Valve amp has started to hiss and pop

I started to hear popping/ticking noises coming from my speakers today. The culprit appears to be my prima luna prologue 5 power amp. I swapped all the valves for different ones and it is still doing it.

Even with the preamp off there is a hiss if you put your head by the speaker and the occasional loud tick on both channels.

Any ideas?

Thanks
Mark

 

hiss/pop

Hi Mark

What speakers are you using..? Is the sound from both speakers or only through one..? Did you try swapping the speaker connections etc..?

I recently had the same problem from one of my Quad ESL 57 speakers, problem was a EF86 valve in one of my original Quad II valve power amps had went/or was going, changed the valve and it's perfect again.



Best wishes - macvisual
my retro hi-fi site > http://macvisual.webs.com/index.htm

 

Hi macvisual,

hiss from both speakers and the sound is still there after I swapped all the valves for different ones.

I think I will have to send it for repair.

Can anyone suggest someone in the midlands?

 

you have either dirty vavle base or pins ..cleaning both will eradicate the rustling pops and clicks

 

Thanks zanash.

Whats the best way of cleaning the valves bases?

 

Just took the valves out and hoovered the top of the bases.

Clicks and hiss have gone! Thanks Zanash, have a good christmas.

 

great result .......

I've used allsorts to clean the pins ...consistently good is duraglit wadding brass cleaner ...thought you need to make absolutely certain all the rsidue is removed . This can be nearly as tricky as the original task , but at east the stuff wipes off rather than remaining stick to the pins ....

sockets are a different matter ...using valves with cleaned pins normally is sufficient ..but I've used contact cleaners when stubbern stains remain .

have a good one too !

 

Just make certain you don't have a snake in the chassis.

 

it sounds like a screen grid resistor.

i've had this happen with valve amps previously. it's an easy fix if you have any skills with a soldering iron and an understanding of circuits. failing that it is a trip to the mendors...

 

It fixed it for a few hours but started again last night.

blake audio - I can use a soldering iron but dont have a circuit diagram for the amp. Do you mean the resistors on back of the tube sockets?

 

without a circuit diagram i might be cautious to recommend fixing it yourself, but you could check the values are in spec on the resistors. that may give you an indication.

however, yes it should be the resistors coming off the tube sockets.

apparently the introduction of various eu directives have restricted the materials that can be used in consumer electronics.

the replacement materials are supposedly less stable and can deteriorate from spec. i've had two valve amps that have suffered from this problem. the manufacturer corrected the problem for both and the amps sound perfect again. the manufacturer said he has switched suppliers having found one whose new compliant resistors are more reliable without detriment to sound quality.

 

Hi

I would check the grid resistors, rectifier valve (if it uses one) and any other common part to BOTH channels if the clicks come out of both channels at the same time and are the same level.

The cleaning thing probably did nothing, it was the fact that it was off for a long period of time while cleaning, maybe gave some of the components time to 'heal' before going back into HOT action.

Check the solder joints below the valve bases also.