I know Baz has assured me that I can use normal speaker wire, but I'm still fussing, as this is all new to me. Can anyone just clear up and answer a couple of things to put my mind at rest.
The back of the Reditune states 100V or 50V output. The two outermost being 100V, the two innermost being 50V, leaving "CT" in the middle. I note there is no -neg or +pos terminal indication, for the 100V or 50V outputs. So there's the first question, how to determine the polarity.
If we take that the 100V terminal's on the reditune, and the fact the speaker states Input 100V, that screams to me that there is 100V travelling to the speaker. As far as my numpty brain sees it, 100V line out of the reditune into the speakers transformer primary, this steps it down on the secondary, to match the chosen wattage(6W, 3W, 1.5W, 0.75W) tapping for the 8OHM speaker.
So question two, surely I can't or shouldn't use, STD speaker wire to carry 100V to this speaker. That the Heavy-Duty 2-Core 100V Line, 15A double insulated cable I have ordered, is what I should be using and hence why I bought it in the first place.
1. Polarity shouldn't matter as long as its consistent throughout the installation for all speakers wired in parallel (to avoid phase errors).
2. you just connect the red flying lead to the tapping you want for the power output and the 100V line to the block connector. Any suitable cable that can handle 100V is fine to use for such an installation - thinner speaker cable, or even CW1308 (telephone cable, after all there is over 100V on a telephone cable when it rings!). However I can see where the heavy duty stuff could be useful if you consider something like an outdoor village fête and the horn PA speakers mounted on posts - if only to reassure people doing risk assessments that the setup is safe!
The stuff you have is very similar in appearance to speaker cable I remember being used for rave/disco sound systems (which are generally standard 4-8 ohm setups with higher currents going through the cable)
Hi and thanks Alex, you've answered my queries perfectly, and my mind is now at rest. 👍
So it turns out, although the cable I ordered might be considered overkill for my little indoors installation, it is in fact good that I ordered it. Especially considering I've only got puny stranded lengths of old speaker wire cast-offs. Therefore, I was right to be concerned about them not being suitable to carry 100V and hence why I ordered the other cable.
Still waiting for that cable to arrive, but now I have the speaker I want to test the Reditune and the carts. For temporary testing, I'll use a length of mains cable.
There isn't any play, stop, or rewind, just power on, volume and track select for manual/auto choice. I believe it's an on power, constant run state motor. Insert the cart, and it immediately starts playing, hitting eject, appears to just disengage the cart, as I say, I believe the motor would still be running.
There's one of those Little fuse breakers in the line, it's perfectly fine, operating it cuts main power. There's only two wires going to the motor and as far as I can see it's getting 235V, there is no obvious reason as to why it's not running, certainly is not seized.
I'm hoping there's not a board missing, and it's just an option not fitted. There is a floating plug up top, but no PCB stand-offs remain. No manual, no cct, so I'm working blind, but as I say, I only see two wires to the motor, no logic controlling or detecting. Only thing I can think to do is remove the motor and independently supply it with 240V.
The trouble is that if you measure the resistance of the motor windings then an open-circuit may be just that, or the presence of a cap in the windings. I'd have the motor apart - sadly, you have little to lose at the moment 🙁
I know Baz has assured me that I can use normal speaker wire, but I'm still fussing, as this is all new to me. Can anyone just clear up and answer a couple of things to put my mind at rest.
The back of the Reditune states 100V or 50V output. The two outermost being 100V, the two innermost being 50V, leaving "CT" in the middle. I note there is no -neg or +pos terminal indication, for the 100V or 50V outputs. So there's the first question, how to determine the polarity.
If we take that the 100V terminal's on the reditune, and the fact the speaker states Input 100V, that screams to me that there is 100V travelling to the speaker. As far as my numpty brain sees it, 100V line out of the reditune into the speakers transformer primary, this steps it down on the secondary, to match the chosen wattage(6W, 3W, 1.5W, 0.75W) tapping for the 8OHM speaker.
So question two, surely I can't or shouldn't use, STD speaker wire to carry 100V to this speaker. That the Heavy-Duty 2-Core 100V Line, 15A double insulated cable I have ordered, is what I should be using and hence why I bought it in the first place.
Anyone..... or am I being really thick?
The very cheapest ordinary speaker wire from RS states the pvc insulation is rated at 60V, but hang on a moment as that would be 60V for each core, therefore it should withstand 120V between each core as it is two core flat (figure eight shape cross section ie. two cores laid side by side which are easily separated or pulled apart if you like
The data sheet is sparse as it just just says the PVC is rated at 60V, so not really clear, however cable data usually only gives the basic spec for one core no matter how many cores are actually in a given cable.
Another thing is this is not a power feed cable it is a signal cable for want of a better term, as this signal is a constantly varying AC (music/speech) and is not constantly kicking out anywhere near 100V AC for anything but the very loudest peaks of the signal and only for the briefest moments depending on the material being played back of course, also that is 100V AC max across the pair and not a 100V to each core.
The data sheet is a PDF which cannot be attached here of course, take note of the cross sectional drawing in the data sheet to see what I was referring to in my above post.
It's unlikely they'll take on such a small machine but do you have any motor re-winders near you?
I had no idea, so did a search, the first on the list, and there's one within walking distance. Suspect as you say, they laugh when I say It's for a vintage tape player, or charge an absolute fortune for a bespoke piece of work, No harm asking though.
R F Nunn Ltd, Bishop Auckland | Electric Motors AC-DC MOTOR REPAIRS & REWINDS SUPPLY NEW & RECONDITIONED MOTORS GENERATOR REWIND - REPAIR. Our Products & Services. AC- DC Motor Repairs
@crustytv Well, you never know - they may find it an interesting curiosity and so take it on. I've certainly had help from the most unlikely of places when I've told them what something is for - it piques their interest in some cases.
I visited the local electrical motor specialist company this afternoon. It was such an amazing place, very old school, and so much of the kit in there was relatable. Plenty of old meters, vintage tin signs all over the wall, coil winders etc, it was like stepping back in time, and the smell, oh so vintage Anyway, a two chap outfit and the chap I spoke to, Ian, was ever so helpful.
We took the motor to his bench and he confirmed my findings, the motor does have an o/c winding. He took it apart and could see corrosion on all of the 4 windings.
Ian stated he would have happily rewound it for me for free. However, he further stated that this motor would have had all the windings originally done by hand, it cannot be done on any of his winding machines. This due to the limited space in the casing, doing it on the machines, would leave the coils too large to fit. He showed me that the people who made it, faced the same problem, and this is why he knows it was done by hand. The coils are so close to the case, it had been insulated to avoid shorting.
Due to this being a direct run motor (no motor run cap) there are special copper plates installed. To repair this manually means it has to be done in situ, feeding the wire through and looping, ensuring the windings are exactly placed with these copper plates. The time involved would be astronomical. I asked what the cost would be, as I was prepared to pay. He stated it was not the money, the sheer time and PITA of doing it, was the problem.
He said he could get me the wire and show me how to do it, but equally, and he said, it would not be for the faint-hearted. Ian estimated around 500+ turns on each winding, and there are four of them. They would have to be unwound and counted. As much as I would like to have the machine running, I'm not up for this task either. Ian reckoned a new motor with the correct speed and 5 mm shaft, could likely be sourced from suppliers, it might need some adapter plate to mount it into the machine.
He then rushed off to find some books and when he came back had a 1400RPM (same as the reditune). It was the same diameter, the only difficulty, it's a bit deeper and the shaft is greater than 5 mm, Ian powered it up, and it worked fine and said, “you can have this FOC, it helps in any way”. He also gave me a number of a local engineering company and said they would reduce the shaft for me and probably for free too, if I mentioned him.
I thanked him for his kind offer of a motor, also for being so helpful and spending so much time testing, and offering advice.
So there we are, I'm now going to try and see if I can make an adapter plate to mount this motor, and then get its shaft reduced. I can use the base of the original (on the left) to make the adapter plate, to mount the new motor (on the right). If all this can be done, I should be back in business.
He did ask what it was for and why. I explained I repair vintage TVs and other bits, that I had a little private museum that I've laid out as a shop. That I dearly wanted to have a period background music system running. Coupled with the fact this unit was Rediffusion, and their factory used to be only a couple of miles from where I lived, made it all the more relevant to my collection.
Wow! - WHAT a result!!! Not only to find someone willing to take the time out to explain how it was made in the first place, but to actually have a motor!!
I know what he means about winding by hand: I have that onerous task awaiting me one day, except in my case it's damaged deflection coils on my Baird T18/C...
Yes indeed, a very helpful chap, you were right about folk being intrigued, guess it's a rare departure from the normal things that pass across their benches.
Taking some measurements this evening
The old motor casing depth was 46 mm, the replacement motor casing depth is 66 mm. The shaft lengths protruding from the case are different, 46 mm and the replacement 66 mm, nice whole numbers. This means to fit inside and have the same clearance, the shaft needs to be shortened by 40 mm, though I may have a little leeway.
Not forgetting, the shaft also has to be decreased in diameter from 10 mm to 5 mm. This will then allow me to fit the brass collar, that slides onto the shaft, for the belt to sit on. If you look at the previous photos, you will also see there was a very large plastic fan that sat right on the top of the shaft. This was to provide cooling, I doubt there will not be enough shaft or room to fit this, I will need to see. If not, my solution will be to take a 12V tapping from somewhere from the cct, and fit a PC fan to provide the necessary cooling.
The motor has cleaned up very well.
All my projects since Jan 2021 when I started the G6, through to the 4K and now this, all have had major stumbling blocks. Missing parts or failed essential parts. 😥
All my projects since Jan 2021 when I started the G6, through to the 4K and now this, all have had major stumbling blocks. Missing parts or failed essential parts. 😥
That goes with the territory I am afraid Chris, this is common in the world in which you, and most of us like minded souls on these types of forum want to play in.
The replacement motor is back from Shildon Engineering, the shaft is now the correct diameter to attach the collar for the drive belt. Now the next tricky bit, fit this into the Reditune machine, which will entail new mounting holes to be drilled. Then, due to the increased size of the motor body, reduce the shaft length, so it fits inside. Hopefully leaving enough shaft to fit the belt collar. If I'm lucky hopefully the fan can be attached to the end, but I've a sneaking suspicion, there will only be enough for the collar, if so that will suffice.
