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mikey



Joined: 20 May 2013
Posts: 11

PostPosted: Sun May 26, 2013 10:25 pm    Post subject: Reply with quote

Hi,

As you suggest to confirm VCC at Q100, I am waiting right time for steady
hand and not to test yet unless 100% sure and confident. (have not done this before and try avoid shorting any vital pin)

At pin #9 (5V), is it ok to test at bold line (refer schematic diagram page 2Cool
where spot marked +5v-1 to get the reading ?
At pin #36 (IF VCC (5V)), is it ok to test at spot marked "C565 KETSU" as test point or better along bold line (I try the foil trace to safer joint) ?

Appreciate you kind feedback and support, otherwise I really do not have a slight idea. Thank you again.
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JTS1957



Joined: 21 Jan 2009
Posts: 2394
Location: Far, Far Away

PostPosted: Mon May 27, 2013 4:03 pm    Post subject: Reply with quote

In your pdf viewer there is a box that tells you which of the 54 pages you are viewing. This would be a better reference, since not all actual pages have numbers. I prefer to use the whole schematic pages and enlarge/reduce as needed, rather than try to use a "portion." Makes it easier to follow a line from beginning to end, imo.

Sharpening probe tip to needle point helps a little. Wink

Try to measure at pin or as close as feasibly possible, especially if it looks like the IC has been resoldered/changed. The "+" side of C120?
In a car, you can measure voltage at the battery itself, but this doesn't tell you if that voltage is making it all the way to the starter terminal.
Either side of LA04 is fine.
mikey



Joined: 20 May 2013
Posts: 11

PostPosted: Tue May 28, 2013 9:06 pm    Post subject: Toshiba CRT TV Model 21S1ES No picture Reply with quote

Hi,

Thanks for your detail description which helps a lot.

I have checked the IC (Q100) and measured VCC (in volts) as the following reading:
( To confirm 5 Volts DC):
Pin#9 = 5.12
Pin#25 = 3.39 (had double check to make sure)
Pin#36 =4.89
Pin#44 =4.76
Pin#55 = 5.13

To confirm 9 Volts DC:
Pin#29= 9.34
Pin #49=9.27

Hope the above readings mean something on the IC (is there problem due to test on pin #25 on insufficient 5 Volts reading ?) and hoping you can shed some light here. Wonder if reading on Pin #36 & #44 ok ?

Noted that the IC had marking on top read as "21S1ECMVT" on first row,
then "8801CPCNG4UD7" on second row and last row tiny "324KA".
Appreciate your generous assistance.

Smile
JTS1957



Joined: 21 Jan 2009
Posts: 2394
Location: Far, Far Away

PostPosted: Wed May 29, 2013 1:28 am    Post subject: Reply with quote

Voltage readings can vary by +/- 20%. That's 2 volts on a 10 volt point, 1 volt on 5 volt point. ALL readings appear to be within spec.
That said, Pin 17 and pin 25 are both taken from the same source in the power supply area. Pin 17 is just identified as "H-Vcc" but is never expressed as any specific value and pin 25, I'm not even sure of its label "Dlgl -5V" (lower-case 'L' is my guess). Being only 270 ohms apart and the fact that you have high voltage (menu and other evidence of a lit screen) I presume voltage on pin 17 is similar to pin 25.

The labels of the IC pins to the left of the line inside (Q100) could be described as part of the microprocessor area and to the right would be everything else needed to process the various A/V signals as well as to start to generate Horizontal and vertical sweep. ('TV in a chip' chip)

Does your set have QT01 and QV01 ICs installed?

EDIT (I hit the wrong button):
When I learned about electronics I was taught to treat a documentation-limited IC as a 'Black Box.' We've just verified that it has proper power getting to the appropriate pins. Also, you DO have control over the sets fucntions (Vol/Ch up & down, selection of menu items, etc.) Next would be to verify signal inputs and outputs to it. Since you don't have a scope there is no definitive way to do so. The only things we can prove is that the OSD and audio inputs are being routed correctly. I can't even tell you to compare voltages on rest of IC pins to what is on schematic as it doesn't show any.

Numbers on part are (most likely) Model/chassis - Part number - date or production code.

With the limited info on hand, it is quite possible that IC is defective, but unless you have another set that has one, I doubt you will be able to find one. I'd feel much more confident had we been able to scope videos IN & Out, check for sandcastle waveform, etc., but it is what it is.

Sorry I couldn't be more help.
mikey



Joined: 20 May 2013
Posts: 11

PostPosted: Wed May 29, 2013 6:46 am    Post subject: Toshiba CRT TV Model 21S1ES- No picture Reply with quote

Hi,

Your explanation on the various pins is clear and easy to understand.
To answer your question, my TV set do not have QT01 (52 pins as per schematic) and QV01(16 pins as per schematic) ICs installed and have double checked on actual board just now.

It's too bad that I do not have another similar set with the same IC (Q100) as I picked this old set from a salvage yard. Also, it's a pity that I do not have an oscilloscope to check video in/out as I have not been able to afford one yet.
However, I will still keep the TV set as it is and maybe to wait for someday someone with an old set willing to donate the IC or make a good offer.

Even though you couldn't be more help, I really felt you have put your best effort and your precious time in guidance. All is not lost; thru this I have learned quite a lot from you.

Thank you & I appreciate all you have done.
Very Happy
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JTS1957



Joined: 21 Jan 2009
Posts: 2394
Location: Far, Far Away

PostPosted: Wed May 29, 2013 6:56 pm    Post subject: Reply with quote

You're welcome.
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