Re:preamp sputtering noise

Tualek53 · 4th February 2006, 03:50 AM

Hi there ,

Bought a valves preamp it consist of two 12ax7 and two 12au7 with diodes retifier of Ebay .

Test it it has sputtering noise on one channel with all tubes pull out or plug on

it get louder as the volume turn up

Wonder where to start could it be a short circuit at the pot

or ....??need help

cheers

sbrads · 4th February 2006, 09:17 AM

If it's new then it's most likely a poor solder joint. Just have a good look for nice joints that have flowed, i.e. the components were 'wet' with the solder when it was molten and have a shape that looks like it was once wet with a meniscus.

If you don't get anywhere with just looking, try tapping components with a plastic biro to see if the noise changes. I always wear thin gloves when I do such things >100volts.

Tualek53 · 4th February 2006, 09:30 AM

Hi sbrads

It a old preamp built by Sound Audio Limited ..

Allergro Tube Line amplifier Model -18.
I
t has six 1000uf 250volts capacitor which four of them are bulge look like they going to blown

would that be the case.

Cheers

sbrads · 4th February 2006, 04:01 PM

You've answered your own question. New caps throughout methinks.

poobah · 4th February 2006, 04:17 PM

Yup...

Tualek53 · 4th February 2006, 06:07 PM

Cheers

New capacitor on it way

4th February 2006, 03:50 AM	#1
Tualek53 diyAudio Member Join Date: Aug 2005	Re:preamp sputtering noise Hi there , Bought a valves preamp it consist of two 12ax7 and two 12au7 with diodes retifier of Ebay . Test it it has sputtering noise on one channel with all tubes pull out or plug on it get louder as the volume turn up Wonder where to start could it be a short circuit at the pot or ....??need help cheers

4th February 2006, 06:07 PM	#6
Tualek53 diyAudio Member Join Date: Aug 2005	Thanks you guys Cheers New capacitor on it way

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4th February 2006, 09:17 AM	#2
sbrads diyAudio Member Join Date: Jun 2005 Location: Kent, UK	If it's new then it's most likely a poor solder joint. Just have a good look for nice joints that have flowed, i.e. the components were 'wet' with the solder when it was molten and have a shape that looks like it was once wet with a meniscus. If you don't get anywhere with just looking, try tapping components with a plastic biro to see if the noise changes. I always wear thin gloves when I do such things >100volts.

4th February 2006, 09:30 AM	#3
Tualek53 diyAudio Member Join Date: Aug 2005	Hi sbrads It a old preamp built by Sound Audio Limited .. Allergro Tube Line amplifier Model -18. I t has six 1000uf 250volts capacitor which four of them are bulge look like they going to blown would that be the case. Cheers

4th February 2006, 04:01 PM	#4
sbrads diyAudio Member Join Date: Jun 2005 Location: Kent, UK	You've answered your own question. New caps throughout methinks.

4th February 2006, 04:17 PM	#5
poobah diyAudio Member Join Date: Nov 2005	Yup...

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