# Vintage Oxford Speaker Terminal Question



## ampdude (Mar 17, 2011)

While trying to debug a rattle in a vintage Oxford speaker in a 2x12 tall Fender cabinet, I got a nasty jolt touching the speaker mounting bolts while playing. When I metered the speaker terminals, it appears that they are common with the speaker frame, based on how the white speaker terminal is common with the rivet that mounts the terminal tag board to the frame. 

What's the deal with this? 

On all my modern Weber speakers, the terminals are completely isolated from the frame.


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## nonreverb (Sep 19, 2006)

2 prong plug on the amp?


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## greco (Jul 15, 2007)

I have never seen this before...but I am not all that experienced compared to others.

I did find this pic:










in this thread: http://www.tdpri.com/forum/attachme...-terminals-fender-oxford-oxford-terminals-jpg

Will be following with interest!

Cheers

Dave


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## ampdude (Mar 17, 2011)

Thanks Dave! Same exact scenario. Why would they common that terminal to the rivet??

- - - Updated - - -

Originally yes. 3 prong now.


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## greco (Jul 15, 2007)

ampdude said:


> Thanks Dave! Same exact scenario. Why would they common that terminal to the rivet??


When I searched "Images" through Google, I found several pics of this scenario. 
Why would they do that?, you ask ....not a clue, sorry.

Cheers

Dave


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## epis (Feb 25, 2012)

Manufacturer of the amp wanted to have speaker basket grounded.


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## ampdude (Mar 17, 2011)

Thanks Epis! I won't go poking around in there anymore! I fixed the rattle and closed 'er back up. Sounds simply amazing now!! It's a '63 Showman head on a vertical vintage 2x12 Fender cab.


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## epis (Feb 25, 2012)

You're welcome :smile-new:


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## Electraglide (Jan 24, 2010)

Only time I've seen that is old single speaker wire car audio systems. Everything grounded through the car frame. The old Sears 8 track deck is like that. So's the Ford tube truck radio. Nothing else I have that has a speaker in it has a speaker to chassis ground set up. The Fender XFL 1000 power speaker uses 1/4 mono connections to the speakers. The only speakers I have like this are a couple of old car speakers.


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## greco (Jul 15, 2007)

epis said:


> Manufacturer of the amp wanted to have speaker basket grounded.


Just curious...Why ground the basket? (i.e., what is the electronics logic/advantage of doing this?)...especially when this is not a "typical' practice. 
Also, it is a cab and not an amp, so the manufacturer would have to expect that it would/could be used with various heads/amps.

Cheers

Dave


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## nonreverb (Sep 19, 2006)

If you're getting a shock, what else besides the amp were you touching? To get a shock there must be a ground fault somewhere between the amp ground and whatever else you were touching as you became the conduit to ground.....not good.


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## epis (Feb 25, 2012)

greco said:


> Just curious...Why ground the basket? (i.e., what is the electronics logic/advantage of doing this?)...especially when this is not a "typical' practice.
> Also, it is a cab and not an amp, so the manufacturer would have to expect that it would/could be used with various heads/amps.
> 
> Cheers
> ...


Hi Dave, it's just a safety precaution, defined by electric standards, all metal parts of equipment accessible by operator plugged to the mains must be grounded.
For speaker manufacturer it's easier to leave that bridge than make two versions of speakers for combo amps and sealed cabinets.
And by the way, I acquired recently two vintage speakers, Utah and Oxford, both have the same grounded negative speaker tabs.
Cheers, Damir


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## nonreverb (Sep 19, 2006)

That's not entirely true. It's totally optional. Some decided to do it and some didn't. Even manufacturers that implemented the ground strap didn't maintain it permanently and on all models. 



epis said:


> Hi Dave, it's just a safety precaution, defined by electric standards, all metal parts of equipment accessible by operator plugged to the mains must be grounded.
> For speaker manufacturer it's easier to leave that bridge than make two versions of speakers for combo amps and sealed cabinets.
> And by the way, I acquired recently two vintage speakers, Utah and Oxford, both have the same grounded negative speaker tabs.
> Cheers, Damir


- - - Updated - - -

Is that the Utah with the silver and orange label? If it is, poor you....
You wouldn't happen to be the guy selling all that stuff on Kijiji are you?


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## jb welder (Sep 14, 2010)

nonreverb said:


> If you're getting a shock, what else besides the amp were you touching? To get a shock there must be a ground fault somewhere between the amp ground and whatever else you were touching as you became the conduit to ground.....not good.


 Yes, you said you were playing and you touched the speaker frame and got shocked. Your guitar is connected to amp chassis, the speaker frame should also be, so there should be no potential for shock.
But you mentioned "white" terminal. Do you mean the white spkr. wire from the amp was connected there? In that case, you would get a shock proportional to how loud you are playing. The white wire should go to the red dot terminals. Then the black wires will connect the speaker frames to chassis ground.


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## epis (Feb 25, 2012)

nonreverb said:


> Is that the Utah with the silver and orange label? If it is, poor you....
> You wouldn't happen to be the guy selling all that stuff on Kijiji are you?


It is orange - silver. I got it both in Kustom cabinet for $50, cab vent to garbage, to heavy and smelly, speakers, I'll keep.
And, no I'm not the guy who is selling them .


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## nonreverb (Sep 19, 2006)

That shouldn't make a difference since a human body to ground is substantially higher impedance than the 8ohms to ground potential of the winding.... I think there's something far more nefarious going on here like a broken ground blade on the plug or the ground wire not connected or...dare I say it....something worse.



jb welder said:


> Yes, you said you were playing and you touched the speaker frame and got shocked. Your guitar is connected to amp chassis, the speaker frame should also be, so there should be no potential for shock.
> But you mentioned "white" terminal. Do you mean the white spkr. wire from the amp was connected there? In that case, you would get a shock proportional to how loud you are playing. The white wire should go to the red dot terminals. Then the black wires will connect the speaker frames to chassis ground.


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## epis (Feb 25, 2012)

nonreverb said:


> That's not entirely true. It's totally optional. Some decided to do it and some didn't. Even manufacturers that implemented the ground strap didn't maintain it permanently and on all models.


Grounding ALL metal parts accessible by user isn't optional, when we're talking about grounding the speaker, I don't know, but that looks like only logical explanation.


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## nonreverb (Sep 19, 2006)

Many companies didn't ground the baskets of their speaker and most don't today. It kind of defies logic that they'd only start that once the ground plug was introduced and at some point discontinue it altogether after a time....weird and kinda redundant. Probably some CSA thing.


epis said:


> Grounding ALL metal parts accessible by user isn't optional, when we're talking about grounding the speaker, I don't know, but that looks like only logical explanation.


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## ampdude (Mar 17, 2011)

@nonreverb and jb welder, you may be on to something....attached is a pic of the actual speaker. The other one is wired the same. From the post above, it would appear that the wires are backwards. This would explain the shock while playing and touching the basket, since I would be putting current through it?


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## epis (Feb 25, 2012)

If the wires are properly connected at the jack, yes it is wired backwards, but you shouldn't get any shock from the amp output, there is very small voltage present at the speaker jack. Btw. you need to improve your soldering skills .

About getting shocked, you must check out you amp ground or even your mains wall outlet ground. That's not a problem caused by speakers wiring.


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## ampdude (Mar 17, 2011)

Was the previous owner's soldering job...I swear! I just got this rig! 

So at the jack, the white should be tip and black should be ring?


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## Church-Audio (Sep 27, 2014)

Its also a good way to say hey this is the negative terminal on the speaker. But as far as I know it was done for some goofy safety standard. Roland also did this on some of the amps they made the jazz chorus series comes to mind.


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## epis (Feb 25, 2012)

ampdude said:


> Was the previous owner's soldering job...I swear! I just got this rig!
> 
> So at the jack, the white should be tip and black should be ring?


LOL ! yes, black wires are used for ground connections.

- - - Updated - - -



Amprepair said:


> Its also a good way to say hey this is the negative terminal on the speaker.


:applouse:


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## greco (Jul 15, 2007)

Reading the thread with interest...and confusion.

Cheers

Dave

- - - Updated - - -



nonreverb said:


> That shouldn't make a difference since a human body to ground is substantially higher impedance than the 8ohms to ground potential of the winding.... *I think there's something far more nefarious going on here* like a broken ground blade on the plug or the ground wire not connected or...dare I say it....something worse.


This is a post that I would be paying attention to for sure. 

Cheers

Dave


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## epis (Feb 25, 2012)

nonreverb said:


> 2 prong plug on the amp?


@ Ampdude, I see we went to wrong direction with this discussion, did you pay attention to nonreverb's post ?
Are you sure your jolt wasn't caused by electrostatic discharge ? (you were wearing sneakers with rubber-plastic soils on carpet ?)
If not, take it seriously before continuing to use that amp.
Check out first continuity from power plug ground pin to the amp chassis.(I assume power cable was changed to 3 prong)
If it's still two prong, you must replace it.


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## ampdude (Mar 17, 2011)

Thanks everyone. I did check the ground pin on the power cord and there is continuity to the amp chassis. It's a really crappy cord though, so I may replace it. 

I am going to rewire the speakers tonight, give the amp a good look over, and then report back....


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## ampdude (Mar 17, 2011)

Okay, after a looooong night of work, here's the scoop....

I rewired the speakers properly.

I installed a new 3 prong power cord to replace the 3 prong cord that was in there, that had almost completely disintegrated!! I can't imagine that was safe the way it was! 

No more shocks touching the speaker frame or any other grounded part while playing....phew!! It's late here now, so I couldn't really throttle up the amp and hear how the speakers sound now that they're properly wired. Will test that tomorrow...

One thing I noticed inside the amp is that the V3 and V4 power tube sockets are quite loose. When I powered the amp back up, the V4 power tube is cutting out intermittently. I swapped power tubes around to make sure it wasn't a bad tube. It appears to be something with the socket. 

Well, I've officially exceeded my repair skills, so will have to take it to a local tech...

One thing I will say with all due respect to Leo Fender....he may have designed his guitars for mass production, but getting the amp chassis out of a blackface Fender is an exercise in hair pulling frustration!!!!


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## greco (Jul 15, 2007)

Congrats! .....Good troubleshooting, some repairs done and then wisely concluding to take it to a tech once you exceeded your comfort level with repairs.

Enjoyed the thread...sorry that it had to begin as a result of you getting a shock.

Cheers

Dave


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## nonreverb (Sep 19, 2006)

Well done! If you're feeling brave, you can first try and re-tension the socket pins before going further.
Glad to hear you replaced the plug and AC cord. I've seen light shows from bad cords that would rival most bar dance floors.....


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## epis (Feb 25, 2012)

@ Ampdude :sSig_goodjob2: As nonreverb recommended, try first to retension the conntacts in the tube sockets, it's not hard, you need small size flat screwdriver and a little bit of patience. Amp tech is gonna want, most likely, to replace the sockets. 

@ nonreverb Why you don't like Fender Utah orange-silver sticker loudspeakers ? It work very well with my home brew Fenders (champ, deluxe reverb and tweed 5e3)
It's low efficient speaker, but for me -a bedroom player, that's even an advantage. Cheers, Damir


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## nonreverb (Sep 19, 2006)

Might be good for a bedroom player, not much good for anything else. They show up for only a relatively short time in Fender amps probably due to the fact that they didn't sound that good. I suspect they were cheap and that's why they used them. Most of the amps I've heard them in sound dark and farty....including my own '74 Deluxe reverb. I couldn't get rid of it fast enough.



epis said:


> @ Ampdude :sSig_goodjob2: As nonreverb recommended, try first to retension the conntacts in the tube sockets, it's not hard, you need small size flat screwdriver and a little bit of patience. Amp tech is gonna want, most likely, to replace the sockets.
> 
> @ nonreverb Why you don't like Fender Utah orange-silver sticker loudspeakers ? It work very well with my home brew Fenders (champ, deluxe reverb and tweed 5e3)
> It's low efficient speaker, but for me -a bedroom player, that's even an advantage. Cheers, Damir


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## ampdude (Mar 17, 2011)

Hey everyone, 

Thank you so much for all of your help with this! I took the amp apart again and retensioned the power tube sockets. All 4 tubes glowing nicely now!! I'll take some gut shot pics before I close 'er up and post later....


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## epis (Feb 25, 2012)

nonreverb said:


> Might be good for a bedroom player, not much good for anything else. They show up for only a relatively short time in Fender amps probably due to the fact that they didn't sound that good. I suspect they were cheap and that's why they used them. Most of the amps I've heard them in sound dark and farty....including my own Deluxe reverb. I couldn't get rid of it fast enough.


Thanks Richard :smile-new:

- - - Updated - - -



ampdude said:


> Hey everyone,
> 
> Thank you so much for all of your help with this! I took the amp apart again and retensioned the power tube sockets. All 4 tubes glowing nicely now!! I'll take some gut shot pics before I close 'er up and post later....


Cool ampdude :sSig_goodjob2:


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## nonreverb (Sep 19, 2006)

It's too bad really. Utah made some very good speakers prior to this offering. I had a '64 Concert amp once upon a time that was factory loaded with Utah 10LXC1's and they sounded great.
But I digress....no hijacking the thread! As you were....



epis said:


> Thanks Richard :smile-new:
> 
> - - - Updated - - -
> 
> ...


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## epis (Feb 25, 2012)

nonreverb said:


> It's too bad really. Utah made some very good speakers prior to this offering. I had a '64 Concert amp once upon a time that was factory loaded with Utah 10LXC1's and they sounded great.
> But I digress....no hijacking the thread! As you were....


Well, the tread is already finished, all the problems solved :slash:, and I wanted to learn something new as well :smiley-faces-75:


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## jb welder (Sep 14, 2010)

nonreverb said:


> That shouldn't make a difference since a human body to ground is substantially higher impedance than the 8ohms to ground potential of the winding.... I think there's something far more nefarious going on here like a broken ground blade on the plug or the ground wire not connected or...dare I say it....something worse.





epis said:


> If the wires are properly connected at the jack, yes it is wired backwards, but you shouldn't get any shock from the amp output, there is very small voltage present at the speaker jack. Btw. you need to improve your soldering skills .
> 
> About getting shocked, you must check out you amp ground or even your mains wall outlet ground. That's not a problem caused by speakers wiring.


At 50W power to the speaker, there is about 20VRMS there. I know it is small, but it may have been a small shock he received. When you get an unexpected shock, you jump :smile-new:, and don't often get to measure the voltage that caused it.
I have got minor shocks from speaker outputs, it's a bigger concern with large PA amps, but it can still happen with guitar amps. That's why they have those little plastic covers on the vintage Fender speaker plugs. Take one off, stick your thumb in there and hit a power chord if you don't believe me 
As Epis mentioned, it could have also just been an unexpected electrostatic shock.
Ampdude mentioned there was continuity from 3rd prong ground to chassis, and he wasn't touching any other piece of gear other than his guitar that was grounded to chassis. So that leaves either static shock or the audio voltage at the speaker as the only causes I can see.
Even if it was a 2 prong, and he was only touching his guitar, how could he get an AC line type shock from touching the speaker frame?


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## epis (Feb 25, 2012)

We didn't see actual amp inside, all this was just guessing. I can't believe I can feel 20V AC, but you might be onto something, let say if speaker connection was intermittent ,
it was possible to get higher voltages generated by unloaded output transformer.


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## nonreverb (Sep 19, 2006)

Well unless he was floating, his feet were touching the floor...:smile-new:. Remember, he just posted that the original cord was disintegrating. That's a pretty strong indication that there might have been a ground fault. Either way better to inspect and replace if at all in doubt!




jb welder said:


> At 50W power to the speaker, there is about 20VRMS there. I know it is small, but it may have been a small shock he received. When you get an unexpected shock, you jump :smile-new:, and don't often get to measure the voltage that caused it.
> I have got minor shocks from speaker outputs, it's a bigger concern with large PA amps, but it can still happen with guitar amps. That's why they have those little plastic covers on the vintage Fender speaker plugs. Take one off, stick your thumb in there and hit a power chord if you don't believe me
> As Epis mentioned, it could have also just been an unexpected electrostatic shock.
> Ampdude mentioned there was continuity from 3rd prong ground to chassis, and he wasn't touching any other piece of gear other than his guitar that was grounded to chassis. So that leaves either static shock or the audio voltage at the speaker as the only causes I can see.
> Even if it was a 2 prong, and he was only touching his guitar, how could he get an AC line type shock from touching the speaker frame?


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## jb welder (Sep 14, 2010)

I have no doubt the AC cord should be replaced for safety's sake. I have no argument with that and do not mean to derail the thread. I'm just trying to understand the shock mechanism and also point out that power amps generate AC voltage and can produce shocks.
Yes his feet would have been grounded. But he would be grounded to chassis if he were touching his strings. And with the speakers wired reverse phase, there would be AC voltage (signal) present on the frames due to the strap connecting minus terminal to frame.
Even with the 3rd prong ground removed, the only way you could get a shock touching _only_ your own amp is if the death cap was shorted. If that were the case, he would have blown the outlet's circuit breaker when he turned the amp on after replacing the AC cord.


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## greco (Jul 15, 2007)

Still following..and getting more confused...LOL

Cheers

Dave


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## nonreverb (Sep 19, 2006)

Understood....my question was what he might have inadvertently touched while going into the back of the cab. Pretty hard to be playing AND play with the speaker. Granted if he played a note and then touched the basket, he would feel something perhaps but a nasty shock??....I always side with caution regarding this as I have had nasty shocks when playing around with ungrounded tube stuff....mostly Hammonds and they are really nasty! Getting yourself between it and a grounded item...say a microphone....brutal.



jb welder said:


> I have no doubt the AC cord should be replaced for safety's sake. I have no argument with that and do not mean to derail the thread. I'm just trying to understand the shock mechanism and also point out that power amps generate AC voltage and can produce shocks.
> Yes his feet would have been grounded. But he would be grounded to chassis if he were touching his strings. And with the speakers wired reverse phase, there would be AC voltage (signal) present on the frames due to the strap connecting minus terminal to frame.
> Even with the 3rd prong ground removed, the only way you could get a shock touching _only_ your own amp is if the death cap was shorted. If that were the case, he would have blown the outlet's circuit breaker when he turned the amp on after replacing the AC cord.


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## ampdude (Mar 17, 2011)

Guys, thanks for the continued concern and interest in this. Here's what I can tell you....

When I was debugging the cabinet rattle, I had the back cover off the cab, and the head on the floor behind it. I was sitting on the floor (carpeted) holding my guitar on my lap. No shock whatsoever touching the guitar strings. I was playing loud single bass notes to try to locate the rattle. I first touched the back of the speaker magnet, and heard a high pitched noise, while my finger was on the magnet. I then touched one of the speaker mounting bolts inside the cab, all the while playing single notes on the guitar, and that's when I got the shock. I wouldn't say it was as strong as a wall outlet shock, but it did travel up my forearm, which is still tingling even today. The only metal I was touching was the guitar strings and the speaker frame.

If there was a ground fault in the amp, wouldn't I have gotten the shock as soon as I touched the guitar strings?

Also, the previous owner was using the amp in his home studio with other speakers (EVM-12L's). I suspect that he put the Oxfords back in a hurry, when he agreed to the sale, and wired them backwards.

While the original 3 prong cord was in rough shape, I did meter a good ground connection from the 3rd prong to the chassis. If there was a short in the cord, that should have tripped my outlet's circuit breaker when I plugged it in, no?

Here's a lousy pic of where the original 3 prong cord connected (the ground wire is not visible in this pic, but was firmly attached to one of the power transformer mounting bolts on the chassis). You can see how degraded the wires are though...

Is that the "death cap" in blue under the ground switch?


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## Church-Audio (Sep 27, 2014)

Might want to also make sure that socket in the back of the anp gets looked it to make sure it's wired correctly often they are reversed. I never retention a socket for $4 I replace it if it needs to be retentioned that means it's old and worn out.you can also take out that .047 cap soldered to the chassis from the polarity switch you don't need it. If the amp has a three prong plug.


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## nonreverb (Sep 19, 2006)

I've seen new sockets that need to be re-tensioned. Part of the problem is that some companies use different diameter pins on their tubes (JJ in particular for a time) and some new production tube sockets holes are too big allowing the contacts inside to get loose. 
I've done many retention jobs on sockets that I knew were perfectly fine with no trouble or returns. Cleaning them and re-tensioning them properly is essential. 
There is a point however, where it's not worth trying to save and replacement is the only option.


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## Church-Audio (Sep 27, 2014)

Your using the wrong sockets. I use only the Belton sockets with the two metal tabs on ether side of the pin. They work the best and never need re tensioning if you get something new that needs that I would not use it as it will be unreliable in the long run. I don't fuck around for $8 it's better to just stick new sockets in loose tube sockets are the number two reason why tube amps fail. And for the cost of $8 it's so cheap it's not even wirth talking about. Takes me 5 minutes to put them in. I guess the other issue is I don't use JJ unless I absolutely have to. Like the 7027 or the 6v6 won't use the el34 or the 6l6 way to many failures for these tubes.


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## ampdude (Mar 17, 2011)

Back to the mystery of why I felt such a shock, I was doing some math on the current that could have been flowing through the speaker frame. Without knowing the phase angles to do a proper AC power calculation, I took P=I^2*R, with P=80W and R=4ohm, that would result in approx. 4 amps of current going to the speaker. You would definitely feel 4 amps at 20 - 30 volts! Is my math correct?


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## nonreverb (Sep 19, 2006)

Sorry but this discussion is deviating far from the topic. If you want to discuss further, we can start a new thread.




Amprepair said:


> Your using the wrong sockets. I use only the Belton sockets with the two metal tabs on ether side of the pin. They work the best and never need re tensioning if you get something new that needs that I would not use it as it will be unreliable in the long run. I don't fuck around for $8 it's better to just stick new sockets in loose tube sockets are the number two reason why tube amps fail. And for the cost of $8 it's so cheap it's not even wirth talking about. Takes me 5 minutes to put them in. I guess the other issue is I don't use JJ unless I absolutely have to. Like the 7027 or the 6v6 won't use the el34 or the 6l6 way to many failures for these tubes.


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## ampdude (Mar 17, 2011)

I think I can run an experiment to recreate the shock issue....I will connect my multi-meter to the speaker plug tip and ring, and then measure AC volts and current. We'll see what kind of readings I get with the amp at full power and hitting the strings hard.


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## nonreverb (Sep 19, 2006)

To do that experiment effectively you'd need a 60hz signal applied to the input. Anything deviating from that will give you a wrong reading as a multimeter VAC setting is fixed @ 60hz.



ampdude said:


> I think I can run an experiment to recreate the shock issue....I will connect my multi-meter to the speaker plug tip and ring, and then measure AC volts and current. We'll see what kind of readings I get with the amp at full power and hitting the strings hard.


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## jb welder (Sep 14, 2010)

You can't do any kind of calculations regarding current because you have a high resistance. That's why I specified the 20VAC present across the terminals at 50W output.
From your description you had one hand on your strings, the other hand on the "hot" speaker terminal (because they were wired backwards and the frame was strapped to the minus terminal). As you said, it was not as strong as a 120V shock, but still a tingle you could feel.
To get a shock, you need to be connected to 2 points of different potential (voltage). Your 2 points were chassis ground (strings) and speaker hot (white wire).
Also important are where on your body you connect the 2 potentials. In your case from hand to hand, across the heart, which is much more dangerous than if you have one finger across the plus and minus of the speaker. A shock across your hand might burn it, but won't kill you.
The biggest hazard is when you get a live chassis. This could be due to a mis-wired or 2prong plug amp and shorted/leaky death cap. Now you have 120V at your guitar strings. You are usually insulated from ground by your shoes, but if you are barefoot you can get a lethal shock because your feet are grounded. But more likely you will get the lethal shock because you touch some other ground point, such as a mic stand, grounded mic (with your lips), or another guitar which is properly grounded.
So the main thing is that to be shocked there must be a difference of potential between 2 points you are touching. 
Properly grounded 3 prong equipment means all exposed metal parts of all the gear will be grounded. Assuming the building is wired right, there can't be any difference of potential.
Another way to avoid shocks is with wireless systems. Because you have no cord grounding your strings to your amp chassis, you can't get a shock via your strings.
Dave, does that help or just confuse everything more? :confusion:

P.S. Anyone check to see if they can get a shock off their speaker yet?. Just use one hand or finger across the speaker terminals :smile-new:.


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## ampdude (Mar 17, 2011)

@ nonreverb....thanks for the clarification!

@ jb welder...thanks for the additional insight. I really appreciate all this. As I really analyze this, while I was playing the guitar to test for the rattle, I was using a plastic pick. So, I fretted a bass note with my left hand, plucked the string, and then removed my left fretting hand from the strings and touched the speaker frame with my left hand. So....I actually wasn't touching the strings and the speaker at the exact same moment. The different potential would have been my left hand on the speaker, and my body sitting on the floor.

Again, if there was a power to ground short in the amp, I should have been shocked (severely) when I fretted the strings, but that wasn't the case. I only got the shock when I touched the speaker after fretting a loud bass note.


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## jb welder (Sep 14, 2010)

Any chance your right hand was still touching the strings or resting on the bridge?
Anyway, it's all conjecture at this point, and a bit of safety info.
As far as those ground straps on the speakers, in a closed back cab they could wire them up however they wanted, no risk of shocks. Series parallel wiring would require some of the frames to be "hot" in terms of signal.
But in an open back combo, I think the minus terminals would always be wired to black for safety.


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## ampdude (Mar 17, 2011)

Thanks jb.

I'm going to open 'er back up tonight to re-do the 3 prong wiring to remove the "death cap" and have the black power wire go to the fuse before the switch, just to be on the safe side.

I've also reached out to Keith McNeil locally here in Calgary to see if he can take a look at the amp and make sure all is well. I want to play this amp without worry. I didn't buy it as a collector's item.


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## ampdude (Mar 17, 2011)

So, I did this tonight....









And it turned out like this...









So, no more "death cap", and since it's a nice .047 vintage cork sniffer cap, I may use it as a tone cap in my Strat! 

The amp powered up with no issues, no shocks, it's completely quiet, and sounds unbelievable!


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## nonreverb (Sep 19, 2006)

Nice! Cool amp BTW!


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## jb welder (Sep 14, 2010)

Nice job.
One more thing about the accessory AC outlet. I think Chris mentioned earlier that they are often wired backward. If it is a polarized type socket, one of the slots is bigger. That should be the neutral (white). Looking at the back of the socket it is very difficult to see, it can look opposite to what it really is. Double check with your meter that the larger slot is connected to white, not black.


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## greco (Jul 15, 2007)

jb welder said:


> Dave, does that help or just confuse everything more? :confusion:


Yes, it did help. Well explained. Thanks!

Cheers

Dave


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## ampdude (Mar 17, 2011)

@jb welder....Does this matter if I never intend to use that outlet? the blades are just serving as a connection point inside the amp.


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## jb welder (Sep 14, 2010)

No, if you're not going to use it, it makes no difference. But if it gets used there is a possibility of a reversed polarity situation.
It may be wired right anyway, but next time you're in there, check it and reverse if wrong. I believe it's screw terminals so fairly easy to switch around if needed.


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## ampdude (Mar 17, 2011)

Great! Thanks!


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## epis (Feb 25, 2012)

Just measure ac voltage when the amp is plugged in from ground connection ( or chassis) to the bigger slot, it should read zero.


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