WX5812
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I can only find these schematic for the 12 V PA. Unless I’m overlooking it. Does anyone have the schematics for the 24 V version?
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Schematic for 24v VHF MASTR III PA
- Thread starter WX5812
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No such thing as a Mastr III mobile.
Are you sure you have a 24 volt VHF PA? The only 24 volt Mastr III PA I'm aware of was for 800 MHz, all my VHF & UHF M3 PA's are 12 volts. Perhaps post the part number of the PA in question.
12dbsinad
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All of the newer Mastr III's are 24V, doesn't matter on the band. Your V&U PA's are the older style if they're 12V
It came to me in a dream.radioman2001
Member
Harris used both the 12 volt and 24 volt PA in the later MASTR III (White Stripe)series design, we had both. and are interchangeable. So if you are talking about the MASTR III PA 24 volt one prints are not available. I had to reverse engineer it myself as Harris contracted out that design and wants to do the repairs in house only. I even tried calling the company that did the design work and was informed that Harris held the rights and could not release it. I won't go into the nonsense with Harris about it, but they lost all other bids in relation to VHF base equipment with us as a result.
For the VHF it's a simple design, I just followed the RF flow and found 90% of the time it was the first driver, and a close replacement was available from Mouser or the likes. Out of 5 bad units I worked on I got 4 working pretty easy, and the fifth we used a parts donor.
I am not familiar with a 48 volt version anything for locomotives? Most train radios take 72 or 32 volt and switch it down to 12 volt.
For the VHF it's a simple design, I just followed the RF flow and found 90% of the time it was the first driver, and a close replacement was available from Mouser or the likes. Out of 5 bad units I worked on I got 4 working pretty easy, and the fifth we used a parts donor.
I am not familiar with a 48 volt version anything for locomotives? Most train radios take 72 or 32 volt and switch it down to 12 volt.
Well, we are talking some fairly old stuff. Once was when all the cab electrical was 48 volt, even dome lights.
The radios were frames from masterII mobiles stuffed with masterIII boards.
Big warning label saying "48 volt positive ground only"
I see a lot of Kenwoods in the UPRR cabs so no doubt have 12 volt.
That hurricane lamp up front is still 48 volt.
I think all the newer masterIII PAs are 24 volt, older 12 volt. Or you noticed the difference is the device ratings.
That would have little impact on the schematics. Board layout likely different.
Cheers
The radios were frames from masterII mobiles stuffed with masterIII boards.
Big warning label saying "48 volt positive ground only"
I see a lot of Kenwoods in the UPRR cabs so no doubt have 12 volt.
That hurricane lamp up front is still 48 volt.
I think all the newer masterIII PAs are 24 volt, older 12 volt. Or you noticed the difference is the device ratings.
That would have little impact on the schematics. Board layout likely different.
Cheers
Railroad "clean cab" radios typically have a built-in power supply which knocks 72 VDC from the locomotive electrical system down to 12 VDC for the radio. They use a standard (and very expensive) large 4-pin connector for power, two pins for 12 volt supply and the other two pins for the 72 volt supply; this way they can use the same radio in a locomotive, or in a vehicle with standard 12 VDC power.
In addition to the standard power connector, "clean cab" radios are also a standard size, so you could pull out a Kenwood and drop in a Ritron, or a Wabtec, or whatever radio you happen to have lying around.
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WX5812
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I have a few of both. I also have old bag style cellular phone hand sets that plug into the repeaters. I dug them out today and played around with it. While the changes you can make on it is limited its still very cool!! I will take some pictures and post them tomorrow. Has anyone on here used one on a mastr iii?
WX5812
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Here is a few pics of that
WX5812
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