Hello, I have a texas star dx 350 that has worked great for years. i noticed when i went to turn it on, it was super hot and drained my battery in my truck. the amp turns on and preamp works. I did a visual inspection and can't see any burnt/damaged components. Why is my amp getting very hot when off?? Any help would be greatly appreciated. Thanks
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Texas star dx 350 staying hot when off?
- Thread starter rflegacy
- Start date
Is the relay disengaging? I believe if the relay hangs up, even with the power button "off" you will still be "keying" the transistors...this would explain the box heating as it's basically transmitting the whole time.
As Ranch has said, even with the power turned off, the board is hot all the time, the relay can be open and it's still hot.
There is something shorted and drawing enough current to heat up the amp and kill the battery.
73
Jeff
There is something shorted and drawing enough current to heat up the amp and kill the battery.
73
Jeff
That I don't know, but you definitely have a drain somewhere. It just can't be a direct short or something would have popped, either the fuse or a trace on the board. It's got to be one of the caps I just wouldn't know which one.
Let it cool, then feel inside for what part gets hot before it gets everything else hot.
that sounds like a good approach, before i just start shotgunning a bunch of parts. Thanks
I've seen before where the normally open side of the input contact of the relay gets shorted closed even though the contacts are unkeyed. This causes the base bias supply to turn on heating the transistors up. When this happens the meter light stays on whenever the power switch is on. If the meter light stays off until the amp is keyed, you don't have this problem and the relay is fine.
Another possibility I have encountered is one of the RF transistors has massive reverse leakage of the Emitter/Collector junction. This can be checked by lifting one collector at a time then power up and see if the heating problem goes away. If one of the transistors is leaky, might as well replace them both.
Another possibility I have encountered is one of the RF transistors has massive reverse leakage of the Emitter/Collector junction. This can be checked by lifting one collector at a time then power up and see if the heating problem goes away. If one of the transistors is leaky, might as well replace them both.
Two ways to make the large RF power transistors draw current on standby.
Abuse it until it fails, and becomes a resistor on the inside.
Cause DC current to feed into the base circuit of the transistors. Requires a voltage between a half Volt and 0.6 V to turn on that kind of transistor. Question is: where is this base current coming from?
This may be like finding a short on a printed circuit board. You follow where it goes taking solder off pads where a component led or jumper wire carries the circuit. Eventually you unsolder something that clears the short. Now follow from that spot.
See what DC voltage you have on L2. Should be zero while receiving. Problem is, if L2 is hot, the light behind the meter should also be lighted. The 5-Watt ceramic wirewound resistor R10 is right next to L2. Should also have zero Volts on each end while receiving. Still a bit of a puzzle.
73
Abuse it until it fails, and becomes a resistor on the inside.
Cause DC current to feed into the base circuit of the transistors. Requires a voltage between a half Volt and 0.6 V to turn on that kind of transistor. Question is: where is this base current coming from?
This may be like finding a short on a printed circuit board. You follow where it goes taking solder off pads where a component led or jumper wire carries the circuit. Eventually you unsolder something that clears the short. Now follow from that spot.
See what DC voltage you have on L2. Should be zero while receiving. Problem is, if L2 is hot, the light behind the meter should also be lighted. The 5-Watt ceramic wirewound resistor R10 is right next to L2. Should also have zero Volts on each end while receiving. Still a bit of a puzzle.
73