KV-1800UB barn find

[djrm]

Greetings,
I rescued this today from the barn at my sister's house.
This set was bought new by herself and never failed in service.
Last time it was used the picture was dim just before it was replaced.
it will be interesting to see if it still works.
I might even attempt to clean it a bit!
I wonder if there are many of these still working.
This one was certainly reliable but it may not have been run for about 25 years perhaps.
perhaps the screen bias just needs turning up rather than the tube being flat.
I imagine the service data is readily available but haven't had chance to look yet.
Kind regards David.
   

[Mr Hoover]

There's an interesting thread here on the KV1800
https://www.vintage-radio.net/forum/show...hp?t=15018
It didn't have any gate controlled switches in(GCS) which the 1810 did which helped reliability.
The crt may be a bit weak,I'm not familiar with the 1800 but have a couple of the 13" sets..These do respond well to reactivation,later trinitrons apparently don't so not sure how yours would come up.

[djrm]

The set has been sitting in dry conditions for a while now and yesterday I had a chance to try it.
There is a raster and it responds to a signal in the aerial input, sound is working.
But there is nothing much besides flyback lines on the screen, somethinsg not right.
I found some service data from Television magazine but have yet to see a schematic of the signal stages.
Does anybody know of stock faults which could cause the symptom Ive seen. if it was an old hybrid set I'd expect the video output valve.
Maybee this set uses something similar to drive the luminance.
Has anyone got a schematic please?
Kind regards, David.

[Richard_FM]

I had ones of these for a couple of years in the 1990s, which came from when a friend of a friend had a clearout.

I still regret getting rid of it, but I was offered a newer set, & as my interest in old technology wasn't big at the time I sold it for a token amount.

As I was still living with my parents I didn't have anywhere to store it, & they were loath to have any "junk" hanging around.

It worked quite well apart from the picture being a bit red & squashed slightly.

[Murphyv310]

The 1800 was a good set. During my time with Sony in the 90's we saw a few. Mostly they suffered with low emission CRT's. We used the trusty B&K and discovered that the "clean & balance" was kinder to the tube. For the fault I'd check all HT lines first, you may have lost the supply to the video amplifiers. Three things come to mind but this is from memory, I don't have a manual. Leaky or O/C cap, faulty feed resistor or diode in the supply line (200v).

[djrm]

Thanks Trevor,
I havn't taken the back off yet, when I do I'll check some voltages and have a good look at things.
Kind regards, David.

[Mark Hennessy]

This reminds me of my KV-1820, which is pretty much the only survivor of my "TV cull" a few years back (all were given away rather than dumped, so hopefully live on. I still regret giving away my Philips set with a Teletext printer). Anyway, I think I must have been very lucky, as I've never had a failed CGS, but unlike the notorious 1810, there's only one in the line output stage, and it seems to be very reliable in the 1820.

Over the years, I saw many 1820s, and all had tired CRTs, but the one I've kept is unusual as it's like new - pin sharp and bright. Good greyscale too - normally the tracking between guns goes bad as the tube ages, meaning compromises are required when setting up. I've seen lots of faults, but usually capacitors - the big blue film caps on the timebase board, normally. One thing that did help me fairly early on - there was a later PSU with over-current protection, so timebase faults in the set wouldn't then immediately take out the PSU. I don't care about originality - that PSU has been in my set for as long as I can remember, and has been invaluable!

I haven't powered it for 20 years or more, but I'm sure it'll work with minimal effort. It's been stored inside all that time I've owned it. I do have another, that was given to me about 7 years ago, and that has works well (apart from the usual soft CRT). It has a marginally better cabinet, so you can guess what's going to happen if I ever manage to clear enough space in the workshop...

Anyway, all that's a little OT, but I do have a soft spot for these sets, and am keen to see some progress with this one. I haven't seen a schematic, but I'm fairly sure the 1820 used colour difference drive rather than RGB drive for the CRT (I remember that because I really wanted to install a teletext decoder, and that added to the complexity), so the 1800 likely did too. Not that that guarantees anything, of course - the fault could be anywhere.

I'm guessing the cabinet might be the biggest challenge. How has the wood survived the damp? Is it chipboard?

[colly0410]

My parents had one of these , they bought in the early 1970's, it never went wrong & was still going strong in 1995 when my sister had it after Mam passed away.

I was fascinated on how it soft of converted PAL to NTSC to get round PAL patents. Remember reading somewhere that dropping a line of chroma & repeating the last one with a delay line should not have worked very well in theory, but in practice it worked brilliantly. I remember the sharp, vivid pictures it showed. The only thing Mam didn't like was the rotary tuner: she'd often tune it into a channel up in the 40's/50's/60's where Sutton Coldfield & Waltham lived & get a fuzzy picture (the aerial was a group A verticaly polorised) instead of the 20's where Nottingham TX lived, I put sticker's on the dial for the channels but she'd still get it wrong sometimes...

[djrm]

   
Today I have had another look at the Sony, removed the chassis and cleaned it with paintbrush and vacuum cleaner.
The first photo shows it really needed cleaning.
The Television magazine reprin was enough to help me find a problem.
The 170 volt HT to the video output is missing, it is fed through a small inductor (looks like a resistor to me) but anyway its open circuit.
I replaced it with a 10R resistor, switched on and it burnt and bley the trip,the set is still ok now as that one is open now.
I suppose one of the output transistors could be short or anything else really. I havnt looked further yet.
I'm sure this explains the lack of video on the picture with just a blank raster and flyback lines.
Here are a few more photos of the inside of the set, a bit rusty in places but mainly in good condition.
               

[Murphyv310]

Just what I thought.
Check the diode (supply rectifier) most likely shorted or breaking down. Needs to be suitably rated a IN4007 Will not do I'm afraid. A fast diode is a must. Possible one of the driver transistors or the supply decoupler short.