SVA service info needed

[kf4sqb]

i have an NTN5487 SVA here with audio problems, and need a schematic for it for troubleshooting, or some advice from someone who has seen this problem before. The audio out of the accessory connector pins 20 & 21 is "muddy". Sounds for all the world like a blown speaker, but it does it through a regular amplified SVA speaker, or my signal tracer. It isn't the audio out of the radio, as the radio sounds fine on it's own, and out of the SVA's accessory connector pins 7 & 8 (direct audio from the radio's accessory connector). Something has to be breaking down inside the SVA. Can anyone help me out here?

[kf4sqb]

OK, scratch that. Stupid me wasn't paying attention to what I was doing, and was using unshielded leads on my signal tracer. That's why the audio sounded muddy out of the back of the SVA. Using shielded input leads, the output of the SVA is clean. The problem is definately in the amplified speaker. Anyone have a schematic for an NSN6054A?

[Tom in D.C.]

I have the schematic and parts list for the 6054A 12-watt speaker unit.
PM me your mail address and I'll snail mail a copy to you. If you
have access to a Motorola file the pages you want are 3 and 4
of 68P81108C39-A.

Regards,

[kf4sqb]

Tom, thanks for the offer, but I've got it taken care of. Found that one of the PNP TO220 transistors in the amp was blown. I'm pretty sure I also found out why it blew in the first place. I had it mounted with a metal bracket (bracket from an old-style, metal cased Moto speaker), and either by design or by a problem with an insulator somewhere inside, part of the circuit is connected to the metal rear case of the speaker. I found this out after I got it repaired, and started to reinstall it in the vehicle it goes in while everything was powered up. As soon as I touched the bracket with the speaker housing, I got a loud "pop" out of the speaker (although it thankfully didn't blow the amp again). I insulated the bracket from ground, and everything appears kosher now. Lesson learned!