Tube mic pissing me off!

[nevetslab]

Freon, like component icer?

I have that.

I have a couple spray cans of it. I take a petri dish, spray some into that to get some of the liquid, dip my sable brush into it and quickly apply that to the diaphragm and work the area being treated. It evaporates quickly, so you do have to work fast. It cleans like nothing else I've seen on mic diaphragms. Shame that substance is so harmful to our ozone layer.

[g1]

I don't think the modern freeze spray has Freon in it. I think it's 134A like they now use in car AC.

[drewl]

I have a couple spray cans of it. I take a petri dish, spray some into that to get some of the liquid, dip my sable brush into it and quickly apply that to the diaphragm and work the area being treated. It evaporates quickly, so you do have to work fast. It cleans like nothing else I've seen on mic diaphragms. Shame that substance is so harmful to our ozone layer.

Cool, I'll try that prior to baking.

What's a "sable brush" you mean like the thin metal acid brushes with brown soft bristles?

Edit: looked it up, ah, like the soft paint brushes, got it.

[nevetslab]

Cool, I'll try that prior to baking.

What's a "sable brush" you mean like the thin metal acid brushes with brown soft bristles?

Edit: looked it up, ah, like the soft paint brushes, got it.

I bought my sable brushes at a good arts supply shop years ago. It's very soft bristles. You should be able to google them. The Acid brush bristles are way too coarse to use on a microphone diaphragm.

[drewl]

Yeah, I have some.

Also old school freon circuit chiller.

[drewl]

Okay, so after some cleaning and baking the volume appears to be stable.

I had also read that these are supposed to have an 12AY7 (?) Not a 12AX7?

With a 12AY7, cathode voltage is stable, no fluctuation.

It still has a little random popping, so, more cleaning and baking I guess.

[nevetslab]

Okay, so after some cleaning and baking the volume appears to be stable.

I had also read that these are supposed to have an 12AY7 (?) Not a 12AX7?

With a 12AY7, cathode voltage is stable, no fluctuation.

It still has a little random popping, so, more cleaning and baking I guess.

Sounds like you're making some progress. I like the 12AY7's. There's another tube that find their way into tube mics, though on the pricey side. OH, rats, I already shut down my index to go find the number. I'll look it up later. Ah, found it in my Altec 439 Mic Preamp spec sheet.....type 6072.

[drewl]

Well, I think I may have fixed this thing.

I found some replacement elements that weren't too expensive.
Installed one and it was working and sounding really good, except low frequency bursts would still cause a little rumbling and noise.

While poking and prodding around one of the transformer wires came off.
Re- soldered it and mic is working fine with no noise.

It may have been hanging on by a strand or two, with vibrations causing noise or signal problems.

This thing is real sensitive, just tapping this on my phone the mic is picking up the "thumps" from lying on the same bench a foot away.