Batboard

Ok heres the machine:- GR300 setup - used for paging with our FD.

Rx radio: Lowband maxtrac
Tx radio: M1225 40 watt UHF
Motorola Rick interface
Internal power supply
Housing with fan (on all the time)


The tx radio was setup at 25 watts, working fine. 3 weeks ago, we raised the tx power to 40 watts since our license allowed, and heres where I think the power problems started. One week ago today, I blew the fuse on the power supply. Replaced it, and it all started working again. Thursday night, fuse blew again. This time I figured, ok maybe it's the power supply. Changed the power supply to an Astron RS20A, and added a fuse to each radio (20a) to see if one radio was maybe no good. Worked fine till earlier tonight when it blew the fuse on the new power supply. Went to change it, and the power supply is shorted internally. Neither fuse on the radios were blown, just the 5a on the back of the Astron. Now I am puzzled. Part of me says I am just underpowering the setup, and need a 35amp power supply, but part of me says maybe something else is going on here.

Any suggestions?

Anyone know the actual power draw of: Maxtrac low band on RX, Rick, Fan, M1225 40 watt on TX??

Any help or suggestions welcomed.

Thanks!

Power surge on the AC line??

MaxTrac receiving is 350-500 mA. M1225 is probably similar to a MaxTrac, and at 45 watts on UHF, it's drawing 9-10 amps. There's not much in a RICK or the fan, so I'd think you should be safe with 12 amps of continuous capacity. Certainly a 20A Astron supply should deal with that.

If the Astron fuse blew, either you have some spikes on the AC input, or the supply itself has failed. They're pretty much bullet-proof as far as DC overloads or short circuits are concerned. I've had fuses in my RS35M supply blow for no reason, with just a receiver connected.

The supplies are fairly simple to repair. If the primary (AC) fuse blows, the main rectifier or filter caps are likely the culprit, and these can be checked with an ohm-meter. It's also possible that something has shorted out against the pass transistors on the heatsink - their cases are connected directly to the unregulated +24v supply, and if they connect to ground, the fuse will blow. Any fault after the pass transistors will likely cause the unit to go into current foldback or voltage shutdown, or both. Schematics for these units are available on the web.

Bob M.

Does this happen while transmitting only?

You could check the incoming 120 volts. Also check if there is any voltage between the neutral and ground. There should not be any. If there is, suspect an open or poor neutral from the power company to the fuse panel or circuit breaker panel. This can even be a problem outside the building at the transformer on the pole.

Also if the original supply still works, plug it in as well and see if it still blows the fuse without any load on it. Are there any other items in the building that are acting up.

Nand.

Ok, did some more testing tonight. First, it blew the original power supply totally also. This was an AStron SL-12. So this makes 2 power supplies cooked I took the tx radio out, and hooked it directly to a 12v battery with a 15a fuse. Keyed the radio into a dummy load till it was almost red hot. No problems. Draw was 10-13 amps. I ordered a replacement Astron RS-20BB power supply. 16a cont draw. Any more ideas or suggestions?

get an electrician to check out your power. Something is definately wrong on the 120V side.

any electrical work done at the building around this time?

any other (like carpentry) work done., I have seen wiring get messed up by carpenters (no offense to carpenters, they are ok guys!)

any other problems in the building?
sounds like a 120vac problem.

by the way, I wouldn't bother to raise the power from 25 to 40 watts.
I dont think you would notice a difference out in the field units AND you will keep your transmitter happier for a long time.

Good luck with the problem, and definitely report your findings here!!!

Mike in CT
(across the river)

this may be WAY off base, but if it happened with a power increase and only w/ a transmitter that's cooking the fuses on the UTILITY side of the powersupply, i'd look at the antenna & cable-age for the system...you might be getting enough bleed to trip the astron...EMF can be a mother.

Ok, so I will get someone to check the incoming power. What if I told you that there is another machine (MTR2000) plugged into the same outlet with absoultely no problem........

I don't care what the specs say for the RS20A...they are crap. We had several of them blow with low-band M216 repeater set-ups. Total draw was about 13-amps continuous, well below the 20A peak & 16A continuous rating of the supply, yet they blew repeatedly. I forget what make/model we eventually replaced them with, but we never had a problem afterwards.

odd

I'm with fish and wavetar on this one. EMF and Astrons are TERRIBLE. I had a few that were giving me intermit problems, so I switched them to Lamda's... I've never had a problem since (3 years.)

The control circuits are way to easy to tweek w/ EMF. It makes even more sense since you said that you increased your power, then had problems.

2nd choice would be 110AC problems. It's too much of a coincidence that there would be a 110VAC at the same time you increased your power. From a power supply standpoint, increasing your power out by that much should cause a HUGE change in power consumption on the 110AC side.

Just my experience
tpg

As others here have said, Astron power supplies are not very good arround ANY RF, they will fail... a piss poor design.

I replaced these with DuraComm's and havent looked back.

BTW, DuraComm makes the replacement PS for the GR series for Motorola.

Try a PS-30 THEY WORK!!! or a RM2512, these are what is used in cell sites. They also have a battery backup adaptor for them too.

http://www.duracomm.com

We have found that the astron 20 amp power supply
has a number of models.They make one that is 20 amp.
inrush and only 10 amp cont.

The 13 amp load is too
hard on it.
Try the new supply with the battery also wired up.
at the same time.

The trouble does not seem to be at the 120 volt ac side by what you said.

Like everyone has said the ps is the trouble maker.

Try the radio at 35 watts.We have seen many bad pa's.

For a repeater 40 watts is high .What is the duty cycle
of the system?

UPDATE:

Replaced the power supply to an Astron RS20BB. Today is one week with no problems. We also swapped the tx radio with another and lowered the power to 30 watts. I fused this thing 3 times... From the B+ on the power supply to a 15 amp fuse. From there, a 2amp for the fan, 5 amp for the RX radio and a 15 amp for the tx radio. I also put an ammeter inline. So far the current has not exceeded 8 amps.
Thanks for all the suggestions!