Topic: Strange fault using Oktava MK-012s with Marantz PMD661

[goldenhours]

Hi there,
I've been getting this rather strange occurence when using my Oktava MK-012s with my Marantz PMD661.
It's hard to describe, some sort of electrical discharge sounding like an out of tune oscillator. This occurs randomly in the middle of an otherwise clean recording.

I don't get this when using other mics with the PMD661, and vice-versa I don't get this when using my Oktavas with another preamp.

Here is a short audio clip of the fault. You can hear it in the right channel from 0'06" onwards. I would be grateful if you could have a listen and tell me if you have ever come across anything like it before.
https://dl.dropboxusercontent.com/u/6566507/OKT_MK012s_fault_1.mp3

[goldenhours]

With Multimeter set to '200m' I'm getting a current of 190.2mA between pin 2 and 1 on both channels at a voltage of ~44.5V - can this be correct?

[goldenhours]

Sorry, I am a bit confused now. I don't think my multimeter has a mV setting for AC.

Setting it to 200VAC I am getting ~96VAC between pin 2 and pin 1.

FWIW, I also checked DC voltage between pin 2 and pin 3 (it should be 0, right?). However, I am reading 19.7mV between pin 2 and 3 of the left channel, and 7.2mV between pin 2 and 3 of the right channel.

[goldenhours]

Do you have an autoranging multimeter (most are, except cheap new ones or older analog models)?  Because 96VAC is pretty much impossible.

I don't know why there would be a difference in pin 2 to 3 VDC, unless the inputs have different internal leakage currents.  That's a bit scary if true . . .

It would be of the cheap new variety...: http://www.simpower.co.nz/images/products/med/QM1523.jpg
As far as I can see there is no mV option in the AC range.

I'm positive about the difference in voltage between channels in pin 2 to 3...

I have sent this PMD661 back to the store twice already as a warranty claim. The first time apparently they exchanged the preamps. When I got the unit back it seemed to be working okay, however, I still got a lot of noise with phantom power on and no mics, so I decided to send it off again. When I got it back the second time they said they couldn't find any fault.
I keep thinking that something is wrong with this unit. Unfortunately I don't have the expertise to prove it. My Oktavas are working solidly with other devices (including my friend's PMD661!), so it can't really be them.

Any further advice on how to approach this and make my case would be greatly appreciated.

[DigiGal]

My Oktavas are working solidly with other devices (including my friend's PMD661!), so it can't really be them.

Out of curiosity are the two PMD661's identical models or one a PMD661 MKII with the other an original model PMD661?

[goldenhours]

My Oktavas are working solidly with other devices (including my friend's PMD661!), so it can't really be them.

Out of curiosity are the two PMD661's identical models or one a PMD661 MKII with the other an original model PMD661?

They were both bought at the same time, i.e. they're both the original PMD661s, and, according to Doug Oade who checked their serial numbers for me, both from a 'dodgy' batch...

[DigiGal]

With Multimeter set to '200m' I'm getting a current of 190.2mA between pin 2 and 1 on both channels at a voltage of ~44.5V - can this be correct?

If that was actually your meter that you linked then these are the scales it has:

http://www.kenma.com.au/qm-1520.html
DC Voltage: 200mV, 2V, 20V, 200V, 600V ±0.5%
Overload protection: 250V RMS for 200mV range/600V DC RMS AC for other ranges
DC Amps: 200µA, 2mA, 20mA, 200mA, 10A, ±1% on most ranges. Overload protected (not 10A)
AC Volts: 200V, 600V, ±1.2%. Overload protected
Resistance: 200, 2K, 20K, 200K, 2M ±0.8%. Overload protected
Resistance: Audible Beep for Continuity Test.
Diode teting
Transistor testing

The colored 200m scale is mV DC and the white 200m scale is mA DC.  Measuring current with a DMM is different than measuring voltage... How to Measure Current on an Electronic Circuit