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What does a bad power supply filter sound like?
Group,
I need an expert opinion on a Swan power supply. I have a 350c and 117xc. The transceiver has problems I will deal with later. For now, without any test gear, I want to rule out power supply because I'm putting it on ebay. The rig I'll have to sell seperately to a swan tech. on a reflector like this. The radio has a consistant loud "CRACKLE" noise on receive. ( there is No 60 cycle hum.) All bands, all volume levels, all rf gain levels, with/without antenna. crackle noise is steady. Without need to warm up. This is my 4th swan and I always thought a bad filter cap would hum, not crackle. And I've had shorted caps blow fuses. On transmit I get full power out without noise on seperate monitor.(when it decides to oscillate). Quiet carrier on CW an clean modulation on ssb. The rf detector works, because I can hear stations through the crackle when it decides to ocillate. The rig also has an intermittant oscillator problem. RX and tx blink on and off as I turn vfo dial or turn rf gain knob or key relay over and over. There are no vfo "hot spots' where the oscillator quits or starts. It is random and changes spots in dial travel on each try. Same thing on rf gain. I'm not going to try to fix the rig, but is worth restoring to a collecter due to near museum cosmetics. All that later. I just want to know if power supply is probably ok. No other rigs to put supply on and no scope to look at wave forms. I need an educated oppinion for now. Does a bad power supply CRACKLE? Thanks for reading. ac6ts Escondido, ca. |
John Williams wrote: Group, I need an expert opinion on a Swan power supply. I have a 350c and 117xc. The transceiver has problems I will deal with later. For now, without any test gear, I want to rule out power supply because I'm putting it on ebay. The rig I'll have to sell seperately to a swan tech. on a reflector like this. The radio has a consistant loud "CRACKLE" noise on receive. ( there is No 60 cycle hum.) All bands, all volume levels, all rf gain levels, with/without antenna. crackle noise is steady. Without need to warm up. This is my 4th swan and I always thought a bad filter cap would hum, not crackle. And I've had shorted caps blow fuses. On transmit I get full power out without noise on seperate monitor.(when it decides to oscillate). Quiet carrier on CW an clean modulation on ssb. The rf detector works, because I can hear stations through the crackle when it decides to ocillate. The rig also has an intermittant oscillator problem. RX and tx blink on and off as I turn vfo dial or turn rf gain knob or key relay over and over. There are no vfo "hot spots' where the oscillator quits or starts. It is random and changes spots in dial travel on each try. Same thing on rf gain. I'm not going to try to fix the rig, but is worth restoring to a collecter due to near museum cosmetics. All that later. I just want to know if power supply is probably ok. No other rigs to put supply on and no scope to look at wave forms. I need an educated oppinion for now. Does a bad power supply CRACKLE? Thanks for reading. ac6ts Escondido, ca. I believe your power supply is OK. sounds like an output transformer or output tube to me. Unplug the output tube and see if it stops the noise.If it doesn`t stop the noise ,it would be transformer shorting..If the volume control changes the noise then it could be a shorted IF can..NO 1 RULE, make sure all tubes are good first...good luck W4PQW |
I always thought a bad filter cap would hum,
Correct. A bad filter capacitor typically creates a loud hum that does not change when you move the volume control. Phil Nelson |
Yes, a bad capacitor can cause this problem. So can a lot of other
things. A capacitor which is arcing internally (dielectric breaking down) sounds just like you described. Chances are it'll be a bypass or coupling cap. Other things to try are; wiggling tubes (corroded sockets), look for cracked resistors, cold solder joints. Good luck! Steve p.s.-a bad filter cap usually causes hum which you'd hear in the speaker, and possibly on your transmit audio....filter caps can also arc internally, but in my experience, thats not as common |
Just sell the darned thing "as-is". I've sold many Swans on ebay.....it
doesn't make much difference if it is a "tech special" and needs work or is of average, working condition. They get about the same price. Just be honest on the description......if it is complete and needs a little work, there are many guys looking to pay good money if it is clean and just needs some simple bench work to get it going right. "John Williams" wrote in message news:1106574247.460460@smirk... Group, I need an expert opinion on a Swan power supply. I have a 350c and 117xc. The transceiver has problems I will deal with later. For now, without any test gear, I want to rule out power supply because I'm putting it on ebay. The rig I'll have to sell seperately to a swan tech. on a reflector like this. The radio has a consistant loud "CRACKLE" noise on receive. ( there is No 60 cycle hum.) All bands, all volume levels, all rf gain levels, with/without antenna. crackle noise is steady. Without need to warm up. This is my 4th swan and I always thought a bad filter cap would hum, not crackle. And I've had shorted caps blow fuses. On transmit I get full power out without noise on seperate monitor.(when it decides to oscillate). Quiet carrier on CW an clean modulation on ssb. The rf detector works, because I can hear stations through the crackle when it decides to ocillate. The rig also has an intermittant oscillator problem. RX and tx blink on and off as I turn vfo dial or turn rf gain knob or key relay over and over. There are no vfo "hot spots' where the oscillator quits or starts. It is random and changes spots in dial travel on each try. Same thing on rf gain. I'm not going to try to fix the rig, but is worth restoring to a collecter due to near museum cosmetics. All that later. I just want to know if power supply is probably ok. No other rigs to put supply on and no scope to look at wave forms. I need an educated oppinion for now. Does a bad power supply CRACKLE? Thanks for reading. ac6ts Escondido, ca. |
If it doesn't need to be warmed up to hear the crackle, does it have solid
state rectifiers? Will the noise come thru with the volume turned all the way down? -- 73 Hank WD5JFR "John Williams" wrote in message news:1106574247.460460@smirk... Group, I need an expert opinion on a Swan power supply. I have a 350c and 117xc. The transceiver has problems I will deal with later. For now, without any test gear, I want to rule out power supply because I'm putting it on ebay. The rig I'll have to sell seperately to a swan tech. on a reflector like this. The radio has a consistant loud "CRACKLE" noise on receive. ( there is No 60 cycle hum.) All bands, all volume levels, all rf gain levels, with/without antenna. crackle noise is steady. Without need to warm up. This is my 4th swan and I always thought a bad filter cap would hum, not crackle. And I've had shorted caps blow fuses. On transmit I get full power out without noise on seperate monitor.(when it decides to oscillate). Quiet carrier on CW an clean modulation on ssb. The rf detector works, because I can hear stations through the crackle when it decides to ocillate. The rig also has an intermittant oscillator problem. RX and tx blink on and off as I turn vfo dial or turn rf gain knob or key relay over and over. There are no vfo "hot spots' where the oscillator quits or starts. It is random and changes spots in dial travel on each try. Same thing on rf gain. I'm not going to try to fix the rig, but is worth restoring to a collecter due to near museum cosmetics. All that later. I just want to know if power supply is probably ok. No other rigs to put supply on and no scope to look at wave forms. I need an educated oppinion for now. Does a bad power supply CRACKLE? Thanks for reading. ac6ts Escondido, ca. |
For what it's worth, all of the HV caps in my Swan 350/117 needed
replacing. They big ones for the transmitter were oozing gorp. Yours caps are probably from the same era, and should be replaced too. Henry Kolesnik wrote: If it doesn't need to be warmed up to hear the crackle, does it have solid state rectifiers? Will the noise come thru with the volume turned all the way down? The 117 powersupply is solidstate, and so the crackling is very likely the filter caps preparing to go blorp all over the place. -Chuck |
John Williams wrote:
Group, I need an expert opinion on a Swan power supply. I have a 350c and 117xc. The transceiver has problems I will deal with later. For now, without any test gear, I want to rule out power supply because I'm putting it on ebay. The rig I'll have to sell seperately to a swan tech. on a reflector like this. The radio has a consistant loud "CRACKLE" noise on receive. ( there is No 60 cycle hum.) All bands, all volume levels, all rf gain levels, with/without antenna. crackle noise is steady. Without need to warm up. If the volume control varied it, I would have suggested bad caps in the IF transformers. See my page http://www.geocities.com/wa2ise/radios/repair.htm about half way down. I'm not familar with this radio, it's a tube set, yes? If so, try pulling the audio output tube. Still crackle? Put the tube back and pull the audio driver (probably a triode like a 6AV6). If you can get silence doing this, then the problem exists somewhere closer to the front end. |
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