Project 1960s Rediffusion Reditune TP48A

@richardfrommarple I forgot to mention that another report from 1961 was that a farmer in Darlington used to play music put out by the BBC, the Third programme or Radio 3 as it is now, to his herd of cows but organ music, when it came on, used to upset them. He then stopped the music but milk yeild went down and so he rented the Redifusion Reditune player, tapes and speaker and milk yeilds increased by 4% and all was well.

That's interesting, swampy came from a farm barn, near Haywards Heath. I had assumed someone just happened upon it and stored it. I'm wondering now if it was used in a similar manner, keeping the cows happy. How bizarre!

@crustytv They may have used it for backround moosic.

Posted by: @jcdaze

backround moosic.

🤣 now that creased me up

It wasn’t that terrible 90’s song that went on about moo moo land was it?!

@lloyd That tune was justified..... and ancient. 

Found this on Amazon, not listened to it but it shows Reddifusion used top stars of their day.

Swampy's Journey Thus Far

After much thought, mixed with a little procrastination, I figured out the best way to get into this, three snipped wires later, I'm finally in.  Now I can get on with the task, and get all those failed electros replaced. One good thing I did find was the AD149's are socketed.

p.s.

Thank heavens for my bench scope, as even under a mag lamp my eyes could not work them out. Looks like some if not all the corroded metal can transistors are AC181's

AC181s seem to be readily available from eBay as well as Langrex if needed. 

Managed to get in closer with the scope on the smaller of the two sub PCBs, the others are AC151, makes sense.

So the transistor line up is as follows

• 2 x AC151 pnp ge
• 3 x AC181 npn ge
• 1 x NKT228 pnp ge
• 1 x 2N4061 pnp Si
• 2 x AD149 pnp Si
• 1 x  ** unknown **
• 2 x ** not yet determined **

Anyone have an idea what this Philips electrolytic is value wise? It states 64V 2.5/N.

Normally, I've come across them with U for uF. Surely it cannot be for nano Farad. 2.5n would be .0025uF ! for an electrolytic surely not.

Only thing I can think of is 2.5uF non polarised.  Is that a black band on the RH end of it or lighting effect?

Yep black band, which usually denotes -ve there’s 2 of them the other is 4 / N @48V

I wonder if the N is a red herring. Looking elsewhere in the cct there's a Philips electro labelled 125uF 16V and that also has an N. More fun from Philips.

I would have gone with 2.5uF as well, but the N threw me. Anyway, I've put in 2.2uF and 4.7uF all 63V, and replaced the Hunts .25uF /150V with an orange drop .22uF 250V.

@crustytv I did wonder if it was a code letter for the voltage rating, or maybe even tolerance? 

You need an old Philips /Mullard databook. 

Posted by: @cathovisor

I did wonder if it was a code letter for the voltage rating, or maybe even tolerance? You need an old Philips /Mullard databook. 

I just so happens I do have a 1972 Mullard capacitor book, but for some reason I didn't think Philips would be in there, so did not reference it. Indeed, as you rightly suggest, the code is voltage rating. I just find it odd they print 63V on the cap but also the N code for 63V voltage rating! I/we, all, never stop learning, and that's a good thing. 👍 

That's all the leaky Philips electros replaced, I've not replaced the two huge cans, there's no sign of leakage, unlike the Philips.

I'm in two minds about tackling them, one says desolder everything up top, remove to test and reform on the bridge. The other says leave them, just variac it, they should/may reform OK.

No doubt I'll ponder that one overnight, once decided, it's just reassembly and the anticipation, will it play the carts, or have the transistors suffered too. Next episode of this coming soon.......

The top deck PCB refurbished, I had a panic when the little pre-sets just fell apart, due to corrosion. I removed them and thankfully underneath it was stamped 1M. I've decided to variac, rather than having to dismantle and disturb all the wiring on top of the main TX. It's all put back together, ready for this a little later today.

I'm at work and just by chance, I am staring at a Vishay 021-series electrolytic, the modern production of the Philips caps in question.

That is labelled 150u-M 25V.

On examining the datasheet, 'M' indicates a tolerance of 20%.