Hitachi CSP680 - frame linearity issues

[AidanLunn]

... (or the story of how everyone on TV got flat heads)

Hello everyone!

For those awaiting the latest in my Ekco 405-line TV saga (last updated some time in spring or summer this year), there will be an update in the next few weeks, as I've been spending the past 6 months or so sorting out various aspects of my life that have had to be prioritised over old tellies.

However, I decided to treat myself to the luxury of colour TV, by pulling out of my storage what I thought was going to be a reliable TV, based on experience of early colour Japanese TVs and these models in particular. How wrong I was!

The TV has a frame linearity fault at the top of the frame, within the top third or so. It also had problems with low HT and a slightly off-lock colour reference oscillator. Also the red static convergence magnet was slightly out and the red purity... could be better.

The story so far:

The low HT was down to the HT pot being set too low. It was at around 95V, so I reset it to 120V as the RTVS book specifies. Much better!

The top nonlinearity was down to maladjustment of the V. Bias pot. This has been reset and now perfect linearity. This is the reason for the jokey thread title - camera operators use a rule of thumb called the "rule of thirds" when framing up people - their heads (or faces if shooting a close-up shot) should not be below the bottom third or above the top third of the picture, and the same applies horizontally as well. Because of this, some people's heads were at the top third "dividing line" of the screen, at the exact point where the raster lines were compressed together, making people look like they had flat tops to their heads.

The reference oscillator was slightly off, as I was getting barber pole unlocked colour on my DVD player, yet my Freeview was fine. Reset the reference oscillator and this enabled locked colour on feeds received from both devices through my RF modulator.

I then set the purity on a solid red raster and got solid red all over the raster by adjusting the purity rings and moving the scan coil assembly back and forth (of course). I then gave the red static convergence a very slight tweak and this improved convergence no end. I've read that the electrolytics on this board can end up giving trouble, so I replaced those as a matter of caution. I still need to learn how to do the dynamic convergence (for this is the first time I've ever worked on a delta tube), as it's acceptable but it could be better. Or maybe, as I've only seen colour CRTs of the in-line type thus far, this is the best it can get? The top and bottom red/green look slightly out, especially in the corners, and the blue vertical is also out in the bottom left (along with the horizontal red/green). However, unlike the red/green - which have left and right vertical controls, there is no such control to adjust the blue verticals at the side. Is that normal or is it a feature applicable to only this model?

I'm thinking this TV must have been seen by the Phantom Twiddler of Potentiometer City, as most of the ones I've had to adjust were definitely just maladjusted. the reference oscillator may have been set like that since it left the factory, as I've read that non-broadcast sources can sometimes cause barber-pole unlocked colour.

Now, as a 27 year-old who was only brought up well into the era of the in-line CRT, I really must stop occasionally looking up close at the screen at the triad phosphor dots of a delta gun CRT!

I think I've been bitten by the colour bug!!!

[1100 man]

Hi Aidan,
When I was at school in the mid '80's, I was often given old delta gun TV's as people upgraded to more modern stuff. I would often spend hours (or days!) on the whole convergence & greyscale setup. There are an awful lot of adjustments which are all interdependent. There was always the feeling that you could get it that little bit better, but in the end you had to accept that it was not possible to get perfect convergence. It was great fun trying though! Yes there are less controls for the blue, but also a 'blue lateral' static adjustment.
I got used to the British sets Pye 697, Thorn 2000 (I recently got back the set I last played with in 1983!!) Thorn 3000, Philips G8 etc, so when I was given a Hitachi from the same era as yours (can't remember the model) I was stunned by the quality of design & manufacture: it was miles better than the British stuff. Everything was small- no great wire wound resistors causing print burn up's and good quality capacitors. No wonder the Japanese obliterated the British TV industry! I was equally impressed when I was given a Toshiba in the mid 90's- It's never gone wrong and I've still got it!!
PIL tubes were a revelation- tiny yoke assembly and no convergence. Mind you, the tube life was often not up to delta gun standards and they would rarely rejuvinate successfully unlike the delta's.
It would be nice to see some internal pictures of your one.
Good luck with it
All the best
Nick

[ukcol]

Back, probably in the early 1970s, my best pal bought a brand new Hitachi CSP680. His first wife used to watch it for many hours in the day time as well as the evening until, when it was 15 years old, the CRT went low emission.

Until then it had been 100% reliable and we concluded it was worth while fitting spending money on a new CRT. After I had replaced the CRT the set continued to be reliable for many more years. Sadly the quality of Japanese sets from this period was the main cause of the demise of the UK TV manufacturing industry.

The downside of a set with such a good reliability record is that there is no database of common faults to fall back on. I wish you good luck with your restoration.

[Nuvistor]

We sold Hitachi and Toshiba Japanese TV’s as well as U.K. ones. There is no doubt they were reliable, however the early sets were all small screen ones, the largest we had was the Hitachi CNP190. Scanning power supply etc was much reduced, less heat and it must have helped reliability. Small 19/20 inch U.K. sets tended to use the same chassis as their bigger CRT sets.

Reliability degraded towards the end of the 70’s for those two Japanese makes when they started selling the larger screens. These were made in the UK but to Japanese designs and parts so I cannot blame the UK assembly on this for the reduction in reliability.

The CNP190 had a poorer picture than the U.K. sets but customers seemed not to notice and were happy that in general they just worked.

They did have stock faults but not many, the Hitachi CNP190/192 had tuner push button failures and the 192 had tuner failures, but it would be just once in the service life of the set.
The Toshiba had problems with the feed throughs on the double sided print, any intermittent faults succumbed to just resoldering the lot. There were many of them on the mother board and in the various screened PCB’s but not a difficult job.

Both these sets stock faults were fixed in the home, no need to return to the workshop and once fixed they would carry on working.

Was it the quality of these sets that caused the demise of the U.K. industry? Well there were claims of “dumping” by the Japanese, selling sets and CRT’s that the U.K. makers could not compete with, I am not in any position to know if that’s true but Hansard is worth a read about the Mazda CRT factory in Skelmerdale and its closure.
The UK industry was in a mess long before the Japanese sets were imported so it’s probably a number of things that brought our TV industry to its knees.

[mark pirate]

I have one of the early Hitachi sets, cant remember the model but probably a 19" with four tuner pusbuttons.
I got given it in the mid 80's by it's original owner, I was told it never had a service call since new.

I last powered it up about five years ago, and apart from a dirty volume control, it is was still working fine.

The Japanese certainly produced some extremely reliable sets back then, sadly something the British sets could not compete with.

Mark

[ukcol]

Originally Posted by Nuvistor

Was it the quality of these sets that caused the demise of the U.K. industry? .....

I don't think the Japanese were competing on price at the time. If I remember correctly (and that is a big "if" given the time that has past) a Japanese set was of the order of £60 more expensive than a similar UK manufactured set.

[Nuvistor]

Must admit I don’t remember the prices of any of the TV’s.

[Nuvistor]

For completeness from my post number 4, this is the link to Hansard, an interesting read if nothing else.
http://hansard.millbanksystems.com/c...vision-factory

[Welsh Anorak]

This was the American look TV which was nothing like we had here. Even the tuning was different! I think it had a low focus CRT so the pictures were a bit soft but compared to a Thorn 8000 or (shudder) Pye CT200 the Hitachi (and of course the Sony) was streets ahead.
Also they didn't go wrong much. Frame transistors or capacitors, the aerial socket breaking and the clunky tuner not resetting were the main faults - the latter more noticeable as the decoder was always a bit critical to lock in. Oddly, the HT always seemed to have drifted low and a tweak would often sort out lots of faults as you've discovered. This set and the 190/2 and 200 series cemented Hitachi's reputation as a good reliable set maker. Even the disastrous Instavision didn't dent them much as they swiftly provided free replacements.
Now Hitachi are a part of Argos. Hmmm.
Glyn

[AC/HL]

Originally Posted by Nuvistor

Was it the quality of these sets that caused the demise of the U.K. industry?

I always thought that lot of our problems stemmed from our relatively small market. Overseas manufacturers could rely on much greater economy of scale, even allowing for adaptations to our national standards. Competing on price, which was another of our problems, meant lower quality to compensate.

[AidanLunn]

Originally Posted by Welsh Anorak

Frame transistors or capacitors, the aerial socket breaking and the clunky tuner not resetting were the main faults - the latter more noticeable as the decoder was always a bit critical to lock in.
Glyn

Hi Glyn,

I think mine must have either (or both) a decoder and tuner problem, as it seems to have developed a fault.

The colour gradually disappears and you have to adjust the fine tuning for it to come back. As the TV warms up, this gets more and more critical - you often have to use the fine tuning to tune it into a sideband for the colour to come back and then slowly and very carefully advance the fine tuning back to get rid of the sideband yet try and keep the colour. Advancing the fine tuning can also act as a kind of chroma control - the colour intensity can be adjusted by the fine tuning over a short turn of it. As the set warms up, it seems more and more of the fine tuner's travel results in a black and white picture, the tuning to get a colour picture gets more critical until it is nigh-on impossible to get a colour picture. Also, when the colour is weaker (but still there), increasing the chroma control can actually weaken most of the colour to monochrome but allow primary colours through? When doing that it looks very similar to those adverts where they've filtered out most colours to black and white, but still allowed one or more colours on to the image. When the TV is behaving like this, the colour control isn't acting in reverse, as decreasing it in the normal way decreases the colour (as expected). The colour control acts normally when full colour is obtained (usually well into a sideband, with patterning on the screen!)

Thinking this was a decoder issue, I went to give the reference oscillator (L1005) a twiddle, only to find it completely jammed either way (when turning it would only make a crunching sound!) and my screwdriver with small iron filings on the end when I pulled it out!

Oh !

I'll come back to this one as I have a similarly-aged CEP180R to be getting on with, that has similar top linearity and convergence issues. I hope it doesn't have the faults this one currently has!

[AidanLunn]

The fault seems to be temperature-related. I switched it off for several hours this morning, switched it back on again and everything seemed fine, before the colour or tuning began to drift off again. Left it on for several hours, then switched it off for two minutes, then back on again, and the TV is now no different to what it was like just minutes before, when I turned it on.

[1100 man]

Originally Posted by AidanLunn

Thinking this was a decoder issue, I went to give the reference oscillator (L1005) a twiddle, only to find it completely jammed either way (when turning it would only make a crunching sound!) and my screwdriver with small iron filings on the end when I pulled it out!

Tut Tut Aidan: adjusting the oscillator core with a screwdriver is usually a sure fire way to break it Also the screwdriver, being steel, will affect the tuning. A nice, plastic, hexagonal trim tool is what you need. That puts much less stress on the fragile core. Don't worry, I've done similar myself and then kicked myself after
Best of luck with it
All the best
Nick

[Lloyd 1985]

Hi Aidan,

I have the little version of your set here, well 2 of them actually! The CFP-470, and one of them is showing similar faults to yours. The tuner mechanism is slowly self destructing too, takes a bit of jiggling to get it to work.

If you are short of a trim tool, I've probably got one kicking about!

Regards
Lloyd

[Studio263]

The CSP-680 is one of the first Hitachi PAL models to be sold here, they date from around 1971-1972. Bearing this in mind, the need to re-adjust a few things isn't much to ask really, imagine how many triplers, line transformers, power transistors, droppers, mains switches (etc) the typical British set would have got through to get this far! I've never replaced any of these things in any early Hitachi set, although they more than made up for it in the 1980s...

They were pretty reliable but the small electrolytics in the frame generator / driver stages were a known weakness. Similarly, many decoder problems resolve to the transistors, which always seem to read alright in a simple check but don't necessarily work correctly in the circuit. The 2SC460 was one of their favourites, I always try these first in the area of interest before getting too stuck in. A BF240 makes a good /cheap / easily obtainable replacement, although do note that the pinning is different.

The decoder in these is pretty simple (unlike the Sony sets of the era) but it is badly printed in the R+TV S books, all the interesting stuff seems to get lost in the cuts they made to fit it onto the pages.

[SiriusHardware]

I went to give the reference oscillator (L1005) a twiddle, only to find it completely jammed either way (when turning it would only make a crunching sound!) and my screwdriver with small iron filings on the end when I pulled it out!

I wish I could say that this had never ever happened to me, but I can't.

I'd suggest you completely unsolder the coil assembly from the board so you can handle / look at it from all angles in good light. The end of the core you tried to adjust is probably beyond redemption but if you look into the coil from the other end, assuming it is open at the bottom, you should see a clean, unbroken end on the other end of the core. This unbroken end is your second and last chance to get it right.

Using the correct tool this time, unscrew the core out through the bottom end of the coil and remove / blow out any broken fragments before putting what's left of the core back in the top of the coil with the 'good' end upwards of course. Unless you've really broken it up there should still be enough of the core material left to obtain the range of tuning you need, you may just have to screw it in a little further than it was before.

[AidanLunn]

Hi all, I've put the TV to one side now because I have TVs with easier repairs than the tuner and decoder board on this one is going to be to be getting on with, so I'll try all your suggestions when I get back round to it, so thank you very much for the help offered.

Are the cores easily replaceable if this one turns out to be totally stuffed?

Cheers,
Aidan Lunn

[Focus Diode]

Worth a mention the output from a UHF modulator sometimes differs from the factory settings.

On a few occasions I've encountered problems with those Maplin UHF modulators in the days of analogue. While off air reception was ok the modulator was slightly off resulting in a B&W image from the modulator. Over-riding the CK revealed the usual horizontal bands of unlocked colour. Slight adjustment of the reference oscillator core sorted that out, only to give B&W on off air reception.

With great care it was possible to adjust to give the correct colour with both the modulator and off air analogue.

One situation I recall was on a single standard G6. After replacing the LOPT, focus resistors, the BC108 in the luminance channel and the PFL200 it was set up using a DVD of test patterns via the Maplin modulator.

Only I forgot to check it on off air analogue reception!

I soon got an Email, "There's no colour". I immediately realised what had happened!

[PsychMan]

Hi Aidan,

Just to add to this as I passed this set on to you, I didn't do anything with it myself, except watch a few episodes of old TV shows on it, and I don't believe the chap I got it off did anything with it either, but before that - who knows!

I used one of those mercury RF modulators when I used it and didn't notice any issues for the short time I used it. That said, I know very little about televisions!

Best of luck with the set!

Cheers
Adam