Batboard

Does anyone know if the 125 Watt PA for a VHF MSF5000 is 12 or 24 volts? I see in one of my schematics 24V but my unit seems to be 12V.
Thanks...

should be 12v, draws about 28-32 amps



doug

The MSF5000 power supply high current DC runs 13.2 to 14.5 volts controled by a feroresonate transformer with a flyback winding with a capacitor.

The msf5000 we work on are 13.6 volts
on the RF amp.

It's been so long that I don't remember the details, but SOME units were 24 volt. An FTR was telling of 'Bad things' that happened when the 24v PS was used with a 12 v PA.

some of the 400-500w 900 mhz paging amps use 24v

i think those are the only ones tho...and they don't look ANYTHING like an MSF PA... they're anodized aluminum... and Freakin' HUGE

the VHF high power (350w) uses a 40w driver and a 350w final, each driven by a standard 12v MSF power supply...i.e. two power supplies, two PA's...

the UHF hipo stations (225w) use the same setup, but i believe the driver is 110w (standard 110w UHF MSF PA) and the final is the 225w...again, each driven with a standard MSF power supply (2 PA's / 2 PS's)


doug

Thanks for all your help. The problem I have is that the unit as I bought it has a 12v PS and a 125 watt PA(VHF) It is working OK but only puts out 68 watts. I don't know if it because of running on 12V or if I have a bad PA. I was thinking someone may have swapped the 24v PS for a 12V.

Harold wrote:Thanks for all your help. The problem I have is that the unit as I bought it has a 12v PS and a 125 watt PA(VHF) It is working OK but only puts out 68 watts. I don't know if it because of running on 12V or if I have a bad PA. I was thinking someone may have swapped the 24v PS for a 12V.

Where are you measuring 68 watts - at the output of the PA, or the output of the filter? If at the PA, then that's what it's set for. If it were making significantly less than the controller wanted it to, it wouldn't be making anything - these drop in a fraction of a second if the feedback loop isn't happy. If you're getting 68 watts at the ouput of the filter, that's not too far from what's expected - about 80 watts. There's a proceedure for tuning the filters (RX AND TX) that has to be followed. Essentially, it goes like this: you inject a signal into the antenna side of it, and sniff a signal in each filter stage. Last stage - where you're injecting the signal gets adjusted for a peak, and and then you adjust the next stage back for a null at the same test point. Move the probe back, and adjust the next stage back (not the one with the probe in it) for a null...etc. You need the book, and you need to follow the instructions, or they DO detune with temperature changes, day of week, color of sky, etc. Someone may have adjusted it for peak power pass, which doesn't cut it. You may even be burning up some of your power in the receive filter.

Thanks Bob, I'll check that. FYI the part numbers I have are :
VHF PA - TLD2692A
PS - TPN1263A

Nope, Still 60 watts direct out of the PA...

So, what happens when you adjust the power out pot up and down on the controller?

Comes up normally until you get to about 62 watts and then the pa shuts down. Actually the controller shuts it down.

I don't have the manual in front of me, but... to do some testing, you will to move the PA protect jumper - it's really got a different name, and it's location varies with the type of controller. Disconnect the exciter from the PA. (or if there's a filter between the exciter and the input of the PA), the filter. Measure the power from the exciter. Check it against the manual. Adjust the PO pot, and see if you get a decent range. Also, type putting a couple of watts into the PA, and see what you get out. Check the PA current, and see if it's reasonable for the power - 60 watts should be much less than 20 amps at 12 volts. 110 watts is around 25 amps at 12 volts for VHF.

I checked the exciter and it is putting out about 10 watts. The PA looks good as well. Soooo I guess that the PA is supposed to run on 24 volts. I don't know why my unit has a 12 Volt supply...

Don't assume that unless the manual says so. Another possible way to know is to look at the finals transistors, and look their part numbers up in the Mot. transistor manual, and see if they're 12 or 28 volt devices..... Don't let the magic smoke out.

I'm with you. That's the last thing I want to do. The PA manual does say it's 24V. I was just concerned as I got it with the 12V supply in it
Thanks..

Old thread bump~

I have a VHF station with the TLD2692A PA. 5.8W in gives me 105W out at 154 MHz (with a 24V supply), but only 45W at 147 MHz even though that's within its 146-174 rating. Before I go trying to rework the input and output networks, has anyone ever done one of these and can point me to what needs to be changed? It has no circulators and nothing inside it is natively tunable.

Might anyone have the part # for the high power (350w) PURC5000 PA? I have to troubleshoot a bad one and I don't remember what the metering is without the book.........and I don't have a book.......