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Old 24th Dec 2016, 8:24 pm   #1
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Default Sony KV-1300UB / KV-1310UB / KV-1330UB notes

I was recently given a non working Sony KV-1300E TV set, one of the German market variants of the 2nd generation of Sony Trinitron sets. Here are some notes for those intending to overhaul one of these sets, or have one in their collections.

The UK models in this series are the KV-1300UB and KV-1310UB, which are plastic-cased portables and the KV-1320UB Mk II and the KV-1330UB, which have the same style of wooden cabinet as the original KV-1320UB. They all have 13” tubes (330AB22) and switch mode power supplies. Although the BRC 3000 was the first set available in the UK with a switch mode converter, the Sony circuit represented perhaps the first truly modern interpretation of the concept. The BRC design still needed a mains transformer and a linear regulator to produce the 30V supply that gets the whole thing working where as the Sony circuit was self starting and produced a single 110V output, the other supplies coming from the EHT and line output stages. The 110V supply line was a well chosen value for the home market in Japan, where the mains is either 100V or 110V. Here though it leaves a lot of volts to drop, a function performed by a heavy and expensive mains transformer in the KV-1320UB and KV-1800UB.

The power sections of this set work in an unusual way. 110V DC from the switch mode circuit is applied to the converter stage whose transformer load looks like the LOPT of an ordinary set. This supplies EHT and the horizontal static convergence (HSTAT) voltages to the tube (the connection which sticks out of the tube neck), as well as a few other minor supplies. Since the converter is driven at line rate and is synchronised to the broadcast line frequency a secondary winding on the converter transformer also supplies the drive directly to the line output stage, whose output transformer is a small ferroxcube unit on the timebase panel. This supplies the line scan energy as well as the tube’s first anode and focus voltages. Width and EW correction is applied by varying the supply to the line output transistor collector using a small linear regulator whose output changes dynamically at frame rate. The picture size is also stabilised against changes in EHT loading at this point by feeding a sample of the beam limiter signal back into the regulator. Once the set is up and running the switch mode power supply is synchronised to the line oscillator too, so that any disturbance caused by the chopper action is static in the picture and does not “run through” the image, which would be far more noticeable to the viewer.

These sets have similar habits to the (in)famous KV-1810UB, in a much as they work well for a number of years and then fail catastrophically, consuming a large number of unusual transistors in the process. This took longer to happen with the smaller sets, by which time they were too old to be of any great interest, therefore the procedure for dealing with them is less well known. Never the less, a haphazard approach to repairs will lead only in disappointment, so it pays to become well acquainted with their habits. Like most Sony sets, repairing these models isn’t really a task for a beginner – small errors quickly lead to big problems that give little or no time in which to assess their root cause.

Although there are no GCS devices in these sets, many of the other transistors are quite special and are not easy to substitute. Equal care therefore must be taken, as big blow-ups can quickly tear through now irreplaceable stocks of components. Decaying electrolytic capacitors are one possible instigator of failure, so these must be looked at carefully. If you have one of these sets that still works it is still a good idea to inspect the vulnerable capacitors listed below as simple replacements at this stage could avoid a long search for other hard to find components later. New Matsushita electrolytic capacitors are still available from RS components so it makes sense to use them, do not try to fit tatty old ones from your junk box. I use the Matsushita “FC” series (105 Deg. C) where the capacitor is near a hot component or is subject to line frequency ripple. Elsewhere the cheaper “M” series (85 Deg. C) is a good replacement. Other important rules are:

1) Don’t apply mains power to the set until all the major faults are cleared. In particular there must be no short circuits across the 110V supply.
2) Don’t attempt to start the set up slowly using a variac; this defeats the two “kick start” circuits in the power supply and the line output stage and may destroy the power transistors in both.
3) Never adjust the line hold control when the set is running, inconsistencies in the line drive can cause serious damage. This is a good rule for all Sony sets of this era, most particularly the KV-1810UB.

Since there were many versions of this basic design there are also many different circuit diagrams, some of which have different component numbering. Therefore I will try to describe the various components rather than giving their numbers. You will need the correct circuit diagram for your set in any case. The red R+TV S covered the main UK variants.

Most frequently the set will be found to be completely inert, with the mains fuse blown or the cut-out button at the back sprung. Further investigations will show the chopper transistor (mounted on the chassis side plate behind the IF panel) short circuit and a short circuit somewhere on the 110V rail. As this set uses a series chopper configuration failure of the chopper transistor leads to the HT rail briefly rising to over 300V, hence the chain reaction nature of the failures. Conversely, there is little in the way of short circuit protection so faults which overload the 110V supply will usually cause the chopper transistor to fail, hence the need to exercise great care.

The first thing to do is the move over to the line output and converter (EHT) output transistors on the right hand side of the degaussing shield. If a short circuit is registered across the C-E connections of either then this is where you start. A quick way to check further is to suck the solder away from the E and B pins to check the transistors fully. Various types were used and all carry a number which ranks their gain. A resistor in the base circuit of each must be changed to match this number so if you replace the transistors you must check the resistors too. Since these transistors are no longer obtainable the most likely source is from another set, so hopefully the correct resistors will still be there. Do check though, here are some representative values:

Line output 2SC1034:
Rank 3 – 2.7R
Rank 4 – 4.7R
Rank 5 – 5.6R

Converter 2SC1316
Rank 2 – 10R
Rank 3 – 15R
Rank 4 – 18R
Rank 5 – 22R

There are other reasons for short circuits here too; the tuning capacitors seem to be reliable but the damper diodes can fail. Normally you’ll find an SB-2B or an SB-2C here; a BY228 seems to be a workable alternative. I’ve yet to encounter a faulty EHT transformer, which is one good piece of news. Once this little panel is in good order you can move onto the timebase PCB beneath. This looks like the same one as one finds in the KV-1340UB but there are many differences and the two units are not interchangeable. There are two transistors (usually 2SC1124s) on this panel on small alloy heat sinks, remove each and check them carefully. A good replacement for faulty 2SC1124s is a BF460 and a BF422 connected as a Darlington pair. The pinning of the BF460 is the same as the 2SC1124 so all one has to do is to drill an extra hole in the transistor’s heat sink tab so that the mounting screw fits through in the original position. The base is the centre pin; I cut a bit of the PCB pad away so that it can pass through without making a connection and then add the BF422 on the print side of the PCB (see photos). One 2SC1124 is the EW modulator; it works by varying the supply to the line output transistor. Failure of the latter invariably destroys the former, so always replace them as a pair. The other 2SC1124 is part of the frame output stage, if it has failed then the other frame output transistor is suspect – always check it in any case. It is usually mounted on a small heat sink by the RGB cut-off controls on the decoder panel. A small resistor (usually 27 ohm) will be found burned out if these two transistors have failed; it lives next to the heat sink of the 2SC1124 associated with the frame output stage on the timebase panel. Now cast a critical eye over the electrolytic capacitors on this panel. I remove the larger ones one at a time and check them for crusty deposits underneath, which condemns them on the spot. If the outer wrap is discoloured or shrunken they should also be renewed, use only the Matsushita types mentioned above. There is a prominent 47uF / 160V capacitor in the kick start circuit of the line oscillator, change this as a matter of course. Similarly, the capacitors around the EW 2SC1124 must be absolutely perfect to be left in place, renew them with “FC” series components if in any doubt. The line oscillator contains two 2SC1364 transistors, check these out of circuit and replace them if they read oddly or look corroded. A BC547B makes a good replacement for these. Now apply an 18V supply to the line oscillator circuit (it is clear where to make the connections if you look at the circuit diagram) and make sure that a decent 15625Hz signal is present at the base of the line driver transistor. Two PP9 batteries are the time-honoured method but a bench supply will also do since the set isn’t connected to the mains supply at this stage. Now is the time to adjust the line hold control if the frequency is somewhat distant from the value, not when the set is running on mains power. The 2SC1364s are the usual reason for faults in this area.

Now move over the power supply unit, where the chopper transistor will probably be found to be short circuit. This is usually a 2SC867, for which there doesn’t seem to be a workable alternative in this circuit. The good news is that the sound output transistor is also a 2SC867, which is often still found to be OK. The sound stage will still work if an MJE340 is used (as in the BRC 8000) so that frees up a 2SC867 for the chopper. The frame output transistor on the little heat sink by the decoder is also a 2SC867, but this is more difficult to substitute effectively. Many Sony sets of this era use the 2SC867 so scruffy examples with irreparable faults or poor tubes can also yield useful stocks. In some sets a further 2SC867 is used as a kind of “crowbar” device which shorts the collector of the chopper to the chassis via a 39R resistor if the power supply output becomes excessive. This could also be used if you modify the circuit to use the thyristor arrangement used in the bulk of these receivers – the CV-12E thyristor needed is still fairly easily obtainable. Both of these protective devices must be checked if the chopper has failed, most particularly the CV-12E which will cause a repeat performance if faulty. Remove the IF panel to reach the chopper, the connecting wires are normally long enough to swing it comfortably clear. Make sure the plastic insulating sheet is fitted correctly over the transistor before putting the IF panel back. With these matters dealt with there should be no short circuit present across the 110V line or across the converter / line output transistors. If you still get a low ohms reading in any of these places carry on checking until you find it.

The next thing I do to have a look at the electrolytic capacitors on the power supply panel. The ones to change as a matter of course are the kick start capacitor (usually 22uF / 400V) and one which decouples the supply to the chopper driver transformer (usually 1uF / 160V). The big multiple canned capacitor rarely gives any trouble although it can look quite dented from the clamp which holds it in place. Since the chopper transistor is transformer coupled to the rest of the circuit its failure usually doesn’t cause any further damage in this area, although it is wise to check the handful of small transistors in the power supply circuit to ensure that none of them are faulty or corroded. The network of diodes in the base circuit should also come under some scrutiny, also the HT rectifier which is connected to the emitter of the chopper transistor with its cathode grounded.

Following all this work the set should be ready to go. Before applying the power check once more that no leads have fallen off the back of the timebase and power supply panels and that the E and B pins of the converter and line output transistors have been re-soldered correctly. Check that the cut-out is pushed in and that a suitably low resistance is present across its two terminals. With a voltmeter connected across the 110V supply, plug the set in and switch it on. If you are lucky and you haven’t missed anything the set should start up and function, the neon lamp behind the tuning knob is a good indicator as to what is going on since it is connected across the 110V line. The tube heater too is run from the power supply; it receives its feed from a small transformer which recovers surplus energy from the chopper choke. The heater glow should be visible and is often slightly more yellow than the dull orange colour of a normal tube. These sets use the Sony “non-PAL” decoder , most problems in the signal circuits come down to small transistors which have lost gain or become noisy (like the “lockfit” types – BC148 etc – do in British sets). Tune in a test pattern as soon as you can to check that the width, EW and frame linearity are approximately correct; cold checks are the best way to go in this area as a small slip with a probe or screwdriver can lead to disaster and put you back right where you started.

And so the KV-1300E, which you can see in the attached pictures. This required most of the attention detailed above, it is hard to tell exactly what happened but at a guess the line output transistor’s damper diode went short circuit and caused the chopper to fail, along with the EW regulator transistor. The high HT rail then took out the two frame output transistors and a few resistors. Luckily the line output and converter transistors survived, but quite a few of the electrolytic capacitors looked the worse for wear and so were replaced. The tube tester had already showed good emission on all three guns so it was no surprise when an excellent picture appeared. This set needs a 220V supply which isn’t a big deal since most of the chopper circuit can easily cope with 10% more voltage. The only part which will require attention is the tube heater supply, since the excess voltage is dropped partly across the chopper choke. UK sets have a voltage tapping here for 220V or 240V so it is clearly critical, I will add a resistor in series with the heater instead once I have worked out the correct value. Until then I’ve been running it on a carefully pre-set variac. As well as having dual UHF / VHF tuners, this set also has a similar decoder arrangement to the KV-1810UB. A feature of this is the “auto color” mode which bypasses the hue control and makes the set far more conventional to operate. In this case “auto color” is engaged when the AFT button is pushed. Other jobs still to do include a general tidy-up of the cabinet and making an adaptor for the 300 ohm aerial sockets – I have the large 2 pin plugs for these somewhere. Sensitivity is good though, it picks up a clean BBC1 picture with just a short screwdriver pushed into one side of the UHF input from the modulator system we have here.
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