Where can I get an inductor for Power Brake?

[Ralle]

Hi. I have a Marshall Power Brake, and I would like to get hold of an inductor for the PB... I'm suspecting a failure of the inductor ( 1 mH according to the schematics ) in the Power Brake. I have looked everywhere, but I can't find any manufactures for this one... Please help
Regards Ralle

[dai h.]

hey Ralle,

what happened to it? Did it go open or short out some of the windings? The inductor manf. I googled (before) and came up with North Devon Electronics. My guess is it's something custom and cheap. Shouldn't be hard to find a 1mH inductor. Look at places that sell speaker crossover components (for inductors). You need something that:

a) has the right value (or value that you want)
b) is capable of handling the power that will go through it
c) (probably) you want something that isn't so heavy or comparable in weight (from the way the PCB is supported)

The original looks like a ferrite core inductor. I've seen some ferrite ones for speakers and since they were pretty cheap (a few dollars) compared to the other types avail. (such as air core, etc.), I'm guessing that's why Marshall used them (to keep cost and weight low). Also, if you want to try tweaking it, it's okay to use a smaller value (such as 0.5mH or whatever), and you can also "tune" the effect the inductor has by sticking a resistor (of adequate wattage) across it (in parallel) as well. This will tame the high frequencies and help make things more stable (less prone to oscillate). Randall Aiken in a very old Plexi Palace post (which is probably not there any more since they switched servers a few times) recommended 22ohms (or thereabouts) 25W (this will get warm in use). The Marshall SE100 speaker emulator (which has pretty much the exact same network) uses 33ohms IIRC.

[Enzo]

The 1mH choke in the Power Brake (PB100) is Marshall part number INDT00006 and lists for $8.95. ANy Marshall dealer can order it for you or you can order it from www.marshallparts.com.

Parts Express sells some 1mH coils for crossovers at about $9.

Why do you think yours is bad? Disconnect its wires from the rest of hte circuit and measure it for continuity. If it has continuity and is not shorted to its frame, then it is probably OK. Unless it is all burnt up or something.

[Ralle]

Thanx guys. Well, it's like the sound gets less high ends... as if the inductor slowly wears out... it's not as bright and edgy as it used to be... I looked at it, and it showed some green oxid between the wirings... it looks poor... as simple as that...
Allso I've looked around... and I'm lost... I can't find it at marshall parts, nor NDE... not any where else for that matter ( I must be dumb or something )
Does any one of you guys have a link to where I could get the right indoctor... Please...
Thanx

[dai h.]

(enzo has given you the part number, so) have you tried the local Marshall distributor?

::| EM Nordic |::

also have you tried measuring the inductor (resistance, inductance)?

[guitician]

What about the 12.5mh inductor? Does it look as bad? How hard to you drive this? A dimed 100w Marshall may be too much for it. It is basically a single side of a OT and you may know how those can be abused.

[Jag]

If you're leaving the amp cranked to 10 all the time and using the Brake to control level, I'd be suspecting worn out output tubes first. Try a new set of output tubes and see if the highs come back.

[Ralle]

(enzo has given you the part number, so) have you tried the local Marshall distributor?

::| EM Nordic |::

also have you tried measuring the inductor (resistance, inductance)?

Yes he has, thanx enzo... but I couldn't find it there. I've read somewhere that the PB is out of production, so I couldn't find it there either... And sadly I don't have the instruments or the knoledge to messaure the inductor...

[Ralle]

What about the 12.5mh inductor? Does it look as bad? How hard to you drive this? A dimed 100w Marshall may be too much for it. It is basically a single side of a OT and you may know how those can be abused.

Isn't it the 1mH inductor that takes all the beating? That's the one that gets warm...

[Enzo]

When you say you can't "find it there," do you just mean it is not listed on their web site? CALL THEM or email them. They don;t list every part in their inventory, not even close.

It is a part. They are a Marshall dealer. If Marshall has them, he can get them. Just because a unit goes out of production doesn;t mean all the spare parts disappear overnight. They may or may not have this part, but that isn;t why.

[hovis90]

Sorry to bump up an old thread, but did anyone manage to find where to get a 1mH and 12.5mH choke?

Does anyone know the part number for the 12.5mH inductor so I can see if a Marshall dealer has it?

[Enzo]

I can't look up that part number any longer, when Korg dropped the Marshall line, I let my relationship with Marshall lapse. But "12.5mH inductor L2 from the Marshall Power Brake PB100" should be sufficient.

But same advice I gave above CALL or otherwise CONTACT Marshallparts and ASK them if they can supply the part. Don't just look on their web site. No dealer will have them in stock on the shelf unless you have a tremendous stroke of luck. 99% of Marshall service shops will never have a need for those parts, and so wouldn;t stock them. And if there is an exception, someone will point it out.