GR1225 Repeater has 1 second of TX power

[radioservice]

I have a problem with a UHF GR1225 Repeater. The GR1225 Repeater has 1 second of TX power upon PTT and then the rf goes bye-bye even though the red transmit light stays lit.

any ideas?

[Batwings21]

Here's a good start...
1) You have high swr caused by a bad antenna, line, connector etc.
2) Bad power supply
3) You have a damaged the PA by either too much use or #1

I would check the antenna system and check output power into a dummy load or known good antenna. If it fails into good antenna, check power supply voltage and then re solder PA transistors or replace the pa.

[radioservice]

Thanks...I'm sorry, but I should have detailed my steps a little better.

I'm transmitting into a 50 ohm load through a telewave meter. I read the 12 volts on the PA collector and it stays there, dropping slightly when keyed. The antenna works well with a backup repeater in place.

I'm thinking it could be the PA or the surrounding caps....there's green rubbery stuff that looks like it oozed out of the collector caps....is that normal?????

Is there protection circuitry on this model?

I can barely hear a small relay sound when it pukes.

[chartofmaryland]

No relay, just a bad PA, new are under 300.00 from MOL

Just replace it unless the customer can afford 2 hours of cap replacements and or other finals components

I have had god luck in making 18 watt PA's from the originals since the parts that blow leave the original driver parts alone. And with the size of the heasink, the PA has no real reason to ever fail again. There has been one in use in a almost continuous mode without failure. It floats from 14 to the 17 watts it does under use but keeps on trucking

CoM

[Bat2way]

Just replace the two 56 pf caps at the input of the final PA transistor. Clean up the input/output with solder flux removing the excess old solder. You do not have to remove the Collector-side output caps (with the green stuff). Just clean up around them and the base and collector tabs making sure they have a good connection after you resolder. Touch up emitter contacts too. This problem has always been related to running the repeater at full power output, which causes too much heat, resulting in the input caps having their solder melt and reharden repeatedly, resulting in poor output power and eventual failure. Check the output circuit and touch up the coils, caps, etc if they look suspect. This PA is not suitable to be ran at full power in a repeater mode. I always turn down a repaired unit to 25-30 Watts.

[arlojanis]

CoM, please give us the exact details of your mod to the PA.