Toshiba 27A50 no width adjustment


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Toshiba 27A50 no width adjustment

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marylou778
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Feb 25, 2003, 5:18 PM

Post #1 of 13 (1523 views)
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Toshiba 27A50 no width adjustment	Can't Post

I have a Toshiba model 27A50 TV with considerable horizontal overscan and I can't adjust the width. The reference number on the screen changes as I try to make the adjustment but the width never changes. Other adjustments seem to work correctly. Any Ideas?

Marylou

BL_Thompson
TV Repair Authority

Feb 26, 2003, 4:17 AM

Post #2 of 13 (1515 views)
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Re: [marylou778] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

Try the EW adjustments.
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Bryan Thompson
Spyder Byte Services
Albuquerque, NM

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Feb 26, 2003, 5:25 PM

Post #3 of 13 (1510 views)
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Re: [BL_Thompson] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

The two EW adjustments (parabola and corner) do not make any significant difference. In fact, the position is the only horizontal adjustments that works seems to work correctly. BTW, all the vertical adjustments work just fine. I still can't reduce the width and any help would be appreciated.

Marylou

BL_Thompson
TV Repair Authority

Feb 26, 2003, 5:44 PM

Post #4 of 13 (1507 views)
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Re: [Guest] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

Hmmm... I just looked up the manual, you're right... there are only the two EW adjustments. Sorry, I had a similar model that had the same symptom. The "WID" adjustment had no effect. I don't remember what EW adjustment cured my problem, but it was not either of the two available in this model.

I do know that there was an H-width coil, but the slug was glued... unadjustable. Your model may be different... worth looking in to. Do you have the manual?

I suppose it's possibly an EEPROM problem, but the fact that the data changes indicates an EVR problem. You might want to figure out which chip contains the EVR's, & try changing it. I would save changing the EEPROM as a last resort.

I'll look into this while I await your reply.
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Bryan Thompson
Spyder Byte Services
Albuquerque, NM

marylou778
New User

Feb 27, 2003, 2:41 PM

Post #5 of 13 (1500 views)
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Re: [BL_Thompson] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

Bryan,

I also found a coil with the slug glued firmly in place and it could be the factory setting for the width. I will have to get a service manual to pursue this further. Wouldn't the diagnostic test verify correct processor/EEPROM operation? And what is "EVR"?

Your help with this problem is greatly appreciated.

Marylou

BL_Thompson
TV Repair Authority

Feb 27, 2003, 6:47 PM

Post #6 of 13 (1496 views)
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Re: [marylou778] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

The diagnostics may or may not catch a bad EEPROM. EVR stands for Electronically Variable Resistor... this is the hardware that allows replacement of variable resistors with, er... EVR's ^_^ The EVR's usually are incorporated in the jungle IC, but not always. Vague enough?

Don't try to adjust the H-width coil... trust me, it will crack before it will move!

If you have broadband and the upload space, I can send you the SM. Let me know.
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Bryan Thompson
Spyder Byte Services
Albuquerque, NM

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Feb 28, 2003, 11:41 AM

Post #7 of 13 (1490 views)
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Re: [BL_Thompson] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

Bryan,

Thanks for enlightening me on EVRs. Most of my TV service experience was back when TV sets had vacuum tubes - not CRTs but the other kind.

I appreciate you offer for the manual. No problem with the download, I have 640k DSL and plenty of room. How do we do it?

Marylou

BL_Thompson
TV Repair Authority

Feb 28, 2003, 4:14 PM

Post #8 of 13 (1485 views)
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Re: [Guest] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

Send me your e-mail address & I'll send you a reply with the file attached.
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Bryan Thompson
Spyder Byte Services
Albuquerque, NM

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Mar 1, 2003, 4:55 AM

Post #9 of 13 (1481 views)
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Re: [BL_Thompson] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

apstumpf@qwest.net

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Mar 4, 2003, 5:55 PM

Post #10 of 13 (1475 views)
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Re: [Guest] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

Update on my Toshiba 27A50 horizontal width problem:

Put a scope on the output of the deflection IC. The output signal did not change while I was changing the width. Since I can't find any discrete components that were meant for adjusting the width, I must assume that the deflection IC (Q501) is bad. The coil I mention in an earlier post is the horizontal linearity adjustment.

I'm trying to decide whether to replace a 56-pin IC or live with the overscan. Right now I am leaning toward the latter.

Marylou

mickhayafe
TV Repair Authority

Mar 7, 2003, 9:47 PM

Post #11 of 13 (1466 views)
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Re: [Guest] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

before you go changing ic's, try checking the caps in the horizontal output circuit, not just the electrolytics

marylou778
New User

Mar 9, 2003, 1:55 PM

Post #12 of 13 (1464 views)
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Re: [mickhayafe] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

It's possible that a bad cap in the horizontal section is causing excessive width and I'll check into this. However, it still does not solve my problem with the width adjustment which, I assume, is supposed to modify the horizontal deflection signal in the IC and this signal does not change as observed at the output of the IC or base of horizontal driver.

Marylou

Guest
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Mar 9, 2003, 3:02 PM

Post #13 of 13 (1463 views)
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Re: [marylou778] Toshiba 27A50 no width adjustment [In reply to]	Can't Post

if you have a bad cap in the horizontal, most likely, it will lock up the adjustement. same goes for vertical width, same on projection tv's if you have a problem in the convergence circuit you can't adjust the convergence

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