Boots MTV45 4.5 inch B/W minature TV (Samsung?)

[sexton_mallard]

On my many car boot adventures in the past, lots of miniature TVs turn up and this one was appealingly small in a white rectangular case and £2 later it was home, cleaned up and showing a bright sharp black and white picture on its 4 1/2 inch screen with acceptable sound. Recently I fancied giving it a run. Unfortunately, the polarity of the coaxial power 12v plug was set incorrectly this time...PHUT...BANG! Now I expected a protection diode to prevent numpties like me connecting the power with wrong polarity. The set is now dead, power applied from the battery compartment was also tried.

I opened the case to reveal a tiny and rather exquisite CRT and a circuit board populated with Samsung branded components with the 3 stars branding. I started checking from the power socket and already can see some mischief with what looks like some modifications close to the power in socket and seemingly no protection diode!

I can't see any identification on the board to help get a circuit. I checked closely for any burnt up or popped components but found none. The main fuse is intact but there are several holes drilled and other work which looks very unlikely to be from the factory,

Does anyone here recognise this set, and if so could point me to a circuit diagram? Many thanks in advance.

[SiriusHardware]

Even though you have what look like alterations or non-standard rework in that set you have the singular advantage of knowing that the set did work before you accidentally reverse polarised it, so change absolutely nothing in that area - it worked as it is.

Lovely little thing, well worth saving. The perfect companion for a late seventies / early eighties monochrome home computer or video game console. I hope you get it going.

[sexton_mallard]

Originally Posted by SiriusHardware

Even though you have what look like alterations or non-standard rework in that set you have the singular advantage of knowing that the set did work before you accidentally reverse polarised it, so change absolutely nothing in that area - it worked as it is.

Lovely little thing, well worth saving. The perfect companion for a late seventies / early eighties monochrome home computer or video game console. I hope you get it going.

Thanks SiriusHardware. I agree. It has a quality feel and appears to be made by Samsung. That tube faceplate is identical to one set in a Saisho ghettoblaster of similar age I acquired when I was in my miniature TV collecting phase. the control pots on the back are even in a identical position. The ghettoblaster is very well made and fully functions. I must look inside at some point and do a 'show and tell' on this forum. I bet it was made by Samsung also.

[SiriusHardware]

It sounds as though you may have an identical, working chassis in that other unit to make comparisons from.

My guess is that something which is placed directly across the supply has been taken out - something like the audio power amp IC or some other IC running more or less directly on the 12V rails.

If you are lucky some or all of those ICs will have very low value 'fuse' resistors in the +ve supply to their stage and one of those may be the only casualty.

[Maarten]

It can possibly be identified by any small print / code numbers, sometimes even on the type label, but the pictures don't show the details.

[hamid_1]

These 12v portable TVs usually have a linear voltage regulator circuit between the 12v input connector and the rest of the TV. I would expect this part of the circuit to fail first if the supply voltage was wrong.

It looks like there's a zener diode D601 near the power input socket. It could have gone short-circuit when the polarity was reversed. If it provides the reference voltage for the regulator, that would mean zero output since there would be no voltage drop across the s/c zener diode. The voltage regulator transistor (Q601?) appears to be on a heatsink directly behind the power socket - that's another suspect. Other things to look out for : low value resistors (typically 10 ohms or less) that have burnt out, particularly if you saw smoke. Sometimes the contacts in the on-off switch burn out.

Good luck with it - I'm sure it will be fixable. I'm afraid I don't have a circuit diagram but I do have a 7 inch screen Boots MTV7 which looks almost the same from the outside (a cube-shaped red plastic case). It also appears to have been made by Samsung in 1988 and was similarly acquired in perfect working order from a car boot sale for litle money. In fact I've seen what appears to be the same TV badged as Samsung, Fidelity and Dansai as well. The circuit boards often have holes for components that are not fitted, depending on the country they are exported to. For example, no VHF TV tuner or band I/III switch in UK models. Sometimes the same board is used in different models with extra features such as radio or alarm clock. Apparently missing parts and wire links are nothing to worry about, as long as it worked when it was bought.

[Richard_FM]

I've got a similar 7" version made by Dansai in Korea.

I picked it up about year ago & it only needed some switch cleaner on the volume pot.

It didn't come with a power supply or RF adaptor, so I've not used it much apart from the odd test out.

I've also seen a Fidelity badged one.

[hamid_1]

That Dansai MTV701 was the one I was thinking of. It looks just like my Boots MTV7 apart from it's white plastic instead of red. I'm sure they were all made by Samsung in Korea.

Was Dansai a real manufacturer? I think it was just a random Japanese-sounding name used by an importer or retailer, like Saisho or Matsui were used by Dixons / Currys stores in the UK. Going back to 2001-2002, Tesco supermarkets sold some Dansai DVD players DVD852 and DVD-1010 which were made in China. Of interest because they were easily made multi-region by pressing a few buttons to reveal a hidden menu. The Dansai DVD players displayed the Tesco helpline number on the startup screen "In case of difficulty, call ..." I assume that Dansai was a Tesco store brand, and that Tesco simply did a deal with whichever manufacturer offered the best terms. Rather like Boots, who are a retailer that doesn't make TVs themselves.

[Richard_FM]

Originally Posted by hamid_1

That Dansai MTV701 was the one I was thinking of. It looks just like my Boots MTV7 apart from it's white plastic instead of red. I'm sure they were all made by Samsung in Korea.

Was Dansai a real manufacturer? I think it was just a random Japanese-sounding name used by an importer or retailer, like Saisho or Matsui were used by Dixons / Currys stores in the UK. Going back to 2001-2002, Tesco supermarkets sold some Dansai DVD players DVD852 and DVD-1010 which were made in China. Of interest because they were easily made multi-region by pressing a few buttons to reveal a hidden menu. The Dansai DVD players displayed the Tesco helpline number on the startup screen "In case of difficulty, call ..." I assume that Dansai was a Tesco store brand, and that Tesco simply did a deal with whichever manufacturer offered the best terms. Rather like Boots, who are a retailer that doesn't make TVs themselves.

I've got the feeling they were made by a company in Korea who could badge engineer their products to buyer's requirements.

[Maarten]

Samsung fits that description but so do Goldstar and Daewoo and possibly some smaller companies.

Looking at the label, there's no code number. I think Goldstar and Daewoo usually printed those on the labels (not if the label was slapped on by the importer of course), so the probablity of Samsung having made the set is a bit larger.

[Tractorfan]

Hi,
Seeing this thread reminded me of the 'Boots' branded set that we bought from them in Chester many moons ago. We were caravanners and often stayed on sites without mains electricity, so needed something compact and versatile. The CRTV5 fitted the bill as it was a 4.5" TV, cassette player and an FM/MW radio. , It worked on 12 volts DC and AC mains as well as many 'D' cells. It also had the option of a rechargeable battery pack that fitted into the battery compartment and plugged into a little connector. I think we paid something like £110 for it, which was a lot, now I think back.
It was made in Taiwan and, no doubt, sported many brand names. I saw one other a few years ago in red plastic.
I tried it today, and it still works apart from needing the tape deck belts sorting. What puzzled me though, was how long the tube heater took to warm up. Considering how tiny it must be, I expected a faster response.
Cheers, Pete.

[Richard_FM]

Originally Posted by Tractorfan

Hi,
Seeing this thread reminded me of the 'Boots' branded set that we bought from them in Chester many moons ago. We were caravanners and often stayed on sites without mains electricity, so needed something compact and versatile. The CRTV5 fitted the bill as it was a 4.5" TV, cassette player and an FM/MW radio. , It worked on 12 volts DC and AC mains as well as many 'D' cells. It also had the option of a rechargeable battery pack that fitted into the battery compartment and plugged into a little connector. I think we paid something like £110 for it, which was a lot, now I think back.
It was made in Taiwan and, no doubt, sported many brand names. I saw one other a few years ago in red plastic.
I tried it today, and it still works apart from needing the tape deck belts sorting. What puzzled me though, was how long the tube heater took to warm up. Considering how tiny it must be, I expected a faster response.
Cheers, Pete.

Ingersoll was another branding these had.

I think you can record the TV sound on the tape recorder, which was useful in the days when most televisions didn't even have an earphone socket.

[Outrun_uk]

Is it me or does the transistor in the top middle of the second picture have a hole in it?

Kev

[winston_1]

I was asked to look at a Sony 9-306UB some years back. The owner did not have the Sony 4 pin connector and had managed to push a standard 2 pin figure 8 connector on to the 12v pins and apply 240V!

I had a look and found with the correct connector I could get sound but no picture. Further investigation revealed the CRT heaterwas open circuit but apparently no further damage. I told the owner the tube was burnt out and probably expensive to replace. He told me to keep it for spares. Some while later I was talking to my friendly CRT regunner who took quite a bit of business from us and he said that he would regun the CRT as a sample FOC. Good as his word he did. I've still got that Sony, one of the sets I run from my Aurora.

[McMurdo]

Another little mystery chassis trick that sometimes works is to Google the number of the LOPTy. There's always somebody somewhere who purports to stock them.

[Tractorfan]

Hi,
That's right, Richard_FM, you could, although mine does have an earphone socket.
The tape deck has a permanent erase magnet, so the recording quality isn't great.
Cheers, Pete.

[Richard_FM]

Originally Posted by Tractorfan

Hi,
That's right, Richard_FM, you could, although mine does have an earphone socket.
The tape deck has a permanent erase magnet, so the recording quality isn't great.
Cheers, Pete.

It would be useful for the sort of people who like to collect TV themes to listen to.

[sexton_mallard]

Originally Posted by McMurdo

Another little mystery chassis trick that sometimes works is to Google the number of the LOPTy. There's always somebody somewhere who purports to stock them.

Great idea! The LOPT has a label with FBE-4535AL and a Google took me to an Australian arcade site where a person with a 'Speedie Walkvision ST200' appears to have repaired their set with a recap. The CRT is apparently a Samsung 4ADC4.


His chassis reveals a slight variation to mine:
https://www.aussiearcade.com/forum/a...93#post1420493


Radiomuseum has a VHF/UHF variant here: https://www.radiomuseum.org/r/yoko_m...on_bw_450.html

Originally Posted by Outrun_uk

Is it me or does the transistor in the top middle of the second picture have a hole in it?

Kev

The hole appears to be a dimple molded in the plastic package. I've not had a chance tonight to check more components yet but will do so when I can. I'm unable to retrieve photos from my phone at the moment but will post these later.

[Maarten]

Indeed a good way to find parallel models (same factory) and/or clones (similar or licensed design from other factories).

Looking at the Yoko pictures at rmorg doesn't immediately reveal the manufacturer behind the set. At this stage it doesn't really look like Goldstar, Samsung or Daewoo to me. The most identifying code is in the copper layer and reads HWE-451 HWE-452 which might be the generic model number of such sets. It might have been made by an unknown smaller Korean manufacturer.

Besides the FBE-4535AL, is there any other code on the FBT?

[sexton_mallard]

I was not holding much hope of resurrecting this set. I went over the board with the iron to reflow any dodgy looking solder joints. I applied power to try and see how far the voltage could be measured from the socket and it sprang into life! I could not find any damaged components. Power consumption was around 560mA and I rustled up a 12V wall wart and connected a plug with the correct polarity. For the life of me I can't believe it still works. Something did go 'phut..bang' inside... the re-soldering probably cured an open connection.

Once again a nice bright picture is displayed but I will find a better PSU as there seems to be some noise and vertical hum bars from the wall wart. Here are some more pictures and to give a sense of scale, it is pictured with an AVO 8 and a can of 'magic spray' for size comparison.

More of a general question here - what is the cause of buzzing on sound when test or other bright contrasty patterns appear on screen?