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Audio & Hi-Fi Reditune TP48: Earlier Model, Non Automatic

 
crustytv
(@crustytv)
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Posts: 10845

Amazingly, another Reditune TP48 has come my way.

If you recall, Swampy was the Reditune TP48A, the "A" denoting automatic, meaning it had the additional circuitry and solenoid to auto change tracks. However, the TP48A also allowed the operator manual track selection, this achieved via the manual dial on the top deck.

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There are some subtle presentation differences, notably the top rear plate, I've included some Swampy photos for comparison.

Swampy's top plate is covered in leatherette, the TP48 continues the fake wood effect. This newly acquired TP48, is the slightly earlier model, it's just the basic TP48, no automatic change, thus no solenoid. It plays 1 track for an hour, then will repeat. You can of course at that point manually change track, thus it still gives, like the TP48A, a maximum of 4-hours playback.

Being earlier, there are zero lockfits to be found in what I assume is the little preamp board under the top plate. You can also see the TP48, has a fair less amount of components below decks. The transformer looks a lot healthier than the TP48A.

As you can see, this unit is in much better condition, and that also goes for the heads. The original belt (see below) was intact, but had turned solid with lots of fractures. Eager to see what state it was in electrically, I cleaned the heads, oiled the motor and fitted a new belt, the one that I had made up from a cut length and glued.

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Upon power up, everything worked as expected, motor runs nice and silent, tape transport functions correctly and track selection works fine. The only problem, the volume has to be up at max and I can then just hear it. Whereas Swampy at max volume, is unbearably loud, looks like I have an amplification fault. Finding the cause, that's my next task. Time to swot up on the likely causation of low volume in an amplifier.

At least instead of groaning “Oh no, not another Thorn!" you can all groan " Not another Reditune". 😉 

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Topic starter Posted : 25/05/2022 4:19 pm
AncientEngineer
(@ancientengineer)
New V-Ratter Registered
Posts: 14

They must be attracted to you, like moths to a bright light! Just when you thought you'd never see another one.

It's certainly in better condition than the previous one. The transistors in the 'new' (but older) one look as though they might be germanium types. It will be interesting to unclip them from the retainers, to try & see the type numbers.

I have a vast collection of transistors here if you get stuck.

 

David.

 

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Posted : 25/05/2022 5:28 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10845

Hi David, they certainly do look like Germaniums, there were a few in Swampy below deck, it only had the lockfits on the little board up top, whereas the new(old) has germanium up top as well.

If you have any more belts in stock and were willing to sell one, I'd certainly like to purchase one for this unit. As I mentioned above, I'm using a cut and shut affair for now. I could steal swampy's, but I really don't want to upset him, nor give him the impression he's going to be abandoned. They will both time-share responsibility for providing museum entertainment.

What I also need to do now is find a mother load stash of tapes.

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Topic starter Posted : 25/05/2022 5:44 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10845

Update:

Perhaps readers of the previous TP48A thread may recall (swampy), the unit had been poorly stored, also apparent was the state of the small Philips blue electrolytics, they were pretty much all shot.

This new(old) TP48 has clearly been more looked after, and even though a few years earlier than swampy, it still has a number of these electrolytics. On an initial inspection, they all looked to be in reasonable condition, though that as we know cannot be relied upon.

Dismantling the lower deck to gain access to the various sections of the circuit, I did find a 20uF that had puked and another, a 64uF up top. Checking these two in-circuit, shows the 20uF reads as leaky and high ESR. The 64uF has risen to 261uF.

Without a circuit diagram, I'm hoping the 64uF that has leaked and gone high, is possibly the culprit for the extremely low audio output. The positive side of this cap is connected to the positive side of the audio head. The other cap, the 20uF, appear to be connected to one lead which goes off to a Varley relay.

Time to delve in, I think I'll try the one connected to the audio head first.

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Topic starter Posted : 25/05/2022 8:24 pm
Nuvistor
(@nuvistor)
Famed V-Ratter Registered
Posts: 4158

The small ceramic capacitor across the screened lead looks interesting, I wonder if it was to help stop radio breakthrough on the amplifier.

 

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Posted : 25/05/2022 10:46 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10845

Well that was a simple fix, the extremely low audio was as suspected, a result of the 64uF 25V electro, in the feed from the audio head having risen to 289.2uF. 

Replaced with a new 68uF 25V, I now have bags of volume. I'll leave this one running for the rest of the afternoon and evening to see if anything else develops. The good thing on this one is the tone works, as you can probably hear from the demo, more bass.

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The other cap, 20uF 25V that was connected to the relay was also replaced as when out of circuit it tested as 1uF. No idea of its function.

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Demo Video here

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Topic starter Posted : 26/05/2022 2:33 pm
Lloyd liked
Jayceebee
(@jayceebee)
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Posts: 1632

Sometimes it's nice to have a simple fault especially when you have limited information. I wonder how many carts a typical setup had and in the case of the manual track change who changed the track and made the choice of what carts to play? Today it's all managed remotely but you might have a chuckle at a service call I had the other day. Don't know who the contractor was in 2019 but media player simply had the wrong IP address.

IMG 2363

 

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Posted : 29/05/2022 9:22 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10845
Posted by: @jayceebee

I wonder how many carts a typical setup had and in the case of the manual track change who changed the track and made the choice of what carts to play?

I've wondered that too. From what I can gather, and there's very little info out there, it varied. Early machines had to be purchased, then they moved to a rental only business model, which is why so few machines survive. The tapes, as far as I can tell, went the same way, rental only. I think you paid rental for one tape, could send it back in their special boxes, and receive a different tape back.

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I suspect Reditune had various rental plans, a business with a bit more cash flow might have rented a suite of tapes. I did read on another site a chap worked in a shop where they had the same tape for years, and it drove him nuts listening to it day in day out, and he looked forward to the Christmas tape just for the change.

As for track change, I guess that's why the TP48A came in with its auto track change. Then successor the TP80, which took track change from mechanical solenoid to shift the head up and down, to a fixed 4-track head with electronic track switching.

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Topic starter Posted : 29/05/2022 10:37 pm