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YardBird
Advanced Member
USA
427 Posts |
 Posted - 01/25/2006 : 5:24:43 PM
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OK, we've got a bunch of Tom/Freights equipped with the "Executive EXC-550" AM/FM/CASS stereos with the PA system (preamplified microphone hardwired to the stereo's final amp) and these cheap units are failing miserably. I have taken it upon myself to repair them. So far, so good. The problem I'm having is that I'm unable to find a schematic diagram of the EXC550 units. Guessing just isn't good enough with some of these things.
I'm sure that this radio chassis (Probably Panasonic-built) was/is used in many different, similar stereos but I can't seem to narrow down a model number for any one of them so I can get a schematic.
These units use a preamped source-switching (via the PTT switch on the mic) method to switch the line input to the Toshiba TDA1518BQ final audio amp from the stereo's line-out (preamp) signal to the microphone's line-out (preamp) signal so the music cuts out and the mic audio is heard when the mic is keyed. I would imagine it's similar to the way the cassette player switches out the radio's preamp output to the final when it's activated.
I have the datasheet for the TDA1518BQ final amp IC, but I need to see it in-circuit with the rest of the EXC-550 so the entire circuit makes sense to me.
I want to be able by seeing how that one's wired up to wire the preamp PA mic to pretty much any stereo the same way. (we could upgrade to CD players and keep the PA function...)
The EXC-550 is marketed by MITO Corp. All attempts to email the rep or tech support have gone unanswered. They might even be out of business since '03.
Does anybody know what other makes this unit might be similar to or marketed as that I could contact their tech support people for a schematic diagram?
I suppose I could just wing it with a replacement stereo that has a line input jack, but then I'd still have to figure out the switching arrangement to silence the music on key-up.
Any assistance or a point in the right direction would be greatly appreciated.
TIA.
Yardbird |
Edited by - YardBird on 01/25/2006 5:26:57 PM
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buster133
Top Member
USA
512 Posts |
Posted - 01/25/2006 : 7:03:55 PM
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I recently installed this exact radio/PA system in my 01 Thomas Freightliner to replace the broken REI unit that the bus came with.
You're right about the cheapness, I ordered a brand new EXC-550 online for about $20.00+ S/H. The only problem I have had is with the LCD display only showing half of the digits once an awhile, but it's better than nothing. I wanted to put in a Kenwood AM/FM CD/MP3 headunit, but my voice doesn't travel very far, so I needed to stick with a system with a PA, but if you do find a way to wire up a PA system with a regular stereo system let me know. I still have the radio manual on the bus, so I'll check it out tomorrow and see if there is any info that might be helpful. |
[URL=http://s7.photobucket.com/user/buster133/media/6f2e0703-1970-4ac9-bb1f-b6b9d7c12297_zps1741e113.jpg.html] [/URL] |
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hastings
Senior Member
USA
162 Posts |
Posted - 01/27/2006 : 05:25:35 AM
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Hello,
My name is Matt Hastings, A rep from Michigan Bus Parts in Brownstown, MI, I am a MITO Corp. distributer. We carry a full line of replacement parts and complete radio/P>A> systems. Please give me a call @ 1-734-479-4805 and I will figure out a solution to your radio issues. Mito is not out of business, they just only try to deal with distributers, and there aren't many, for some wierd reason, but their parts are good quality and very reasonablely priced. |
Matt Hastingshttp://www.michiganbusparts.com/
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Need technical info on EXC-550 stereo/PA system
