Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 14th August 2007, 05:42 PM   #1
jives11 is offline jives11  Europe
diyAudio Member
 
jives11's Avatar
 
Join Date: Mar 2004
Location: Hampshire
Default popping noise through 1 channel on Radford STA15

Hi,

I have a Radford STA15 Mk III. I bought it second hand about 18 years ago. It had been heavily used and was very noisy. Over the following years I replaced all the resistors (the originals were starting to crumble) The wiring and the caps. Most caps were replaced with either Polycarbs (coupling) or Polyprop Solens (PSU decoupling)
. The result was the amp has been virtually silent in terms of background noise and has given me 15+ years of pleasure. A slight mechanical hum up close is the only noise audible.

Today I noticed random popping noises through the left channel. Not at full volume and not a crackling noise as I've had before with bad joints. It seemed to increase in frequency with temperature, but was essentially random in nature. The pops sounded like little electro drum beats. (no jokes about modern music please )

Anyone know what this might be ? I'll take a look at the board. I think there are a few electrolytics which are about 15 years old in the cathode bypass. The tubes might need replacing, I just wondered if popping is symptomatic of a specific issue ?


Thanks
  Reply With Quote
Old 14th August 2007, 06:44 PM   #2
m6tt is offline m6tt  United States
diyAudio Member
 
Join Date: Aug 2007
I had the same problem with a monstrosity of a hammond organ amp which was transplanted into a combo I made...essentially I went through and redid some of the solders on the tube sockets that looked sketchy...I would bet that some of that ancient solder in there has been slowly heated and cooled over and over again for a long time. I would retouch it and then try again, but for goodness sake make sure no accidental shorts were created resoldering the tubes (especially with 7 pin and B9A tiny sockets). Also, try cleaning around all the sockets and b+ wiring with an exacto knife or pipe cleaner or other tool, to prevent arcing. Are any of the sockets charred? Tubes sometimes pop as well, so swap the right channel tubes with the left channel (assuming they are the same) and see if the popping stays or moves. Worst comes to worse it could be an output transformer but I doubt it.
  Reply With Quote
Old 14th August 2007, 08:31 PM   #3
jives11 is offline jives11  Europe
diyAudio Member
 
jives11's Avatar
 
Join Date: Mar 2004
Location: Hampshire
Quote:
Originally posted by m6tt
I had the same problem with a monstrosity of a hammond organ amp which was transplanted into a combo I made...essentially I went through and redid some of the solders on the tube sockets that looked sketchy...I would bet that some of that ancient solder in there has been slowly heated and cooled over and over again for a long time. I would retouch it and then try again, but for goodness sake make sure no accidental shorts were created resoldering the tubes (especially with 7 pin and B9A tiny sockets). Also, try cleaning around all the sockets and b+ wiring with an exacto knife or pipe cleaner or other tool, to prevent arcing. Are any of the sockets charred? Tubes sometimes pop as well, so swap the right channel tubes with the left channel (assuming they are the same) and see if the popping stays or moves. Worst comes to worse it could be an output transformer but I doubt it.
Thanks m6tt - so very good advice. I'll start with valve swapping, then examine the sockets. I'm sure your right. I guess the PSU is fine as it would affect both channels.

When you clean the sockets with a pipe cleaner do you use any solvents , alcohol or switch cleaner ?
  Reply With Quote
Old 15th August 2007, 06:13 PM   #4
m6tt is offline m6tt  United States
diyAudio Member
 
Join Date: Aug 2007
if they're ceramic sockets you could probably use some solvents, but I am not sure what bakelite or other plastics might require in terms of cleaners which won't dissolve them. If they are ceramic, you could carefully use acetone on a q-tip, but be very careful and for goodness sake let the thing dry out really good, acetone is very flammable. That stuff will eat most plastics, so keep it away from insulation and capacitors etc. I just used an exacto knife and carefully scraped dirt and debris off the sockets while trying not to scratch them. Generally though popping is often a loose contact being wobbled some how...on my amp I had an input RCA that was wobbly into the first tube. It sounded like someone was writing a thesis on a rusty typewriter in the next room. If it's a tube the swap will put the popping on the other channel, and if it's arcing, cleaning may help (you will see charred sections of socket in this case), or you may have to replace the socket. I'd still keep my money on a loose connection somewhere heating up and resonating open and closed really fast.
  Reply With Quote
Old 20th August 2007, 02:39 AM   #5
monk2 is offline monk2  United States
diyAudio Member
 
Join Date: Mar 2006
Location: Ann Arbor, Michigan
Popping is a symptom of a gassy tube. Swapping the tubes is tedious, but
will help you identify the culprit. A tube tester would be helpful.

dpn
  Reply With Quote
Old 28th September 2007, 07:44 PM   #6
jives11 is offline jives11  Europe
diyAudio Member
 
jives11's Avatar
 
Join Date: Mar 2004
Location: Hampshire
A big thank you to one and all.

I followed your advice and swapped valves until I traced the problem (a bad ECF82 on one channel). I' now back to total silence with just a hint of analog dither
.
....(50Hz if I hold my ear to the cone)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
popping and static noise in an Altec 1592A lassoharp Solid State 7 14th March 2009 02:25 AM
Amp causing popping noise? guitarguy12387 Car Audio 7 15th April 2008 01:58 AM
Popping Noise = Clipping ? liggs17 Tubes / Valves 5 28th November 2006 07:16 PM
NAD 2400 popping noise Sarge Solid State 3 8th May 2006 12:38 PM
Question about popping Noise Derrick Tubes / Valves 5 27th February 2004 10:34 PM


New To Site? Need Help?

All times are GMT. The time now is 12:54 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2