Test LOMC

[wanders]

About six months ago I purchased an Audio Technica AT ART9, LOMC cart. While it was in use, a workman started drilling something on an upper floor in the wall where the turntable was plugged-in. (pipes, electrics, who knows?) There was noise, rumbling, and the cart started behaving erratically; and subsequently would not produce sound. I'm assuming that some form of electric current spiked the cart and burned the coils.

Two questions: 1) Is there a way to check the cart with a DMM without risking possible further damage? 2)
Are there companies, like Sound Smith, who could diagnose and possibly repair this type of damage, or after-market repairs generally limited to re-tipping or cantilevers?

The Art9 turned out to be a wonderful cart and losing it would be a significant setback to both my system and my bank account. Any advice would be appreciated.

 

[SY]

If the coils got blitzed, they probably went open. If you want to make sure that your DMM isn't going to cause a problem, put a 10k resistor in series before measuring resistance. if it still shows 10k, your coils are likely fine.

 

[rayma]

There was noise, rumbling, and the cart started behaving erratically; and subsequently would not
produce sound. I'm assuming that some form of electric current spiked the cart and burned the coils.

Did you try a different cartridge, to make sure the preamp itself is ok?

 

[kasey197]

Not in the USA but these guys are pros I think: Cartridge Repairs - Northwest Analogue

Note never tried them and no affiliation.

 

[sreten]

Hi,

A DMM on a resistance setting will not harm moving coils.
Each channel should measure 12R.

rgds, sreten.

 

[lcsaszar]

I measured 1.4 mA in diode test setting and 0.4 mA in 200 ohms range of my DMM. For security I would put a 10k resistor in series and measure in the 20k range.

 

[SY]

To put that in perspective, 0.4mA across 10R is 1.6 microwatts. I think the coils might survive that.

 

[wanders]

Thanks for all the thoughts.

I tried a second cart - denon dl-301II - within a few seconds it started chattering, like the ART9. Naturally, I stopped playing it.

Here's some more background: the preamp is a new diy 6sn7 tube pre (still in the cake-pan mode) which is supposed to replace my mac c-27. I'd been playing cd's through the pre and getting superb sound for about a week before trying the vinyl. The ART9, had behaved like the denon, but stopped outputting completely. Also, I'm using the Salas, FSP MJFET phono stage. It's been on-line and producing great sound for 6 or 7 months.

At this point it seems likely that I damaged the ART9; and, that the jfet stage and the tube pre don't like each other much. I'm going to go over to the Salas build thread and ask him for guidance on that. In the meantime I'll try testing the ART9 as suggested; but I've got a feeling I'm going to have to try to get it repaired.

I'll post more when I know something. Thanks again.