Any electrocutions in the house? I have an electricity question

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gnd567 said:
I have an electrical question and hope someone could help because I know nothing about this sort of thing.

I'm a professional guitarist and one of my main pieces of gear died, an old 70s tape-echo. Anyway, they were made in the UK and mine was one of the export models made for the US so it runs on normal US 110v power.

Anyway, since mine died, I had to find a replacement but the only one that I found that was in mint shape was a UK 220-240V model. I bought it anyway.
I also purchased a 500watt step up-step down transformer. My question is, will using it to power my British-made device be too much and trip the breaker? I can't afford to be tripping breakers at every gig because of my equipment.

I must admit I'm a little afraid to try it when it arrives because I don't want to ruin the machine or worse, electrocute myself. Any help would be much appreciated.
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I'm an electronics engineer by trade here, designing power circuits and with 23+ years experience in the trade.

Do you happen to have a model number or schematic available for this? I could certainly give best advice based on information from the manufacturer that shows the internal circuitry. Other than that, I can give some general guidelines:

1. Going from 110V to the 220V through the transformer should not be a major issue unless the power draw on the item is too high. If it wants more than 500W of power, you won't be able to run it successfully off the transformer you have. The transformer core will saturate and you won't be able to get more power out of the transformer, things won't run properly. There might be a label on the device somewhere that tells how much power draw it takes in either watts (W) or amperes (A). Either way, you're not going to trip any breakers that you wouldn't have tripped with the old unit, the power draw is likely the same. Where the 110V may have taken 1A to run, the 220V model will take approximately half that, or 0.5A. No matter, the step-up transformer also limits how much power you can pull, and 500W is not enough to trip any normal household breaker.

2. The difference in 50Hz vs. 60Hz will not give an issue unless there is circuitry inside that specifically uses that frequency to do something. If the motor runs directly off the AC line based on the frequency, it will run faster here in the States. If instead it is a DC motor, then there is a circuit inside that converts the AC to DC and the motor won't see any difference. There are very few electronics that actually rely on the line frequency anymore, and a huge amount of modern electronics are designed to run from either 110V/60Hz or 220V/50Hz without needing anything to be done save ensure you have the right plug for the wall socket.

If you can get us some info on this thing, I can do some digging and see if I can come up with some specs or a schematic for it and give definitive answers on compatibility. Hell, with a schematic and an idea of what actually happened to the old one, it might even be repairable, 70's tech is much more easily repaired than anything modern. The older stuff was done with individual transistors (or tubes, depending on age) and components, items that can be easily replaced once the bad area is located. Newer stuff just runs straight into a custom IC, where it's easier to just replace an entire board or get a new item (I should know, I repair my own test equipment).
 
Just as an aside, I did a little research on what a tape echo is and it looks like it uses analog tape recording to loop the sound back in after a delay. It looks like a lot of these use old cassette tapes, and this will likely not give any issues with the internal motor, as the motors on those things are all small things, below 1W of power, so I doubt you'll run into any power issues with this. The motor also does not run on line frequency, it exists just to wind the slack tape onto the reels, and the speed of it is entirely controlled by the rollers that keep tape speed constant. Almost all of these things will run off low voltage DC, so I'd bet everything is converted from AC to DC and then run from there.

I'm still interested in how the old unit failed, it might be possible to repair if you've got an interest in doing so.
 
RubberJin said:
Sorry to be blunt but slomo is totally wrong about any danger with 50/60 hz especially in something old and analogue.

The worst that's likely to happen with the wrong frequency is the motor will run 20% too fast.

Almost NOTHING cares about 50/60 hz as almost everything converts the AC mains to much much lower DC voltages before doing anything and it's incredibly rare for anything other than ancient CRT TV's or AC motors to sync with the mains frequency.
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Yes old and analog won't care. Look back at what I wrote though. Electronics, especially newer ones will have a inherrent danger to them if you connect the wrong herts to them.

I stand correct, and I know this because I do electrical design engineering for the military and international businesses. I've come across exactly this same issue before, and I can confirm if you hook up newer 50htz equipment to a 60htz supply, then you will have smoke, and possibly fire.

Like I, and the others, have ready said though. The OP will probably be just fine with his older equipment. I tend to err on the side of caution though, hence why I recommmended the extinguisher. I keep one in each of my cars, two in my house, and even one more in my work shed. So far they've been the best money I've ever wasted (never used). May all extinguishers be a waste of money forevermore.

And ps. Exactly what hidden continent do you live on where NOTHING runs on AC because it all converts to DC first? I guarantee you that isn't the US or UK.
 
Still waiting on it to arrive. Should be here soon. I hope all goes well. My old one is in the shop getting repaired so if all goes well I'll have TWO instead of one. Starting to feel a little better about it since everyone seems to think it'll be just fine, including some people who work on music gear. Keeping my fingers crossed.
 
Let us know the cost of the repairs on the old one, please.
And don't worry any further repairs that may eventually be needed as virtually everything involved can be replaced, repaired or fabricated on your kitchen table (or a nimble-fingered friend's).

By the way, as the new one is coming from our end, checking it over for rust would be worthwhile.
 
gnd567 said:
Any electrocutions in the house?
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I've had plenty of electrocutions in the house and elsewhere. I'm pretty much impervious to electrocution though so they were really just shocks. I even test the ignition components of engines with my bare hands, and I can tell you the magnetos on small engines put out far more power than anything I've experienced on bigger engines with distributors. But really not much compares to touching a large, charged capacitor in a big old cabinet type CRT TV (you know the old ones that came built-into large wood cabinets), high voltage plus high current.

Anyway, back on topic, I'm an electrician and electrical engineer and electronics repairman and many other hobbies as well, and what I would have said has already been said by "ade" and "AnalogRTO" (i.e. I agree with them).

Oh and don't go electrocuting yourself, for electrocution is, according to the dictionary "the act of killing or putting to death by electric current".
 
Now this just happens to be a field that I know extremely well. I can't say why that is, because I will 'out' myself due to my high web presence elsewhere.

First off, I think you ought to try getting your original echo unit repaired. Electronics don't 'die', faults develop and faults can be fixed. It might not be cost effective to fix, indeed it might be counterproductive to your music-making, but normally the only thing that puts a tape-based machine beyond economic repair is head wear and that doesn't happen suddenly.

Now, regarding running the UK unit on 60Hz. Most echo units (you don't say which model you have) use induction motors which are frequency-dependent. A 50Hz induction motor WILL run 20% fast on 60 Hz, and while this won't affect the pitch (because you are playing back your own recording) it WILL make the echo delay time 20% shorter, and may slightly affect the frequency response unless adjusted, because this depends on tape speed. That is the only likely effect of 60Hz on the unit, and subject to mechanical interchangeability this can be corrected by either a) fitting the 60Hz motor which will have slightly different windings and a different capstan diameter, or b) if possible transferring the 60Hz capstan to the UK motor. There is a slight snag if the 60Hz motor is 120V and the 50Hz is 230V, and there is no 120V tap on the power transformer or it isn't large enough to auto-feed the motor. Some units can tolerate this mod, some can't.

Regarding the transformer, the input power to a transformer is governed by the load. If you connect a load of say 50W, which is about all a tape echo will use, the transformer will consume the 50W plus its losses, which on a 500VA transformer might be an extra 10W. It is much smaller than the transformer in a microwave oven, so even with the inrush (a kind of current surge that transformers consume at the moment they are switched on) any outlet that will power a microwave, or a refrigerator, will be quite OK with a 500 or even 1000VA transformer. Of course, if the echo only uses 50W, you don't need to schlep such a large transformer around!

There are lots of other effects (mostly minor ones) of using equipment on the wrong frequency, especially using 60Hz equipment on 50Hz which sometimes causes it to run hot, but the specific effect depends on the particular design of the equipment. I won't go into detail about those here because we are talking specifically about a tape echo unit, and I don't want to confuse things. Some devices are completely unaffected, some won't work quite correctly and very occasionally, some might be damaged.

Contrary to Slomo's comment, most modern electronics (apart from large industrial machinery) are frequency independent and often worldwide-compatible for voltage too. I am standing in a warehouse of many thousands of pieces of equipment from all around the world, that we ship all around the world on a daily basis. With the exception of the UPS units (uninterruptible power supply) which are both voltage and frequency specific, I don't think a single device in the warehouse would care which frequency you gave it. To the best of my knowledge, out of the hundreds of thousands of pieces of equipment I have been responsible for, nothing modern and purely electronic has ever blown up due to incorrect freq. Wrong voltage, yes; but not wrong freq. OTOH washing machines, record players, welders, fluorescent lights, frequency will have an effect, possibly critical, on all of them. But I've just cast an eye over the equipment in my lab; about 120 electronic devices, not one of which is frequency dependent. About 1/3 of them need the voltage selected manually, the other 2/3 you can plug in anywhere in the world.
 
Paxe said:
Now this just happens to be a field that I know extremely well. I can't say why that is, because I will 'out' myself due to my high web presence elsewhere.

First off, I think you ought to try getting your original echo unit repaired. Electronics don't 'die', faults develop and faults can be fixed. It might not be cost effective to fix, indeed it might be counterproductive to your music-making, but normally the only thing that puts a tape-based machine beyond economic repair is head wear and that doesn't happen suddenly.

Now, regarding running the UK unit on 60Hz. Most echo units (you don't say which model you have) use induction motors which are frequency-dependent. A 50Hz induction motor WILL run 20% fast on 60 Hz, and while this won't affect the pitch (because you are playing back your own recording) it WILL make the echo delay time 20% shorter, and may slightly affect the frequency response unless adjusted, because this depends on tape speed. That is the only likely effect of 60Hz on the unit, and subject to mechanical interchangeability this can be corrected by either a) fitting the 60Hz motor which will have slightly different windings and a different capstan diameter, or b) if possible transferring the 60Hz capstan to the UK motor. There is a slight snag if the 60Hz motor is 120V and the 50Hz is 230V, and there is no 120V tap on the power transformer or it isn't large enough to auto-feed the motor. Some units can tolerate this mod, some can't.

Regarding the transformer, the input power to a transformer is governed by the load. If you connect a load of say 50W, which is about all a tape echo will use, the transformer will consume the 50W plus its losses, which on a 500VA transformer might be an extra 10W. It is much smaller than the transformer in a microwave oven, so even with the inrush (a kind of current surge that transformers consume at the moment they are switched on) any outlet that will power a microwave, or a refrigerator, will be quite OK with a 500 or even 1000VA transformer. Of course, if the echo only uses 50W, you don't need to schlep such a large transformer around!

There are lots of other effects (mostly minor ones) of using equipment on the wrong frequency, especially using 60Hz equipment on 50Hz which sometimes causes it to run hot, but the specific effect depends on the particular design of the equipment. I won't go into detail about those here because we are talking specifically about a tape echo unit, and I don't want to confuse things. Some devices are completely unaffected, some won't work quite correctly and very occasionally, some might be damaged.

Contrary to Slomo's comment, most modern electronics (apart from large industrial machinery) are frequency independent and often worldwide-compatible for voltage too. I am standing in a warehouse of many thousands of pieces of equipment from all around the world, that we ship all around the world on a daily basis. With the exception of the UPS units (uninterruptible power supply) which are both voltage and frequency specific, I don't think a single device in the warehouse would care which frequency you gave it. To the best of my knowledge, out of the hundreds of thousands of pieces of equipment I have been responsible for, nothing modern and purely electronic has ever blown up due to incorrect freq. Wrong voltage, yes; but not wrong freq. OTOH washing machines, record players, welders, fluorescent lights, frequency will have an effect, possibly critical, on all of them. But I've just cast an eye over the equipment in my lab; about 120 electronic devices, not one of which is frequency dependent. About 1/3 of them need the voltage selected manually, the other 2/3 you can plug in anywhere in the world.
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I didn't know offhand what type of motor a tape echo unit uses. If it is just a simple cassette motor (some of them look like this is all they have), it is likely running from some internal DC rail. These motors are small, otherwise we wouldn't have things like the Sony Walkman. Having a schematic and more information beyond just what the device is always helps when you don't know the internals of a piece of equipment beyond the front panel.

You are absolutely correct about most modern electronics. Rather than being designed for one voltage and frequency, they are now designed to handle any of the different worldwide standards. People should also be aware that this also means that they are often capable of running to 50% high and 50% low on these voltages as well, as line voltage (though not line frequency) can vary a huge amount. All most people have to do is look at the rating on the little brick supply for your laptop to see that it works on both 110V and 220V systems, you just need the proper plug. I will admit, such a thing made my last visit to my daughter in Australia really nice since my laptop, cell phone chargers, etc. all just needed a plug adapter and not a transformer!
 
All the units I've worked on, Copicat, Echoplex, Selmer, VOX, Fender, all used induction motors. There are present-day units with DC motors, even combined with tube electronics (e.g. Fulltone) but the oldies such as the OP was referring to were induction, just like the open-reel recorders of the era (except for the exotics). In the tape echo's heyday electronically commutated DC capstan motors were rare and expensive, used ony in machines like the Nagra and Uher, as were chopper controlled hysteresis motors as in the Studer. Brush motor speed regulation by centrifugal governor was never great and by external TG feedback was again expensive, and the brush motor was noisy and had a limited service life. So induction was the obvious choice for a basic 1/4" semi-pro tape transport when AC power was available. By the late 1970s brush motors with TG control started creeping into places they shouldn't really have been, including otherwise decent semi-pro decks with good audio specs but flimsy transports.

So yes, OP, if your unit is late enough to have a DC motor, then it will run at the correct speed even on 60Hz, but as you are into old stuff I think this won't be the case. It would be helpful to know what model of echo unit we're talking about here though!
 
Paxe said:
All the units I've worked on, Copicat, Echoplex, Selmer, VOX, Fender, all used induction motors. There are present-day units with DC motors, even combined with tube electronics (e.g. Fulltone) but the oldies such as the OP was referring to were induction, just like the open-reel recorders of the era (except for the exotics). In the tape echo's heyday electronically commutated DC capstan motors were rare and expensive, used ony in machines like the Nagra and Uher, as were chopper controlled hysteresis motors as in the Studer. Brush motor speed regulation by centrifugal governor was never great and by external TG feedback was again expensive, and the brush motor was noisy and had a limited service life. So induction was the obvious choice for a basic 1/4" semi-pro tape transport when AC power was available. By the late 1970s brush motors with TG control started creeping into places they shouldn't really have been, including otherwise decent semi-pro decks with good audio specs but flimsy transports.

So yes, OP, if your unit is late enough to have a DC motor, then it will run at the correct speed even on 60Hz, but as you are into old stuff I think this won't be the case. It would be helpful to know what model of echo unit we're talking about here though!
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It's a Copicat: the solid-state version, not the tube version. Late 60s-early 70s. I live in the US and it's a UK machine.
 
OK, I looked one of these up online and the capstan motor does run directly off the mains line. So, yes, that motor is going to run a different speed and there is no simple way to adjust one of those.

Paxe obviously has had a lot of experience working on these, while I'm coming at it from the direction that I do electronics for a living and am just trying to help with my knowledge and experience. I'd definitely follow Paxe's advice here, it sounds like he's had his hands directly inside one of these before.

Looking at a schematic for the IC version of these, it's not a complex thing. Depending on what went wrong, it could be an easy fix or could be more involved. There's four op amps (741 op amps, still can be found in abundance today) and a couple power transistors in the oscillator section (those look to be obsolete, but can likely be cross-referenced to a newer device). Beyond that, it's just discrete resistors and capacitors together with the transformers.

My first bets, knowing the age of the equipment, is that some of the capacitors need replaced. It looks as if there are a couple big electrolytic capacitors that come straight off the transformer to generate the supply for the 741's and electrolytic caps are known to dry out over time. Having a cap or two go open in there could definitely cause some problems.

It all depends on how things 'failed' in there that caused you to need it repaired. Transformers rarely fail, so one of those going is unlikely. The capstan motor could have problems (moving parts are always prone to issues), and depending on how easy it is to find a replacement there, that could be hard to fix. As for the rest of it, repair is certainly possible.
 
The UPS truck just dropped it off but I have to go to work so I won't be able to try it until tomorrow. Hopefully I don't blow up a $700 piece of vintage equipment. The old one is in the shop and should be ready in a week or so. The guy said some caps probably need replacing.
 
Here's me deferring to Analog, who's deferring Paxe.
I was trying to see if these brands had a 12v DC option , them being portable and all, I don't know if that would be a worthy or possible modification as the PCBs seem to have significant variations.

Another thing is that from my reading up, I got the impression that these machines, and some other makes, lie behind the modern folklore of the electrocuted rock guitarist, so it would definitely be advisable to have it checked out by a pro and ask for any other advice related to powering or modifying.
 
OK so with the solid-state Copicats, there are two different power arrangements. If it is the MkIV - transistor not IC-based, then you might be lucky and find it has a 110-120V position on its voltage selector, in which case you won't need your transformer, simply attach a grounded plug to the cord and select 120V. Note old (pre 1970s) UK colours: Red=hot, Black=neutral, Green=ground. New: Brown=hot, Blue=neutral, Green/Yel=ground.

If it is the Super-IC then it may have a motor-transformer, i.e. combined motor and power-transformer. This consists of a regular shaded-pole induction motor with a low-voltage secondary winding wound onto the motor stack. These were popular in that era for electronics with very low power consumption, such as basic record players and tape recorders. In this case provided there are eight wires coming from the motor-transformer, it can be reconnected to work on 110-120V by re-soldering the leads to different terminal tags, and changing the fuse to a 500mA type. Or, of course, leave as-is and plug into step-up transformer, making sure the grounding is carried through from the transformer's supply cord to the echo unit.

In either case the electronics will work fine, but if there ever was a difference between the 50Hz and 60Hz machines, the echo delay will be 20% shorter on the UK machine due to the motor running faster. But the more I think about this, the less clearly I recall the versions. It occurs to me now that the capstan is actually the motor shaft itself, there is no removable part that could be swapped for the different frequencies. To clarify, UK and US motors will both rotate at the same speed on 50Hz, and both 20% faster on 60Hz. If there is a difference on account of frequency, it is in the capstan diameter not the motor itself. It will be interesting to confirm whether the capstan on the UK machine is larger than on your US-supplied version.
 
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Paxe said:
OK so with the solid-state Copicats, there are two different power arrangements. If it is the MkIV - transistor not IC-based, then you might be lucky and find it has a 110-120V position on its voltage selector, in which case you won't need your transformer, simply attach a grounded plug to the cord and select 120V. Note old (pre 1970s) UK colours: Red=hot, Black=neutral, Green=ground. New: Brown=hot, Blue=neutral, Green/Yel=ground.

If it is the Super-IC then it may have a motor-transformer, i.e. combined motor and power-transformer. This consists of a regular shaded-pole induction motor with a low-voltage secondary winding wound onto the motor stack. These were popular in that era for electronics with very low power consumption, such as basic record players and tape recorders. In this case provided there are eight wires coming from the motor-transformer, it can be reconnected to work on 110-120V by re-soldering the leads to different terminal tags, and changing the fuse to a 500mA type. Or, of course, leave as-is and plug into step-up transformer, making sure the grounding is carried through from the transformer's supply cord to the echo unit.

In either case the electronics will work fine, but if there ever was a difference between the 50Hz and 60Hz machines, the echo delay will be 20% shorter on the UK machine due to the motor running faster. But the more I think about this, the less clearly I recall the versions. It occurs to me now that the capstan is actually the motor shaft itself, there is no removable part that could be swapped for the different frequencies. To clarify, UK and US motors will both rotate at the same speed on 50Hz, and both 20% faster on 60Hz. If there is a difference on account of frequency, it is in the capstan diameter not the motor itself. It will be interesting to confirm whether the capstan on the UK machine is larger than on your US-supplied version.
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It's a MkIV. Curiosity got the better of me and I tested it out earlier today. It works fine as far as I can tell and doesn't seem to be giving me any problems. I haven't had a lot of time to use it for more than 10 mins but I think everything will be okay. It's the bottom one in the picture. The top one is the old and it's being repaired now so hopefully I'll have two working units.

COPICAT.jpg
 
Now that's music to our ears.

And no smoke escaped either! That's a good thing, the smoke is supposed to stay inside the wires so it can run everything (it's very similar to how steam works).
 
It would be interesting to know, when you get your original unit back, whether the capstans are the same diameter. The electrolytic caps in these are all of an age where they may fail regardless of the usage it has or hasn't had. If that's what your old one needs, then once done it should be good for another few decades. You might of course need to do similar maintenance to the new one, if it hasn't been done already. A lot of early S/S gear is still running with at least some original electrolytics, but they are starting to become a liability for performance environments and can detract from audio quality.
 
Though I'm not one who has handled these units before or worked on them, I do take a little pride in having the knowledge of what the primary fault on the unit most likely is. I'm glad to hear you've got one unit working and the other one getting repaired. Additionally, it's good to know you didn't have a problem getting the new one up and running. It will be interesting to hear what they do for the 50Hz vs. the 60Hz difference, whether they just adjust the capstan diameter or not. Given that the difference in capstan diameter would be slightly less than 10%, it might be hard to determine if that's what they do.

I looked at the schematic for the Mk. IV version, and it doesn't use the op amps like the follow-on version. It looks like a lot of the gain isn't controlled by negative feedback like the version with the 741's would, but instead comes from the resistor ratios for emitter vs. collector. Not quite as well-controlled, but it still works. If the transistors have been damaged, cross-reference devices may or may not be available, but these are not as likely to have an issue. As Paxe agreed, the problem is likely the electrolytic caps in it.

As for all electronics, yeah, we do it with smoke and mirrors, which is why they stop working when you let the smoke out.
 
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