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Thread: 5E3 whistling noise until warmed up

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    5E3 whistling noise until warmed up

    Hi guys,

    I have a 5E3 clone that I built from a Mission kit a few years back. It's a good sounding amp, which has served me very well. I've used it mic'ed up at gigs for several years and it has been completely reliable. Somewhere along the line I added power scaling for small gigs, which has also been in there for a long time with no problems, except for a little residual hum which I couldn't filter out.

    The amp has started making strange noises -- difficult to describe, someone said it sounds like the noise you get when you stretch the neck of an inflated balloon and let the air out. If that rings any bells, it's actually a good description of the noise. Like a scratchy whistling sound that goes up and down in pitch.

    After a few minutes, when the amp is thoroughly warmed up, the noise goes away.

    I am not an expert in amp building. I have built a few, but mostly from kits, where the design/layout/troubleshooting expertise came from someone else. I don't have a scope or any advanced testing tools, just a multi-meter.

    I have chop-sticked throughout the amp without coming up with anything. In terms of layout, I have moved wires about with the chopsticks, in terms of components I have examined everything and tapped everything. I have replaced the preamp tubes with new TAD 12AX7s. (The amp has had a 12AX7 in V1 from the word go). I changed the power tubes a short while ago and the noise was there both before and after.

    So I wondered if anybody might have a clue where I would start to look for the cause of this -- perhaps there is an application of logic which can narrow the field?

    Any help appreciated.

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    Supporting Member The Dude's Avatar
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    Is the noise from the speaker or from the amp internals? From the description of the noise, it sounds like a cap with a popped top.

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    Quote Originally Posted by rdh006 View Post
    Hi guys,

    I have a 5E3 clone that I built from a Mission kit a few years back. It's a good sounding amp, which has served me very well. I've used it mic'ed up at gigs for several years and it has been completely reliable. Somewhere along the line I added power scaling for small gigs, which has also been in there for a long time with no problems, except for a little residual hum which I couldn't filter out.

    The amp has started making strange noises -- difficult to describe, someone said it sounds like the noise you get when you stretch the neck of an inflated balloon and let the air out. If that rings any bells, it's actually a good description of the noise. Like a scratchy whistling sound that goes up and down in pitch.

    After a few minutes, when the amp is thoroughly warmed up, the noise goes away.

    I am not an expert in amp building. I have built a few, but mostly from kits, where the design/layout/troubleshooting expertise came from someone else. I don't have a scope or any advanced testing tools, just a multi-meter.

    I have chop-sticked throughout the amp without coming up with anything. In terms of layout, I have moved wires about with the chopsticks, in terms of components I have examined everything and tapped everything. I have replaced the preamp tubes with new TAD 12AX7s. (The amp has had a 12AX7 in V1 from the word go). I changed the power tubes a short while ago and the noise was there both before and after.

    So I wondered if anybody might have a clue where I would start to look for the cause of this -- perhaps there is an application of logic which can narrow the field?

    Any help appreciated.
    I had a similar problem when flipping the standby switch to playing position with my 2204 clone. I was running JJ EL34's at the time and switched other EL34's in without help along with all preamp tubes.

    Also, I tried cleaning every damn pot, socket etc. before that and still the noise was there.

    It would start like this, but a lot less severe, barely audible, and would turn into that air balloon type of thing (or long tearing with pitch shifting) you mentioned until finally disappearing:

    https://www.youtube.com/watch?v=-CBJSzC88Lg

    I had some Mesa 6L6's laying around so I adjusted bias range and popped them in. To my surprise the noise stopped; I figured thicker pins did the job since tubes were a lot tighter in the sockets.

    I hope someone knows exactly what's the cause of the problem, but everybody I asked couldn't give me an exact answer. Everyone said dirty pins/sockets/jacks etc.

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    Quote Originally Posted by The Dude View Post
    Is the noise from the speaker or from the amp internals? From the description of the noise, it sounds like a cap with a popped top.
    Thanks for helping out. The noise is definitely coming through the speaker.

    Do you mean filter caps?

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    Last edited by rdh006; 01-10-2018 at 12:40 AM.

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    Quote Originally Posted by m1989jmp View Post
    I had a similar problem when flipping the standby switch to playing position with my 2204 clone. I was running JJ EL34's at the time and switched other EL34's in without help along with all preamp tubes.

    Also, I tried cleaning every damn pot, socket etc. before that and still the noise was there.

    It would start like this, but a lot less severe, barely audible, and would turn into that air balloon type of thing (or long tearing with pitch shifting) you mentioned until finally disappearing:

    https://www.youtube.com/watch?v=-CBJSzC88Lg

    I had some Mesa 6L6's laying around so I adjusted bias range and popped them in. To my surprise the noise stopped; I figured thicker pins did the job since tubes were a lot tighter in the sockets.

    I hope someone knows exactly what's the cause of the problem, but everybody I asked couldn't give me an exact answer. Everyone said dirty pins/sockets/jacks etc.
    Thanks for replying. The noise in your youtube link is more of a crackle than mine. I saw a post where someone talked about the noise from a tea kettle -- it's a bit like that, but varies in pitch. Also reminds me of the interference/squelching noise you'd get with old radios.

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    Does the fact that the noise goes away when the amp warms up give a clue?

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    Yep. I meant filter caps. You'd be more likely to hear the noise from the chassis than speaker, but I suppose it could still be a cap. Did you use radial caps for the build? If so, inspect them and see if the tops of any are split.

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    Quote Originally Posted by rdh006 View Post
    Thanks for replying. The noise in your youtube link is more of a crackle than mine. I saw a post where someone talked about the noise from a tea kettle -- it's a bit like that, but varies in pitch. Also reminds me of the interference/squelching noise you'd get with old radios.
    See my post; it would start as ripping/crackle but would turn into the sound you described. Mine would go from higher to lower pitch a couple of dozen times and then stop.

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    Quote Originally Posted by The Dude View Post
    Yep. I meant filter caps. You'd be more likely to hear the noise from the chassis than speaker, but I suppose it could still be a cap. Did you use radial caps for the build? If so, inspect them and see if the tops of any are split.
    The caps are inline. I can't see any cracks or blisters.

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    Quote Originally Posted by m1989jmp View Post
    See my post; it would start as ripping/crackle but would turn into the sound you described. Mine would go from higher to lower pitch a couple of dozen times and then stop.
    Right. Sounds like a similar issue, then, except that changing tubes has not fixed it for me.

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    What effect do the controls have on the problem?

    What happens if you allow to warm up, turn off and then on again?

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    that sound in the vid is usualy leaky coupling cap or caps.
    very small dc hitting a tube grid sounds just like that and its common for it to go away when it heats up.
    seems to get worse in the video!

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    Quote Originally Posted by nickb View Post
    What effect do the controls have on the problem?

    What happens if you allow to warm up, turn off and then on again?

    The Normal volume has little effect on the noise.
    The Bright volume has much more effect on the noise.
    The volume controls are somewhat interactive on this amp which confuses the issue to some degree.
    The noise goes away altogether with the tone control turned down -- but then the whole amp is shut off anyway.


    If I allow it to warm up, turn off and then on again, it is the same before and after -- the noise is still there, to the same degree, as far as I can tell. If I turn it off and back on while the noise is there, the noise is still there. If I turn it off and back on while the noise is gone, the noise is still gone.

    Thanks for helping.

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    Last edited by rdh006; 01-10-2018 at 03:28 AM.

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    Quote Originally Posted by dstrat View Post
    that sound in the vid is usualy leaky coupling cap or caps.
    very small dc hitting a tube grid sounds just like that and its common for it to go away when it heats up.
    seems to get worse in the video!
    Thankyou. Is there a way to test, or is it a question of replacing caps?

    The answer to nickb's question above may be highlighting something about the Bright channel -- would that narrow down your focus at all?

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    Do you have a scope?

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    Quote Originally Posted by The Dude View Post
    Do you have a scope?
    No, 'fraid not -- just a humble multi-meter.

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    If you don't have a scope, try pulling V1. See if the noise goes away. If not try V2. See if you can at least isolate what stage the noise is coming from.

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    Quote Originally Posted by The Dude View Post
    If you don't have a scope, try pulling V1. See if the noise goes away. If not try V2. See if you can at least isolate what stage the noise is coming from.
    Pull V1 = noise still there, unchanged
    Pull V2 = all noise gone

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    do you have a schematic or what did you build the amp from?

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    Quote Originally Posted by rdh006 View Post
    The Normal volume has little effect on the noise.
    The Bright volume has much more effect on the noise.
    The volume controls are somewhat interactive on this amp which confuses the issue to some degree.
    The noise goes away altogether with the tone control turned down -- but then the whole amp is shut off anyway.


    If I allow it to warm up, turn off and then on again, it is the same before and after -- the noise is still there, to the same degree, as far as I can tell. If I turn it off and back on while the noise is there, the noise is still there. If I turn it off and back on while the noise is gone, the noise is still gone.

    Thanks for helping.
    OK quick test - try subbing the 0.1uF coupling cap in the bright channel.

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    Quote Originally Posted by dstrat View Post
    do you have a schematic or what did you build the amp from?
    I built the amp from the layout provided by Bruce at Mission amps, which I can't post. However, the amp is basically the original 5E3 circuit as shown on the Fender schematic and layout which is out there on the internet. I'll find a link when I have some spare time later today.

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    Quote Originally Posted by nickb View Post
    OK quick test - try subbing the 0.1uF coupling cap in the bright channel.
    Thanks -- I'll try that a little later today.

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    Quote Originally Posted by rdh006 View Post
    I built the amp from the layout provided by Bruce at Mission amps, which I can't post. However, the amp is basically the original 5E3 circuit as shown on the Fender schematic and layout which is out there on the internet. I'll find a link when I have some spare time later today.
    5E3 schematic
    https://cdn.instructables.com/F8P/XH...DN7.MEDIUM.jpg

    5E3 layout
    https://cdn.instructables.com/F4X/D8...DN8.MEDIUM.gif

    Some of the component values are slightly different. The filter caps are 22uf and the coupling caps are .047uf

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    I changed the coupling cap in the bright channel, as per nickb's post above. Noise appears to be gone. I had been intending to reduce that cap from .047 to .022 to cut a little of the lows, so killed two birds with one stone. The amp sounds great.

    Hopefully that's it. Thanks nickb for the fix, and thanks to everyone who helped here. Learned some stuff and got my amp back together -- what more could I ask?

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    Quote Originally Posted by rdh006 View Post
    I changed the coupling cap in the bright channel, as per nickb's post above. Noise appears to be gone. I had been intending to reduce that cap from .047 to .022 to cut a little of the lows, so killed two birds with one stone. The amp sounds great.

    Hopefully that's it. Thanks nickb for the fix, and thanks to everyone who helped here. Learned some stuff and got my amp back together -- what more could I ask?
    Woo Hoo!

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    Quote Originally Posted by nickb View Post
    Woo Hoo!
    I hope I'm not the only curious one here... How did that fix the problem and how did you know it would?

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    Quote Originally Posted by Chuck H View Post
    I hope I'm not the only curious one here... How did that fix the problem and how did you know it would?
    dstrat pointed out the probable general cause in post 12. The test with the controls in post 13 narrowed it to the bright channel. There just the one cap with large DC across it. Plus luck of course

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    I just love it when these thinks work out. I'm sitting here smiling - I can't think of any other forum where so much expertise, patience, understanding and care goes into helping someone fix their problem.

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    Quote Originally Posted by nickb View Post
    dstrat pointed out the probable general cause in post 12. The test with the controls in post 13 narrowed it to the bright channel. There just the one cap with large DC across it. Plus luck of course
    So do you suppose it was a microphinic cap or a leaky cap. I didn't suspect a leaky cap because it's a newer amp and I didn't suspect a microphonic cap for the same reason. I don't think I've ever seen a newer microphonic film cap. Anyway, this is something I wouldn't have caught for a while longer yet. So good instincts.

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    Quote Originally Posted by Mick Bailey View Post
    I just love it when these thinks work out. I'm sitting here smiling - I can't think of any other forum where so much expertise, patience, understanding and care goes into helping someone fix their problem.

    Amen to that. You guys are brilliant. I used the amp at a gig last night -- no issues and the amp sounded great.

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