Thanks. Forgive me, but what do you exactly mean by fretting the cord? Also I'm a bit confused when you say 'on new stuff do what Mooley says.' Are you saying change the cord and add fuse on all new 'vintage' amps?
So the fuse get wired in between the switch and the transformer? As always thanks.
So the fuse get wired in between the switch and the transformer? As always thanks.
I think PRR means don't take anything for granted.
Wiring as I described follows the wiring colour convention of your country. Adding the fuse to the live incoming is standard good practice. Having the switch on the incoming live rather than neutral is good practice.
Throughout I have assumed that the house wiring would be correct although PRR seems to suggest that it is not uncommon to find reversed polarity.
Making the appliance you are working on comply is all we can really advise on here. If the property wiring is suspect then that needs checking as a separate issue.
Wiring as I described follows the wiring colour convention of your country. Adding the fuse to the live incoming is standard good practice. Having the switch on the incoming live rather than neutral is good practice.
Throughout I have assumed that the house wiring would be correct although PRR seems to suggest that it is not uncommon to find reversed polarity.
Making the appliance you are working on comply is all we can really advise on here. If the property wiring is suspect then that needs checking as a separate issue.
PRR is correct in his assumption that it is not uncommon to find reversed polarity. I actually tested the outlets in my home when I first moved in. I have some reversed receptacles, and a couple with open ground. The wiring in my music room is correct. I had to rewire it. They had 3 prong receptacles put in but the grounds on them were not connected. Spotty electrical works seems to be in abundance.
So what would happen if I plug this thing into a reverse polarity receptacle? Will it blow up on me? I have the new cord installed and will be powering it up tonight when I get home from work.
Just to make sure, will I wire the fuse onto the hot lead coming in to the amp, then to the switch? Or, do I take the the transformer primary, tap that with the fuse then wire to the switch? Thanks.
So what would happen if I plug this thing into a reverse polarity receptacle? Will it blow up on me? I have the new cord installed and will be powering it up tonight when I get home from work.
Just to make sure, will I wire the fuse onto the hot lead coming in to the amp, then to the switch? Or, do I take the the transformer primary, tap that with the fuse then wire to the switch? Thanks.
Reversed polarity is only a danger to the person delving inside the appliance.
A ceiling light and its wall switch with reverse polarity would work just fine. Its only when you stick your fingers in the socket (with the switch off) that you realise there is still line voltage present at the socket.
The fuse should be the first thing the incoming voltage meets simply because the fuse can only protect what comes after it. So the incoming live wire should be fused at the earliest practical point in the unit.
A ceiling light and its wall switch with reverse polarity would work just fine. Its only when you stick your fingers in the socket (with the switch off) that you realise there is still line voltage present at the socket.
The fuse should be the first thing the incoming voltage meets simply because the fuse can only protect what comes after it. So the incoming live wire should be fused at the earliest practical point in the unit.
> what would happen if I plug this thing into a reverse polarity receptacle?
Like he says. Works fine. BITES you if you carefully observe white/black convention and then go inside and stick your finger on the "less live" white wire, which is really 120V hot.
If building new, do "the right way". But anybody working in this vintage amp (probably only you) should be very wary. In that case I would leave the vintage work as much original as convenient, just for nostalgia.
Like he says. Works fine. BITES you if you carefully observe white/black convention and then go inside and stick your finger on the "less live" white wire, which is really 120V hot.
If building new, do "the right way". But anybody working in this vintage amp (probably only you) should be very wary. In that case I would leave the vintage work as much original as convenient, just for nostalgia.
> assumed that the house wiring
This borders on politics-- delete it if you must.
There's just enough difference between UK and US that "it matters". There is a lot of old work in the US, less in the UK. There is a lot of DIY home work in the US (every town has a Home Depot), less in the UK. UK regulations are a bit tougher and apparently enforced better. In the town I live, electrics are inspected only on significant building, and even then slack. Homeowners can do almost any electric work short of the meter box, and often evade any oversight. US electric inspections are purely visual; in the UK they must break N from G, apply high voltage, and show low leakage.
A UK author proposed a tester which *relied* on the blue/brown convention to expose the Neutral to a user. I thought this was frightening; he thought it was quite safe. We do live in different places.
BTW: in the US and I believe in some UK installations, the "Neutral" may be several Volts "live" normally. Mine can run over 3V to dirt, despite 5 dirt-rods. In the US the "N" is only a neutral for the large loads, small loads that happen to all fall on the same side cause large "neutral current". In the UK, inside most dwellings, it isn't a Neutral at all. While 3V is hardly lethal, it can cause odd currents (and TV buzz-bars).
This borders on politics-- delete it if you must.
There's just enough difference between UK and US that "it matters". There is a lot of old work in the US, less in the UK. There is a lot of DIY home work in the US (every town has a Home Depot), less in the UK. UK regulations are a bit tougher and apparently enforced better. In the town I live, electrics are inspected only on significant building, and even then slack. Homeowners can do almost any electric work short of the meter box, and often evade any oversight. US electric inspections are purely visual; in the UK they must break N from G, apply high voltage, and show low leakage.
A UK author proposed a tester which *relied* on the blue/brown convention to expose the Neutral to a user. I thought this was frightening; he thought it was quite safe. We do live in different places.
BTW: in the US and I believe in some UK installations, the "Neutral" may be several Volts "live" normally. Mine can run over 3V to dirt, despite 5 dirt-rods. In the US the "N" is only a neutral for the large loads, small loads that happen to all fall on the same side cause large "neutral current". In the UK, inside most dwellings, it isn't a Neutral at all. While 3V is hardly lethal, it can cause odd currents (and TV buzz-bars).
And that's before you look at the rest of the world. Even in AU and NZ which share the same rules (AS/NZ 3000) you see lots of variation due to state-by-state legislation and, most importantly, the passage of time.
Many people get nasty shocks (to the wallet) by (slightly) renovating an old house only to discover they have to re-wire the entire building before the power (or gas) can get turned back on.
Having added a gas point in the lounge of one house I had to rebuild the entire kitchen as the relationship between the stove and built in cupboards no longer met code 😱
Thanks everyone for walking me along this rebuild. It has been greatly appreciated. I was wondering what is correct protocol to take before powering the amp back up. Obviously checking connections and the likes. Any other thing to take into account before restarting it? Thanks for your time.
If you have doubts then its always good to do a quick resistance check across the live and neutral of the mains plug. Make sure you get 'infinity' with the switch off and a lowish reading when on, that reading corresponding to the mains transformer primary DC resistance.
You should not read a short circuit but it will be low ohms you see. That's normal.
Then its the usual precautions of a 200 yd mains extension lead, tin hat and volunteer to throw the switch... only kidding... get it turned on 🙂
You should not read a short circuit but it will be low ohms you see. That's normal.
Then its the usual precautions of a 200 yd mains extension lead, tin hat and volunteer to throw the switch... only kidding... get it turned on 🙂
Well....It powered up and stayed on for perhaps a minute then the fuse blew. After looking it over, with everything being seemingly correct I installed a new fuse and powered it up. This time it stayed powered up for a longer amount of time, but, in the end ultimately powered down again. I was wondering, if I may be using an underrated fuse?? The fuse I have is 250mA fuse. Is this too small of a value? as always your time is appreciated.
Get a "light bulb limiter" aka "dim bulb tester"
Also sit down and work out what current each stage of your amp should be drawing. And then all the heater current. Turn that into watts, then back into mA of mains current. 250mA @ 110v is near enough 27W. With three tubes that should be easy (but I've got a cold and my head hurts :-( so I'll leave that to you). Gut says that's about right but it'd be close.
With the correct lamp wattage (about the same as your amp should draw) you'll get a better idea of what's playing up without risking damage to your equipment. If the lamp lights brightly, turn it all off and start debugging. First with all tubes out, then rectifier only, then pre-amp tube, finally output tube until you find the fault.
Also sit down and work out what current each stage of your amp should be drawing. And then all the heater current. Turn that into watts, then back into mA of mains current. 250mA @ 110v is near enough 27W. With three tubes that should be easy (but I've got a cold and my head hurts :-( so I'll leave that to you). Gut says that's about right but it'd be close.
With the correct lamp wattage (about the same as your amp should draw) you'll get a better idea of what's playing up without risking damage to your equipment. If the lamp lights brightly, turn it all off and start debugging. First with all tubes out, then rectifier only, then pre-amp tube, finally output tube until you find the fault.
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250ma is very small. Fuses also come in two types, fast and slow blow. A fast blow running right on the edge could be blown by a slight mains transient or conversely, a slight power dip and then a return to normal voltage.
You have three valve heaters to power up plus what the circuit uses, plus the inefficiencies of the mains transformer. I would say realistically you need at least 1A slow blow to prevent nuisance blowing.
You have three valve heaters to power up plus what the circuit uses, plus the inefficiencies of the mains transformer. I would say realistically you need at least 1A slow blow to prevent nuisance blowing.
Thanks everyone. I used a 250mA FAST ACTING fuse. As opposed to the time delay type. After looking into it, I guess I got the wrong type of fuse. Also, can the heater current be determined by a data sheet?? And will the amp have to be on to monitor the reading? Or am I just showing my ignorance here? I greatly thank you all for your time.
Yes, too small. Something on the order of 500 - 750mA MDL type would seem more appropriate.
Amp obviously needs to be on to monitor the current, and filament current rating is in the data sheets.
Amp obviously needs to be on to monitor the current, and filament current rating is in the data sheets.
And just to add that the filament current isn't directly related to the current you draw from the mains.
For example, a perfect transformer with a turns ratio of 10:1 (ten to one) would deliver 10 volts output for 100 volts across its input. If you drew 10 amps on the secondary, the primary current would be just 1amp.
So, I went down to the hardware store after I dropped the kids off at school. I reviewed their selection and the only thing available was a 1 amp fuse. I picked up a pack. Got home put it in and......😀 It's alive!!!
First impressions are amazing! I can't believe the difference in the sound. Just so awesome. I'm pushing it pretty hard too, no failure's at least not yet. Sounds so much better and runs cooler than it used to. Man, I wish I had off work today.
The only thing I can notice is a slight hum when the volume is maxed out. Just slight. A ground loop? How does one go about resolving this? Again, it's only audible when I have the volume maxed out. Thanks.
First impressions are amazing! I can't believe the difference in the sound. Just so awesome. I'm pushing it pretty hard too, no failure's at least not yet. Sounds so much better and runs cooler than it used to. Man, I wish I had off work today.
The only thing I can notice is a slight hum when the volume is maxed out. Just slight. A ground loop? How does one go about resolving this? Again, it's only audible when I have the volume maxed out. Thanks.
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A bit of hum could be intrinsic to the unit... in other words normal. Although it is possible to get noise/hum levels of high impedance valve circuitry down to low levels it isn't really a selling point of something like this.
So... with nothing apart from a speaker connected, and the input in use shorted (fit a shorting link or plug) does it still hum ?
So... with nothing apart from a speaker connected, and the input in use shorted (fit a shorting link or plug) does it still hum ?
The input jack "should" have an extra finger which shorts the input when nothing is plugged in. Very standard on guitar amps.
If the chassis is open, you can short with a jumper clip. (Please do not get killed!)
I often shoved a potentiometer shaft, .22 gun cleaning brush, or a 1/4" bolt in the hole.
Yes, there will be a residual hum, more or less depending on obsession and luck. Play loud, don't stop, nobody will know.
If the chassis is open, you can short with a jumper clip. (Please do not get killed!)
I often shoved a potentiometer shaft, .22 gun cleaning brush, or a 1/4" bolt in the hole.
Yes, there will be a residual hum, more or less depending on obsession and luck. Play loud, don't stop, nobody will know.
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