Project 1960s Rediffusion Reditune TP48A
I had a bit of an OMG, planets aligning moment this morning.
I contacted a chap online who relaps tapes heads and also sells replacement tapes heads. Furthermore, I asked him about my TP48 and whether he might have something suitable. He requested some inductance or at least some resistance readings. As I don't have a way of measuring inductance, and no access to a working demag tool, I sent him some photos first. This is where it went bonkers! Terry recognised the head instantly, you see It turns out he was the technical director of the company that designed and made the tape head for the reditune machine!!!!
Long story short, I have managed to buy a brand-new tape head for swampy. To say I'm stunned is an understatement. What are the chances of me randomly searching google, finding a UK tape head website, and the chap who runs it, turns out to be from the company that made the original head.
Amazingly small world.
<falls off chair in amazement>
@crustytv when you think about it, it's not just planets aligning with this, it's entire universes!
If I hadn't been Googling information about the Rediffusion Guildford set Google's algorithm wouldn't have guided me towards the Rediffusion Facebook page and I wouldn't have asked you if "these Reditune tapes are are use?" 😱
Amazing finding a head,& a new one at that, - and then from it's original source!
With your luck in sourcing parts, maybe you can conjure up a 'sleeping CRT re-gunning' person, who still has the physical equipment & technology available...
Please form a neat queue, Mazda tubes first!
You ought to pick the lottery numbers this week then Chris ! 😉
The new head arrived, pristine condition compared to the one in the Reditune, and now I can really see by comparison, the wear on it.
I'm facing a real dilemma, though, I'll try to explain.
The Reditune uses a rather unique head mount. Two plastic blocks joined by two flexible copper strips. The back end then secured to a mounting plate to the chassis. The front end plastic block, holds the tape head, basically a floating head. The head is secured to the front mount section via a threaded protrusion on the rear of the tape head. The track selection cam, when rotated either automatically or manually, bears down via its contoured edge, on the white block, thus bending the copper strips to position the head for tracks, 1,2,3 &4.
The problem is this, the original head's mounting nut, has seized due to heavy rust, remember the rust was everywhere on this device. This is further complicated by limited access to get good purchase on the nut. Further aggravated by the head lead-out poles. I removed the wires, and carefully as much as I dared, gently bent the poles. I managed to get some thin nose pliers on the nut, but it's well and truly stuck.
My main concern is twofold, first shearing off the nut leaving a stub in what, I believe, is a threaded insert to the front plastic end. Second, is inadvertently breaking one or both of the poles, or the entire head mount assembly, rendering the unit inoperative.
I think if I proceed, my luck has, or may just be about to run out.
I'm faced with a machine that is working, and I'm enjoying, albeit the head having seen better days. After all the hard work getting to where I am now, I could potentially end up reducing it to a non-working example, and I really don't want that to happen.
As such, I think I need to pause and come up with a plan, rather than forging ahead and thus having to react to a self-made disaster. My initial thoughts are to try to replicate the head housing, not sure how or what materials. Initial thoughts were to invest in a 3D-Printer, however, I don't want the expense for a one-off or having to learn Autocad, it was bad enough getting my head around CNCs Flatcam & GRBL controls. I think this should be possible to manually create, if I can source a small bar of semi-hard plastic. I could then carve and form, I'd then just need to source two correct size strips of copper.
This year is turning into the year of building rare of missing parts, what with 4K vertical deflection, CNC for 4K thick films, Motor conversion for the Reditune TP80 and now this TP48 head challenge.
I'd be tempted to try gently heating it up but I realise you would need to be very careful due to the plastic involved. That is if penetrating oil doesn't work. Amazed with the circumstances and luck you've had finding a new head.
Soldering iron to heat it up? More direct and less likely damage anything else around it.... Works with record players
How about a Dremel to grind the nut away?
Then, rather than heat - freezer spray on the stud if necessary?
The thread looks rusty to me, but aside from that, it is possible that a thread-locking compound was used upon inital assembly. It could be worth applying a small amount of paint or varnish stripper to the thread close to the nut and seeing if this helps.
If it is actual rust that has caused it to seize, then maybe a rust-eater could be carefully applied. Has to be worth a go.
I've ordered this from Amazon, will be here tomorrow. Maybe snake oil, maybe not.
With the application of some Plusgas, once the deruster has had a chance to do its stuff. If that fails, I like the Dremel idea. Sods-law mine broke, I'll have to get another.
I've ordered this from Amazon, will be here tomorrow. Maybe snake oil, maybe not.
If it's even half as good as Evapo-Rust, it should be fine, but also, do you have an ultrasonic cleaner? That's another way to shift crusty rust and could be worth trying whilst waiting for your rust remover arriver.
do you have an ultrasonic cleaner? That's another way to shift crusty rust and could be worth trying
Hi Marion, no I don't have an Ultrasonic cleaner, besides I couldn't use one if I did. From what I've read on other forums, including AudioKarma, using one is a sure fire way to kill the tape head. As I've mentioned above, I don't want to make things worse and end up with a non-working machine.
The rust remover arrived this evening, it's a Japanese product and comes with all sorts of warnings regarding inhalation 😷 and getting on hands. I was planning on doing this at the bench under the scope, change of plans now, this will be attempted outside. I'm pinning my hopes on this.
I found a MSDS for it, it appears to be based on ammonium thioglycolate.
I looked up what that is used for: if your mother or any relatives ever permed their own hair, you'll recognise the smell instantly!
It's now possible to present the extent of wear, compared to new. Hard to show here, but where the new head has a curved surface, the old has a distinct flat spot through the middle. Quite remarkable to me that tape can do this, then again these machines were on for probably 7-hours a day, week in week out for years.
As I've mentioned, I've no audio experience to call upon, but even a fool such as myself in this area, will realise this will explain my poor, scratchy, tone lacking, audio playback.
It is certainly quite badly worn, the flux gap very visible on the first photo.
Once installed, some fine adjustment of the azimuth should result in a good treble response.
New head installed in the reditunes unique, flexible mount.
I'm filled with excitement and dread! Excitement that this will vastly improve things, dread that it won't or that I've made things worse.
By the way, no tape head alignment adjusters on the TP48. The only adjuster you have is the small clear plastic grub screw on top of the flexible head mount. This crudely lifts or drops the track selection cam. When it is rotated either automatically or manually, the selector bears down via its contoured edge, on the clear block, thus bending the copper strips to position the head for tracks, 1,2,3 &4. I don't think folk realise just how crude of a machine this is. After all, music fidelity for what is essentially a mono background music system for a busy shop, does not appear to have been high on the design list, nor should it have been.
Success ! 😎
Wow, that has given me huge amounts of volume, all the scratching, popping and general muffled-ness, has now gone. I don't think there is any need to replace the transistors (famous last words) as it sounds wonderful.
I think this head will outlast me now, this brings the thread nicely to a close, thanks for following.
Amazing result! Especially when you consider what you started with!
Back in the old days of my Amstrad CPC 464 I'd occasionally adjust the head alignment so it gave the "crispest sound" which meant less "Read Error A" incidents. I had no alignment tools or tapes, just a set of cheap Poundstretcher mini screwdrivers.
Chris, that's FANTASTIC!! Interesting to note that the new head has slip-on connectors as used on pickup cartridges. I had to say I sort of expected the vast improvement you have described.
Now, do we get treated to a new YT video of it and equally, are you planning to digitise the tapes for posterity?
(Edit; as soon as I posted that, the notification popped up!)