Apex 420 modifications

Hi,
thx crazeydoc. I did put c1 back but it didnt change the noise. I didnt change the fet yet, the one in there is marked K30A Y 9B. I will try to hunt down a replacement and swap it out.

PP, thx for the reply. The transformer is oblong so I think the only possibility is its in backwards so it would be stepping up towards the output not down.
Would this add noise? Could it be tried the other way withoput blowing anything.

As for the electrolytic caps, they have all been swapped out for polypropylene.

Thx for the replies.

A
 
Another possibility is that the noise has always been there, but you couldn’t hear it due to poorer sensitivity (which would have been improved with the transformer mod). Does it seem to require the same amount of gain that it did before the mods, or less?
 
apex mods

Hi Tim,
i think the sensitivity is the same but im guessing at this as my test files got corrupted.

This mic should not be that noisey though, this is one of apexs more expensive mics and the cheaper ones i have are much quieter.

Thx, Andybot
 
Cool, Andbot. I will take a peek inside. I have a bench , dry wick ,various solder and stuff. Ready to rock. I follow you on the deconstruction. No doubt, I will mark stuff, and a few digi's won't hurt either..

Ok. next questions. What makes a good laminent?
Where do I get the laminent?

thanks for the info.
 
Apex Mods

BHL,
check out earlier in this thread there are links to where and how to get them.
The firm that does them will send out samples if you ask.
Good luck n all.
A
 
Andybot said:
As for the electrolytic caps, they have all been swapped out for polypropylene.
Click to expand...

Andy,

Obviously, something wrong is happening... Did you swap electros for polypropilenes of the same values? It might be hard, as polys of the same Mf are much bigger and wouldn't fit. Check it, as some electros are in voltage filtering, so the noise might come from there.

Also, if you did not connect the trafo the right way, you could get get noise because of impedance mismatch.
 
mic mods

Hi,
I checked some things....the trafo is in correctly. I tried the original electrolytics
and some metal poly caps of higher values and it did not make a difference.

The noise I hear is something I beleive to be self noise always there, not dependent on signal. Whats a boy to do.

If the trafo was the other way round so that it stepped to the output would that also mean the signal would require less gain. Just curious if the impedence mismatch in this case ie 3 to 1 would produce so mich noise.


Thx
 
bringing this one back from the dead................just wondering if andybot ever figured out the noise problem.

who else has relaminated? which mic? how was the end result compared to the original?
 
the 435 (similar to the 420 but with a highpass filter switchable) is not a noisy mic, it's actually fairly quiet, certainly much quieter than many of my expensive mics. So there's something funny going on with your mods. I'd bet you (almost) that there's something that is wrong with either the caps you put in (poor choices or wrong values or fried during soldering) or the transformer somehow was damaged when relaminating it (or removing it).

Not meant to suggest you don't know what you're doing, but with being one of your first mic mods it's always possible there was an error made, I mean, who knows, could have been a faulty part in there that was about to die and a little extra heat on the circuit board killed it completely. Could be a capacitor you didn't even remove, just one on the board that died while the mic was opened.

I'd suggest checking each part with scopes etc. I can't tell you how, but the info is out there on the web somewhere...

Best of luck, hope your 420 is awesome now anyway!

Cheers
 
I know this thread is ancient, but thought I'd post for the benefit of future readers, if there are any.
One thing the poster should have checked regarding the noise of their mic, is if they had sufficiently cleaned the main PCB and top PCB after the mods.
Left-over solder flux will cause trouble and noise. It needs to be cleaned thoroughly with 99% rubbing alcohol and a little brush (often a toothbrush will work well). Typically, you clean it with rubbing alcohol, then with DISTILLED water (not filtered, not spring, not purified, NOT tap). Then let it dry out well (put it under a lamp or use a hair dryer on low - stay away from the capsule or just cover it well). Even "No clean" solder can sometimes cause trouble.
Also, make sure you didn't completely melt through the teflon sleeve at the 1Gohm resistor - if you did, replace it (good luck finding one though, try ebay for a teflon standoff - you'll likely have to enlarge the hole though).
AT
 
Cold solder awesomness... Apex 420

Hey guys, as above, i know this post is very old, but i had a mishap during a move and all three hot cold and neutral came loose. Have d/l the schematc but can't seem to make sense of it. Tried a couple of soldering options but could not get it to work. Anyone feel like posting a photo of theirs so i can copy the pathway?

Thanks in advance.

ButchIMG_0379.jpg
 
Looking at the solder posts from left to right...
terminal 1 - Red wire from rear of diaphragm
terminal 2 - Red wire from front of the diaphragm
terminal 3 - white wire from right case

Hope this helps.
 
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