wiring and pins in the Sumiko shell and be sure that there isn't any stray contact between unrelated wires.

Then I would get a DVM and measure between the right signal pin on the cartridge and the right ground pin on the cartridge. Be careful, and just hold the meter on the pins long enough to get a reading. You should get continuity between these pins, and there should be no continuity between these pins and either of the pins for the other side. Same thing is true on left side. There should be continuity between the left side signal pin and the left side ground pin. But, there should be no continuity between either left pin and either right pin. If these measurements are all correct, then you have a cartridge that is internally miswired with the wires for one side misplaced. Sumiko has bungled the job. There is a risk that the fine wires in this moving coil cart won't take the current from the DVM, but you can make this decision. If you don't want to test, I'd take the cart and the turntable to the dealer and tell him to fix it, or send cart back to dealer and ask for an exchange and see if new cart is equally bad. You can also ask the dealer if you can test cart with a DVM.

Now take either the right side or the left side and reverse the signal and ground wires and see what happens. If the cart now works right, take it back, or send it back and scream and yell. Sumiko, or the dealer, should make good on a bad cartridge. My experience with lowly Shure is that they are real good about fixing their mistakes, (and they have fixed my mistakes, too) Sumiko, the pride of Japanese high end manufacturing, should be at least as good.

And good luck from the old guy firmly mired at the way low end,

Joe Z.

[Hanuman]

The two other cartridge/headshell combinations I have play those tracks as they should. It's just this BPS that is giving me problems.

If you haven't done so already you should try the BPS in one of those good headshells. It's an odd symptom, indeed. The 2 channels are evidently being summed electrically - this is surely the only explanation for the complete disappearance of the out-of-phase track. I can think of one test that might help to narrow this down: alternately disconnect each channel's wires completely from the cartridge pins and play the channel orientation tracks of the test record. If you hear both of the left/right voices out of each output pair then that would indicate the summing is occurring inside the cartridge or, perhaps, outside the cartridge between the pins. In this test the audio output should switch sides no matter what happens. If the audio stays centred during both playbacks then the headshell is doing something unwanted. Just a thought: if a headshell were wired for dual-channel mono from a 2-pin mono cartridge I could imagine it doing something like this if a stereo cartridge were unwittingly mounted.

[steve195527]

Thanks for the idea Steve, but its not that. Preamp is in stereo mode. I'm confident that the down stream system is correct because all I am doing now is swaping out cartridge/headshell combinations. The two other cartridge/headshell combinations I have play those tracks as they should. It's just this BPS that is giving me problems. All I am doing is swaping headshells and setting the traching force.
Is it possible that the cartridge internals share a common ground or something like that?
Anyone out there with a BPS or a Blackbird that can confirm these tests?

I don't think sharing a common ground would cause problem you're describing:-the grounds do end up "common"(unless you're running a balanced system?) anyway,as long as the lives are seperate,all each channel does is generate a potential difference(voltage)between that hot side and the ground,it sounds as if the two hot connections are connected together internally??(faulty cartridge!?):-did you buy it new?if not the original purchaser may have specified it for mono reproduction,both live and grounds wired together,ie left and right hot common and left and right earths common,that's way a cartridge is wired for mono lps(lateral mono cuts)

[Michael Lafont]

Ooo! I think we may be on to something.. I unmounted the cartridge and the headshell constancy checks out fine with the DVM. But all three of your comments has triggered an idea. Because the BPS is an open body design, I'm wondering if the fine wires leading to and from the coils may be touching before they reach the mounting pins?? I can see them crossing in and under the "body" on their way up to the mounting pins of the cartridge with my naked eye. (those wires are really small. So small I really don't want to put the DVM on it) Now, if I can find that eye sloop...I'll let you know what I find.
Thanks for the comments guys.

[Blue Angel]

Ooo! I think we may be on to something.. I unmounted the cartridge and the headshell constancy checks out fine with the DVM. But all three of your comments has triggered an idea. Because the BPS is an open body design, I'm wondering if the fine wires leading to and from the coils may be touching before they reach the mounting pins?? I can see them crossing in and under the "body" on their way up to the mounting pins of the cartridge with my naked eye. (those wires are really small. So small I really don't want to put the DVM on it) Now, if I can find that eye sloop...I'll let you know what I find.
Thanks for the comments guys.

Hi

It could be that the metal coil core is shorting the coil wires. Armature cores are usually lacquer insulated before winding the coils. It is therefore possible that the insulating lacquer on the armature core and that on the coil wires have failed. An easy way to check would be to set your dmm to "continuity" and measure for continuity between the L+ and R+ (white and red) pins while disconnected from the headshell.

There will be no danger of burning the coils. On the BPS or any MC cartridge at least, there should be no continuity between the two channels - only between R+ and R- and likewise for the left channel.

ba

[Michael Lafont]

yep. it's shorted...
Red to white show a short. Guess there is nothing else to do but pitch it.
Thanks for the help confirming this.

[steve195527]

can you not see if its just a stray bit of wire causing it and move it with a fine pin?or are the lead outs from the bobbin touching?separate them!what have you got to lose?you can't really make it much worse can you?Expest stylus can rewind the coils nowadays,not sure if its financially worth it though