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Project 1960s Rediffusion Reditune TP48A

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crustytv
(@crustytv)
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Hi David,

The replacement belt for the TP48 arrived today, wonderful, I cannot thank you enough for your generosity. I shall waste no time and get that fitted this afternoon.

I hope I have the opportunity, at some point in the future, to return the favour. It's not much, but I noticed you didn't have access to the forums service data library, you do now. 👍 

Chris

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Edit:

Also found a much better rear scale for the volume knob,  for the one that was missing. The one I had thought reasonable (see above), was too big, this one is near perfect (see below).

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restored
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Topic starter Posted : 08/03/2022 1:59 pm
jcdaze
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Hard to believe that that machine is the same one that you started out with and that it actually works. Just shows what perseverance and determination can achieve. Anyway, I was going to say that the speaker output on the 2 pin socket would probably just been to monitor the audio output. As the tape player is designed to be used for background music in a hotel/factory/shop or whatever, then I suspect that an output at line level was taken from the 3 pin din socket and fed to a more powerful amp with 100 volt line capabilities, to feed as many speakers as may have been required. The wattage tappings on the 100 volt line speakers then allow for audio levels to be set different in different areas on the same system as required. 

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Posted : 08/03/2022 3:08 pm
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Cathovisor
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@jcdaze The symbols on the two DIN sockets indicate a microphone for the 5-pin and a record player for the 3-pin. 

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Posted : 08/03/2022 4:14 pm
AncientEngineer
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Posted by: @crustytv

Hi David,

The replacement belt for the TP48 arrived today, wonderful, I cannot thank you enough for your generosity. I shall waste no time and get that fitted this afternoon.

I hope I have the opportunity, at some point in the future, to return the favour. It's not much, but I noticed you didn't have access to the forums service data library, you do now. 👍 

Chris

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Thanks Chris, 

You're welcome.

Thanks for the link to the service data. I have most manuals, but there's always the odd one that I don't have.

As you've probably gathered, my career was very varied; I started off in domestic Radio & TV, an apprenticeship with Rediffusion. After colour emerged, I was head-hunted by an advertising agency, as Studio engineer & projectionist. So I then got to grips with the then state-of-the art TV cameras, Telecine flying-spot scanners, professional audio /video machines and 35 & 16mm projectors.

Further down the line, I moved on to broadcast equipment, but this was with suppliers, not a broadcaster. I was therefore lucky enough to be able to keep up with both the broadcast & domestic kit. Strangely, after may years, & just before retirement, having been made redundant for the nth time I took a local job refurbishing returned Plasma & LCD TV's.

That was a very interesting time, as my employer was a slave-driver, & we had no test equipment or service manuals. (or spare parts!) So I took to downloading the relevant IC data when I needed to fault-find to component level, then work backwards to see how the set manufacturer had utilised the particular chip in their sets. I did complain that things should have been the other way round: That I should have started off in the early '60's with microscopic SMT devices, & then progressed on to international octal valves etc, as my eyesight now has to rely on microscopes to see the components... 

 

This is why I have such a vast collection of components/spares etc that cover a wide range of electronics.

Enough, I digress.

Back to the TP48; I do agree with others who've suggested that although the machine now works perfectly as it should do, that you might think about digitising the tape content, before it deteriorates further. If you have any spare cartridges with fairly worn out tapes inside, you could of course re-load them & make  some new tapes!

The 100v line idea would be good, you could then distribute the sound around your museum area. You've made such a wonderful job of that refurbishment, it almost looks like new,

 

David.

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Posted : 08/03/2022 4:34 pm
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jcdaze
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@cathovisor I'm only guessing that the 3 pin din socket has audio out as well as in. The only way to know for sure would be to trace the wiring back or put a scope on there and look for audio as there is no circuit diagram. 

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Posted : 08/03/2022 8:35 pm
WayneD
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BLIMEY! 😎 

I've been away from the group for a few days and come back to this! Seriously amazing work there, Chris!

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Posted : 08/03/2022 9:46 pm
Cathovisor
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@jcdaze Agreed - although I think given this seems to be a very basic unit compared to the other one Chris has, I can't help but think a few speakers in series-parallel would be enough for a small shop, driven from what's likely a 10W amplifier.

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Posted : 08/03/2022 9:50 pm
jcdaze
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@cathovisor It is basic indeed and you may well be right and I'm thinking of it's use in a larger area than for what it is intended for. It would good to find some info on it somewhere. 

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Posted : 08/03/2022 11:05 pm
crustytv
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Posted by: @jcdaze

It would good to find some info on it somewhere. 

Indeed, it would, however, there is virtually no info out there, believe me I've looked. Radios-TV VRAT is rapidly becoming the site with the most info. It is now the only source with lots of detailed pictures and findings on the TP80/TP48A. As and when I glean more info, I'll try to incorporate it.

This is what I'm piecing together on the product range. I guess the Stereo TP80 would be for a smaller setting, like a club or restaurant, certainly not a large supermarket, that would have been the TP80 option.

redihist

 

Reditune:

TP-1 Used a Möbius loop tape that looks like a standard NAB B/C size cart, but the head spacing is different, so not compatible. The pinch roller rises up through a hole in the bottom of the tape cartridge, just like a NAB. Speed 3.75ips, single track.

£56 p.a. rental only

p.s.
There's a TP1 for sale online, though the price, ouch!

TP-48 The cartridge is the same size as TP1, but it has an integral pinch roller. Speed 1 7/8 ips and a head that selects one of 4tracks by lifting the head (like an 8-track domestic cart).

Price: unknown

TP-48A MKII As above, tape speed 1 7/8 ips - this allowed the cartridge to be halved in depth from TP1. 10W output 4-hours continuous music.

Price £60

TP-Mini For smaller establishments which previously could not justify the price TP1 or TP48. The TP-Mini is sold outright in kit form and includes a playback machine, two loudspeakers, all connections and instructions for do-it-yourself installation.

Price £38

TP-80 As above but more powerful amp (100v line) and cart area enclosed.

Price: unknown

TP-80S As above but stereo

Price: unknown

RM1, RM2, RMA Continuous compact cassette. RMA was the separate amplifier.

Price: unknown

RM3 As above but CD version

Price: unknown

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Topic starter Posted : 09/03/2022 12:51 am
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Cathovisor
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Posted by: @crustytv

I guess the Stereo TP80 would be for a smaller setting, like a club or restaurant

Many years ago (as in, forty) we frequented an Italian restaurant in town. The music in the restaurant was provided via a high-end Clarion auto-reverse car cassette player with multiple amplifiers and IIRC Pioneer loudspeakers in the ceiling; the restaurant owner's brother owned a shop that sold car audio...

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Posted : 09/03/2022 12:35 pm
crustytv
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Finally, the two 22K log pots have arrived from the Netherlands. I can replace the non-functional tone control with one of them, however, the other will be put into stock. I cannot use it to replace the volume control, as it does not have the centre tap.

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I've no idea where I will ever find a 20-25K centre tapped log pot, so it looks like I'll be stumped.

I'm curious, could David @ancientengineer or Mike @cathovisor explain. What the consequences of using the other spare 22k Log (non centre tapped) for the volume pot? What function would be lost, would it render just the tone control inoperative, or mean minimal function, or no function tone/bass achieved?

I would dearly like to have replaced the volume pot, although it's much better than it was, I feel it's far from ideal condition, but if I can't, then I can't.

If it were possible, I take it, I just remove the 1uF from circuit?

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Topic starter Posted : 14/03/2022 12:38 pm
Cathovisor
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@crustytv Does the other end of that 1uF cap go to earth, so to speak? (it looks like it does) If so, just leave it out of circuit and fit the new pot. All you'll lose is the top cut at low volume settings. 

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Posted : 14/03/2022 1:33 pm
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Cathovisor
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Of course, if you wanted to go mad, you could built a stepped attenuator using a 1 way 12 pole switch, and then you would have ready access to a tap...! 

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Posted : 14/03/2022 1:41 pm
crustytv
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The old tone pot fell apart when removed, to be honest, I cannot tell any difference with the new tone pot installed. If there is any change in tone, my cloth ears are not detecting it.

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Posted by: @cathovisor

Does the other end of that 1uF cap go to earth, so to speak? (it looks like it does) If so, just leave it out of circuit and fit the new pot. All you'll lose is the top cut at low volume settings

Thanks, Mike, yes, the top end of the 1uF does go to the chassis, in which case I will replace the volume pot as well.

The speaker cabinet turned up, boy has that made a difference too, lots of volume.

fin

Edit:

Replaced the volume, and now I have total control from min to max.

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Topic starter Posted : 14/03/2022 2:28 pm
crustytv
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Out of curiosity, I took apart the old tone control, quite evident why it was non-functional, no carbon to speak of left on the track.

tone1
tone2
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Topic starter Posted : 15/03/2022 12:07 am
crustytv
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I have two Reditune carts that won't play. Upon further investigation, one tape's pinch roller does not freely rotate. This was down to the bearing having seized. The second is due to the cart using, in my opinion, an inferior pinch assembly, the plastic has just disintegrated, as there is immense pressure from the spring. I often despair when I find plastic and metal used when they are under combined force. The original design was all metal, and holds up well after all these years.

Anyway, I've ordered a new set of bearings for the one good pinch, and will have to share this roller between the two carts, rotating when necessary.

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bearings
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Topic starter Posted : 15/03/2022 4:27 pm
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WayneD
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@crustytv I've always been fascinated how endless loop cartridges like this work. Do these ones have the twist in the tape like the larger ones so it plays both sides?

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Posted : 15/03/2022 7:06 pm
Boater Sam
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@wayned Is that the mobius loop?

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Posted : 15/03/2022 9:53 pm
WayneD
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@boater-sam Techmoan took one cartridge apart and showed how the tape runs in his Reditune video.

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Posted : 15/03/2022 9:58 pm
crustytv
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Posted by: @boater-sam

Is that the mobius loop?

Yes 👍 

Just for information. The larger carts are not compatible for the TP48A, as they were recorded at a speed of 3¾ ips. Whereas the smaller cart runs at 1+78  ips, the speed the TP48A MKII runs at, which is how they managed to get 4hrs playback from one cart. I've 10 of the medium carts, so that's 40hrs of music before a repeat. The larger cart runs in the TP80 machine, having a larger spool hence more tape, I believe these also run for 4hrs.

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Note:

The TP80 carts (large) are physically the same size as the very first TP1 carts. However, they have an internal pinch, whereas the TP1 had just a large hole where the TP1 machine would swing up its pinch into the cart. The swing up pinch is the same method my SIS Music Master S2 employs. This design was also used on broadcast carts such as the Soniflex etc.

TP1, TP80, TP48

tp1 cart
tp80 cart
tp48 cart
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Topic starter Posted : 16/03/2022 9:48 am
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