Truvox R. 42 Reel to Reel Check Out

[DMcMahon]

Mid 1960's 2 track, 3 speed (single motor), 7" max spool size, solid state tape recorder, using the Magnavox 363 Tape Deck, sold as not working.

Externally reasonable condition, internally quite a mess.

2 of its 3 rubber tyred idler wheels in good condition, the third idler (wind on) not as good. Biggest problem I think is the motor pulley, much of its rubber coating has turned to a gooey mess and on one side particularly, down to the metalwork in places. From manual operation looks like the motor pulley will not drive the idler wheels, may well require some inventive fix.

All 3 piano keys extremely difficult to push down, at times impossible, the keys are Play, Rewind and Wind On, there being no Stop key. Operationally to select the required function the bottom of the respective key is pushed fully down, to deselect that operation the top of that key is fully pushed down.

Did quite a big strip down on the respective parts which were all heavily gummed up with old semi hard very sticky grease (somebody had previously gone overboard with greasing I would say).

One of the main culprits was the interlock plate which was so heavily gummed up that when a key was deselected the associated actuator lever retracted, but the interlock plate only partially moved back to its rest position, then stopping all 3 key actuator levers from being operated.

Probably could have cleaned it all up without striping down but easier to clean properly once stripped down. Most of it straight forward but re-assembling the various parts for the keys assembly was tricky.

After cleaning and re-lubricating, key operation now is very good.

Visually checking other areas found that the 47 Ohm resistor (R47) connecting the reservoir capacitor (C28) to filter capacitor (C29) is open circuit.

David

[wd40addict]

On the 1965 R44 I used to own the area around the bias oscillator had been seriously modified in 1967. I always wondered if there'd been a recall?

[DMcMahon]

In the Service Manual for the 40 Series (covering the R.42 and the R.44) that I have, there is a 1966 Addendum detailing a modification to the Bias Oscillator, to avoid potential destruction of transistor TR11 (OC81Z).

Have yet to check my R.42 & R.44 to see if they have been modified.

David

[Reelman]

Good luck with this machine, I hope you find a solution to the motor pulley issue. Deterioration of this part is so common that it tends to make the machines in general U/S.

Peter

[wd40addict]

Does your machine have a T03 bodied transistor fitted as part of the amplifier?

Seemingly not all motors had rubber idlers, see https://www.vintage-radio.net/forum/...=103812&page=2

[DMcMahon]

Not sure will have to have a close look at the amplifier.

The OP in that Thread said his motor pulley was metal ?

Looking at the drawing in Post 24 of that Thread and also photos in other Threads it looks like the diameter of the rubber on the motor pulley is virtually the same diameter as the diameter of the large metal step (bottom one of the 3 steps) that it interfaces to, this means that mine has lost a lot of the rubber (similar also for my R.44).

David

[wd40addict]

I can confirm they are the same diameter.

[DMcMahon]

Thankyou for the confirmation. Currently filing down an Allen key to fit the 2 securing grub screws for the motor pulley. May also remove the motor for better access to the pulley screws.

David

[ben]

It looks like the problematical motor rubber section contacts other rubber idlers, in which case you could, in theory, use any suitable material as a substitute, if rubber gets too hot in that situation. Maybe some rubber cut from vehicle parts like hoses might be man enough for the job. Trip to local scrapyard?!

[wd40addict]

The difficulty is that the rubber replacement section needs to be heatproof and perfectly balanced so it doesn't affect W&F. It would be interesting to know if the aluminium version described in the thread above was a factory change or someone's repair.

[ben]

True.
I suppose an aluminium collar fixed with a grub screw or something might be ideal. This is one of the few reel to reels I don't currently own, otherwise I'd be experimenting with all this myself! My only experience of them dates back to the 80s, when they were used in student machines in school language lab.

[DMcMahon]

I see in some older Threads some people were suggesting using Pinch wheels/Pinch wheel tyres, not sure if these would be robust enough and not easy to fix in place securely.

David

[wd40addict]

I actually quite like the 363 deck, but mine bit the dust in the 80s due to the rubber failure we're discussing. Back in those pre internet days I ran out of ideas. I did try a piece of hose trued up in a lathe, but when it got hot it expanded Now I think I'd try machining a collar in brass or maybe send it to the USA for re-rubbering

[DMcMahon]

After filing down Allen key managed to remove the 2 very tight grub screws but so far no sign of the pulley coming off the motor shaft, feels absolutely stuck solid.

No idea how much it would cost to get it re-rubbered but guess pretty expensive and probably too expensive for this particular recorder. If after some sort of temporary repair to the pulley the recorder ends up working reasonably well, then may check out the cost of getting the pulley re-rubbered.

There is no TO3 transistor in this unit.

David

[wd40addict]

My pulley came off ok, but I can't remember the details. I'm wondering if the '66 bias mod wasn't sufficient so a '67 mod swapped the OC81Z for a higher powered TO3 device. My machine is long gone so can't investigate further.

[DMcMahon]

The September 1966 bias mod (Addendum No. 1) replaced the Germanium OC81Z with a Silicon 2S1002 and associated component changes

David

[Borderer]

If that section of the stepped sleeve is just for take-up drive, it should not affect W & F significantly and a slice of rubber hose should suffice. The o/d probably isn't too critical.

The sleeve is probably a sliding fit on the motor shaft and has corroded internally over time, in which case repeated warming with a heat gun may loosen it.

Not difficult to make a brass or aluminium collar to replace the rubber, or even to make a complete replacement sleeve. If you have nobody local with a lathe I could do it.

[DMcMahon]

Yes I was thinking it was for just for take up drive (to be 100% confirmed later), if the replacement rubber/sleeve affects the motor shaft balance then that theoretically may affect W & F during Playback.

Been tied up with family health matters so have done no more yet. Will have another go at removing the sleeve and if no good still will try some heat.

Do not have any local contacts with a lathe, thank you for your offer, will first see how I get on with repairing it.

I see from another older Thread someone stretched 2 or 3 rubber sleeves over the metal sleeve, although did not says how well that worked. The sleeves looked similar to Hellermann sleeves which I was previously thinking might be a possibility.

Somewhat annoyingly I used to have a large a pair of Hellermann sleeve fitting pliers which several years back I decided I would never use again, so threw them away because they were old and rusty.

David

[Borderer]

A collar made individually just to a set of measurements would only have an average chance of fitting properly, so the best way would be to finish-machine it after fitting to the pulley to ensure it is concentric. But let us know you you get on.

I don't think balance would be an issue in practice as it is a very small diameter piece compared with the motor armature and there are plenty of other wobbly bits in the drive train, and you have to consider how good it was originally - probably not startling although it looks to be quite a well made deck.

[DMcMahon]

I think the rubber covered section is all part of the 3 stepped pulley, i.e not a separate collar, will find out for sure later once I get it removed.

David