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I just picked up the Newall 18 watt from Mario, which sounds great btw, and I get a very loud "pop" through the speakers most of the time I go to Standby. The couple of times I've played the amp for more than 1/2 hour and then let it sit for a couple of minutes (with volume down) it shuts down very quietly. If I only play for a 10 -20 minutes or so I get the "pop". Anything I can do about it? it's damned annoying and makes me afraid to flip the switch :smile:
I've swapped out the tubes btw with no impact (except it sounds better than ever with the JJ's.)
I've tried to get ahold of Martin Newall with no success so far.
 

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Peavey Wolfgang EVH Wolfgang Charvel Style 2
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Could be the switch acting up at certain temps. Try flipping the switch real slow and see if this makes it worse then flip it fast see if it's better...
Maybe it's not the switch but it's easy for you to try.

Khing
 

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Dave: this is a common symptom for amps fitted with Standby. With age the contacts wear and popping is the result. Sometimes the switch ratings for DC Volts are marginally spec'd. I recommend simply replacing the switch to solve the problem.
 

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Thanks guys, I'll look into the switch. Both my Bandmaster ('69) and Traynor ('67) are completely silent and they're a damn sight older than this Newall. LOL.
 

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Discussion Starter #6
Capacitors discharging or switch bounce? I'd be interested to find out if it was either of these two issues.

I should add that I know very little about tube technology.
I was kinda leaning towards the capacitors myself. It just sounds like it's discharging a bunch of static. I'm just not sure why playing it longer would matter, which seems to be the case. :confused-smiley-010
 

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I was kinda leaning towards the capacitors myself. It just sounds like it's discharging a bunch of static. I'm just not sure why playing it longer would matter, which seems to be the case. :confused-smiley-010

It's obvious, Dave. The amp behaves itself longer so that it will aggravate you all the more when it does act up! :tongue:

What kind of switch is being used for standby? It shouldn't be a mini-toggle but be at least as big as the one used in your Traynor.

Some designers add a cap of a value somwhere between .02 and 047 mfd after the standby switch to ground. It should be rated 630 volts or better, to handle the plate voltage and a bit of spiking when the switch is thrown.

I warn you, the cap doesn't always work.:mad:

Those bigass switches you find in Home Depot will work fine, as long as they have the switching action you need.

The problem is that nobody rates their switches for the 450 volts DC to put a tube amp into standby. Why bother? In your profession you can understand how a manufacturer won't spend the money to determine such specs for .00002% of the market, which sadly is what we tubeheads represent. So amp designers took a bassackwards attack on the problem. You take a switch rated at 250 vac. Every electrician knows that most switches will handle at least double their AC rating when asked to switch DC. Then you look for such a switch with at least a 6 amp or better current rating. When you go to stores like Home Depot you always find there's an industry standard switch that meets or exceeds those specs.

No one can hand you a spec sheet saying that such a switch will be suitable for use in a tube guitar amp but no one cares. Experience has shown that these switches last for years and years, ever since they were first adopted back in the 50's.

I admit I've never seen your amp with the problem but some of the desigers nowadays seem a little light on some details, like how rugged a switch needs to be for use in standby switching. A mini toggle is rated 3 amps @120 vac. This is fine for a power switch in an 18 watt amp but I wouldn't use it for standby.

Any chance of a picture of the switch?
 

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My Traynor amp does the same thing. If I let it sit for a few minutes b4 switching to standby; it doesn't make that snap sound or if I power it off with the main power switch. I picked up a switch at the local electrical supply; an Ideal rated at 20 amp/125vac or 10amp/277vac. replacing the switch didn't solve the problem. The original Traynor switch 2a @250v. Home Depot also has a good selection of toggle switches, don't waste your time looking at Radio Shack or the Source.

http://www.idealindustries.com/supplies/index.htm
 

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davetcan said:
Looks good AND sounds good.
Well then Dave, I'd try a .022 mfd 630 volt cap on the amp side terminal to ground. If that doesn't work I'd try putting the cap across the switch contacts.

If that still doesn't work I'd go for a beer!

:food-smiley-004:
 

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here's another idea, although it's a slight modification to the circuit. Traynor uses this frequently in tube amps (older ones is what I'm referring to) .... instead of interrupting the DC high voltage, use the standby switch to interrupt the power transformer secondary centre tap (if the circuit uses one). If the circuit has a 4 terminal solid state bridge rectifier, there won't be a centre tap.
I had a fellow ask me to install a tube rectifier into his old Magnatone amp with a switch to go from ss rectifier to tube. Upon completion of this mod, the standby always made a pop - only the first time it was operated, but it was annoying. I moved the switch to the centre tap and the noise never occured again.
As for the tube rectifier, I couldn't detect the sag the fellow was after, but he was happy with the mod. I don't think I played the amp hard enough to pick up the difference using either 5Y3 or 5U4.
 

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here's another idea, although it's a slight modification to the circuit. Traynor uses this frequently in tube amps (older ones is what I'm referring to) .... instead of interrupting the DC high voltage, use the standby switch to interrupt the power transformer secondary centre tap (if the circuit uses one). If the circuit has a 4 terminal solid state bridge rectifier, there won't be a centre tap.
In that case, just put the switch from the (-) terminal on the bridge to ground.
 

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I have the same problem with my 18 watt TMB.I wait a couple of seconds and turn the volume down on the guitar and there is no pop.
Martin uses Carling switches rated properly for the amp and I have used the same switches in many amps for years with no problems.Some amps are prone to that standby popping and a capacitor usually solves the problem.Unless the switch is really a low quality one I highly doubt the switch itself is the cause.
Give Martin a chance to respond.His mother is sick right now so that's probably why you can't get a hold of him.I'll try him today and see if I can get through.We are good friends and I know he will work with you to try and solve the issue.

www.claramps.com
 

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Discussion Starter #17
Thanks for the info. Please tell Martin there is absolutely no rush on this. Looking after his mother comes before everything, never mind this trivial stuff.

Everything in the amp looks to be top quality and it's beautifully done. The more I play it, the more I like it. :smilie_flagge17:


I have the same problem with my 18 watt TMB.I wait a couple of seconds and turn the volume down on the guitar and there is no pop.
Martin uses Carling switches rated properly for the amp and I have used the same switches in many amps for years with no problems.Some amps are prone to that standby popping and a capacitor usually solves the problem.Unless the switch is really a low quality one I highly doubt the switch itself is the cause.
Give Martin a chance to respond.His mother is sick right now so that's probably why you can't get a hold of him.I'll try him today and see if I can get through.We are good friends and I know he will work with you to try and solve the issue.

www.claramps.com
 
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