MK 012, needs a waranty badly

[Marik]

<I don't see any 68/63s either. Mine all had 47/40s instead of 33/63s though. There's also a tiny 1uF that needs to be changed to a 4.7uF or even 10uF. It needs to be 35V.>

Sure thing you dont see them--they don't exist.
Look at PK series 22/50. 8 of those will do. For 68Mf use 3 in paralel, for 33/63 two in paralel. For 1/50, as Flatpicker suggested 4.7/50. The signal cap from the capsule change to Wima FKP-3 1000Pf. It is gonna be a tight fit and you should be inventive. You will need to resolder the transistor and some resistors to the other side of PCB.

<Also what would be the minimum equipment I would need in order to make my own cables...I am eager to give cable buliding a try since those darn things are so expensive now. I know about the mogami wire and neutrik plugs, but what about the solder, the iron , the flux?>

Hurmth, it is really very easy. After a few cables you gonna be a pro. To do it a $14 small 40W Hakko iron with little tip would be quite sufficient. However, I would still recommend to get a silver solder (sorry Flatpicker ). Scroll down to Welbornelabs solder for $25 a pound, also read a solder primer on the bottom:

http://www.welbornelabs.com/solder.htm

Besides of Mogami I would recommend Canare star-quad, which I use myself. You can get it bulk, as well as Neutriks, at

www.markertek.com

 

[Flatpicker]

...However, I would still recommend to get a silver solder (sorry Flatpicker )...

No need to apologize. I didn’t think 2% silver would make all that much difference, but if you like it, I’ll have to give it a try. What do you use to clean the flux? Alcohol?

 

[bongolation]

I don't see any 68/63s either. Mine all had 47/40s instead of 33/63s though. There's also a tiny 1uF that needs to be changed to a 4.7uF or even 10uF. It needs to be 35V.

I pulled apart the other one and also saw the same caps as I listed, 68/63s and a 33/63. The FETs were different, though. One was a plastic one ABM7 and the other was metal, 3BH1. [shrug]

My guess is that with a nominal 48V phantom power, at least a 50V rating on the components would be a good idea. Scott Dorsey said some time back, if I remember correctly, that there were different boards with different components in these. I dunno for sure. He may have been talking about MK-319s.

I'm sort of reluctant to substitute different component values unless I'm relatively sure we're talking about the same circuit.

 

[Flatpicker]

...I'm sort of reluctant to substitute different component values unless I'm relatively sure we're talking about the same circuit.

Yeah, it’s the same circuit. The 33uF or 47uF is just a filter cap for the phantom power voltage so it’s not a big deal. Bigger is probably better up to a point. 48V isn’t everywhere in the circuit as it gets divided down for the FET. The 1uF only has about 20V on it (I use a 35V cap here)

Everyone I ever looked at had the ABM7s in them and as far as I can tell they’re real close to the 2SK170s. Scott says the 2SK170s are less noisy, but I can't tell much difference. As far as the metal 3BH1, they must have ran out of the ABM7s that day and grabbed it for a sub.

Most of the sound improvement comes from the cap upgrades and the 2G resistors, specifically changing the 680pF mono to a 820pF COG mono and the 1uF to a 10uF tantalum or electrolytics.

I going to try and post some before and after clips (really, this time ). Comcast changed some things around and I haven't had time to go back and figure out how to put stuff online. They make it a real pain to get to. I posted some before via Ozraves, but had not changed the 1uF to a 10uF then. When I did, it made a world of difference so I need to re-post them. Changing the 1uF tamed the high-end a little and made it more open.

Also, the tantalums sound way different than the electrolytics here. You should try them both. 2 of mine have electrolytics and one has a tantalum, so I get a variety of flavors. The electrolytics are just some standard grade ones I had lying around. I’m going to get some higher grade Panasonics and put in there when I get time.

 

[bongolation]

What do you use to clean the boards and for conformal coating (which is critical on these circuits)?

All the different conformal coatings I see in the catalogues are spray-can stuff, which is sort of inappropriate for boards this small.

 

[Marik]

<What do you use to clean the flux? Alcohol?>

This solder leaves almost no residue (as advertised). I use isopropyle alcohol, but would think, since it is water based, you could clean it with water, just never tryed it. If you want I can check it for you. What I like is that this solder spreads very nicely and evenly.

<What do you use to clean the boards and for conformal coating (which is critical on these circuits)?>

The traces on Oktava's PC boards are plated (Russians seem to do it a lot), so you won't need any coating there.

 

[bongolation]

<What do you use to clean the boards and for conformal coating (which is critical on these circuits)?>

The traces on Oktava's PC boards are plated (Russians seem to use it a lot), so you won't need any coating there.

If you do work on the ultra-Hi-Z parts of this circuit, all those components, the standoffs and that part of the board need to be scrupulously cleaned and carefully conformal-coated.

If they aren't, almost anything will short across those 1G-3G resistance paths, including condensation and flux. Poor cleaning/coating is one of the bigger problems on stock Oktava microphones and it only gets worse when the resistors are changed to higher values.

Scott Dorsey (among others) has made a big point of mentioning it. That's where most of the work actually is, getting rid of contamination schmutz and protecting that part of the circuit from future contamination.

 

[Marik]

When I opened the MK012 first, I was amazed how much flux was left there. They don't clean it at all! Of course, the very first thing to do is thoroughly clean the board. BTW, on mine and all other Oktavas I saw, the standoffs are sealed.
Yes Bongolation, you are right--it actually IS a good idea to coat it. For some reason it slipped my mind. Thanks for the tip.
I usually coat the PCBc with fast dry laquer, so it probably will work here as well.
Have a look at the attachement--that's how Russians used to build mics ones. On the very left is a CKBK--pay attention--completely silicon sealed--reduces microphonics and keeps moisture away from the board.

 

[Flatpicker]

This solder leaves almost no residue (as advertised). I use isopropyle alcohol, but would think, since it is water based, you could clean it with water, just never tryed it. If you want I can check it for you. What I like is that this solder spreads very nicely and evenly...

I'll have to try it. Thanks for the tip!

 

[Flatpicker]

When I opened the MK012 first, I was amazed how much flux was left there. They don't clean it at all!

All three of mine were very clean. They even had the coating on them. If you want to see some nasty flux, open up a MXL 603s.

 

[steelpetals]

I tested out for the first time my new mk-012 pair and jesus did it make a noticeable improvement in the sound of my overheads. I've been using those ECM8000's and there is absolutely no comparison. For Blues/rock, those silly little oktavas I bought form guitar center are the shit. Now lets hope they dont generate 2 pages of posts like the last guys experience did.

 

[ozraves]

I tested out for the first time my new mk-012 pair and jesus did it make a noticeable improvement in the sound of my overheads. I've been using those ECM8000's and there is absolutely no comparison. For Blues/rock, those silly little oktavas I bought form guitar center are the shit. Now lets hope they dont generate 2 pages of posts like the last guys experience did.

For all the obsessing that goes on with home rec'ers over what's the best mic for $$ or Chinese mic no. 1 versus Chinese mic no. 2, people should be checking out the Oktava MK012s. They are probably the most musical low priced mic in existence.

 

[bongolation]

I usually coat the PCBc with fast dry laquer, so it probably will work here as well.

I'm wondering.

We're talking about 3,000,000,000 Ohms here with those 3G resistors, and almost anything looks like a dead short compared to that. I'm figuring if you're going to coat a section operating in that range, you're going to have to have some pretty special stuff with virtually no conductivity at all. Does common lacquer fit the bill? I dunno. I see a bunch of different conformal coatings from the same manufacturer and I wonder which one is suitable for this sort of thing and if it's available in a bottle for small applications like this...

I guess I should axe Scott and see what he's using, as he was the one who brought it all up when he started modding these things, and I know he's given the contamination question a lot of thought.

BTW, this is a very real concern. I have personally heard condensation in this part of the circuit mess things up until it dried out from the heat from the phantom power warming up the circuit. I had no idea what was causing it, and Scott told me when I explained the symptoms.

I've been lucky in that none of the Oktavas I've bought had a flux problem, though a couple do not look like they've been decently conformal-coated.

 

[Flatpicker]

I'm wondering.

We're talking about 3,000,000,000 Ohms here with those 3G resistors, and almost anything looks like a dead short compared to that. I'm figuring if you're going to coat a section operating in that range, you're going to have to have some pretty special stuff with virtually no conductivity at all. Does common lacquer fit the bill? I dunno. I see a bunch of different conformal coatings from the same manufacturer and I wonder which one is suitable for this sort of thing and if it's available in a bottle for small applications like this...

Lacquer is a type of plastic that when dry, has no conductive properties but acts as an insulator with a much greater impedance than air. There are, however, different types of lacquer and this is where problems can arise. Some types are less elastic with age and less resistant to long term heat exposure than others. They will eventually become very brittle, crack, and loose their ability to protect against moisture.

The type used for electronic circuits (I always knew it as conformal coating) is made much more elastic and is less likely to crack with age. I’m not sure what they call it now, but it’s sold at most electronics suppliers and was avaliable in small quantites last time I checked. We have some in jugs at work. I'll check Monday and see what it is.

 

[Flatpicker]

...The type used for electronic circuits (I always knew it as conformal coating) is made much more elastic and is less likely to crack with age. I’m not sure what they call it now, but it’s sold at most electronics suppliers and was avaliable in small quantites last time I checked. We have some in jugs at work. I'll check Monday and see what it is.

It's called Humiseal type 1B31. Here's the web site so you can track down where to buy it.

 

[Marik]

<I've been lucky in that none of the Oktavas I've bought had a flux problem, though a couple do not look like they've been decently conformal-coated.>

Somebody just brought to mod: