Sounds like the electrolytic filter capacitor on the input hot side.....
OR the big diode on the hot wire.......
OR the big diode on the hot wire.......
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Texas star dx-350 hdv repair (toasted)
- Thread starter Eldorado828
- Start date
I appreciate that @Ranch55 , I walked away from it shortly after it petered out but I'll come back to it this evening. The electrolytic was replaced when I did the pills but the diode I didn't touch. I can see a bad cap because I've had bad caps before but the diode I've never had one fail without a cause so that will be a new one for me.
I'll report back when I dig into it this evening.
Well I spent some time on it this evening and got nowhere. I checked c15, c18, c19 and d4 but went ahead and changed c18 because capacitance was a bit off. As soon as I put power to the amp the fuse popped again. WTH! Now it's back to the schematic to study up.
I appreciate your help!
More to come.
I appreciate your help!
More to come.
Either a RF transistor or a protection diode. The power button only shuts down the low-power circuits. Juice to the high-current circuits is always connected. The RF transistors get switched on by the base voltage from the relay.
73
73
I'll be back to it some time this evening some time. After replacing parts and following the schemo last night now the reality is that there's a toasted pill or pills, even though there's no other evidence aside from popping fuses. Geez.....
I've got another set of pills but I'm not sure about dropping them in or just sending it down the line....
I've got another set of pills but I'm not sure about dropping them in or just sending it down the line....
Well, if the amplifier is popping fuses as soon as you connect it to voltage power after replacing the fuse, then it is just a simple matter of determining which component or components is shorted directly from the voltage supply directly to ground.....
Several components are connected directly from the voltage supply to ground.....
Just keep looking, and the power transistors are one of the components. An internal short in at least one of them will cause that alright......
Several components are connected directly from the voltage supply to ground.....
Just keep looking, and the power transistors are one of the components. An internal short in at least one of them will cause that alright......
too long didnt watch: he basically adds a small current source to the tips of the probes on a DMM (set to mV) to make a really effective short circuit tracer. Skip to 15:00 for demonstration.
Eldorado828,
I feel your frustration!
Yes, you may have a shorted component that goes from the B+ line to ground, but because this is a Texas Star amp there is another very common possibility.
you may have a component lead on the underside of the board that is too long, or one of those washers that go underneath the board may be shorting the positive trace to ground.
since you know that its before the power switch, that narrows the areas you need to look at.
you're going to have to take the whole amp apart again and remove the PC board and look everything over.
get a small file or other similar implement and file down any component leads on the bottom of the board that look suspect (too long).
also, either glue or solder those washers right to the bottom of the PC board so they won't move around on you when putting the board back in.
its a pain in the butt but welcome to working on Texas Star amps!
hope this helps.
LC
I feel your frustration!
Yes, you may have a shorted component that goes from the B+ line to ground, but because this is a Texas Star amp there is another very common possibility.
you may have a component lead on the underside of the board that is too long, or one of those washers that go underneath the board may be shorting the positive trace to ground.
since you know that its before the power switch, that narrows the areas you need to look at.
you're going to have to take the whole amp apart again and remove the PC board and look everything over.
get a small file or other similar implement and file down any component leads on the bottom of the board that look suspect (too long).
also, either glue or solder those washers right to the bottom of the PC board so they won't move around on you when putting the board back in.
its a pain in the butt but welcome to working on Texas Star amps!
hope this helps.
LC
I'll bet he's right. We got in the habit of sliding a layer of fish paper under a Texas Star circuit board when this would happen. The gap between the solder side of the circuit board and the heat sink surface is quite thin. Component leads are clipped dead-flush with the board surface when it's built, just for this reason. A meter on continuity setting gets hooked to the power leads in place of the power supply. Odds are it will show a really low resistance. Loosen the four screws on the circuit board's corners one at a time, and (gently) lift that corner of the circuit board upwards just a bit. If this breaks the continuity you know where to look for a clipped-off lead wire that's sticking out too far.
Maybe. Worth a try.
73
Maybe. Worth a try.
73
I just repaired a 350HDV, that a shop tried to repair, around the keying circuit. I pulled the board and found a bottom side solder blob, causing intermittent keying of the amp.
I don't think I'm done though. I suspect there may be self oscillation that was the root cause of the first repair.
SL
Great tool, Mike that works for Texas Star many years ago tried to get them to use a insulation sheet under the PC boards and it was no...
73
Jeff
Yeah, I have got to the point where any time I do work on any Texas Star amplifier, I always pull the board/boards out for inspection underneath.
And when I reinstall the boards, I put a thin layer of Teflon sheet under the board just to prevent that very issue......
Good call.....
And when I reinstall the boards, I put a thin layer of Teflon sheet under the board just to prevent that very issue......
Good call.....
Great call,this often happens when someone tries to replace parts of a damaged amp and will not remove the board to do it properly....
73
Jeff