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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Mon Feb 26, 2018 2:34 pm
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flygandejacob wrote:
stratele52 wrote:
Yes and I answer


Sorry, I'm not following you completely?



Read my answer Posted: 25 Feb 2018 16:07


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Mon Feb 26, 2018 3:42 pm
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"The buzzing noise is audible even without the speaker being plugged in"

Again, don't power up your amp without a speaker or a dummy load connected.

Chokes and transformers can make sounds when a signal passes through them -- it's called "magnetostriction". They don't cause the sound; they're just crudely reproducing the signal passing through them.

With the chassis out of the cab and no speaker connected you're probably hearing the choke, but that's most likely an artifact of the noise problem, not the source of the noise.

And it's possible the choke only "sings" when the speaker is disconnected, because the whole circuit is under stress.
--------------
This stuff is a bit over my head. The real amp techs on this thread are much more qualified to help you.

I only butted in because it seemed to me that they may have been missing the fact that you were hearing the sound inside the chassis while apparently having the speaker disconnected.
------------
First thing to do is what Stratele52 said -- actually test the caps. Or replace them if you don't have the proper multimeter to test them.


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Mon Feb 26, 2018 11:58 pm
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stratele52 wrote:
JJ made good tubes, I will trust their caps

Did you check bias circuit filter caps too , If filtering is wrong you will have buzz / hum at the speaker

How much AC volts ( yes AC not DC ) do you read at each main power supply filter caps
C78, C80, C83,C84

Do same reading at Bias circuit filter cap

Report

Sorry @stratele52, I will investigate this and get back with my findings.

strayedstrater wrote:
Again, don't power up your amp without a speaker or a dummy load connected.

This has been noted. I wrongly thought not having the the speaker hooked up meant that no current would pass through the circuit. Will not do this again.


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Tue Feb 27, 2018 2:14 am
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flygandejacob wrote:
I wrongly thought not having the the speaker hooked up meant that no current would pass through the circuit. Will not do this again.



You are right , no current can pass.
That is why you can damage output transformer ; it need to discharge current in a load , speaker or resistor


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Thu Mar 01, 2018 9:55 am
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stratele52 wrote:
How much AC volts ( yes AC not DC ) do you read at each main power supply filter caps
C78, C80, C83,C84

Do same reading at Bias circuit filter cap
Report


So I measured at the above mentioned points. Was a bit unsure which cap that was the bias circuit filter cap so I measured C87 and C86 that where the closest to the bias adjuster. Please let me know if this was wrong.

Here are the data:
C78 - DC: 427.0 V AC: 3.300 V
C80 - DC: 427.6 V AC: 0.070 V
C83 - DC: 322.2 V AC: 0.000 V
C84 - DC: 285.0 V AC: 0.000 V
C86 - DC: 58.00 V AC: 0.076 V
C87 - DC: 45.00 V AC: 0.000 V

Will soon try to desolder the caps on the power supply PCB, measure them and get back with my findings.


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Thu Mar 01, 2018 2:29 pm
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I don't like what you read at C78 ; 3 volts AC
It could be good or bad , I' not sure
It is lot of AC voltage , but it is the first cap after the rectifier diode

C86,C87 are the bias filter caps

All other voltages look good.
Just put another good know 47 mfd in parallel with C78. No need to remove the "old one". Check AC
If same reading 3 AC volts, cap C78 is good . If 0 volts, C78 is bad, leave the new cap there, no need to remove C78
Noise should be gone.


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Thu Mar 01, 2018 7:24 pm
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Actually, 3 VAC is pretty good on a first stage filter cap. Adding another cap across C78, as stratele52 suggested, could help reduce that AC voltage, which could reduce the noise.

The noise could be due to the Illinois caps that fender uses (maybe even mechanical vibration), and changing all of the power supply caps to better caps, such as F&T might be the best option.

Is there anything such as silicone, or hot-melt glue, holding the power supply caps in place? If not, some hot melt glue in the right places might help. If you change the power supply caps, be sure to use hot melt glue to hold them down and prevent vibrations.

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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Fri Mar 02, 2018 3:15 am
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Shimmilou you may be right about 3 volt for the first stage of filter cap , I can't remember.
Power supply look good , issue is elsewhere :(

I use home silicone to fix amp capacitor ; this give me trouble , it may conduct


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Fri Mar 02, 2018 4:04 am
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My HRDlx had 7 VAC on the first stage filter cap, producing a little noise. I added another cap to that first stage and brought it down to 3 VAC. Of course I changed all the filter caps to F&T at the same time, so that helped also. With the new caps and some prudent lead dressing, my HRDlx is as quiet as the proverbial church mouse.

I just wonder if it is a mechanical vibration in the power supply. New caps still might be a good idea.

And yes, I use hot melt glue, I don’t like silicone either.

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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Fri Mar 02, 2018 8:54 am
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shimmilou wrote:
Is there anything such as silicone, or hot-melt glue, holding the power supply caps in place?

There is some glue or silicone holding the caps in place.

So, it seems like a switch of the caps is the next move. Just to make it clear, which caps are classified as the "filter caps"? Just so I can order the right ones.

Seems like https://www.hificollective.co.uk/ is selling F&T caps here in Europe, which is good. If anyone else knows any other store based in Europe selling these caps, please let me know.


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Fri Mar 02, 2018 5:25 pm
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The filter caps are the electrolytic caps.

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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Sat Mar 03, 2018 2:01 am
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shimmilou wrote:
The filter caps are the electrolytic caps.

Alright, thank you shimmilou.

So I started browsing the internet to locate all the caps needed. To clarify I searched for all the electrolytic caps in the schematic posted by me earlier (see below). Are these the right ones? Anything missing?

I could not find any radial caps from F&T. Do they sell these? Anyhow, I replaced these with Nichicon caps below, anyone know if these are any good? The brand "Elna" also hade the caps, on the same website.

Radial:
10 uF 50V (C90, C91) (http://bit.ly/2H200t5)
22 uF 450V (C82, C83, C84) (http://bit.ly/2oLkRJZ)
100 uF 100V (C85, C86) (http://bit.ly/2oMz0GO)
470 uF 50V (C88, C89) (http://bit.ly/2FOnlzj)

Axial:
22 uF 500V (C80 ) (http://bit.ly/2FlHYFm)
47 uF 500V (C78) (http://bit.ly/2FlHYFm)
100 uF 100V (C87) (http://bit.ly/2FlHYFm)

Thank you evereyone for all the help so far!


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Sat Mar 03, 2018 3:38 am
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Nichicon are not the best one , many amp manufacturer use them.

Yes most of the best caps are axial or radial with bigger connector like JJ' caps


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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Sat Mar 03, 2018 2:27 pm
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flygandejacob, looks like your list is complete, that's all of them. I don't see any radial F&T, other than multi-section caps, so your choice is limited there.

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Post subject: Re: Hum/Buzz from Supersonic 22 power supply
Posted: Mon Mar 05, 2018 2:47 pm
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Okey, so I've been going up and down this site (https://www.hificollective.co.uk/) trying to find the best replacements possible. Since most of the radials are either Nichicons or Elnas I Googled to see what the internet had to say about the two brands. Seemed like Nichicon was the winner (most of the time). However, some of the caps I've found on the site are 85C and not 105C. Is this an issue? What's in the amp right now?


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