Late 70's Sanyo CTP-1401 mini TV

Looks like these were very popular sets then! 

I’ve been prodding at it some more, found something is oscillating at about 15khz, so I guess the line oscillator is running, seems to be detectable all over the power supply too, I’ve also discovered the audio stage has power and is operating, as injecting signals into it produces noises from the speaker, as yet no life from the frame stage. I think I’ve found one of the power supply rails, should be 80V but is actually being dragged down to 35v, I found this when I must have shorted something and a couple of resistors went up in smoke, and the rail went up to 88V with the 2 resistors removed, and I could hear a very quiet line whistle. So I’m guessing it’s either something dragging the supply down, or the power supply isn’t able to deliver enough grunt. I did find a suspect diode in the power supply, it seemed to be o/c on the continuity tester of the multimeter, but when removed and put on the component analyser it came up ok, it’s forward voltage was around 1.3v, and measuring it on ohms range showed 3.3M ohms one way and open the other, so it might be ok! I couldn’t find any info for it, and Sod’s law it’s the only one of that type in the set, so nothing to compare it to, it’s a plastic bodied thing with ‘HC-2’ moulded into it, no data at all online, except for modern SMD zener diodes. 

 Regards 

Lloyd 

First light!

Frame stage is doing something, as is just about everything else, so I'm pointing the finger straight at the power supply now, 80V line is down at about 38-40V with the 80V +B pot maxed out. Can't get a signal through it, I guess there isn't enough power for the tuner to work, although twiddling the VHF tuner around CH4 (my Aurora!) produces some disturbance on the screen.

I think it might have been running like this all along, but I've not been able to hear it, I think I've finally lost the ability to hear 625 line whistle 🙁 Luckily the frequency counter part of my Fluke multimeter can detect 15KHz!

Regards,

Lloyd.

Posted by: @lloyd

Looks like these were very popular sets then! 

 

Hi Lloyd, well I'll be first to break the silence and offer my moral (if not technical) support! I'm looking forward to seeing how you get on with this little beauty. There seem to have been several on offer on ebay lately, both in twin and single tuner versions. Did you get the tinted clip-on perspex screen guard with yours? I think they are often missing. I've always found it intriguing that Sanyo's colour logo of the era has red, blue and yellow segements, rather than red, blue and green...

Anyway now you've got some light on the screen, so that's a great start. Good luck!

Steve 🙂 

There is a single standard version of this on the Bay, looks to be missing a knob or two, but I can't help wonder if it might contain some useable parts for yours? - Or figure out one, then fettle up the second. . . .

You know, I’m quite tempted to get another that works just as a comparison! There is one just down the road in Newark, the single tuner version, I’m off work in a weeks time so if I haven’t got this one going by then, I’ll grab the other one!

Cheers for the moral support Steve! I certainly need it! I do have the clip on Perspex cover, I’d taken it off for cleaning, that was one of this sets redeeming features, it still had that, all its knobs, and both aerials too, oh and the funny little plug thing with 6 pins that needs to be in when using the set on mains. 

 Regards 

Lloyd 

It's probably just running on the startup current thru the resistor that bridges the main linear regulator and so the big pass transistor isn't conducting. Could be a fault around its driver stage.

Got the little blighter!

So without a manual, and it looking like the set basically worked, just with low PSU volts, I decided the next best course of action would be to trace out the whole circuit, and draw my own schematics, complete with voltage readings and component values...

...But I'm lazy, and that's too much like hard work! So my second best course of action was to get the multimeter out, and test every damned component in front of me, until I found one that read funny, then pull it out and bung it on the component analyser, I knew what area of the board to start looking, started by checking resistors, they were all OK, checked a few caps, one small electrolytic was a little high on the ESR, so got swapped, but made no difference, then I looked at diodes, I did try another in place of D317, which is the one I mentioned earlier that read over 3.3M in one direction, replacing made no difference so I put the old one back. I probed a couple of zener diodes, one was OK, the other, D311, gave some odd readings , it couldn't make it's mind up whether it was a 29pf capacitor, or a 1.1k resistor! Either way, it certainly wasn't a zener diode any more... to make matters really complicated, I couldn't find any info on it! it's markings are -0675s: . Just out of curiosity I replaced it with a 2V7 zener that I had, thought I'd start low and see what happens, I fired up the set again, and this time the 80V line was a bit higher, at 45V, previously it could only get to around 38-40V, this seemed promising! So I had a dig for some other values, found some 6.2V zeners, BZX85-C6V2, I'm sure I had some smaller values, but couldn't find them, switching on this time there was absolutely nothing on the screen! so I turned it off quickly before anything went bang, as it went off there was a very quick collapsing raster came up, guess who had turned the brightness down to nothing?! I turned it back on and upped the brightness, and up came a full screen of snow! I quickly plugged an aerial lead in and tuned it into the workshop RF and got a full colour picture! A check of the 80V line showed it sat at 83V, I gave it a tweak back down to 80V, and it seems to hover around 79.8-80.2V.

I gave the height and linearity a tweak too, as I'd fiddled with them earlier, it all seemed happy enough on test, so I tidied up my soldering, and stripped the set out of it's cabinet for a clean. I also had the UHF tuner apart as it was sticking due to dried out grease, and also one of it's fixings was broken too. The chassis comes out in one piece, after disconnecting the CRT, you don't even need to take the knobs off! The cabinet was given a bath, this will be the last set to be cleaned in that bath, as it's getting replaced in the next couple of weeks with a new shower.

Once dried and re-assembled it was given a polish with Autosol to get the remaining marks off, and a nasty scuff on the perspex front was sanded out and polished too. I thought it'd be a good idea to test it on 12V too before I got too many screws in the back! It works well on that too, drawing just over 2A, I should probably have checked and adjusted the sub 80V +B whilst I was at it, but forgot... I also gave the VHF tuner a quick test with the multi-standard modulator, pleased to say it also works!

Interesting that the set is made with parts from both Sanyo and Hitachi, the tube has both names on it!

Overall, it's a nice little telly, would probably have been quite expensive when new, I certainly remember when I was looking at small 12V TV's back in the 90's they were probably the second most expensive sets after large screen ones with stereo sound. I've got quite a few of these small screen sets of varying ages now, this one is the oldest.

Regards,

Lloyd.

Sorry for the very long post!

Great work LLoyd! Well done for persevering with it. What a little cracker it's turned out to be. You'd better get yourself a 70s caravan, so you can see it in it's natural habitat.  9" is small even for a portable- is it a bit of a strain to watch?

Steve

Hi Steve, It’s not a bad little set to watch, had it on for a good few hours this evening, sat and watched Bob Ross on it alongside the B&O MX2000, the only complaint I had was a little too much height, and too much green in the picture, so I’ll probably pop it open again tomorrow and have a twiddle. It’s not the smallest colour CRT set I have, I’ve got a few of the 5” ones too, some of those are a bit naff to watch because the colour stripes are quite thick! 

I can imagine it Would have been a rather more upmarket caravan to have a colour set in the 70’s! Everyone else sitting watching their 12” Thorn black and white portables! I bet these would have made good monitors for early computers too.

I tried out a few of my other 9” colour sets alongside this one too, one thing I noticed was how much more power hungry on 12V one particular Ferguson set was, drawing 3.5A! I also have a much more modern Goodmans one which I haven’t tried for a while, but I do remember it drawing about 1A. Think it has a 110 degree tube too.

 Regards 

Lloyd 

Posted by: @colourstar

You'd better get yourself a 70s caravan, so you can see it in it's natural habitat. 

I've got one of those! It's a 1974 Mustang, and not in bad shape. It's previous owners used to go to country/county shows with it (I think they kept horses). There's no sign of an aerial ever being screwed to the outside, nor cable entries being drilled. But, it's no stranger to tellies - it houses a lot of my better sets.

If you had this set you might not have needed an external aerial! It comes with 2 telescopic ones attached to the back 🙂 I also noticed the single tuner version has just one aerial, and it also comes with a bow tie shaped aerial that clipped onto the telescopic one and plugged into the aerial socket on the back, which leaves me wondering if the telescopic aerial was actually connected at all? The ones on my set are connected to a plug that hangs out the back and needs to be plugged in to use the internal aerials, I see no such plug on the single tuner set on eBay.

I've opened it up again today to tweak the colours as the picture had a bit of a green hue to it, looks like the tube has a very lively green gun! The green bias adjustment was already set as low as it would go, there are only 2 drive controls, one for green and one for blue, both were set about mid-way, now the blue is set about 1/3rd of the way and the green set just above 0. it now looks comparable to the Ferguson A10R which I sat next to it as a reference. Also tweaked the height pot back down a bit so people don't look quite so skinny!

Another thing I've noticed about this set is just how sharp and crisp the picture is, fine detail can be picked out better on this than the Ferguson. The only downside I've noticed is that the colour stripes on the CRT face are quite noticeable, even at a few feet distance. Oh, and the tuner is very sensitive to noise! It picks up my wireless mouse signal which creates flashing bands on screen, and disrupts the colour too.

Turns out I'm not deaf after all!! I can hear the line whistle of these sets today! Must have just been a bad day..

Regards,

Lloyd.

Looks like this set's going to be more fun than I first thought, turned it on just now to be greeted with a black and white picture, and no, I haven't accidentally turned the colour down! and that slight green tinge that I thought I'd got rid of comes back after the set has been run for an hour or so, or the red fades out slowly.

Well, I was disappointed that I'd fixed it already, after all, I did want a winter project! Lets hope it's not yet another obscure component without a datasheet that has gone pop!

Regards,

Lloyd

Ok, well that's odd! I finished the above post, leaving the set on, switched the DVD/VCR over to DVD, which has the test card on, and it came up in colour perfectly!?! It didn't 5 minutes ago! But the output of my little media player box is still in black and white?! I know that the box has a slightly odd output that some sets don't like, mainly Sony KV-1330's, and it worked fine with it last night! Something's on it's last legs in this set.. Just got to find out what!

Regards,

Lloyd

...and now the media box is in colour too! Got to be a dried up cap in there somewhere.

@lloyd

You don't have a HAL9000 computer, by any chance? - I wouldn't trust it if I were you, says you have 72 hours of reliable communication, but it's just a rouse to get you to go outside - don't go!

[2001, A Space Odyssey]

"If you had this set you might not have needed an external aerial! It comes with 2 telescopic ones attached to the back"

I had a funny experience in the late 60s with indoor antennas on a portable.

Warranty call on a new AWA P4. This model was (unwisely) advertised as "inbuilt antenna gets perfect reception anywhere" !  The fault was reported as "blurry picture".

I drove down the street of beachside cottages with a large sandstone cliff between the street and the transmitters. Every cottage had a 50 foot guyed mast and a large antenna array except the one I was visiting. "Here we go' I thought....

Sure enough, there was the P4 sitting on a table with the telescopic antennas extended. So the first thing I did, in view of the customer, was fold the antennas away and reached around behind the TV to try to find the antenna cable.

"Where's the antenna?" I said.

"Er ... you just folded them away..."

So I expressed disbelief that ANYONE could think that an indoor antenna could possibly work here.

"Have a look down your street. No-one installs an antenna like that if an indoor antenna would work"

"But it's a portable!"

"Yes but it's still subject to the laws of physics!"

I did manage to convince her that I should book an antenna installation.

I remember as a kid being very disappointed by a pocket TV that refused to pick up anything at all where we used to live, especially since I could get a (barely!) watchable picture on an old Hitachi black and white portable with just a wire stump sticking out the top of it! 

This little Sanyo is being difficult again, the colour has gone completely now, and shows no sign of coming back on its own, I’m slowly prodding my way around the decoder, but I have very little idea of what’s what, both IC’s are obscure things, one is a TA7161P, and the other TA7169P. Oh, and I’ve never worked on a colour decoder before either!

 Regards 

Lloyd 

I think I’m going to have to call time on this one, I got hold of a manual for it from someone on UKVRRR, an original Sanyo one too!  I’ve prodded all round the decoder, and as far as I can tell, the 4.433Mhz oscillator Refuses to run, I’ve tried replacing the crystal with several others and it changed nothing. The oscillator is part of the TA7169P chip, which seem hard to come by. I also built a crystal tester and the original crystal oscillates perfectly well on that, so I fed the signal from that back into the set and was able to get unlocked colour on the screen, I also bought myself a nice Iwatsu function generator and tried feeding the output of that into the decoder, which also produced unlocked colour! Sadly the adjustment isn’t fine enough to get it spot on, but all this is making me think that chip is at fault. I also made a big booboo, I tried to adjust the oscillator core on the TV, even with the tool that fitted snugly, the damn core broke... it was one of those horrible ones with the hexagonal shaped hole all the way down it, and I haven’t got any cores spare that are the correct size, so even if I do replace the chip I’ll probably not be able to get it to lock properly because of that now! So I’ll wait and see if another set turns up, I was going to grab the one in Newark, but sods law On the day I decided to buy it someone else decided they wanted it too... 

one daft question, should the 4.43 MHz oscillator run all the time, or only when a colour signal is received? I have found the burst signal, and it’s going to all the right places. I’m also toying with the crazy idea of building a new decoder! Something with a newer, more easily available chip, preferably one that needs as fewer external components as possible.

Regards,

Lloyd.

Other than faults with the sub-carrier, my understanding (which is likely incorrect) is the ref oscillator is running unless the colour killer is operated by the absence of  burst in a B&W signal. However, as I say, I'm often wrong on many things, so don't take my word for it, I'm just an amateur, wait for the trade guys for real knowledge. It's a very good question though. One which makes you stop and think, "hang on how does it work again".