catman Posted June 30, 2015 Posted June 30, 2015 (edited) G'day all, I'm actually pinching myself believe I actually can't believe this! The other day one channel (the left channel) failed on my main system M97x/SAS, and tonight my Ham Shack M97xE has mysteriously failed in like fashion, but this time on the right channel. I got out my multimeter and measured each channel coils and sure enough about 1400 ohms on the working channel and open circuit on the other. What the 'beep' is going on? Two cartridges of the same type independently failing over a couple of days with similar faults! My Ortofon OM 10's are still working fine, thankfully, but how can anybody possibly explain this!? I can't. This is utterly bizarre! Regards, Felix. Edited June 30, 2015 by catman
catman Posted June 30, 2015 Author Posted June 30, 2015 G'day all, well the technician in me thinks that something 'common' must have killed both cartridges but I honestly can't see how that might have happened! Regards, Felix.
ZEN MISTER Posted June 30, 2015 Posted June 30, 2015 Aliens ......yeah. This rings true to me. Are you wearing your alfoil bonnet???? ZM. 1
catman Posted June 30, 2015 Author Posted June 30, 2015 (edited) G'day all, I'm not going to do any more checks tonight, but dry soldered output pins are a possibility so I 'll check on that in the morning on both cartridges. This is all pretty strange though! Regards, Felix. Edited June 30, 2015 by catman
catman Posted June 30, 2015 Author Posted June 30, 2015 G'day all, careful attempts to reheat possible dry joints on the dead channels of both M97xE cartridges this morning failed completely! Oh well, you win some and you lose some, I guess. Regards, Felix.
eltech Posted July 1, 2015 Posted July 1, 2015 Measure to see if you have any voltage from the RIAA pre amps that you are using on the inputs. If you have any voltage there you might have burnt out the coils. Yes- its unlikely and unusual- but that is the only reason I can think for this happening apart from random failure and bad luck. 1
eltech Posted July 1, 2015 Posted July 1, 2015 If the glue that holds the motor to the cartridge body is old, sometimes you can remove the motor by pulling on two of the cartridge pins at the same time - this applies to the M91.
rocky500 Posted July 1, 2015 Posted July 1, 2015 (edited) Measure to see if you have any voltage from the RIAA pre amps that you are using on the inputs. If you have any voltage there you might have burnt out the coils. Yes- its unlikely and unusual- but that is the only reason I can think for this happening apart from random failure and bad luck. Good idea to check the phono stage you are using before connecting another cartridge to it. Edited July 1, 2015 by rocky500
Newman Posted July 1, 2015 Posted July 1, 2015 I sure hope you used a digital multimeter to measure coil resistance. An analog one could blow the coil wire like a fuse...... As for the original complaint, I suspect some prior damage to both carts. Maybe they were both used with the same phono amp at some point in time, and it has or had a fault that put DC across the input.....???? 1
catman Posted July 1, 2015 Author Posted July 1, 2015 G'day all, yes a digital multimeter was used for coil testing. Well I've considered all the suggested possibilities and everything checks out ok. Each cartridge was essentially only used on one separate system yet given the mode of failure, I can't help but think that there is a commonality somewhere, yet there doesn't appear to be any. It's a complete mystery! The Ortofon OM 10's are working fine but if they should inexplicably fail, then I'll have real cause to worry! Regards, Felix.
catman Posted July 1, 2015 Author Posted July 1, 2015 G'day all. News flash! My DIY P06 in here has a serious DC offset fault. Whilst nothing was evident on earlier testing, my DIY P06 when powered on then commenced to intermittently emit a 'phut, phut' sound along with a pronounced 'hiss' through the speakers (suggesting oscillation), and with the digital multimeter switched to the 20 volt DC range connected to the input, its display read a little over 11 volts DC. That would certainly burn out a phono cartridge coil! An LM4562 op amp is installed in the first position closest to the input. Has it failed in some way? Well that possibly explains the cartridge failure in here, but what about the other one? Regards, Felix.
Newman Posted July 1, 2015 Posted July 1, 2015 Hmm, my wild guess turned out to be spot on! No idea about the other one though... are you sure it has never, ever, been on the P06? 2
catman Posted July 1, 2015 Author Posted July 1, 2015 G'day all, well for what it's worth I've just unplugged the LM4562's in my errant P06 and replaced them with new OPA2134's. No DC offsets on the inputs now and all is working and sounding great. Somewhere there has to be a lesson in all this! Regards, Felix. 1
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