Batboard

Hello :
I looked around a bit with the search feature and did find some useful info but im still a bit confused.
I got a Radius M100 model D43LRA73A5AK .
It has a 5 pin bd and im pretty sure it has a freq of 147 to 174 if i was told right.
My problem is the radio wont keep transmitting after its keyed up after a second or so.
I did after reading some old postings find out that the radio does transmit at way over 80 watts as close as i can tell by a watt meter loaned me.
It then quits transmitting till i unkey and start over again with the same problem again.
In a post i saw a reply about a bad chip resistor on the bottom of the pa bd being a posibilty.
I looked at a borrowed maxtrac repair manual and didnt see the HLD3010A 45 watt pa bd i have but did see a HLD4326A 45 watt pa bd.
Im not sure its the exact picture of my pa bd but gonna try to reference from it as much as i can and see if it helps.
Can someone tell me what the schematic part reference n umber would be for the HLD3010A pa bd and a general location of this chip resistor that was mentioned in a older post - it also said this resistor had something to do with the power control circuit.
I also took the pa off and put it on another radio and it did the same thing and the radio that had the bad pa worked ok so im thinking its gotta be something with the pa bd.
Can someone help me please ?
Satelite

That's a 45 watt radio. If you're reading 80w out, something is wrong with the PA (it's going to nuke itself in short order) or your wattmeter/load is defective.

If you are not using a 50 ohm dummy load, you cannot depend on the wattmeter readings. And if the load impedance is way off, that will cause not only the erroneous wattmeter reading, but the PA will shut itself down to prevent damage.

Helo :
But when i tried another pa by taking the one off and putting on a working one for sure it works fine and reads 44 watts .
And the pa giving me fits wont work on the other radio so i'm still thinking its with the pa.
I tried that and made a coment about it in my first post to let everyone know i at least have the trouble with the pa and that it followed the pa not the radios.
Help me ???
Resister shematic refernce number for a HLD3010A please?
Satelite

The HLD3010A is the standard 40W PA for the Radius series. The manual is 6880101W-58A.

I would suspect a problem with the PA current sense circuit which connects to the logic board on P7 pins 3 & 4. If the logic board is not seeing proper PA current it will probably max out the controlled B+ to Q2420 and the PA will run uncontrolled full power.

I don't have a Maxtrac schematic to compare but I believe the PA board is similar to the Maxtrac version.

The power control circuit on the logic board sends controlled B+ to the PA on one of those 5 pins on P7. The microprocessor also measures that voltage, and if it goes too high, the radio stops transmitting. It assumes that things are all messed up. You can do this by setting the power in the service screen all the way up. On a normal PA, you'd be pushing out lots of power, which is not a good thing. This would give you a momentary pulse of RF, maybe for 1/2 to 1 second, enough for your wattmeter to go full-scale.

The power control circuit also monitors the PA current by measuring the voltage drop across a low-value resistor on the PA circuit board. If this voltage drop gets too high, the circuit lowers the controlled B+ going back to the PA, and tries to cut back the output power. The microprocessor would not be aware of this condition. I don't know how long it takes for the circuit to react, but I'd suspect it would be a few seconds. I've keyed MaxTracs with no antenna attached and have watched the DC input current drop significantly after a very short time.

Since you know the problem is in the PA, you should pull the shield off and start checking things like the current shunt or something pulling the controlled B+ line to +12V.

For all intents and purposes, the Radius and MaxTrac boards, PAs, control heads, and cases are identical and interchangeable.

Bob M.