Phil Allison wrote:
David Farber wrote:
----------------------
I'm servicing a Behringer EUROPOWER PMH2000. The + and - 15 volt
regulators need replacing because the leads have failed. The
transistor is mounted to the chassis at a 90 degree angle and then
soldered to the pc board. The problem is that pc board fits very
tightly into the chassis. The leads on the regulators keep getting
flexed with each pc board removal. Anyway, I want to replace them
because a couple of the leads have broken off. They are packaged in
a TO-220 case. The center tab is nonmetallic so it is insulated from
the chassis.
** The *mounting tab* is definitely metal, just coated in epoxy to
insulate it.
Though the schematic says terminal 2 is grounded in the
7815A anyway, I was wondering if it made any difference whether or
not I purchased ones with metallic backing or ones with a plastic
backing.
I just looked at the LM7915 spec sheet and it says that terminal 1
is ground and terminal 2 is the input which is reversed from the
positive regulator. It also doesn't mention whether or not it has a
metal tab, which if it did, would have to be insulated from the
chassis. Do any of you have any experience replacing these
regulators in a chassis mount situation?
** If the originals are held on with a clamp, you need to buy the
same again.
If held with 3mm bolts, you can use the ones you have.
BUT you MUST add insulating bushes and mica pads to BOTH - plus a
smear of white thermal grease.
Bolting the positive one straight to the chassis is likely to result
in ground loop hum.
... Phil
Hi Phil,
The original ones do not have any insulating bushings or mica pads. They are
mounted to the chassis with 3mm bolts and some thermal grease. I contacted
Digi-Key but they could not tell me if their parts were insulated or not.
When I place my order, I will get the insulating pads and bushings just to
make sure.
By the way, you can get a schematic here.
http://music-electronics-forum.com/a...h2000_-et-.zip
Thanks for your reply.
--
David Farber
Los Osos, CA