MTR2000 PA problem

arlojanis · Post by **arlojanis** » Sat Jun 19, 2010 5:39 am

I have a UHF MTR2000 that RF power will come up, then drop to zero, then pulse off-on a few times, then go dead. Any ideas on what causes this?

fineshot1 · Post by **fineshot1** » Mon Jun 21, 2010 4:33 am

No I have no real idea yet, have you tried any trouble shooting or process of elimination?

1. Have you tried transmitting into a good quality dummy load to rule out any feedline or
antenna issues?

2. You did not mention if the MTR is running off the internal or external power supply. If the
MTR is running off the internal supply - try a known good external supply to rule that out.

Give these two a try and start from there.

jeffee1 · Post by **jeffee1** » Fri Nov 26, 2010 8:19 pm

Wish I had noticed your post a couple months ago....I had the same issue with one of ours. The shop said it was a bad PA and sold us a new one for like 3000.00 They wanted to take the old one but I told them I'd just hang onto it. I recently disassembled it and found the solder joint from the PCB to the N connector had just a tiny drop of solder which had burned away. I had to look at the joint with a magnifing glass to see just a hairline space all the way around the center pin of the N connector. I have yet to test it BUT assumption tells me that was the issue all along. This unit would transmitt fine for 5 or 10 mintues then indicate high SWR. I'm currently searching for an MTR power supply as we've upgraded this unit to and MTR3000 (mototrbo) which involves swapping out the exciter, reciever and station control module. If the PA is actually still good with an ample ammount of solder applied to the bad joint I'll have a 100 watt UHF MTR for my amateur radio activities! Might be something to look at if you've replaced the PA and still have it.

Anyone have an MTR2000 power supply kicking around?

Post by **wavetar** » Wed Dec 01, 2010 9:06 am

jeffee1 wrote: Anyone have an MTR2000 power supply kicking around?

Be aware the P.S. for the 100 watt MTR is different than the 30/40 watt models. It's rated for 500VA as opposed to 250VA, and contains circuitry for 28Vdc. This of course also means an extra set of wires to carry the 28Vdc over to the P.A.

I have a couple of the low powered supplies, but none of the high powered, sorry.

Todd

jeffee1 · Post by **jeffee1** » Wed Dec 01, 2010 11:06 am

The million dollar question is...Can I turn the PA power down to an acceptable level and use the 250VA power supply? I haven't ever had my hands on one so I don't have any way to compare them. I suppose I could have opened up the service manual. I've noticed MTR2000 voting recivers being sold pretty cheap but "figured" these also were equip with the smaller power supply so I didn't want to waste the money on a hunch.

Post by **wavetar** » Fri Dec 03, 2010 12:09 pm

jeffee1 wrote:The million dollar question is...Can I turn the PA power down to an acceptable level and use the 250VA power supply?

No...I guess I should've been a little clearer...the high powered PA requires 28Vdc to operate, regardless of where you set the power level, and the 250VA power supply does not supply 28Vdc...just 12-14Vdc.

jeffee1 · Post by **jeffee1** » Sat Dec 04, 2010 5:58 am

Ahh...thanks for clearing that up! That narrows my search down to something that seems nearly impossible to find in the surplus/used market. I'll keep looking though.

Thanks again!

emtprt · Post by **emtprt** » Mon Dec 06, 2010 7:19 am

One of our UHF MTR2000s (of course the main transmit site) had a less then acceptable output which effected fire/EMS paging. The local shop came out and reported that the 100watt transmitter was putting out approx. 40 watts. I was given 3 options repair, refurbished or new PA. You can get a 100 watt refurbished PA for around 1500.00 installed on site

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