AC15 noise

[bazmusicman]

Hi Charlie and Everyone,

The last two days when I switched my AC15 on from cold it makes a crackling and popping type noise until it warms up. Up until then it has never been any problem at all.

It is the Korg 2003 Made in England model with the Roger Allcock EF86 Unit which I fitted along with a new set of Watford matched valves about a year ago.

I suspect maybe dirty valve seat contacts etc. but before I pull it all apart I thought I would ask if anybody else could throw some light onto it.

Best regards,
Baz.

[bazmusicman]

P.S. to my previous post.

I have recently been trying outputting from the Amp. to a PA System. I have just realised that I used the 'speaker out' socket from the Amp. to the PA and think this might be what has caused the problem. I realised that as there is no 'line out' socket I should have miked up the Amp.

I have disconnected everything from the Amp. to aliminate eveything else. I have just switched it on again today and only got a very faint crackle. Any comments would be welcome.

Best regards,
Baz.

[Len]

Hi Baz

This is not a connection I use myself but I understand that you can use the 'speaker out' socket to feed into a Direct Injection (DI) Box, then into a mixer which then feeds into the PA. I think you are right about the set up you tried earlier. You really must use a DI box when going to a mixer. You will then preserve the sound of the preamp on your amp and have a good strong signal coming from the 'speaker out' connection. The DI converts the signal to a "balanced signal" suitable for feeding into the mixer.

I prefer to mike up or if the sound person insists on feeding into the board via a DI then I put the guitar signal through my pod (Roland/Boss GT-3) set to 'Line Out'. With my pod, my preferred method is to feed the output from the pod straight into the power input on my amp using a 'power out' setting on the pod. Then I am using the preamp (several type choices) of the pod rather than the amp preamp. Then I get a good strong signal by a different method. I do not have a 'speaker out' on any of my amps.

The latter part might sound a complicated explanation, however represents some alternatives that you may use depending on what equipment you have. Others may be able to confirm whether I am correct about the first part (using the 'speaker out' socket ), but it may be an alternative to miking up.

I hope this might help.

Regards
Len

[Charlie Hall]

Hi Baz,
Unless the EF86 channel volume control was at zero, I would suspect the EF86 valve. Whilst this noise is occuring, if turning the EF86 channel volume up and down changes the noise, then you can be sure that the noise is coming from that channel.
Regards,
Charlie

[bazmusicman]

Hi Len/Charlie,

Sorry I'm a bit slow replying, but I have given the EF86 a wiggle in its socket and it seems o.k. I have been hanging on to see if it plays up again.

I haven't checked the other valves. The output valves and rectifier valve were purchased new about a year ago from Watford Valves.
Charlie, I read on another thread that you said that the modern EF86 didn't seem to last very long so would it be wise to fit new preamp valves and EF86?

Also could the preamp valves cause the noise I was getting or would that mainly be down to the EF86 and output valves? I couldn't try the volume on the EF86 channel as you suggested because it had stopped making a noise!

Len, thank you for your tips on connections etc.

Best regards,
Baz.

[Charlie Hall]

Hi Baz,
I guess you will have to wait for the noise to appear again before you can track down the cause. Any valve can become noisy (it doesn't have to have anything to do with the pin connections although that can be a cause as well) but the EF86 is more likely to play up before any other preamp valves. I have had several Russian made EF86 valves go noisy and sometimes lose gain as well (meaning you have to turn the EF86 channel volume higher than before) in a quite sort space of time. You don't have to replace any other preamp valves if you know which is the cause of a problem. With output valves, you need to replace as a matched pair (for your amp) or set (in amps that have more than 2).
If an amp is noisy with all controls at zero, and turning any controls don't change the noise, the chances are that the driver valve (phase inverter or splitter, usually the ECC83/12AX7 nearest to the output valves) or one or more output valves are the problem.
Finding a new old stock EF86 is one solution for longer life if you know what to look for, and they might sound better too, but they can tend to be very expensive.
Regards,
Charlie

[bazmusicman]

Hi Charlie,

Thank you for your reply. I think the EF86 might be faulty because it doesn't seem to have the same volume as before. I think I may as well replace it to be sure. What make do you suggest or should I talk to Watford Valves?

Best regards,
Baz.

[Charlie Hall]

Hi Baz,
I would suggest contacting Watford valves for advice, by phone if possible. I have always found Derek Rocco to be very helpful. It is difficult to advise what to buy because the best options are likely to be continually changing.
I would suggest that you ask what alternatives there are to Russian made EF86s, if any.
Regards,
Charlie

[bazmusicman]

Hi Charlie,

Thank you, I'll pull the valve out of the amp. and have a look what make it is, then give Watford Valves a ring tomorrow and let you know how I get on.

Best regards,
Baz.

[Charlie Hall]

Hi Baz,
The brand might not tell you what you need to know as many valves are re-branded. Russian EF86s have a different look to old ones. There used to be a wire mesh that more or less surrounded everything inside the glass. The Russian ones do not have a mesh but instead have a stamped shiny looking plate with a distinctive pattern that tries to look like a mesh. Once you have seen one and identified it you will be fairly sure in knowing where any similar one came from originally.
Regards,
Charlie

[garyallen]

Hi Baz..I have a borrowed amp the same as yours but i get the same noise you describe when it warms up..Does the noise go away on your amp when it heats up....gary

[bazmusicman]

Hi Charlie,

I spoke to Derek today at Watford Valves and the EF86 valve that he recomended was the Philips/Dario made in holland. So I have ordered one of those along with a set of preamp valves. I'll let you know how things progress.

Hi Gary,

Yes the noise on my amp stopped when it warmed up. It only done it about three times on startup, but I felt it was down on power, hence the new valves. They may not make any difference but at least I'll have some spares.

Best regards,
Baz.

[Charlie Hall]

Hi Baz,
I'm sure Derek will see you right. When EF86s go noisy they tend to stay that way, they don't usually quieten down after the amp has been on some time.
Regards,
Charlie

[bazmusicman]

Hi Charlie and everyone,

I changed the EF86 valve for the new one from Watford Valves but it didn't make any difference.
I didn't have time to take the amp to bits to change the other valves before I done a gig on saturday, and guess what? yep' the EF86 channel decided to go 'belly up' halfway through the gig!! I relocated to the normal channel for the rest of the evening which worked fine.

I emailed Roger Allcock and he said send the EF86 unit back and he would check/repair it free of charge.

When I had the chassis out I ran the amp ( with the speaker connected of cause! ) and Noticed the the first preamp valve ( which supplies the power connection for the EF86 Unit ) was running brighter/hotter than the other four valves. I replaced the whole set with the new ones from Watford Valves and they all run perfect.

Now how about this for excellent service by Roger and the post office.

I posted the unit with the last post on monday, Roger emailed me on tuesday and said he had recieved and repaired it ( a capacitor had failed causing a resistor to burn out ) and posted it back that afternoon. I recieved it wednesday lunchtime and resoldered it into the main board
and re-assembled the amp by 2.30pm and it was back to its former glory.

Now that deserves a big round of applause and thank you especially to Roger but not forgetting the Post Office for a 'first class' service.

Best regards,
Baz.

[Charlie Hall]

Hi Baz,
I hadn't considered that a faulty cap could have been the cause.
Glad you got it sorted, and good to know that Roger was well enough to work for you.
Regards,
Charlie

[Deleted]

HI BAZ & everyone,,,
PHILLIPS-DARIO?? holland ,I did not know that these valves were still available...

CHEERS ......barry..