Sony KV-1810UB Mk II

[Stuart R]

Hello,

My 1975 Sony TV has popped its mains input fuse, it's one of those anti-surge fuses with the small spring-loaded 'filament'. No blackened glass so it looks like a fairly unspectacular failure. Until this happened in Autumn 2021, the set was in regular use, once or twice a week.

Under normal circumstances, I'd just chance another fuse, but reading all your horror stories on these sets and their GCS devices, I feel I should be more careful before re-applying power.

Are there any basic checks I could do to reduce the chances of killing it when re-powering? I've got the 'Television Servicing' circuit diagrams from Paul's DVD and might be able to borrow a 'scope, but TV servicing is not my forte and I know these sets challenged the best of you!

These GCS devices don't just self-destruct do they? From my reading it's more of a failure of the various pulses that control them, so these need to be in-spec first?

I can't see any signs of previous modification, there's no after-sales 'Protection' board added. Some solder joints on the PCB track side (including one GCS) have been dabbed with a purple marker of some sort - not sure if that was a factory thing or from a previous fault-finding/repair attempt? If it was a repair, it's held-up for nearly 40 years. I'm imagining it would look more obvious if someone had already been in and carried out the 'Television' magazine mods that I've read about?

Not sure when I'll have time to look at this, but any thoughts would be welcome.

Thanks & Regards,

SR

[hans]

Are the two GCS' still OK? There is one in the power supply and one in the horisontal output. Often both were shorted.

If you search on the forum there should be a good description on how to fault search this problem there are caps and potmeters that should be replaced.

[simpsons]

Hi Stuart

I have 2 of these sets and followed the December 1984 Television article to the letter as recommended by Studio 263 in his post on this site.

I paid particular attention to the mains on/off switch which is said to be the culprit for many "biting the dust."

I do hope that your GCS transistors are not affected but if so, they do appear for sale on ebay every now and then.

Good luck

Chris

[Vintage Engr]

I remember these quite well, not for the faint-hearted!
Along while since I've worked on one, but yes one does need to be sure that the horizonal drive cct is operating correctly.

If you get stuck for a GCS, I may have a couple, just let me know the device type number & I will try & find it.

David.

David.

[Horris]

There was a very informative article in Practical Television several years ago,but I can’t remember when. Probably in the mid 1970’S.

Dave

[Philips210]

Hi.

There was an interesting article in Television magazine, December 1984, "Taming the Sony KV1810UB" which describes replacing the chopper and line scan GCS devices with transistors together with the necessary circuit modifications. The article is essentially for the Mk1 version but details are given for the Mk2 version as well.

Regards,
Symon

[thermionic]

Originally Posted by Philips210

Hi.

There was an interesting article in Television magazine, December 1984, "Taming the Sony KV1810UB" which describes replacing the chopper and line scan GCS devices with transistors together with the necessary circuit modifications. The article is essentially for the Mk1 version but details are given for the Mk2 version as well.

Regards,
Symon

I carried out a few of these modifications at the time, and can highly recommend them. Of course, now you may wish to keep your set as original as possible, but at the time, it was all about getting the set back working reliably!

From memory, the modification used parts from the plentiful Rank A823 and Thorn 3500 Chassis, but I may be incorrect here.

Cheers. SimonT.

[simpsons]

Hi Stuart

For what it's worth, SG613's are freely available both in the UK and USA between £18, UK and £10 US each.

I've ordered 2 for myself from the states, just in case.... as my brother lives there and you're welcome to one of them should Vintage Engr not have one in his "spares" box.

In addition to changing the electrolytics and making sure the mains switch wasn't the problem, you will need a scope to check that the oscillator is working and, with a 18volt external supply, have a variac to prove all is well before applying full mains.

As an ex Norton Radio man, I do sometimes visit old friends there and if so you would be welcome to borrow such test gear but I have no plans just yet.

Chris

[Stuart R]

Thanks everyone for your thoughts and a couple of PMs offering assistance.

This will be a bit of a long term project, I'm going to have a closer dig around the forum and read-up in more detail and track down the Television Article now I know the title - kind people here have offered me a copy if I get stuck. There are some excellent write-ups on these faults but I need to make sure I've got my facts correct, some repair stories are from 13" versions and I need to be sure circuit references are still relevant before I go prodding about with two PP3s.

I presume I can safely buzz-out the CGS pins with a multimeter to check for shorts without the risk of killing a good one?

Best Regards,

SR

[Welsh Anorak]

Yes - they're not that fragile. What they don't like is an interruption of the drive waveform. Then you can assess whether either or both have gone - you might be lucky!

[HamishBoxer]

I thought there was a mod for these power supplies years ago in Television mag?

Think apart from anything else , it improved reliability.

[murphyv310]

Originally Posted by HamishBoxer

I thought there was a mod for these power supplies years ago in Television mag?

Think apart from anything else , it improved reliability.

December 84 David.
There was a few Sony Bulletins on the set but the TV mag mod is not an official Sony mod and any set with such mods fitted were refused by us (SES network) , an official Sony memorandum to all Sony dealers was issued...... But often ignored.

[HamishBoxer]

If I am correct, the mod avoided expensive GCS devices ? They certainly blow without much prompting from what I remember.

[murphyv310]

Hi David.
Indeed you are correct. The issue often was oscillators and other passives around the device. Its a while now but Sony recommended a number of component upgrades and a thorough inspection for poor soldered joints, when done correctly the set was then very much improved reliability wise.

[Philips210]

Originally Posted by HamishBoxer

I thought there was a mod for these power supplies years ago in Television mag?

Think apart from anything else , it improved reliability.

Please see post #6

Regards,
Symon

[Heatercathodeshort]

I repaired a number of these but never liked the crazy GCS devices. Great care was needed to replace all small electrolytic capacitors in the line generator and supply rail together with the on/off switch, mains plug and possibly the two way adaptor plus components recommended in the Sony data. From what I can remember you had to scope the line drive pulse to make sure that it continued for a short duration after switch off. I bright flash would await you if you failed to follow the procedure.

What was wrong with the simple BU208 style transistor? Those GCS's cost a lot of money back then and the slightest error when servicing would blow them up.

Nasty, too critical, time consuming and expensive to repair. Not happy days! John.

[HamishBoxer]

Missed that Post 6 Symon, apologies.

[Welsh Anorak]

I think it was a case of Sony just being Sony. I could never see a reason for the GCS device as opposed to a normal transistor. They used them in geometry correction on the KV2704 (I think), but they rarely failed in that position. It was discovered (probably because they sold far more than expected) that these far cheaper devices worked just as well in the power and line of the 1810s. Cue a very stern bulletin from Sony telling you not to use them in that set! Yeah, right...

[Niechcial,Steve]

I carried out the Practical TV mod once and the set ran for years. It used a basic transistor but I have it in mind that you had to fit a surplus coil or driver trannie from another manufacturer

[Chris55000]

Hi!

If my memory serves me correctly you had to use one line driver transformer from the line scan panel of a Thorn 3000/3500 and another choke or two from a Bush A823 to get the base–drive timing right – all documented in "Sony KV1810 GCS Conversion" in "Television" magazine, and if I'm not mistaken, another similar but much less extensive modification was also described in a later issue to replace the KV1820.GCS as well!

Chris Williams