Project 1960s Rediffusion Reditune TP48A

Well, the old saying “Necessity is the mother of invention”, was all that was left to me. Rummaging through my belt stock, I came across a rather large (in diameter), NOS belt from what must have been destined for a record deck. I was 5mm wide, but more than enough to cut down to the 210mm required. I spliced the belt at a 45° angle and used Gorrila glue, that was all I hadm, not ideal considering the original was 13mm wide. Rapidly rotating the motor drives the capstan wheel, and it appears to be holding, proof will be when it's running at full pace. It's the best I can do under the circumstances.

This at least allows me to now start looking at the PSU. No gung-ho power ups, considering these devices were run for hours on end, coupled with the 50+ years of poor storage, I'm not expecting the main caps to have fared well.

There is a very helpful chap in Hungary, who makes up belt kits for various vintage equipment. He did once off to supply me with a specific belt, as long as it was in his stockpile, and as long as I knew the dimensions -It was on the basis that if I got the dimensions wrong, there was no come back on him, but that was no problem.

He trades on eBay under the name Lozems. It could be worth seeking him out.

Posted by: @katie-bush

trades on eBay under the name Lozems. It could be worth seeking him out.

I tried an advanced search for seller both as business, and private, nothing. How long go was this, as it seems he's not there now.

@crustytv  It would be a couple of years ago I think. I wonder if he's changed his eBay ID. I bought some kits for my N1700 VCRs, and that's where I first encountered him.

I'll have a quick search back and see if I can find him again. Don't go away!

I'm a bit mystified. I kept his ID in my 'saved sellers' - And it's no longer there. Some of my saved sellers have indeed changed their seller IDs, but none match up with his stock in trade.  If I search my purchases, the kits aren't there. It's as if he's been erased from the face of eBay.

Hang-fire a minute, I've just thought - I'm wondering if I can search my feedback, but there's a lot to search through. Don't go away!

Well I'm stumped! - I've just checked all my feedback (buyer and seller) as far back as 2007, and this guy has simply upped and vanished.  It's as if he was never there. His name is Andrassi Gabor, and he is/was based in Budapest. We had quite lengthy discussions via the ebay messaging system, and by email, but they'll have long since been deleted. I remember trying to get him to join the forum, but he said he preferred not to get involved in clubs, forums and societies etc.

If I can find the the envelope that the kits came in, I might be able to get more details from there, but right now, it's not looking too hopeful.

@katie-bush I do have an envelope with the address of Andrassy Gabor in Budapest. I bought something in 2019 (can't remember what). I don't suppose full address would help though.

Posted by: @jcdaze

@katie-bush I do have an envelope with the address of Andrassy Gabor in Budapest. I bought something in 2019 (can't remember what). I don't suppose full address would help though.

It would, if you had his email address as well - From, say, an invoice/sale slip. That's what I'm hoping to find, if I can find the envelope which contained, and still should contain one set, the N1700 belt sets.

I would guess that Chris could write to him and see if he's still there/still supplying kits.

I've encountered this before on eBay. I bought an item, forgot to leave feedback, went to do so a couple of months later, and it was if the item and vendor never existed. I won't be writing to him, but thanks for looking.

So onwards with the electrical side of things this weekend, first a general look over to baseline the condition. I'm fairly surprised, given the obvious poor storage, and condition of the electronics seem to be complete and not as bad as expected.

The obvious stand-outs are the T0-1 package transistors, there's six of them, and the cases are heavily corroded. Whether the external corrosion will have caused problems remains to be seen, at the very least maybe the legs.

A single TO-5 NKT228(AF amp/driver?)

The two T0-3 AD149's (output pair) look relatively unscathed on the large heat-sink. Then on the rear of the heat-sink two small transistors in copper tubed heat-sinks.

Finally, 3-Lockfits up top, 2x BC148B and 1x BC149.

There's only one Black HUNTS!

Nearly all the Philips blue package electrolytics are puking at one end, so all will need replacing, and there's an awful lot of them.

I do so wish I had a circuit diagram though, as I've no idea what the T0-1s (doubt the markings will be present) might be nor what is exactly what circuit wise. Mains TX, rectification, smoothing, pre-amp, amp, output TX and a couple of Varley relays, which I imagine have something to do with operating the solenoid for auto track change.

I'll start with reforming the main smoother and take it from there.

Rediffusion Reditune; Background Music Systems Related Side Note:

Found this in March 1968 RER, it was related to a trade show.

As I suspected, it does date the TP48 machine to mid to late 60s. Also, I've learned there is another Reditune machine, the TP-Mini. So the machine line up was as follows, the very first being TP1, followed by TP48, TP-Mini, TP80 & TP80S and the final RM series (cassette).

Stands 23, 24 and 25 REDIFFUSION REDITUNE LTD

he highlight of the display is the new TP-Mini tape playback machine, which brings Music Service within the reach of many smaller establishments which previously could not justify the price of current equipment. The TP-Mini is sold outright in kit form and includes a playback machine, two loudspeakers, all connections and instructions for do-it-yourselfinstallation. Price 38 gn. Also, new is a playback machine designed specifically for PA, applications. It will fit into standard racks.

The standard playback machine, model TP48A, is transistorised and has 10W output. Any one of four tracks can be selected manually, or it will switch automatically from one to the next to provide four hours of continuous music. Price : 60 g

Reditune players, the device that just keeps giving...... Grief!

So, the fellas at TVR (TeleVision Research in Jersey) decided it would be helpful to make servicing as difficult as possible. I wanted to remove the two main smoothers for reforming, they had other plans. Unhelpfully, the two main caps are riveted to the chassis. The top paxolin plate has short wires going off to multiple points. The various little PCBs below decks, although removable, cannot be easily extracted for the same reasons, multiple point to point wiring everywhere.

I may just dim bulb and variac this, allowing the electros to reform that way. Still not going to be a walk in the part extracting fault components or testing.

I'm amazed that somebody would build something on a commercial basis that didn't make at least some attempt to be serviceable, unless it worked purely on a Return To Base principle - I've had my hands in portable audio mixers that have had me wondering how on Earth they were put together, never mind how you got them apart to service them - the old image of sitting on the suitcase to shut it before going on holiday really comes to mind here!

After all, I'm sure we've all built projects in the past we hope we'll never have to take to bits again - I know I have...

It's just me, having been spoiled rotten by Thorn and their modular design and ease of servicing.

I managed to free the rusted screws without them shearing, from the Heat-sink and the other PCB mount. This has given me slightly better access to the parts and PCB attached to the heat-sink, albeit still very restricted by short attached leads. I think I'm going to have to do a fair bit of wire removal to gain access to the long, shallow PCB.

Onwards....

@crustytv 

They we’re probably designed to last 5 years and be replaced after their value was taken off the books of the business. They probably never failed in their service life so repair access was probably low on the list.

@crustytv Ooh, some of those electrolytics don't look too healthy, do they?

Hi Frank, I was thinking much the same. Looking at the electronics, it appears to be original, nothing having been replaced. These were switched on at the start of the business day and then off at the end of the day, probably 6-days a week for who knows how many years.

The tapes run for 4-hours, and I have twelve. That's two tapes per day, if the retailer ran a  6-day working week, that's two weeks before you'd need to repeat. Of course, they were on rental subscription, so not sure how often they would receive a new batch.

Posted by: @cathovisor

Ooh, some of those electrolytics don't look too healthy, do they?

Indeed, very poorly little fellas, all baked and dried up. Oh well, deep breath and in for the long haul, I don't normally do blanket replacements, but this is going to be the exception to the rule. Hopefully, in once and be done with it, with lots of checking and rechecking as I go, so not to introduce an own goal.

Looks like some old OAxx diodes heat-sinked too

I would have liked to have tried it first, as I could end up wasting a lot of components, if the heads are toast. They do look worn, but I'm no expert, but given the unit is 50+ years old, and likely ran hours on end, they are a concern. As I've mentioned before, audio is a new game to me, is there any method available to test heads other than the coil has continuity? Is it a case of you have to hear how they reproduce to know for sure?

There's no way I'm risking powering it up in this current condition, who knows what untold damage may result, if I threw caution to the wind.

@crustytv 

Probably magnetise the heads if you use DC to test continuity.

From what I've been reading on the old newspaper archives it would seem that there would have been thousands of various Reditune machines out on rental in the 1960's and 1970's. An advert from 1961 states that the 4 hour tapes could be rented from "as little as £65 a year, including rights fees for public broadcasting",also available in over 70 countries. In the 1970's the Happy Eater chain of roadside retraurants (the one with the logo of a head sticking it's fingers down it's throat) was one example of one of their customers along with supermarkets, hotels, pubs, factories and ships. Adverts claim that "changing tapes was as easy as posting a letter" Redifusion had their own recording studios as well. All in all a huge market.

@jcdaze 

I imagine piped music was quite a big thing once it was established.  I don't notice it as much these days in shops, normally PA systems tend to play original songs rather than easy listening (I won't use the term Muzak as it was particular brand of piped music!) versions of them, if any music at all.