Sterling ST44 common failure

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aumamps
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Sterling ST44 common failure

Post by aumamps » Wed Jul 08, 2020 1:21 pm

Greetings,
I have an old ST44 that has a apparently common repeated issue that other owners have, where it is producing alot of noise and static.
I bought a new power supply and that is not the problem.
I did have a loose ground connection inside the 7pin cable but after resoldering that, that is still not the problem.
It is somewhere inside these microphones.

This is a very simple circuit so I am going to trace this when I get home but considering this has been a common problem for other people I figured I'd share the schematic below and see if anyone knew what the culprit is with these microphones.
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Rodgre
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Re: Sterling ST44 common failure

Post by Rodgre » Thu Jul 09, 2020 3:39 am

I have one of these as well. It's a nice mic. I haven't had issues with mine at this point, but I recall having a similar problem years and years ago with an old Groove Tubes GT6 (Sterling is Guitar Center branded Groove Tubes mics). I ended up replacing the tube and it was good to go. If you need to replace your tube and can't find a replacement, drop me a line. I [i]MIGHT[/i] have an extra. I will have to check my stash.

Roger

aumamps
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Joined: Wed Jul 08, 2020 9:14 am

Re: Sterling ST44 common failure

Post by aumamps » Thu Jul 09, 2020 6:07 am

I am going to replace the tube, and the transistor too.
They appear to be cheap online but I'm interested in what you're offering.

I traced around the board a little bit last night and I couldn't find anything obvious.
I have noticed however that there is about a two second delay of clarity, where the microphone works fine when you plug in the cable from a fully charged power supply, before the static kicks in. So it makes me think it's something on the B+ line but im not sure yet.

aumamps
audio school
Posts: 3
Joined: Wed Jul 08, 2020 9:14 am

Re: Sterling ST44 common failure

Post by aumamps » Thu Jul 09, 2020 6:07 am

I am going to replace the tube, and the transistor too.
They appear to be cheap online but I'm interested in what you're offering.

I traced around the board a little bit last night and I couldn't find anything obvious.
I have noticed however that there is about a two second delay of clarity, where the microphone works fine when you plug in the cable from a fully charged power supply, before the static kicks in. So it makes me think it's something on the B+ line but im not sure yet.

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Rodgre
carpal tunnel
Posts: 1631
Joined: Fri May 30, 2003 3:19 am
Location: Central MA
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Re: Sterling ST44 common failure

Post by Rodgre » Thu Jul 09, 2020 6:31 am

That's possible too. Is the schematic for the power supply available anywhere? The easiest thing to do is to make sure that the correct voltages are showing up at the mic end of the cable at the very least.

Roger

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