Batboard

Is there any settings anywhere to adjust the thermal shutdown?

going into dummy load, I can get about a minute or so of TX before it goes into thermal shutdown. PA is cold so no reason for it. and dummy load is fine 1.1/50ohm. I have the triple circ. pa 75w out from the system

Are you certain it is thermal shutdown?
If the pre-filter / post filter is not aligned right, the high SWR shutdown will cut in.
Is this a station that had been working, and is now acting up or is this happening to one you are changing freq on?

I will echo PETNRDX's comment, sounds like a filter alignment issue.

PETNRDX wrote:Are you certain it is thermal shutdown?
If the pre-filter / post filter is not aligned right, the high SWR shutdown will cut in.
Is this a station that had been working, and is now acting up or is this happening to one you are changing freq on?

this is a former base station so no internal pre-post filter, it does have the tube low pass that the base stations came with. right now the output of tx is dumped right into the dummy load.

I have moved it from 453/458 to 441/446

What are your meter voltages doing on the TX jack? See http://www.repeater-builder.com/motorol ... ering.html for more info.

You may be freaking out the power detection on the PA by bending the frequency down so far. The MSF power regulation compares the output of the IPA to the output of the PA. If they're not within a pre-determined ratio, it freaks out and shuts down.

If you change your TX frequency to something around 444.000 (or maybe even up around 449), does it exhibit the same behavior?

Maybe the triple circ is not that broad.
Your problem may be as described in the previous post.
If the IPA and PA values are not tracking each other the controller might be shutting it down.
Try turning the PA output up or down to see if it finds a happy spot.
I have moved lots of these down from 465 and had them work fine.
But they were all either no circ or single circ.
I run a couple at 434 mhz TX.
You might also wanna' program it up higher just to see if that is the trouble.
That thing would go into thermal shutdown pretty fast.
Long before the heatsink gets hot, thats 40 pounds of heatsink.
It is looking at the devices, but I would still think it would be longer than a minute.

Stupid question, but have you tried another dummy load?

d119 wrote:Stupid question, but have you tried another dummy load?

I have not,

I will be rolling up to the shop today, ill get some fresh meter reads on the tx jack see what i come up with

ke4zdg wrote:What are your meter voltages doing on the TX jack? See http://www.repeater-builder.com/motorol ... ering.html for more info.

You may be freaking out the power detection on the PA by bending the frequency down so far. The MSF power regulation compares the output of the IPA to the output of the PA. If they're not within a pre-determined ratio, it freaks out and shuts down.

If you change your TX frequency to something around 444.000 (or maybe even up around 449), does it exhibit the same behavior?

too bloody hot in the shop to stay in for long, meter reading I have

1 - 42
2- 00
3- 20 tx off, 6 tx on
4- 00
5- 38

#1 is super high. Sounds like the thermistor (RT501 100K) that senses the heat sink temp is bad. Check for open. Could also be a bad chip. Check U401 and U402.

ke4zdg wrote:#1 is super high. Sounds like the thermistor (RT501 100K) that senses the heat sink temp is bad. Check for open. Could also be a bad chip. Check U401 and U402.

I was thinking #1 was a bit high, seems (according to the list from rpt-builder) 40 should be the max. once the weather actually cools off where its not 90 and high humidity ill be able to work in the shop longer then 5 minutes and run some checks on things more.

ke4zdg wrote:#1 is super high. Sounds like the thermistor (RT501 100K) that senses the heat sink temp is bad. Check for open. Could also be a bad chip. Check U401 and U402.

well i dropped back the power, #1 on meter is reading 39. TPO is about 75 watts. seems to have fixed the pa shutdown issue