Sony KV-1810UB - the GCS rides again!

[Studio263]

The Sony KV-1810 must be the most notorious TV set of the 70s. Its reputation for expensive blow-ups was unsurpassed, making it the No.1 model that the repair trade didn’t want to see. Introduced in 1975, the KV-1810UB was a compact and strikingly modern looking 18” set whose performance lead the field – remember that the competition consisted largely of the likes of the BRC 8500 and the Pye 713, neither of which could really be described as a “performance” television. The KV-1810UB’s weakness was a special kind of transistor called a GCS (Gate Controlled Switch), two of which were used in the power supply and a further as the line output device. The GCSs required a carefully shaped and completely uninterrupted drive waveform to function reliably which in practice meant that the line oscillator had to start and stabilise before the main HT supplies came up and continue for a short while after they ceased. Once the sets were over five or so years old the systems that did this began to fail, resulting in the frequent failures of these specialised (and expensive) devices. The problem was not helped by the lack of an effective over-voltage protection system on the power supply output, so if the main power GCS failed it would certainly take the line output one with it. These sets were once commonplace but GCS failure (and poor tube life, another bugbear) has now done for almost all of them. You still see loads of the earlier 13” KV-1320UB / 1310UB / 1330UBs and the occasional KV-1800UB but no 1810s it seems.

When forum member Alastair E offered a complete but non-working KV-1810UB on the forum I quite fancied a crack at it (anything that delays me having to resurrect the B&O 3400K!) but I feared the worst. The prospect of a good tube swung it though, that alone was too good to waste. With the great help of Capri Ken (another forum member) the set was brought down here and carefully inspected. The first thing it needed was a good clean, it had obviously been left in a damp garage or cellar for some years and was both filthy and smelly, both making it instantly unpopular in the workshop. The good news was that some years ago (1988 in fact) the line output stage had been converted to use a normal transistor (a BU508A) in place of the GCS and this was still OK. The remaining two GCSs in the power supply were OK too, amazing. The thing NOT to do at this point was to plug the set in (sorry HKS!), these sets need the gentle touch. I’d cut the plug off to get the back off (its still in the garage, I’ve not washed it yet) so but that didn’t matter, the first thing to do is to connect a floating 18V supply to the line oscillator and check the drive on a scope to both GCSs (or a GCS and a transistor in my case). Surprising, up it came, I could hear the whistle and the waveforms looked good. The December 1984 issue of “Television” gives the drill for servicing these sets and the basis of this is the replacement of a big long list of capacitors. This seemed like a terrible chore at the time but compared to doing a 50s set full of waxies it’s not that bad, especially as in this example they had been done already and most of them were still OK. After some more checks and a bit of tidying up I decided to risk the mains using the variac, at 70V things started to happen but at 100V there was a flash and a bang.

My first check was the power supply GCS but amazingly that was OK. Whilst probing around it though I noticed a bit burn up of the printed circuit just above it, there must have been some leakage between one bit which was grounded and the other which went to the GCS “collector”. After scraping away the burned bits (and replacing the crumbling insulating bushes around the GCS mounting screws) I had another go, this time the HT came up and stabilised around the correct 130V. The EHT had by this stage also rustled up nicely but there was nothing on the screen. This is because the KV-1810UB still uses a mains transformer to power the tube heaters, although the rare Mk. II model doesn’t I understand. With full mains a pinky blur filled the screen, so much for a good tube! Over the next half hour things improved dramatically however and with a bit of a tweak up we had the beginnings of a decent television. Inspecting the tube base panel I found two 4.7R resistors twisted together in series with the heaters, at first I thought they must be replacing one of a higher value but the diagram shows nothing, just a 1A fuse (that was still there). Removing the resistors gave 6.32V at the heater; my guess is that the mains must have been a little “high” where the set was originally used so the resistors had been added to extend the life of the tube. Now the set really began to sparkle and some more setting up cleared most of the other obvious faults, other than a kink in the verticals near the horizontal centre line of the picture.

Before this was attended to I removed the front cabinet bezel (the grey plastic part) and washed it thoroughly, the area around the screen seemed to be packed with damp cat hair which look disgusting and smelt even worse. The sun dried the parts quickly and the set was soon back together, time to look at the EW circuit. Both the power supply (PR board) and the timebase (VH board) had received a lot of attention over the years and as this was of a “fix it up” nature rather than a restoration many of the new components were tacked to the back of the panels or not of the exactly correct type or value. I worked through and put all this right, trying the set from time to time. Amazingly it still worked! After checking all the capacitors on the VH board (and changing quite a few) I was still left with the kink – what now? The EW modulator transistor (“pin out” in Sony speak) seemed a good place to start – what’s this? A BD131? Ah. A 2SC1124 belongs there, this transistor has an unusually high gain and as I discovered when I repaired a KV-1340UB (the write-up should still be on the forum somewhere) it is not easy to substitute. My solution with the KV-1340UB was a BF460 and a BF422 connected as a Darlington pair so I thought I’d try the same here – instant success, even though wiring in the driver required cutting the track work about a bit.

The decoder and tuner / IF side of things seem untouched and still seem to be in excellent condition, luckily as the circuitry is quite baffling in places. The set certainly gives a good picture (excuse the poor photo – it’s not that blue really!); it’s streets ahead of any other popular 18” colour model of the period.

There is still some tidying to do and I think the outer cabinet may be a write-off, does anyone have a scrapper (dead GCSs, flat tube) with a tidy box? Actually does anyone else have one of these sets at all, working or not? Could this be the last one running?

[Andrew2]

Excellent! God I hated those sets, and luckily we only saw a few. Before we became Sony agents, a friend from the local Granada branch humped an 1810 onto my bench and asked me if I could 'do anything with it' for him. I said the best thing would be to buy a handful of GCS's and hope for the best. None of us knew of the mods or official repairs at that time.
So he bought some new devices (£18 a time sticks in my head, but I could be wrong), stuck them in and had a look around for anything obvious, like you do. Nothing obvious seen, his hand hovered over the on/off switch...
Cue the workshop banter - "turn it on you ******* big girl's blouse", "go on, it'll be alright!"
So on it went, with a BANG followed by cries of SH!T! and lots of chortling.
Shouldn't laugh.
Anyway, jolly well done, you are a brave and stout fellow.

[Welsh Anorak]

Hi
Amazing how that second photo still sends shivers down the spine!
As you say, the presentation and the picture ran rings round the competition. I always thought the CRT lasted better than the KV 1800, but that's probably because the chassis often died earlier than the tubes in these sets. On the other 1810 thread someone made the very valid point that the mains switch should be checked as they did tend to arc, especially if the set's been damp.
I remember an encounter with one of these belonging to a very posh lady composer. After persuading her that it wasn't just a fuse and it needed to go into the workshop I presented her with a reasonable loan set. No sooner had I got back to the workshop she was on the phone demanding her set back as the loan set was no good. Puzzled I asked why. "Because it's DIRTY - and we only have nice things in our house!" was the reply. Having ascertained the two GCSs had died on her set I was happy to cut my losses and get the set back to her unrepaired and relieve her of the 'dirty' set.
Nice work as usual, Tim - as you say KV13x0 sets are everywhere but one of these?
Glyn

[ed731pdh]

Nice set, reminds me of our first colour telly quite a few years ago, a Sony KV2204UB with remote control (luxury). It's only vice was failure of the LOPX (yes, you guessed it, it was a british made part) and a burnt out drive transistor, fitment of a japanese sourced replacement gave many years of good service.

The only issue with this model I found was purity bleed and the occasional manual de-gauss to clean up the screen. Nobody could work out why, it would just do it at a whim.

[Andrew2]

Originally Posted by ed731pdh

The only issue with this model I found was purity bleed and the occasional manual de-gauss to clean up the screen. Nobody could work out why, it would just do it at a whim.

We were plagued with sudden purity errors at a few addresses in the posher end of town, where people tended to have cleaners or maids. Not being part of the family (and probably not owning a colour set themselves at the time) they'd probably never heard of the warning about using the vacuum cleaner near the TV. Especially turning the vacuum on&off near it. 'I'll take the degausser with me, Mrs Bouquet has been hoovering again'.

Just slightly off topic again (sorry), on one of my very first colour installs while I was still an apprentice, we were going through the install procedure when we noticed a very bad purity error and no matter how much we degaussed the set it wouldn't shift.
To cut a very long story short, after moving the set to another corner and getting a beautifully pure picture, we began to invesigate...
There was nothing in the offending corner so we looked in the kitchen, which was on the other side of the wall. In a cupboard right in the corner was a small lathe! When we heaved it out of the way, the TV was pure again.
The bloke was quite embarrassed and gave us a tenner between us. That was 1969, when a tenner was half a week's wage for many people. I think I was on a fiver a week. Ah, happy days!

[Welsh Anorak]

Hi
For some reason, after a thunderstorm Sony TVs of that era would often show up with purity errors which needed manual degaussing. Rarely affected other makes - no idea why!
Glyn

[Brian R Pateman]

Originally Posted by Welsh Anorak

Hi
Amazing how that second photo still sends shivers down the spine!
Glyn

I was fairly convinced that one of the causes for the poor reliability of these sets was due to the vast quantity of bits stuffed into such a small space. The thermal stresses must have been considerable.

When they worked they worked well. I had a customer who was very fond of his 1810 but I was losing money on it to a considerable extent.

The fault was intermittent and I spent ages driving between his house and the workshop and back again. Eventually I gave him an ex-rental 2240 (he was a friend as well as a customer) and brought the benighted thing back for a prolonged period of soak test. It worked in the workshop, it worked in the flat over the shop, it worked when I gave it to a friend who wanted a second set.

The blasted thing ran for at least three years until eventually it was stolen.

I could never find out why it didn't work in the customer's house.

[Welsh Anorak]

Hi
Another problem that wasn't confined to these Sony sets, though not in such a catastrophic way, was the problem of the solder not adhering to the copper lands of the PCBs. As Hitachi dealers we saw quite a lot of the NP6C series, and in some cases we would have to rework almost the whole PCB. The soldered joint appeared perfect, but could be levered off leaving a tarnished copper pad. I wonder if the Sony and Hitachi boards were made at the same factory? That does seem unlikely, but possibly a new type of solder was common to the two firms.
Glyn

[Hybrid tellies]

Excellant job and great write up. For the problems you have mentioned I don't think there are many of these sets around today. I remember these sets well, never repaired any as we used to send our Sony's over to the local Sony Service/repair centre in Avonmouth. Customers were always happy to pay the higher prices for the repairs though.

[thermionic]

I was 'left' one of these sets during my time as a TV engineer in the eighties. 'Left', as the customer did not accept my quote to repair, as both the GCS's had gone short circuit and said ' you can have it for spares if you like......' and made a rapid exit from my shop!
However, all was not lost as I carried out the excellent PSU & line timebase modification detailed in 'Television' magazine. From memory, it required a line driver transformer from a Rank A823, and a chopper drive transformer from a Thorn 3000. I stand to be corrected on this..... Can't remember what the semis were, but they were run of the mill transistors at the time. The tube was excellent and I used it as a loan set for a few years with faultless operation, until some 'erbert did a runner with it & was never seen again.

Well done for getting this going, and when the PSU GCS decides to go bang, I can recommend the PSU mods.

PS. I seem to remember some discussion about loose connections in the mains plugs causing intermittant GCS drive as well as the documented arcing mains switch.




SimonT.

[Studio263]

Who actually owns this set now...?

Capri Ken picked it up for me and brought it down here last weekend in his mint 4 wheel steer Honda Prelude, surely the coolest FCS ever with two (perhaps overly complicated) Japanese treats in one go!

Regarding the BD131, they are only rated at 45V and don't really have the gain to match Sony's "specials", hence the kink in the middle. One would probably let pass on a normal set but a half decent Sony should look almost as good as a studio monitor if all is well so it's worth sorting these niggly things out.

The next thing to do is to sort out the paper label behind the minor controls. This is a bit of a cheapie thing for them to have done with a "quality" set but when you look at the control panel from the back you can see that there are lots of extra holes for more controls, presumably for other markets. It seems that others also got more than 5 pushbuttons for preset tuning, perhaps Sony (UK) thought that five would be enough after the KV-1800UB with its manual tuning dial...

[hans]

It seems that others also got more than 5 pushbuttons for preset tuning, perhaps Sony (UK) thought that five would be enough after the KV-1800UB with its manual tuning dial...

We had eight buttons

[SonyTV1972]

I must say that I was very surprised to read the negative comments here about the Sony KV-1810UB. I have one that dates from about 1972 (with its original operating manual). It was used quite a bit, has never had any problems and still works! I recall at the time just how much better the single gun Trinitron picture quality was in terms of natural colours and sharpness of picture than just about every other make on the high street. In my view that remained true right throughout the period of CRT use.

Anyway, that’s just my experience. The main reason I am posting is that I need to have a clear out. I don’t want to throw this old TV out and if anyone feels able to collect it from GL5, I would be happy to donate it to a good home.

[Nickthedentist]

Hello and welcome.

You might like to place an "ad" in this section too: https://www.vintage-radio.net/forum/...splay.php?f=27

Nick.

[SonyTV1972]

Hello Nick,

Thank you, I've placed the advertisement.

Best
Mel