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TPN1154A Power supply...max output current?

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TPN1154A Power supply...max output current?

Postby billreed79 » Sun Nov 24, 2002 10:11 pm

Hello, all.
I recently purchased a TPN1154A Motorola power supply. It looked like a pretty nice power supply, and it was cheap. Could someone please tell what kind of current this unit is rated for? I see the AC input is fused for 5amps, so would the output be somewhere in the neighborhood of 25-30amps? (assuming it's just like every other linear-regulated supply I've encountered) I know there are some pro's out there who know. There's probably some trick to decoding the model number, as is the /\/\ tradition. Any other info on this unit would be appreciated (trivia, useless facts, whatever you think is interesting).
Also is there a good source to buy a male connector to mate up to the six pin connector on the front? I may have to convert it to binding posts, or banana jacks if I can't get one...

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motorola 5 amp input fuse

Postby Susan157 » Sat Dec 14, 2002 3:01 pm


Most of the time the 5 amp inputs were for the 12 amps
dc outputs. and do not forget the duty cycle was no
more than 50% most of the time.

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thanks, susan

Postby billreed79 » Sat Dec 14, 2002 11:22 pm

Thanks for the info, Susan. I did some searching around, and found out this was the base supply for the MCX-100. There were 2 models listed, TPN1136A and TPN1154. The 1154 is the heavier of the two supplies, and has 2 pass transistors instead of one. Looks like it should run a 25-30 watt radio no problem.

So far, I've replaced the power cord, repainted the case, and added binding posts/bannana jack connectors on the output. Output DC looks clean, and regulation is stable, but it is putting out 15.5v instead of the rated 14.1v. I'll need to do some tweaking there. 15.5v seems a little "hot" for most 13.8v radios and other equipment I'd like to run.

If anyone has a schematic, I'd like to have a copy for my records.


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Postby Will » Mon Dec 16, 2002 12:48 am

Bill, that is a common problem with those supplies. Two ways to solve that problem, change the zener diode to a lower value, or remove the extra resistor in parralell with the resistor going to ground and the base of the error amp transistor on the circuit board, usally 10k. Or change the value of the resistor, increasing, of the resistor going from the base to the output line.

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Postby billreed79 » Fri Jan 17, 2003 8:25 pm

Just to let everyone know, I got the power supply working just the way I want it now. I did as you suggested, Will. I clipped the extra 10k resistor, and that brought the voltage down, but not enough. It was still about 14.5v or so. I went to the local electronics supply house and got some different value zener diodes. I found that a 6.2 volt zener gave me 13.77 volts out. Perfect! I Never had to put the 10k resistor back in. The factory specs called for a 6.8v zener, and I guess that 0.6v was enough to make the difference. Thanks to all who helped. This supply is now happily running my maxtrac.


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What radios do you own?: MTR2000, CDM1550, HT1250

Re: TPN1154A Power supply...max output current?

Postby wb6fly » Sun Feb 13, 2011 11:22 am

I have posted schematic diagrams for the TPN1136A, TPN1154A, and VPN1013A power supplies in the Power Supplies folder in the Repeater-Builder Group Files section. The first two power supplies are found in the MCX100 service manual, while the VPN1013A is found in the MCX1000 service manual.

The TPN1154A and the VPN1013A seem to be identical, except that the VPN1013A has a 500-ohm pot added at the base of Q2, the reference amplifier. It seems that our Canadian neighbors like to use 14.5 VDC as a radio supply voltage, rather than 13.8 VDC.

Please refer to the many Load Test reports in the folder for some interesting comparisons. The Tutorial explains how the tests were performed.

I own a TPN1136A power supply, and I note that it has two paralleled M9244 pass transistors instead of one M9639 as shown in the schematic. I also found that the TPN1136A is capable of handling a much greater load than allowed by the 2A AC input fuse. Unfortunately, I do not have either a TPN1154A or a VPN1013A to test.

73, Eric Lemmon WB6FLY

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