| Author |
Message |
    
Copake12516
New member
Username: Copake12516
Post Number: 4
Registered: 6-2006
| | Posted on Monday, July 10, 2006 - 11:09 am: | 
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Hi,
I have a solid state amp that is not driven hard at all, when it's used for more than about 3 minutes coversation the bridge rectifier blows. It's a 3510 and all operating conditions are optimum. I don't want to go higher than the 35 amps because I don't want to hurt the amp.
Any ideas?
Thanks,
Rich |
Chad
Advanced Member
Username: Chad
Post Number: 973
Registered: 11-2004
| | Posted on Monday, July 10, 2006 - 2:32 pm: |
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Throw us a bone man, what amp? What output devices, define "not driven hard"
Chad |
Copake12516
New member
Username: Copake12516
Post Number: 5
Registered: 6-2006
| | Posted on Tuesday, July 11, 2006 - 10:33 am: |
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Hi,
The amp is a Gray Base 400 solid state. I use 3 radios with it with meters between the radio and amp to check the wattage input to the amp. I've not put higher than 4-5watts into it on AM/FM and 10w on ssb. My swrs are very low across all bands. I am using an antron 99 and BWD-90 dipole. I hope this helps. I can find no information about this amp anywhere on the net.
Thanks
Rich |
Chad
Advanced Member
Username: Chad
Post Number: 977
Registered: 11-2004
| | Posted on Tuesday, July 11, 2006 - 11:37 am: |
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Do you know what uoutput finals it has and how many, What's the power output your are running?
Another thing to check is for chokes on the DC supply lines going off to the amp to snub back RF.
Chad |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1903
Registered: 9-2004
| | Posted on Tuesday, July 11, 2006 - 6:05 pm: |
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if it keeps blowing the bridge rectifiers, im going to guess that he should find out what AC voltage is supposed to be coming out of the secondary of his transformer, and then measure the voltage coming out of them and see if the transformer is still doing what its supposed to.
i think its a transformer issue.
chad, could a bad filter cap cause this?
matt |
Chad
Advanced Member
Username: Chad
Post Number: 978
Registered: 11-2004
| | Posted on Tuesday, July 11, 2006 - 7:04 pm: |
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Never seena bad filter cap tear up a 35A rectifier. BUT I've seen a bad rectifier tear up a few filter caps 
rectifiers fail from overload like shorted outputs, back EMF/RF, and lightning. I have seen them get torn up pretty bad from oscillations sneaking back up, that's why I was wondering if there were ferrites on the power supply leads coming out of it.
Chad |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 1904
Registered: 9-2004
| | Posted on Tuesday, July 11, 2006 - 10:17 pm: |
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cool, thanks.
and does a transformer tend to increase its output when it "goes" or does it usually not put out anything.
does that make sense?
im trying to learn what happens "usually" to transformers after they get old, are abused, or both.
matt |
Chad
Advanced Member
Username: Chad
Post Number: 981
Registered: 11-2004
| | Posted on Wednesday, July 12, 2006 - 8:56 am: |
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Most of the time the primary (110V side) will go open from overvoltage or large surges, other times overheating. BUT it is possible to be in such extreme conditions that the enamel will melt on the secondary side and short a few turns causing it to have increased voltage. BUT this also causes problems on the primary side because the whole assembly no longer likes to resonate at 60 cycles.
So in a nutshell..... they usually fail open and just quit. |
Tech237
Moderator
Username: Tech237
Post Number: 440
Registered: 4-2004
| | Posted on Wednesday, July 12, 2006 - 9:22 am: |
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Chad,
If the secondary has shorted turns then the output voltage will drop not rise. Vin:Vout = TURNS primary: TURNS secondary.
Also a transmformer cannot creat or loose energy so if you apply 5 watts at it's input the must be 5w at it;s outptu - including the heat generated.
Now if a turn or two on the primary were shouted then yes the output would be higher as the same voltage is applied to the input but across less turns, so you now have a higher ratio of secondary turns and therefore a higher output V.
Transmformers do not really "resonant" at 60 cycles. You can use the same transformer on 60 cylces mains or take it to Australia and use it on 50 cylces mains and it will work quite happily. Of course the voltage out will change but not due to the change in cycles of the mains but because Australia uses 240 VAC instead of the 110 VAC used here. |
Chad
Advanced Member
Username: Chad
Post Number: 982
Registered: 11-2004
| | Posted on Wednesday, July 12, 2006 - 5:00 pm: |
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Secondary voltage.... See what happens when I lack proper caffene in the morning.
As for resonance, they do very much. This is the reason for the push to PWM power supplies because as the freq rises the transformers become smaller. PWM amps still have transformers. Granted the difference between 50 and 60 cycles is not much but there is oodles of information out there about transformers becoming inefficient when the freq is changed by even 10 cycles. Some transformers even have different VA ratings for different line freqs. Note I said VA not watts
This is especially important with high voltage transformers. Which is irrelavent in this conversation on a solid state amp.
Chad |
Tech237
Moderator
Username: Tech237
Post Number: 441
Registered: 4-2004
| | Posted on Wednesday, July 12, 2006 - 5:59 pm: |
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Well I have not come acroos that but will take your word for it. Even I can learn new things form here - one of the reasons I love this forum. |
Chad
Advanced Member
Username: Chad
Post Number: 983
Registered: 11-2004
| | Posted on Wednesday, July 12, 2006 - 7:00 pm: |
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I did not believe it either but got my first taste of it from a bull-headed aussie
Some Gee-tar tube amps are biased on the ragged edge of insanity, when touring from country to country we can change voltage but not frequency. When changing frequency the bias needed to be adjusted on certain designs.
On transformers that are relatively low ratio such as with DC conversion in an RF amp it's really no big deal. On higher voltage designs it's a REALLY big deal. Many HV neon and industrial transformers will have voltage plots for different frequencies.
This occurs because transformers want matching, Be it line transformation, RF, or AF. Without proper impedance matching the resonance will become apparent, in some instances such as in power supplies impedance matching is moot and impossible.
The Bull Headed Aussie Finally beat it into me by declaring that a mains transformer is VERY reactive, and there's NO WAY a load or supply that reactive can pass a flat frequency response.
If I remember correctly Dynaco tube amps imported to different countries running at 50 CPS would live a rather short life, namely the Stereo 70 that had a rather under designed transformer from the get-go.
So in essence you are correct, a well designed transformer SHOULD be able to act as an efficient transformer without bad phase angle deviation in relatively low ratio situations. The HV ones will still be wanting the rated input frequency.
Chad |
Tech237
Moderator
Username: Tech237
Post Number: 442
Registered: 4-2004
| | Posted on Wednesday, July 12, 2006 - 7:33 pm: |
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Got to watch us Chad. We Aussies can be a bit bullheaded. Luckily my Floridian wife is slowing curing me of that. |
Chad
Advanced Member
Username: Chad
Post Number: 985
Registered: 11-2004
| | Posted on Wednesday, July 12, 2006 - 9:41 pm: |
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My first taste was touring with one. It's just the Australlian way of conveying one's point. After I got past the blatancy he and I became VERY close friends. We just spent about 3 days mad at each other Just different styles of communication, I could never tell when he was joking, everything was said with such a straight face. I broke the ice with a handheld voice recorder with a laugh track on it, anytime he'd joke around and keep a straight face I'd hit the button, he could not heep a straight face then. I also had a sample of a baby crying for his "famous" tirades too
Back OT.... Any word on the power output or quantity and type of output finals in that amp?
Chad |
