Before any serious work can commence on this set the line output transformer windings must be warmed up in order to drive out any moisture.
Introduced late 1959 the Stella ST1007U is a development of the earlier models ST8617U and Philips 1768U. Both these models were introduced late 1957. Cabinet apart, the main difference from the 1957/8 models is the tuner unit. The original tuner uses PCC84 and PCF80 valves. In the Stella the RF amplifier is a PCC89.
Noteworthy in the Stella is the position of the front controls, on the left of the CRT. I think it is an attractive set, got a continental look about it.
The polyester cabinet should polish up nicely.
Till Eulenspiegel.
Tuner buttons on the left? Presume the buttons are for the tuner, not that common, usually controls are ether side of the screen on on the right hand side.
Frank
Hi Frank, the buttons are just a gimmick. The top button is the on-off switch and the others are for sound tone and picture quality. The tuner and volume control are on the left side of the cabinet like the models ST8617 and 1768U.
Information for the Stella ST1007U and the 21" ST1001 can be found in the 1960/61 Radio and Television servicing book. Pages 613 thru to 621.
Till Eulenspiegel.
I’ve always thought these sets were designed upside down! I have a Philips 1708U that uses a similar chassis, just doesn’t have those buttons, and is in a more conventional cabinet. There is a thread about the Philips over on the other forum. Very good set, it gives a really nice bright and crisp picture, and stays stable for hours, had mine running for over 8 hours solid at the Festival of Vintage at York racecourse in 2011 as part of a display of vintage TV’s.
Regards
Lloyd
As I said on the other forum, maybe they were designed for left-handed people or perhaps the cabinet drawing was reversed but they had made too many before anyone noticed! They just don't look right...…!
...or....was it so that you could adjust the controls without standing in front of the screen.....?
Initial observation of the underside of the chassis reveals loads of Philips black tar capacitors and the few I've checked so far have really bad leaks. Might get away with reforming the HT smoothing capacitor. Resistance reading between HT and chassis is 50 ohms! No doubt there is a black tar capacitor across the HT supply. Back in the sixties these sets were considered an easy fix. Used to replace quite few line output transformers in them though. That was an easy job because it is a plug-in unit.
Philips TV sets were the favourite make for renting out anywhere far from base.
Till Eulenspiegel.
The short circuit across the HT line has mysteriously disappeared, the reading between the HT line and chassis is 50Kohms, that's OK.
The HT supply electrolytic capacitors C69,C70 and C71 are useless, will not reform so a replacement will have to be found. The capacitor is the type which has the twist tags to secure it to the chassis. A conventional can type capacitor will be used along with a mounting clip.
Till Eulenspiegel.
Yesterday. Clipped out a few black tar capacitors. All found to be leaky. C54, (10,000pF) the line drive capacitor. C57 (56,000pF) and C63 (29,000pF) the boost capacitor and CRT A1 supply smoothing. The frame oscillator, the audio amplifier and focus control are also connected to the A1 supply.
The reason for the unusually high voltage to the audio amplifier is because the anode resistor R26 is 2.7Megohms. R26 along with C28 (560pF) together function as the audio noise limiter.
Today. Changed all the 68,000pF capacitors but the value I'm looking for is 56,000pF. For replacements I'm trying to use as many genuine Philips capacitors as possible.
Till Eulenspiegel.
Hello Till,
I have some new Philips 56 nF - 400 V capacitors.
Let me know how many you need, and I'll send them to you.
Best wishes, Jac
Hello Jac, many thanks for your kind offer. I've sent you a PM.
Regards,
David.
Hi David, i have plenty of NOS Rediffusion Mk1 smoothing caps here. Cant remember value of them, 400/400/100 ?? Malc.
Hi Malc, thanks for the kind offer but I think the Mk 1 smoothing cans might be too large to fit on the chassis of the Stella. I've found a 100 + 200 + 16mfd smoothing capacitor which will fit in the restricted space.
BTW. I still have the Rediffusion Mark 5 for you.
Till Eulenspiegel.
It is a very fine little TV, I like the design, it's funny that the adjustments are on the left side, most common is right :-). On the picture of the Philips H.V. transformer, I note a little black cylinder in the bottom, what is that? What kind of capacitors are mounted in the chassis? Those green/yellow Philips are very good and never change value but the older tar- caps they made in the 50's are awful.
That's all the black tar capacitors removed and replaced with Philips "mustard" ones. The special value capacitors arrived today from Holland. Many thanks to Jac for sending the 0.56mfd and 0.033mfd capacitors.
These are the capacitors that would have been fitted as replacements by a Philips service depot in the late sixties after supplies of the tar capacitors ran out.
So now the HT smoothing capacitor is to be replaced. Chassis must come out and the CRT removed to do this.
Meanwhile the line output transformer is receiving the warm up treatment.
Till Eulenspiegel.
Today the was chassis removed from the cabinet and the CRT taken out and stored in a safe place.
The old HT smoothing capacitor removed and the replacement test fitted on the chassis. It's going to be a difficult task drilling the holes for the condenser clip and it might be much easier simply to solder it in place.
Till Eulenspiegel.
I guess it is too tricky to re-stuff the original capacitor. The issue of the ring with the tags being refitted is one problem I can imagine.
To understand the black art of electronics is to understand witchcraft. Andrew.
The replacement smoothing capacitor was fitted on Saturday evening along with a 10mfd electrolytic which is connected between screen grid and cathode of the EF80 video amplifier.
As the attachment shows the capacitor clip was soldered into position.
Till Eulenspiegel.
The smoothing capacitor has been reformed and there is now a steady 230volts across the HT rail. That's slightly higher than the working voltage. It's time to refit the CRT and test the set.
A new CRT securing band will be made, the attachment shows the condition of the original part, it's rusty and liable to break anytime.
Electrolytic capacitor C76 doesn't look too good.
Till Eulenspiegel
News Flash! Powered up the Stella today without the CRT. After a bit of fiddling about with the line timebase we have a very healthy spark at the EHT connector. I reckon there's 15KV there. The line output valve was a Mazda PL36 but somehow the set didn't work properly with this valve so a Mullard PL36 is now being used, the correct make for a Philips TV of course. For the next stage of the restoration I'll turn my attention to the frame timebase.
Till Eulenspiegel.
The frame timebase was an easy fix. 'scope connected to the control grid of the PCL82 frame OP valve. A sawtooth waveform present but it is apparent that the timebase is running too slow. Check the value of R87 (3.3megohms) and it is >5megohms. After replacing the faulty resistor the frame hold control can be adjusted for 20mS repetition rate. Sawtooth waveform at the anode of the PCL82 is 50volts P - P + flyback pulse.
Till Eulenspiegel.
