Batboard

I have a rack mount OLD motorola power supply that is putting out 15.5 volts instead of the 13.6 it is rated for. The power regulator board has a connector that comes off it. Is there some outside control it needs? Does anyone have a manual or information needed to turn the voltage down? I think it may have damaged the spectra I have hooked to it.

Is 15.5 volts too much for a spectra to handle?

I doubt you would have damaged the spectra.
I had one come in for repair once that been installed on a 24 volt truck for 2 years before it finally said enough is enough
What is the power supply out of.
If it is MSF or similar with the ferroresonance core it will read high until a load is put on it.
key the spectra and see what the voiltage is.

not sure what the heck it is from. Got it from a friend. The spectra has dull red lines across the display. Sometimes it transmitts, sometimes it doesn't. It started powering on and off by it's self.

The device runs at the 15.5 loaded or not.....

There is a voltage regulator board but no adjustments to be made on it. It does show reference to 9.6 volts, could it need 9.6 to run the regulator circiut?

The TPN1110B power supply is used on, among other things, a 75w UHF Micor base station. It provides regulated 9.6V (9.0 - 10.2) and 13.6V (12.9 - 14.5) DC. Each supply has a 4A fuse on the input. There's also unregulated 13.8V DC at 25 amps for a power amplifier.

There are no adjustments. Both regulators use nearly identical parts and schematics. I doubt the Spectra would have transmitted on the regulated output, so I'd guess you connected it to the screw-terminal 13.8V unregulated output. As mentioned earlier, these often supply 15 volts and do a good job holding that voltage.

The supply uses a ferro-resonant transformer for regulation, and 8 17,500uF capacitors filter the unregulated output.

The only thing my manual has is one fold-out sheet that has the board layout, schematic, and parts list. There's no circuit explanation or other ratings.

Bob M.

Yes, I did connect it to the screw terminals on the front. this is the only place that I was able find to connect into it. Was this spot ok for the spectra?

How is hamden BTW, my brother lives there....

Hamden is WET. Been wet since we had 6-8 inches of rain on April 23rd. I'm waiting for a roofing job since then and they delivered material yesterday which got soaked and will probably stay that way all week.

Is your brother a ham? This is where we all live, you know!

That's the only place you will get enough power to run a Spectra in transmit. There should be another connector, either on a cable or on the circuit board, that would give you +13.6VDC and ground, but they don't show anything other than the X-ray view of the board. Since it can't give you more than 4 amps, it would never support the Spectra in transmit mode.

One thing you could do, but I hold no guarantees, is to find a pair of high-current silicon diodes, high enough to let the Spectra transmit. Put them in series with the output of the power supply. This would drop about 1.4 volts, giving you something around 13.6VDC, which the Spectra should be quite happy with.

I recall reading somewhere that the Spectra is sensitive to the voltage you provide it, and while 15V might not hurt, the radio may not want to operate properly at that high a voltage or something below 12V. Also, the ignition control voltage really has to be at the same voltage as the main power cable, so if they aren't hooked to the same point yet, you should do that. If the voltages differ by as little as one volt, the radio may refuse to work properly.

MaxTracs are a lot more forgiving.

Bob M.

kcbooboo wrote: One thing you could do, but I hold no guarantees, is to find a pair of high-current silicon diodes, high enough to let the Spectra transmit. Put them in series with the output of the power supply. This would drop about 1.4 volts, giving you something around 13.6VDC, which the Spectra should be quite happy with.
Bob M.

Bob, good Idea. To add, you may need up to four didoes to get down to 13.2 volts at the radio which IS the voltage the Spectras are designed to work with on TX.

Diodes should be rated at 15 amps current, and 50 volts. Also we add a 330 ohm 1 watt resistor accross the power cable to the Spectra, this keeps the voltage drop accross the diodes during low current drain, or when the Spectra is off.

From my old micor days there is some sdjustment on the cct board but I think that was the crowbar levels.
The supplies were pretty robust and were a hybrid between a regular and a switch mode power supply.
They are rated at 35 amps.
I once had the pleasure of seeing 2 of these in parallel. I warned the guy about it but he didn't listen. One week later "BANG"
One supply was supplying 35 amps and the other was supplyng about 4 amps.
I disconnected the clock cct on a replacement and gave it the same clock as the other one.
Both supplies sat drawing 19.5 amps each