TO-R S15, Do I really need a new Project ?

[tri-comp]

Originally Posted by tri-comp

If still not aligned I'll drop C20 in value to the specified, possibly even lower and add the trim-cap back in.

Obviously make that C12.
Sorry !

[ms660]

It might be worth bending out the last segment of the outer rotor plate in the osc section to see if that brings the pointer back to where it should be.

Lawrence.

[tri-comp]

Tweaking the outer rotor plates does indeed send the pointer in the right direction. Unfortunately not nearly enough, the effect is just traceable if I'm to avoid damaging the plates.

Still, things are improving. Following the replacement of both 100K resistors around the AFC varicap diode, the pointer-error is now halved, down to 1MHz. The 100K grid-resistor of the first triode was also replaced. That will have no influence on oscillator frequency but possibly on noise.
Perhaps the other half of the misalignment comes down to C12 being off specified value.

It seems that the decision to replace a vintage resistor set in a VHF environment shouldn't be solely placed on the resistors resistance to a DC-current.

[tri-comp]

I've had to put the lid on this restoration project because of real-life. It has a nasty way of crossing even the best laid plans.
However, ... I went to Copenhagen over the week-end to visit family and to attend a HAM swap-meeting today.
Some times you can pick-up the most interesting things and info at these meetings and today was no exception.
I started describing my Torotor tuner problem to some of the HAM's. The off-frequency oscillator and the renovation in general.
When an old guy heard he commented on the TO-R S15 and said that he owns the newer S-15u variant. Some odd chance..!
However, it get's better, much better ! He informed me, that not only was the tuner made by Torotor but that the whole IF-strip was also made by Torotor. I asked him how he could be sure and he answered: 'Because it was me who build them at the factory in the beginning of the 60'ies' !! Of course he wasn't the only employe who build tuners and IF-strips at the factory, but at least he was one on them.
He had NO idea what is causing drift following 55 years and I didn't blame him
During the next week there will be time to return to this project and to set the FM-osc. at the correct frequency.
...more to follow.

[tri-comp]

The Torotor tuner went out again and was taken apart.
The last two original Vitrohm resistors were replaced by NOS Philips carbon-on-ceramic (i believe) resistors. Same as every other resistor replaced in the set.
A 4,7K resistor was doing it's best to make the replacement very difficult. For beginners it was placed right under the variable capacitor and then it was, as the only resistor in the tuner, raised above the PCB. Well, the replacement had to be mounted exactly like the original to not upset the alignment of the oscillator any further.
After re-assembling an remounting the tuner it looks like this was a very good decision. The oscillator isn't precisely aligned still but now it's so slightly off frequency that a decision to not exactly align the pointer equally at the ends of the scale is enough to compensate for the remainding about 250KHz off-frequency.
Another good thing happened. The sensitivity at the lower end of the scale improved.
The picture showing the EM87 almost entirely closed when receiving a station at around 91MHz, pushing the AGC to a tad over -9V.

At the HAM swap-meeting yesterday I was fortunate enough to pick-up a couple of TFK EF89's and ECC85's for a song and a dance. The future seems secured for this receiver.

Now I should find a sweep-generator and check the IF-alignment. I think I know where one's stored.

There are some resistors mounted directly on the front pot-meters and switches. I'll most likely replace anything within reach. Some are unfortunately out of reach mounted on pot's and I don't want to stress the pot's unnecessarily by heating the terminals.

[Nuvistor]

That's good news, must admit if the resistor was in spec I would not have thought it would affect alignment, but there it is, learn something new every day.
Excellent restore.
Frank

[tri-comp]

Underneath almost every Vitrohm resistor I replaced that was close to strong heat (All in the tuner, several near the ECL86's) was found a greasy substance like paraffin that must have leaked from the resistors.
No telling what cooking a solid carbon resistor for ages will do to it's electrical characteristics other than it's DC-resistance. The 4,7K resistor measured around 5,1K and the 470K resistor grew to around 510K. Not ideal but also not something that would change the osc. freq. severely. How the internal capacity of the resistor changed is perhaps quite another matter and not so easy to find out.

[tri-comp]

It's not uncommon with vintage equipment that when trying to remove front knobs you find they're stuck to the axle. Corroded and non-removeable.
You try to avoid breaking the set screw and of course it's unavoidable; the screw breakes and then what ...?
Same thing happened with just one knob on the TO-R.
I applied a polygrip plier to the axle sticking out of the pot, between the potmeter and the rear of the front panel.
The pot's fortunately offset behind the frontpanel just enough to give room for the plier.
Applying what max. force I could to the plier fixing the axle and at the same time turning the knob with brute force I was finally able to twist the knob from the axle after several turns. It wasn't the easiest thing to do but the knob is now repairable and the pot survived completely. I'll probably have to smoothen the axle before re-mounting the knob.
Phew ... !

[tri-comp]

This project was put on hold because of lack of knowledge and experience on how to restore a vintage wooden cabinet without damaging it.
After some consulting with the pro's (..also vintage ) I've now acquired the necessary knowledge.
Well, actually I don't know if I have but the pictures will tell.

Yesterday I received a vintage Heathkit TC-2 valve-tester.
In a VERY sorry state that is, but I knew beforehand. I could see from the auction pictures that especially the meter-front was extremely cloudy and scratched, possibly with the aid of a hot soldering iron.
I wasn't disappointed upon receiving it ! It was just as awfull as the pictures showed.
A piece of soft cloth and some Slipol (Fine Polishing chemical for polishing cars) combined with patience and hard work turned the meter front into a shining and fully clear piece of plastic.

I intend to apply the same kind of polishing to the TO-R front scale. It shows scratch-marks around the larger round knobe where nails left their imprint over the years. Before and after pictures to be posted in time.
Then something very good happened. On the domestic forum the schematic for the missing MPX-module appeared.
Now, this is REALLY down to basics MPX decoder-wise. Well, with just a single ECC85 in the works there isn't room for any frills. Otoh it's so simple that it should be possible to replicate it.
Have a look.

[tri-comp]

I made a couple of pictures to show the cabinet before cleaning and sanding.
I'll be using sanding paper grain 2000 for wet-sanding and possibly fine steel-wool to get things started. The grain-2000 paper should make the surface real smooth.
Notice the big scratch across the top-right of the cabinet.
It will be interesting to see how well it responds to sanding...

[tri-comp]

I started the initial sanding and soon found that steel-wool is preferable for starters.
Sanding with grain-2000 will of course work.... if your hands survive
Steel-wool is so much faster taking very much care not to remove all veneer !
Notice how the fairly deep scratch is almost removed using a combination of sanding and polishing with steel-wool.
Tomorrow I'll go buy some Stain and see how it works out.
Possibly Teak-oil is preferable, I just don't know.

Ideas, anyone ?

[Nuvistor]

It coming along nicely, it should great when you have finished.
Frank

[tri-comp]

I had to put the project on hold because of work and family.
It's in no way forgotten and during the winter it will re-appear on the bench.

The radio is not fitted with a stereo-decoder even if one, also valve-equipped, existed.
So, for lack of better I've been keeping my eyes open for any vintage stereo-decoder module.
Today I got lucky and scored a mint, NOS, even in original box, Philips decoder for what amounts to a little more than £2.-
Philips type 4822-214-50075

It will fit nicely in the space located for the original decoder even if I'll also have to fit an additional small PCB mains-transformer with electronics for supply.

The point is that I don't know where to find a schematic for the decoder as I don't know in what radio it belongs.
I was thinking something like a 22RH720 except it isn't. Possibly very close though as the 22RH720 also used lockfit transistors.

Any help appreciated or I'll have to trace the leads and figure out what goes where.
Shouldn't be THAT difficult.

[roffe]

Philips apparently often used a stereo decoder with 7 pins on one side,but here it is with 6 +2 pins:
http://85.144.220.212/nvhr/Philips_22RH786.pdf

[tri-comp]

Roffe, Thank You / Tack så mycket !

I had already checked 22RH781 which is pretty much the same as 22RH786.
I just had a quick look at the PCB and noticed that in the lower right corner, my decoder has components mounted differently and so I discarded the model as being with a different decoder.
When you suggested 22RH786 I had a better look and Lo-and-Behold, even if the 22RH781 & 22RH782 shows different component mounting and orientation, the decoder is THE SAME! Tracing the PCB of my variant reveals exactly the same circuit as shown in the 22RH781/786 manuals.
Trust Philips to always come up with a circuit-variant and to always have a plan-B, in this case for no apparent reason at all !

I quickly checked the on-board electrolytic cap's not really expecting to see much off-value. Vintage Philips electrolytic cap's just don't deteriorate like most other vintage brands.
In this case it wasn't in vain; the input 4,7uF/16V cap' was completely gone. Just infinite ESR and a complete loss of capacity.
Yes, I know; the schematic says 4uF for the input-cap' C301 but in real-life they used 4,7uF. C302 is shown as 64uF in the schematic and of course a 68uF standard value cap' was mounted. The other elektrolytic cap's values are also messed-up on the schematic contra real-life EXCEPT, they actually mounted 2 x 12,5uF cap's on my board. Didn't they have people proof-reading the schematics ...?

[tri-comp]

I took this out of hibernation today.
Come to think of it, possibly it would be more proper to put it INTO hibernation this time of year
Anyway, since this project took off a while ago I've acquired another TO-R S-15, this time the S-15u variant with FM coverage to 104MHz.
That will do for a nice restoration project over the winter. I'm sure you'll se any progress here.

A couple of days ago I received in the mail absolutely FOC 6 x NOS ECL86, four of which are matched Miniwatt's.
That should take care of my so-so stock of used ECL's that will run into grid-current on occation.
The guy who send them to me didn't even want the postage covered. THANKS KIM of Herlev, DK !!
That prompted me to actually finish the restoration now.
Earlier, before I put it aside I noticed that the stations would drift a bit. Not slowly during warm-up but abruptly with a crackling sound, jumping +/- half a MHz.
Wiggling the tuner-valve would also provoke the jumping so I thought the problem was down to corrosion in the socket.
For the umphteen time I removed and disassemblied the tuner.
Looked it VERY carefully over and found nothing looking like a bad soldering. Heck, they're all fresh from replacing most anything inside, so WHAT could act like a bad connection when there seemingly were none ?
Since it had to be oscillator-related I went over the oscillator components again and again until really only one component was left; the main tuning variable capacitor.
Still, it's mounted onto the PCB with a pair of screws for ground besides a brass-lug comming from the grounding-slider on the rotor.
Then there are the two hot pins for oscillator and RF tuning.
Pretty simple and not likely to fail, or ...
I invite you to have a look at a couple of pictures showing the stator-mounting.
There's a before and an after reflowing solder picture.
One oscillator stator-plate was never soldered and doing that completely finished-off the stations jumping all over.
It took all evening, that and getting rid of the few leftover Hunts in the Bass & Treble control circuits.
The sound was somewhat boomy before replacing the Hunts as I couldn't really turn-down bass sufficiently to not overdrive the amplifier when playing music rather loud.
Rather loud beeing somewhere between 3 & 4 Watts per channel in a ECL86 Single-ended circuit.
After the Hunts are gone (1nF's grown to about 3nF and 2nF's grown to more than 6nF) the sound is much improved playing music.
Using 2KV Wima MKP's may be just a tad overkill

[tri-comp]

Following yesterdays success something had to give.
I noticed that after the inspection, resoldering, unmounting and mounting of components the AGC-voltage was lowered.
I.e. the receiver had become less sensitive and that could only mean that the tuner RF-section wasn't optimally aligned.
Since there is no easy way to align the section as with a trim-cap' I took the tuner apart for the umphteen+1 time and wondered, what could be done ?
I decided to slightly cover the PCB-type RF tuning-coil with solder, shorting perhaps 1mm out thereby lovering inductance a bit.
I hoped it would be enough to compensate for the ceramic trim-cap' I intended to put in parallel with the main tuning-cap'.
On the picture you'll see how I mounted the added cap' soldered directly onto the main tuning-cap'.
After re-assembling the tuner I noticed that the RF-section was really thrown-off alignment, a station barely raising the AGC-voltage when tuned-in.
The added trim-cap' was set to full capacity and I tuned-in a station and started adjusting the cap' looking for an AGC-peak within the adj.-range.
Lo-and-behold, it was there with the slug about halfway out. Perfect !
About an extra -2V of AGC on the received station compaired with before I modified the tuner.
Finally mounting the tuner-shield didn't misalign the RF-section so I expect this to be the last time I'll look inside the tuner.

Some time ago I won a German auction on the bay for a bucketfull of NOS EF80 & EF89 made by former East German Werk für Fernsehelektronik (WF) in Berlin.
I replaced the original Valvo's with the WF's and gained an extra -0,5V of AVG-voltage.
It looks like their internal capacitances are a little bit different from the Valvo's and the IF should be re-aligned.
I had that in mind anyway and for that I have a Heathkit IG-57A post-marker sweep-generator.
Maybe not ideal but it'll do the job and It'll be necessary in all cases if I decide to have a go at retrofitting the Philips SS-MPX decoder mentioned earlier.
I have a mounting description for the original valve-MPX decoder with necessary modifications to the FM detector-circuit that says to take apart the detector and replace a cap' inside the can.

This'll all have to wait as my oscilloscope for the moment has left the building....