Wakey wakey Sony KV-1330!

[Studio263]

This set was kindly offered by forum member oldroyd earlier in the year, so one evening after work I jumped in the Ami and sped off (these things are relative of course…) to Hampstead to pick it up. The condition of the set could only be described as outstanding; it was spotlessly clean and free from any dents, marks or scratches. Apart from the inevitable wear in the paint around the tuning knob it still looked new, amazing after 45 years.

With any set it is always tempting to plug it in and see what happens. This gung-ho approach must be resisted with these Sonys however; remember that most have had little or no use since at least when the UHF service ended in 2012, and many have been laid up for a lot longer than that. One also must never attempt to run them up gently with a lamp limiter or a variac either; this will cause even more damage. They are tough and reliable, but since special (and now difficult to find) transistors are used in all the vulnerable locations big blow-ups must be avoided at all costs.

The KV-1330UB was the last 13” Sony set in the distinctive wooden cabinet to be sold in the UK. It replaced the KV-1320UB MkII, which was quite different to the original KV-1320UB. The former two models were the first sets on the UK market to use a proper switch mode power supply – self contained, self starting and capable of powering the whole set. The philosophy of the design is quite different to some UK models – there is no over-voltage trip other than a crowbar thyristor and no over current trip other than the fuse. Both these things only protect the owner from the consequences of a failure within the set; they don’t protect the internal circuitry or components to any meaningful extent. It was the supreme reliability of the Japanese components of this era made this a workable arrangement; the design had an excellent reputation for long, trouble-free service.

I have previously (in a sticky post at the top of this section) erroneously stated that the KV-1330UB (and the KV-1310UB, which is the portable version of the same set) use the Sony ‘non-PAL’ decoder. Studying the service sheet reveals that this is not the case, although you’d struggle to deduce that from Sony’s own promotional material! In fact a full PAL-D circuit is used, but the hue control is retained. This now only alters the phase of the output of a subcarrier regenerator circuit which is locked in the normal manner, so at the centre detent the set gives correct colours under all reception conditions. Just to confuse matters further, there is an error in the service sheets for the KV-1330UB and KV-1310UB around the bistable circuit (Q314 and Q315). The collector of Q314 is correctly shown as being connected to the junction of R309 and R311, but the collector of Q315 isn’t shown as really being connected to anything – it should go the junction of R310 and R312 of course. The same circuits are re-printed in R+TV S, have a look! The correct circuit appears in the manual for the KV-1810UB, which uses the same decoder panel.

So the set is on the bench, here’s what I do. The first thing to do is to check the tube, there’s little point doing much if it is completely flat. This set showed 70% on all three guns, which for these little tubes is virtually as-new condition. A good start then. There is no need to clip out the mains filter capacitor (C601), the Japanese knew how to make these properly and they don’t give any trouble. However, the condition of the chopper transistor (Q903), the converter transistor (Q802) and the line output transistor (Q801) must be checked. There must also be no shorts across the 110V HT line, if there are defects in any of these areas they must be remedied before proceeding. The resistance across the thermal cut-out must also be sensibly close to zero and the correct fuses must be fitted. A general look around for obviously crumbling electrolytics and other signs of distress is also a good idea, keeping an eye out for evidence of previous repair work too. This set was good in all these respects, although the chopper transistor had clearly been replaced at some time in the distant past.

In the majority of early Sony designs it is critical that the line oscillator starts instantly, is stable and runs on for a little after the set is switched off. The power supply of the KV-1330UB has no oscillator of its own and the chopper transistor is biased into conduction to start the set up, so unless the correct line pulses appear PDQ after switch-on the 110V will rapidly rise to an unacceptable level, causing all kinds of trouble. Therefore, before applying mains power one must make sure that the oscillator is working and runs at the correct frequency. I do this by applying 18V from a floating bench supply to point 27 of the VH board – two alkaline PP3 batteries in series will do if you do not have this facility. A healthy 15KHz waveform at the base of the line driver transistor Q504 indicates that all is well. This is the time to clean and exercise the line hold control (VR501), never do this while the set is running normally! Check D513, R573 and C558, these are the 18V supply components. If they are in order the set’s own 18V supply should appear as soon as the converter stage gets going.

Now, leaving the 18V supply in place, plug the set in and switch it on. With any luck everything will start up and the screen will illuminate. This is what happened for me, but there was a vicious crackling sound from the chopper transformer – switch off quick! Since this fault seemed to be in the power supply I disconnected the 18V bench supply – this piece of the set at least seemed to be OK. The nasty noises suggested a corrupted chopper drive (PWM) waveform, so care now had to be taken. A look around showed that C610 (1uF / 160V) looked tired, which made sense given the symptoms. I replaced it and switched on again full on confidence – no change. This time I let the set run on a little and tried to tune in a picture. The tuning knob was seized, so that needed sorting before I could go any further. What happens here is that the inner and outer shafts of the reduction drive get stuck together, but it is easy to take it all apart, wash out the goo with Servisol and re-lubricate with clean LM grease. Time to have another go.

This time a good picture appeared, but there was line tearing evident in time with the noises and the width seemed to pull in when things were at their worst. The 110V line was about correct, but of course the meter responds too slowly to really tell what is going on. Not wanting to run the set for too long like this, I started by changing Q603, Q604 and Q605 – as anyone who deals with Japanese sets of this era knows the small plastic-cased transistors are often the root cause of all kinds of strange problems. Q603 is a 2SC633A which can be replaced with a BC547B, Q604 and Q605 are both 2SA677s which a BC557A will replace, but note that the pinning is different in all cases. None of this made any difference however, so a re-think was required.

It is clearly a bad idea just to disconnect the loads from the power supply in these sets to try and diagnose a fault, seeing that the 18V supply for the line oscillator comes from the converter (part of the line output stage). Instead, I disconnected L803 to disable the converter (and therefore the line output stage too; the line output transistor receives its base drive from a secondary winding on the converter / flyback transformer) and connected the 18V bench supply back to point 27 on the VH board. A 60W bulb was then connected across the 110V supply, with the tube base panel removed to protect the tube heater. The set could now be gently wound up on a variac, where it was noted that the power supply behaved itself until its output reached 110V, then the noises started again with the bulb flickering in sympathy. This was the clue I was looking for.

Faults inside the control loop cannot change the power supply’s output voltage, since they will be instantly corrected for. Using the bulb as a load cleared the rest of the set, so only a few components were left to suspect. These are essentially the ‘set HT’ control VR601 and the resistors which form the potential divider around it. The control itself checked out OK and all the resistors were spot-on, leaving just the thermistor TH601 to check. This has a nominal value of 4700 ohms so can be replaced with a 4k7 resistor for testing purposes. Alternatively, VR601 can be adjusted to its minimum setting and TH601 removed, this will give 110V at the output. Be aware though that the control works the opposite way round to what you would expect. With TH601 removed the power supply ran perfectly with no nasty noises so a replacement from a scrap set was fitted. At last all seemed to be well – see photo 1.

A look at the picture confirmed the tube tester readings; it was bright and sharp with good greyscale tracking. Some EW distortion was cured by replacing C521 (4.7uF 100V), which has become a very common fault with these sets as they age. Uneven brightness across the picture was down to C524 (4.7uF / 50V), which smooths the supply to the RGB output stages. The surprisingly low voltage rating of this component is due to its negative terminal being returned to the 110V line, I wonder why other designers never thought of that? Hanover blinds visible on a test pattern were cleared by adjusting VR304 (delay line level) and T306 (delay line phase), so now things were looking pretty good.

One fault that did remain though was a thin vertical dark band about an inch from the left of the screen and a slightly wider light band about the same distance from the right. At first I suspected a scan modulation issue, but it was hard to see how this could be getting in – there is no linearity coil (and its attendant troublesome damping resistor) in these sets. Eventually, displaying a white raster from the pattern generator showed a little ‘wiggle’ in the relevant places in the video waveform present at the emitter of the luminance driver transistor Q153. This wasn’t as clear cut as it may seem, since similar wiggles exist all over any real television circuit. An embarrassingly large amount of time was then spent, which included replacing the sub-panel where Q801 and Q802 live, the flyback transformer, the tube base panel and the complete VH board, none of which is easy as there are no plugs and sockets in these sets. Nothing made any difference, the lines were still there so the original parts went back in.

Having failed with the ‘change everything’ method I tried something more scientific. Having removed the luminance delay line driver transistor Q151 and connected two 1k resistors in series between its now vacant collector and emitter connections (to maintain the DC conditions of the luminance channel) the set was tried again, with the signal still present to lock the timebases. The expected white screen appeared, complete with the two vertical bands. Disconnecting things one by one revealed that the source of the errant signal was the blanking connection at R160, which was odd as the other end of this wire goes to the VH board which had already been changed. It then became clear what had happened; the wire that runs between terminal 15 of the C (decoder) board and terminal 6 of the VH board can’t be bundled up with the rest of the loom, it must be kept separate to avoid picking up the large line rate pulses which are present in some of the other cables. Separating out the white and green lead removed the two bands completely, it was as easy as that. Embarrassingly, I think I must have been the one who’d absent mindedly put it there to keep things nice and neat, oh dear. Many hours of workshop time were wasted on this one oversight, I don’t think I’ll do that again! My KV-1330UB manual is an early issue which doesn’t show where the looms go but the KV-1320 MkII one does; I carefully positioned everything exactly as the picture shows – this side of the chassis is the same as that of the KV-1330UB. A tiny thing, but it makes a big difference (see photo 2).

After all that all that was left to do was to find out why the channel indicator wasn’t lighting up. Cleaning the prism didn’t help as the neon wasn’t working, and once it was extracted I found that one of the lead-outs had rotted away where it exits the glass. There was just enough left to solder to, so in the interests of keeping things as original as possible I soldered on a thin strand of wire and joined everything up again. Getting this right finished the set off nicely, see photo 3.

I have most of the UK market KV-13 series now, all presentable and in good working order. These are an early KV-1320UB (with ‘instant on’ and the 800mA fuse in the feed to the line output stage which they soon deleted), a KV-1310UB, this KV-1330UB, a KV-1340UB and a PVM-1300 studio monitor. Lovely sets, and not too big...

[HamishBoxer]

Cracking set as I have one here also with a good CRT, however it has not been plugged in for a long time.

[bobbyball]

I have a few of these sets myself, time I "woke" some of them up! Always thought they gave a good picture.

[Nickthedentist]

Incredible write-up as usual Tim, and another piece of history saved. Well done from me.

[boxdoctor]

Worked on a few of these earlier Sonys in the day, and loved 'em! (We sold them only for a short while ).
Such inginuity in design, without anything but the best of performance and good reliability, made them winners.
Looked "the business" too, both inside and outside.
Thanks for a really good write-up on a most interesting "case", Studio263. Tony.

[linescan87]

I don't have any experience of these, however I always liked the presentation of this series of little Sony's and would like one in the colllection. What a thorough write up, very interesting.

Thank you, John Joe.

[Graham G3ZVT]

Thanks for that, a very informative write-up.

The truth is that these Sony Trinitrons were so reliable, many of us got few opportunities to repair them.

[mark pirate]

Cracking set as I have one here also with a good crt,how ever it has not been plugged in for a long time.

Same here, although mine was working fine when tested about three years ago, the rotary tuner had seized up.

these are excellent little sets, I have had quite a few over the years.
I still have the portable version somewhere, but the CRT is clapped out!

Mark

[Hybrid tellies]

These were great little sets and I think the first Japanese colour TV's that I saw back in the early to mid 1970's.
A brilliant write up which I really enjoyed. I think we have all led ourselves up the garden path even on sets that we are familiar with.

[Tazman1966]

I used to have one of these too. It worked beautifully but alas, as I thinned out my collection, it went to another in the television family on here! Excellent write up too!

[Welsh Anorak]

Hi
Looks good - even with the fake wood front panel! I wonder how many sets returned home after repair with that green wire neatly clipped with the others...and how few customers complained?
I have a few of these but most of them have very tired CRTs. One day I'll see if the dead one has a good CRT, but I won't hold my breath!

[toshiba tony]

Excellent write up on an excellent set. We were Sony dealers in the 70's and used these as loan sets. We were not scared of them, but the later 1810's we were. I always thought the 1300 range were gentle sets, are they bother now?
Apart from the dull thud from the degassing coils they were calm. Fond memories, but it is 10 years since I recovered one, exc. cabinet but low tube. Memories boosted, tube not!

[Studio263]

Originally Posted by toshiba tony

are they bother now?

Only in as much as all the key transistors are special and if you are unlucky they can all fail in one go. If for example the chopper transistor goes short circuit it will more than likely take the converter transistor, the line output transistor, the pincushion modulator transistor and the frame output transistors with it. Left alone this is an unlikely occurrence if the set is in good condition but it can easily be triggered by careless fiddling about, such as adjusting the line hold control or changing the focus tapings when the set is running, that sort of thing.

The original KV-1320UB is very tough and the later KV-1340 a bit touchy, the others lie somewhere in between. There are many things in these that never seem to go wrong that give endless trouble in other sets - flyback transformers, triplers, tuners etc, and they don't suffer from poor soldering. Made in Japan - sign of quality.

[mark pirate]

I have a few of these but most of them have very tired CRTs. One day I'll see if the dead one has a good CRT, but I won't hold my breath!

It seems the only weak link in these sets was the CRT, most of these sets never needed any attention at all. They were probably the most reliable set of their era.

My portable set has been in my possession since the mid 80's, although still working, the CRT is as flat as can be. I kept it in hope that another tube could be found, I am still waiting...

Unlike conventional CRT's the Trinitron does not respond well to rejuvenation, upping the heater voltage only gives a marginal improvement.


Mark

[Studio263]

Originally Posted by mark pirate

Unlike conventional CRT's the Trinitron does not respond well to rejuvenation, upping the heater voltage only gives a marginal improvement.

There was a method suggested for doing it on the other forum which supposedly gave some success; I've not tried it though as all the tubes in mind are good.

These weren't bad tubes, its just that the sets lasted so long that in the end many of them just got worn out. It's the opposite to the Amstrad CTV2200, which never went for long enough to take the edge of the 30AXs that were in them...

[oldroyd]

Splendid write up! I'm delighted to see such expertise and enthusiasm lavished on my much loved little Sony.