Toshiba CRT TV Model 21S1ES- No picture

[mikey5791]

Hi,

Recently got this 21" CRT TV from junk yard. After blowing dust off the interior and check visually no burnt components, I plug in the power and all TV channel audio & volume seems to work OK but no picture. Later, I tried connect a DVD player to the input side of TV, audio of DVD played is clear but no picture too.

FYI, I have never repaired a TV and I intend to rescue this set and wish to learn as experience. In the past, I have done some soldering and replaced electrolytic capacitors to restore 2 dead LCD monitors. The tools I have now is a 40 watt soldering set, digital multimeter and a capacitance meter.

Appreciate if someone kind and generous can guide me on how to diagnose and hopefully repair this TV instead of going to the landfill. Thank you in advance.

 

[shrtrnd]

As near as I can tell from your description and pictures, your set is working.
Since it's a CRT, it is designed to accept the old analog input signal for the picture.
Today's over the air signal is digital. All of the new input devices, DVD, BluRay, etc are
digital inputs.
You will need to by a (roughly) $20 RF converter sold by a lot of elec stores.
You input the signal from your DVD player, into the RF converter, which plugs into the
video input of your TV.
The input signal is converted from digital, to the old analog signal your CRT television
can understand.
A lot of people are just tossing the old analog input TV's when they upgrade to the new
digital ones. You know, they want a wide-screen, or a plasma, or LCD, or whatever.
The new televisions accept the digital signal, without the RF Converter box.
Good luck.

 

[sheldonstv]

you say theres sound no picture when connecting via scart lead to your set....depending on the model it is a case of either set up for cvbs signal to be output from your dvd player etc as opposed an rgb signal-havent got the exact manual to hand but the early ones were not set up to accept an rgb signal

 

[mikey5791]

Hi shrtrnd,

The RF converter you suggested is it also called RF modulator ?
As mentioned earlier, I had connected a DVD player to the input side of this 21" CRT TV, and found audio of DVD played is clear but no picture too. However, when I connect the same DVD player to a working Toshiba 14" CRT TV, there is full audio and video.

So, maybe the RF converter still unable to solve the no picture issue as our country still uses analog signal and RF converter is unheard of. Appreciate if you can offer other possible cause and solution.

Thank you for your prompt and clear reply.

 

[mikey5791]

Hi Sheldonstv,

When I connect a DVD player (output) to CRT TV (input), I am using RGB cable (white,red ,yellow) for audio and video. Not sure how to "set up for cvbs signal to be output from dvd player etc as opposed an rgb signal". Maybe you can explain what is "cvbs signal" as I am not aware of this term.

I had downloaded service manual for the Toshiba CRT TV Model 21S1ES for your reference but as the pdf file is 3.4MB (over the forum limit 97KB), thus unable to upload.

If possible, appreciate your further guide on this.

Thank you.

 

[shrtrnd]

My bad, I thought you were in the U.S.
I'm not familiar with what other countries are using.
Let me comment on something I posted once before about an issue like this:
I used to be in the military, and was stationed overseas. Stuff we bought out there,
usually came with selector switches for different countries. The feedback I got when I
said that was, it's not commonly done anymore.
Is it possible this TV was made for use in some other country, and the reason it was
dumped, was that the owner found it 'wouldn't work, where you're at?
sheldonstv is probably onto something here. It's possible the TV video input jack is
just not compatible with what you have where you're at. It's simple here in the U.S.,
because a few years ago we converted to a standard digital signal. Maybe there's
a TV repair shop somewhere around you where you could ask about this issue.
There's nothing special about a CRT TV, over the new types they have now. I just
referenced it because they stopped making CRT TV's many years ago, and it just
tells me that it's old, and made before the new circuitry began.
Heck, maybe telling us where you're at, will perk someone's interest on this site, and
THEY can tell you what the issue probably is.
There are a lot of guys from a lot of different countries here.

 

[mikey5791]

Hi shrtrnd,

Thanks for prompt reply.

The label on the TV rear said " Made in China" and I believe the TV was sold here (Malaysia- the country I resides now) for more than ten years ago. The TV appear used but was thrown away due to some malfunction part. As the set is a CRT type and new technology seem cheaper and sometimes it is more economical to buy a new one in addition to the "buy and throw" society. Our repair shop is getting less and finding the right part sounds so alien; either the technician lack the know how or prefer to repair newer sets such as LCD TV.

I am a newbie plus putting up this new interest to repair the TV set and to reduce our landfill pollution as it is a pity to throw away a repairable item. In the past, I had managed to "rescue" our own home iron set (changing of old iron cable due to burned connection), detect bad wiring and replace home electrical sockets, replaced & soldered new capacitors to our LCD computer monitor (now in good working condition).

Getting back to the TV no picture, it may require someone with more technical experience to understand schematic, power supply, IC, etc than repairing those small
home appliances. Thus, hopefully with your step by step guide and patience, I wish to gain some exposure in repairing the TV set.

Thanking you in advance.

 

[shrtrnd]

Most all of the TV's nowadays are made in China, so that's not unusual.
The issue may be for what market the TV was made (U.S., U.K., or most probably
Asia or the Pacific Rim where you are).
I agree, the set was probably made for your country.
Like sheldontv said, you should be checking to make sure you're inputting the video
signal to the correct connectors, with the correct signal.
Your menu shows-up fine, so my guess is that you have a problem with the tuner.
Since it was alone in the dump, it was probably a family TV. I've run across a few
times when someone has modified a commercial TV to work on a home or business
cctv security system, or something similiar (modified the tuner), but I don't think
that's the issue here.
If you've checked your input signal for compatibility, I'd be thinking I had a tuner problem.

 

[shrtrnd]

I just thought of one other thing to check.
If you've got the remote for the TV, or if you can access the information from your front panel
push-buttons on the main menu:
Check to make sure your tuner is SELECTED to the correct signal you're trying to
read. I don't know all of the possible settings for your TV, but it could be set for a
different input selection.
Tuner, cable, or any other special functions that may have been in vogue when the
set was manufactured.

 

[mikey5791]

Hi shrtrnd,

Replying to your earlier post, you mentioned "you should be checking to make sure you're inputting the video signal to the correct connectors, with the correct signal." Are you referring to video signal from a DVD player as I had tested earlier using a RGB cable (white,red,yellow) connect from DVD player to input side of TV (audio & video). Then press the "arrow" sign on remote for displaying input video mode. Here I can also hear full clear audio of the DVD played but no video picture.

Later, I unplugged the DVD player and set the TV back to TV mode, select our TV channel 1 or 2 or 3 (our local channel) at which I can hear full clear audio of the TV channel selected but no picture.
Is it still possible that it is a tuner problem since I can tune to normal local TV channel ?
If it is a tuner problem, will I be able to fix it ?

In your post, you also said "If you've checked your input signal for compatibility, I'd be thinking I had a tuner problem." Can you guide me how to check input signal for compatibility. In addition, how do I check to make sure my tuner is selected to the correct signal that I am trying to read. Sorry I do not have any idea on this.

The front panel push button allow me to select either TV mode or video input mode (from external RGB connection like a DVD player). This TV is an old version with no text input mode and nothing more sophisticated but I hope it will not go to the landfill. At least I can keep it as my second TV if I manage to repair to a working condition.

Hoping for your further guidance to troubleshoot and many thanks again for the help.

 

[KrisBlueNZ]

Based on your description, and the fourth picture in your original post, I would say that almost all of the set is working fine - the internally generated menus ARE displayed on the screen. This implies a problem in the video signal path. I would suggest looking at the video input selector IC.

This is the IC that chooses which source is used for the video feed to the rest of the video circuitry. It selects between the internal tuner and the auxiliary input(s). This IC could easily have been damaged by ESD coming in through one of the video inputs (yellow RCA phono sockets).

Without a schematic I can't tell you which IC it is, but you say you have a service manual. Email it to me and I'll tell you which IC to replace.

Edit: PM me and I'll give you my email address.

 

[mikey5791]

Dear KrisBlueNZ,

Your reply boost up my persistence to continue on this repair project.

I tried attaching the service manual for your reference but failed due to size in pdf is about 3MB (this forum max file size allowed is abt 100kb). Or you may see this link
http://elektrotanya.com/toshiba_21s1e_21s1es_21s1h_chassis_s3e.pdf/download.html

Sorry I am unable to PM (is it Private Message by cell phone ?) as I am now residing in Malaysia.
Anyway if you still do not have the service manual, you may email your email address to : [email protected]

Thank you and have a nice day !

 

[KrisBlueNZ]

Dear KrisBlueNZ, Your reply boost up my persistence to continue on this repair project.

Oh, did it?... good... :-/ LOL

I tried attaching the service manual for your reference but failed due to size in pdf is about 3MB (this forum max file size allowed is abt 100kb). Or you may see this link http://elektrotanya.com/toshiba_21s1e_21s1es_21s1h_chassis_s3e.pdf/download.html

Sorry, I will not enable JavaScript for that site, because I do not trust it. I will send you my email address so you can send the service manual to me directly.

 

[mikey5791]

Hi Kris,

I had emailed you the Toshiba TV service manual this morning.

Hope the pdf version is readable. Appreciate very much on your further guide
and kind assistance.

Thank you.

 

[KrisBlueNZ]

Hi Michael,

Thanks for emailing me the service manual.

I believe the problem must be in the IC marked Q100. This is a 64-pin custom mixed-signal IC that includes a lot of analogue signal processing and a microcontroller.

The screen overlay text is generated by IC QT01, converted from RGB to YUV by QV01 and fed into Q100 on pins 18~21. This signal path is obviously working because the on-screen display works. Q100 produces RGB output signals on pins 50~52 which feed the transistors on the CRT base board that drive the picture tube. All of that circuitry is obviously working as well.

External (auxiliary) video comes in on the rear AV video connector that is part of connector PV01 and is fed to the switched connection on the front AV video connector (PV02), so that when nothing is plugged into the front video connector, the signal from the rear video connector is used instead. It's possible that this function is not working on the front video connector (although that wouldn't explain the lack of TV picture); you should check that the front video connector also doesn't work.

The signal from the auxiliary video connector, whichever one it is, arrives at Q100 on pin 24. Inside Q100 I expect there is an analogue switch circuit that selects between the auxiliary video signal and the video that is internally decoded from the TV signal, depending on whether a TV channel or the AV input is selected.

My guess is that an electrostatic discharge or other high voltage has come into the set through one of the external AV inputs. and damaged the analogue switch inside Q100 so that it cannot pass any video signal. Whatever that high voltage was, it must have had enough current to cause a damaging voltage to appear across the 75 ohm resistor (RV02) that's connected from the auxiliary video signal to 0V. I guess it's possible that an ESD event could do that.

So I think Q100 is damaged. The service manual describes it as part type A8801CPCN4UD7, Toshiba internal part number 23009669. I've done a web search but was unable to find any information on it. It's not the same as the Toshiba TA8801 (which is a 36-pin part with similar functions but doesn't have a microcontroller inside it).

If you can get a replacement A8801CPCN4UD7 from Toshiba without breaking the bank, I would try that. Otherwise I would dump the set, or give it to someone to use for spare parts.

 

[mikey5791]

Hi Kris,

Your explanation on IC marked Q100 is in detail and clear for my understanding. FYI, I had also checked the front video connector which doesn't work (as in not displaying picture).

Regarding the damaged part type A8801CPCN4UD7 (Toshiba internal part number 23009669)
being a 64 pin IC, I will try to call several electronic shops including Toshiba sales office whether they have such stock. In any event, I will inform you the final outcome.

Thank you for your helpful assistance which at the same time I had gained more knowledge
and deeper insight on TV repair from your guidance. Have a nice day !

Cheers from Michael Chu

 

[Dennis8162]

If you have a old VCR [video recorder] with a scart socket, you could try connecting your dvd/ set top box to the VCR's scart input, then connecting the video to the TV via RF antenna cable.

If you're thinking of taking the Set apart, Keep in mind there are power setorage capacitors in there, that can store 100's / 1000's of volts for years after the set was last used.

 

[KrisBlueNZ]

If you have a old VCR [video recorder] with a scart socket, you could try connecting your dvd/ set top box to the VCR's scart input, then connecting the video to the TV via RF antenna cable.

He said in his first post that TV channels are received with audio but no picture, so using the RF modulator inside a VCR will not help.

 

[mikey5791]

Hi Kris,

For weeks I have been searching and calling shops for the IC A8801CPCN4UD7 (Toshiba internal part number 23009669) but not even one place has this IC as this is an old unit.

Anyway, will keep this old TV until end of this month and later decide what to do.
But if anyone else out there has info on this IC, please kindly inform me.


Thanks and have a good day.