Hitachi CNP860 70s ctv
Yes, I couldn't agree more.....
Thanks Dave, it was an interesting read and the set is much healthier now.
What a cracking picture ?
An excellent result, well done. The only weak spot on all of those early UK models was the aerial socket as you have found, I don't recall ever changing a tripler or LOPT.
Do you know if the set it fitted with the multiband push button unit? We received a batch of sets and at the time everything was given a workshop test before installation. We were surprised after unboxing a few to find none of them would tune, just white noise. After much head scratching it was eventually noticed that the tuning scale was 2-5, depressing and turning each button the brought up 6-12 then 21-68.
Do you know if the set it fitted with the multiband push button unit? We received a batch of sets and at the time everything was given a workshop test before installation.
This CNP 680 has a Uk 21-68 tuner only rather than multiband.
Annoyingly the tuning drift fault re-occurred again. It would drift off tune then snap back in again intermittently sometimes every few seconds then would go for 5 mins or more rock solid before drifting off again. The variable presets all tuned nice and smoothly with no noise and the Chanel could be changed without the press button unit showing signs of being noisy. I disconnected the AFC to the tuner just in case that was dragging it off tune but was still the same but you could see the effect much more clearly without the AFC which had been compensating quite well for the drift. as the 33v TAA550 had been changed already I monitored the tuning volts at the tuner which did indeed drift by by several milli-volts despite the 33v input the the variable resistor bank being steady. Next tried an external supply to the tuning volts pin from my bench psu. Everything was rock steady then even with the AFC still disconnected. I checked the earthy end of the tuning resistor bank but all was well here too. So it seems there must be some kind of electrical leakage going on inside the press button unit resistor bank. For now I have fitted a 47k potentiometer between the 33v and the tuner tuning volts pin and pre set it to ch 36. All is now well and the set is rock steady with no more drift over the last couple of hours. As only one channel required I will leave it like that unless another good press button unit comes to light. Hopefully thats it for this set for now!
The CNP190 you have did have push button problems, I stocked one as a spare, only one they were not that much trouble compared with other makes. The CNP192 I commented on earlier had tuner problems, the push buttons were good, again just stocked a tuner as a spare.
Although the button unit was multiband I don't think the tuner fitted was as no band 1 signals could be detected whilst tuning.
The CNP190 and 192 were UHF only, I never came across a CNP860.
The story continues at my house and so following a visit to Dave Newman last Saturday it was out with two from my collection and in with one. I've always fancied one of these since I first saw one when they were new at a neighbour's house. Well, the late, great Les Lawry Johns used to say get it right in black and white which it is but the colour has sadly run away on the journey from Dave's to mine.
A couple of days later I had some time to myself so first of all, I overrode the colour killer which brought colour back but if you interrupted the signal two out of three times the colour was out of phase. Ident trouble I thought as one out of three times was not a good average and I really didn't want to leave the colour killer overridden.
TR1008 second ident amplifier turned out to open circuit established by voltage check - it wasn't conducting at all. Obviously I didn't have a 2SC458 handy so with a quick look at the voltages involved I bunged in my favourite all purpose NPN, a BC108. Bob's you're uncle, all voltages back to normal and colour returned to the cheeks of young Carol.
A slight tweak on a couple of the controls and all was good.
The cabinet was given a good clean and a touch up in places followed by a good old going over with beeswax. The plastic back cover was filthy after its less than ideal storage before Dave rescued it so into the bath it went.
I'm really pleased with it and am so grateful to Dave for rescuing it. I could do with a replacement pushbutton unit but Dave's workaround will do for now.
There is one more fault which I will investigate in due course. Some rather strange frame non linearity when warm. A band of cramping about a third of the way down the screen and a little foldover at the bottom of the scan. I'll report back when I've had a look into it.
Good to see you back at the bench with this nice little set and it giving you some decoder fun to diagnose, who could ask for more. The cabinet has cleaned up a treat and looks smashing in your last photo. ?
Look forward to your updates regarding the remaining fault.
Time spent in the workshop is sadly short and infrequent but it was nice to spend some time. Apologies for the not very good photographs. Mobile phone camera!
They and the set look pretty darn good to me ?
Looks good, the CRT looks OK as well.
I only ever had one frame fault, an electrolytic capacitor, which one I can’t remember, it was intermittent and a bit of a so and so to find.
Faults were few and far between on these sets and we had sold good number, apart from the push buttons in the 190 and tuners in the 192, even those would only be replaced or fixed once in the sets lifetime.
CSP/CNP860/470 was quite a bit different to the 190 series. the decoder is on separate board on bottom of cabinet covered in lots of crud, rather than on one of the vertically mounted ones like later 190/2.
No colour will be one or more of the 2SC458 transistors on that bottom board--best change the lot!