Grundig TK145 R2R Checkout

[DMcMahon]

My latest purchase (good buy from car boot sale) this late 1960's valve single speed R2R with auto and manual recording, generally in pretty good condition for its age, even the tape spool retaining sponges in the lid are present and in good condition.

After removing the top and bottom covers not surprisingly found all 3 drive belts are broken, but no problem as will have suitable replacements in my drive belt spares. Pleasantly surprised to find that the Rotary Selector rubber roller is in good condition, as often they fall apart into a sticky mess.

The rubber on the fast wind plastic idler wheel has a small section missing and at least 1 split further round the rubber. Not sure best way to repair this, may first try removing the rubber (which looks easy) and glue a flat drive belt in its palce although unsure if that would be man enough. Has anybody found a good solution for this idler rubber replacement ?

David

[Reelman]

Nice machine, one of Grundig’s last valve ones. I don’t think the sponges are original, the only ones to survive intact appear to be from Elizabethan. I would certainly like to find a modern source of these sponges!

It’s worth trying your suggestion for the idler. My only idea in this respect is to find another idler from a scrap machine, there must be plenty about using the same deck. If you have a large spares box it might be worth trying just a similar diameter idler of any origin. If it only drives the FF then wow/flutter won’t be adversely affected by a variation from the original.

Good luck!

Peter

[Cobaltblue]

I have 4 (I have just found another one in hiding) of this series 141, 145 149 etc and all of my example this has either already expired or about to do so on my 149 I tacked a small wide elastic band on it works but its not great.

So I an also interested in the solution to this issue

Cheers

Mike T

[DMcMahon]

Yes I did wonder about the sponges as they look a little too pristine.

I have just scrapped a TK 120 but the rubber was missing off the idler, I threw that idler away. I think now that was a small mistake. Yes must look at a few spare idler wheels that I have.

David

[DMcMahon]

Prior to powering up did a visual inspection of internals, nothing untoward found, no extra fuse like this - https://www.vintage-radio.net/forum/showthread.php?t=187157

Replaced the ever present 13A fuse in the mains plug with a 3A. Slowly powered up the mains voltage supply to the unit and it powered up OK, but the motor did not spin up at all. Found the motor was very stiff to manually rotate, but after many rotations it became much easier to rotate and now spins up nicely when powered. Not yet tried under load, as not yet found replacement drive belts.

All valve heaters lighting up and the Selector switch illumination lamp lighting up, but no display on the EM84 Magic Eye, yet to check out HT supplies.

Looking at the profile on the fast wind idler rubber it looks like it is just broken not a piece missing as first thought, so possibly may be able to glue it back together although there are several big cracks around the rubber so it could easily break again soon maybe.

David

[Uncle Bulgaria]

What about a slice of large diameter heatshrink tubing? If the wheel's nylon it ought to resist the 120C shrinking temperature, though you could make a couple of discs to shield it.

[vidjoman]

Might be possible with a very tight flat belt so that when stretched over the plastic disc it forms a U shape around the edge. A couple of spots of superglue will make it stay there.

[8 Tracker]

Nice machine, I have the exact same model. It gives good performance, especially with an external speaker. Idler on mine still in one piece at the moment.

Magic eye only illuminates when the record button is pressed. I think one of the contacts on the switch just connects the HT to the valve.

[DMcMahon]

Many thanks for all the suggestions.

Found 5 good condition rubber coated idler wheels but all too large.

l have some large diameter heatshrink tubing somewhere but may be difficut to find. First will try superglueing the rubber back together, not confident it will work or last long though. Trying to find my spare flat belts and also round belts to replace the 3 drive belts.

I incorrectly called the idler "fast wind" when it is actually fast forward wind, I was thinking it also did fast rewind which it does not, Peter above correctly referred to it as FF.

I removed the idler to make it easier to work on and found that it was fairly stiff to rotate on its mounting shaft due to dried up oil on the shaft and in the idler shaft hole, after cleaning all good now.

David

[DMcMahon]

Thankyou 8 Tracker, yes I had seen on the schematic that Magic Eye only powered in Record mode,which is different from some of the other TKs. I did try it in Record mode with same result, need to check HT and see if it is being switched through to the Magic Eye valve.

Schematic shows it to be an EM 87 not a EM 84 as I said earlier, I cannot read the last digit on the actual valve itself.

David

[Welsh Anorak]

Nice machine - the top of the range TK 120 with counter and automatic level control. I found the detent roller to be much more reliable in this one rather than the later TK124/144/141 series.

Just had a look and my spares machine doesn't have anything left of the rubber! However I have used a length of narrow slingshot latex rubber tube (eBay) slit lengthwise and glued. As it's only used in the FF mode the slight bump doesn't really matter.

In fact a few 1m lengths of this tubing in various diameters comes in handy for many things.

[DMcMahon]

Most of my small diameter flat drive belts are thin and I found even with 3 fitted they were not thick enough to make contact with the motor driving boss. Found a much thicker flat belt but could not fit as it kept popping off the thin idler.

Tried to glue repair the original rubber with it fitted to the idler but impossible to get it stretched enough to glue the ends. With the rubber removed managed to glue the ends together but then very difficult to stretch it back over the idler wheel. Eventually got it on but the required stretching has made the numerous cracks/splits on the side walls of the U shaped rubber much worse. Will try it, but consider that it will not last very long before one of the splits break right through the rubber.

David

[Uncle Bulgaria]

If the U-shape helps, you could try gluing a length of rubber edge-trim into a ring and using that? This kind of thing.

[DMcMahon]

The Magic Eye display is now lighting up in all 4 record modes.

What was happening before when it did not work is that the base cover was removed so the unit was sitting on the bottom edge of the PCB and pushing the PCB up somewhat , enough for the Play/Record actuator bracket lever not to engage in the Play/Record switch, so it was staying in Playback mode when switching it to record.

The PCB securing is poor in this TK series, very easy for the PCB to move out of correct position.

David

[DMcMahon]

Replaced all 3 drive belts, despite wading through a vast number of belts could not really find a close match for the flywheel to take up table belt, the one I fitted is fatter than it should be and maybe a bit too tight.
ble. This is playback of the Grundig tape that came with the recorder, mainly recordings of adults and children talking & singing.

Play, Rewind and Fast Forward now all working. Fast forward is somewhat noiser than it should be, probably due to the poor condition of the U shaped rubber idler, later will do more to get a better repair, the rubber will probably fail sooner rather than later.

Playback works well on all 4 tracks with plenty of volume and sound quality sounds quite reasonable. Tape counter works well but EOT (End Of Tape) sensor is not working. +25V measured at sensor and it works when shorted down with a screwdriver. The tape silver foil leader looks poor condition so possibly not shorting the EOT supply down.

David

[ben]

For these Grundig idlers, I replaced the entire idler with a 1980s video recorder one (Sharp I think - had to widen the central hole to make it fit properly) and put on a new rubber tyre . Job done!

[DMcMahon]

EOT not working was due to dirty and tarnished EOT brass spacer on the EOT sensor post, after cleaning, EOT now working well but there is a related problem with the tape control which I will detail later.

Main HT voltages all measure good, around 5% high compared to schematic values but that is OK.

Microphone recording works well on tracks 1-3 in manual and automatic recording modes with good playback. On tracks 2-4 Microphone recording only works in Automatic record mode, in Manual recording get good Magic Eye record signal but no playback sound which seems strange, requires more investigation.

A small plastic peg piece around 10mm in length has fallen out of the recorder, did not fall out previously so assume it has recently broken away from something, a quick look cannot see where it belongs. Co-incidently several days back the same piece fell out of my TK 144 and I also have not found where it belongs.

David

[DMcMahon]

I found where the plastic piece belongs, it is one of 2 locating pegs that are on the underside of the plastic top panel and they engage in holes in the metal top panel of the Sound Channel Assembly. The broken off peg is above (when looking down on the switch) the 4 position rotary Record switch and locates in a round hole. The other peg (which looks the same) is to the right of the rotary main Selector and locates in an elongated hole in the Sound Channel assembly.

I will glue it back on and also the one broken off for the TK 144.

David

[ricard]

What is the diameter of the idler? I once had good luck fitting a Philips idler from the EL3542/3536 and EL3546/3547 machines into a BSR TD10 chassis. Both the outer and hole diameters were identical, but the Philips idler needed a bit of shimming to line it up properly.

Otherwise I was thinking in your case to remove rubber completely, spin the idler on a lath or drill, making a slight groove in it, and then fitting a traditional o-ring, perhaps with some superglue to stop it from coming off.

[DMcMahon]

Another good idea thankyou.

Without the rubber fitted it is around 40mm and around 43/44mm with rubber fitted.

The idler is pretty thin at < 1.5mm so may not be easy to machine a groove for mounting an O-ring, especially as I do not have lathe.

I have just realised/remembered that I have a TK 141 in poor condition which I have been keeping as a spares support machine, so I may be lucky if that one has a better condition rubber idler. I just need to locate the machine which may not be that easy. Am also hoping that the 2 flywheel drive belts on the TK 141 may be good as I am not entirely happy with the replacements I fitted to the TK 145.

David