[TechAssist] Re: Toshiba CF3564B immediate shutdown Q480 shorted e-c

  • From: "Keith Trumbla" <ktrumbla@xxxxxxxxxxx>
  • To: <techassist@xxxxxxxxxxxxx>
  • Date: Thu, 30 Oct 2003 17:06:17 -0600

Q480 is your HV regulator that feeds B+ in to the FBT at pin # 2 . This
voltage is monitored via Q485  for x-ray protection. Q480 should have 120V
on collector and regulate to 115V on the emitter. Q481 is the error amp that
drives Q480. D481 is a 4.7V zener on the base of Q481 which gets it's
reference from IC482. Voltages on this IC are as follows from pin 1 to 9:
11.8  4.4  4.3  4.6  0.0  3.6  9.0  9.0  11.8 .   Pin # 2 is the ref voltage
that drives Q481
HTH
Keith Trumbla
BEM Electronics Inc.
Suite 212-530 Century St.
WPG. MB. R3H 0Y4 Canada
Ph.(204)775-2875 Fax.(204)774-9192
SITE UPDATED !
www.bemelectronics.com

----- Original Message ----- 
From: "Larry Eastman" <videotech@xxxxxxxxxxxx>
To: "techassist" <techassist@xxxxxxxxxxxxx>
Sent: Thursday, October 30, 2003 1:37 PM
Subject: [TechAssist] Toshiba CF3564B immediate shutdown Q480 shorted e-c


> Hi Guys,  this 35" Toshiba starts up and  HV immediately shuts down, I
> don`t have the schematic
> and can`t figure out what Q480 is for, but it`s shorted e-c. If I remove
> the plug marked PD03
> from the HV board the set will stay on, (idiot lights on front stay on,
> ) HOT is not shorted,
> and none of the fuses are blown,I have no tech notes on this model,
> Tritronics web page shows the original Q480,  2SD1294(FA)  is NLA but
> show a RCA 2SD1294 (no FA) is available, can anyone tell me what Q480`s
> purpose is and if you`ve seen this one before whether replacing Q480
> will fix it or not? TIA, Larry E
> Larry Eastman
> American TV & Electronics
> Crystal River, Fl. 34428
>
>
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