A cheap 34mm capsule in a t.bone SC450

All about the tools and techniques involved in capturing sound, in the studio or on location.

Moderator: Moderators

Re: A cheap 34mm capsule in a t.bone SC450

Post by Hugh Robjohns »

Andreaux wrote: Wed Oct 13, 2021 10:19 pmWhere could the fault be? The capsule? Some electronics in the mic related to power? If it's the capsule, I'd lean towards doing the same mod you did as it turned out pretty nicely!

Lots of potential things it could be, ranging from the capsule diaphragm shorting out on the backplate at excessive volume, to dry joints on the circuit board, to failing capacitors, to excessive moisture/humidity when singing close and loud.
User avatar
Hugh Robjohns
Moderator
Posts: 32366 Joined: Fri Jul 25, 2003 12:00 am Location: Worcestershire, UK
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual... 

Re: A cheap 34mm capsule in a t.bone SC450

Post by Arpangel »

Sounds really good to me, suits the male voice, unbelievable :think:
User avatar
Arpangel
Jedi Poster
Posts: 9194 Joined: Sat Jul 12, 2003 12:00 am
"Don’t let the noise of other peoples opinions drown your inner voice"

Re: A cheap 34mm capsule in a t.bone SC450

Post by Andreaux »

Hugh Robjohns wrote: Thu Oct 14, 2021 10:30 am Lots of potential things it could be, ranging from the capsule diaphragm shorting out on the backplate at excessive volume, to dry joints on the circuit board, to failing capacitors, to excessive moisture/humidity when singing close and loud.

That "excessive volume" is really just a more powerful plosive, not superhigh sound pressure. A more pronounced "P" is enough to make it "pop". It really feels like a discharge and temporary loss of power. I'll try to reflow solder joints on both pcb-s and I'll see what happens.
Would be good to know if anyone experienced similar behaviour in any mic and if changing the capsule did solve that (I never had a capsule failing so I don't know what that does). I can order a new SC 450 capsule from Thomann, they sell them for not that much actually, but I'd love to be sure before I do :)

Other thing is that there's a small transformer in the base of the mic and when I first opened it, it had plastic corners broken off and small pieces dropped out so I suspect that at some point the mic probably was dropped (I bought it used so I don't know for sure). I don't know what the transformer potentially touching the casing would produce. Maybe that's a clue too...
User avatar
Andreaux
Posts: 3 Joined: Thu Mar 04, 2021 11:29 am Location: Hungary

Re: A cheap 34mm capsule in a t.bone SC450

Post by Hugh Robjohns »

Andreaux wrote: Wed Oct 20, 2021 12:35 pmI'll try to reflow solder joints on both pcb-s and I'll see what happens.

You may well kill it altogether!

The PCBs of most capacitor mics are coated on the solder side to prevent moisture ingress which could cause issues due to the very high impedances involved in the circuitry. Indeed, it may actually be a faulty coating which is causing your problems... but certainly trying to reflow the solder joints will damage that coating.

...plastic corners broken off and small pieces dropped out so I suspect that at some point the mic probably was dropped (I bought it used so I don't know for sure). I don't know what the transformer potentially touching the casing would produce. Maybe that's a clue too...

Could be. Doesn't sound good. I'd certainly check the connecting wires carefully for breaks.
User avatar
Hugh Robjohns
Moderator
Posts: 32366 Joined: Fri Jul 25, 2003 12:00 am Location: Worcestershire, UK
Technical Editor, Sound On Sound...
(But generally posting my own personal views and not necessarily those of SOS, the company or the magazine!)
In my world, things get less strange when I read the manual... 

Re: A cheap 34mm capsule in a t.bone SC450

Post by Andreaux »

Hugh Robjohns wrote: Wed Oct 20, 2021 1:02 pm
Andreaux wrote: Wed Oct 20, 2021 12:35 pmI'll try to reflow solder joints on both pcb-s and I'll see what happens.

You may well kill it altogether!

The PCBs of most capacitor mics are coated on the solder side to prevent moisture ingress which could cause issues due to the very high impedances involved in the circuitry. Indeed, it may actually be a faulty coating which is causing your problems... but certainly trying to reflow the solder joints will damage that coating.

...plastic corners broken off and small pieces dropped out so I suspect that at some point the mic probably was dropped (I bought it used so I don't know for sure). I don't know what the transformer potentially touching the casing would produce. Maybe that's a clue too...

Could be. Doesn't sound good. I'd certainly check the connecting wires carefully for breaks.

I'll look for any coating, but so far I didn't have the impression that there was any coating on the joints. The PCB is coated to protect the traces, but solder doesn't seem to. I'm building circuits regularly, both through-hole and SMD so I've seen coated plates :) Thanks so much for the word of advice though. I'm new to servicing microphones, so there might be as well things I don't know, so I'm grateful for every advice.
Do you have an idea what a defective capsule sounds like, or how it behaves? Can it cause this kind of discharge-like temporary cease-of-function?
User avatar
Andreaux
Posts: 3 Joined: Thu Mar 04, 2021 11:29 am Location: Hungary
Post Reply