[TechAssist] Re: Philips Model 35R502 R5 chassis
- From: "Larry Poffen" <lpoffen@xxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Mon, 26 Jan 2004 13:19:38 -0600
Have 135Vdc at TP4, Q465 will turn on momentarily when pwr button is
pressed. The osc is not running, but will start momentarily when pwr button
is pressed. can see square wave for an instant. have no 8VDC at IC200-35.
when on/off sw is pressed pin 46 of micro (IC300) pin 46 will go low for a
second then back to 5V. VCC at pin 12 & reset pin 17 are 4.87VDC. osc
appears to be running as when I touch the pin the unit is loaded & won`t
start Pin 42 is a good grd. What do you think???? Larry
-- Original Message -----
From: "Gemini Computer & TV" <geminitv@xxxxxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Monday, January 26, 2004 6:23 AM
Subject: [TechAssist] Re: Philips Model 35R502 R5 chassis
> This procedure?
> Whenever AC Power is applied to this chassis, the power supply should
> operate. Check 135V Source at TP4. Is the voltage present?
>
> The Scan system is turned on by the Microcomputer which switches the 13V
and
> 9V sources via Q465. The Micro outputs a low at pin 46 which is applied
to
> IC500 (pin 7). This causes pin 6 to output a high, saturating the base of
> Q465. The emitter rises to about 8.5V which is applied to IC200 (pin 35)
to
> start the Horizontal Oscillator and bias Q903.
>
> To determine whether of not the oscillator is running, check the output at
> IC200 (pin 36) with a scope. There should be a square wave present with
an
> Amplitude of .8v P-P at Horizontal rate.
>
> Is the Oscillator running YES / NO
>
> With the horizontal oscillator running, either check the DC voltage at
> Q500-D or check the waveform there. The DC voltage should be
approximately
> 50% of the voltage applied to the primary ot the driver transformer, or
> about 60V. If the DC voltage is at this level, the primary of the
> transformer is not open and the transistor is getting signal to the
source.
> If the voltage is at source, 135VDC, this is indicative of an open
> transistor. If the voltage on the Drain is at about 0VDC, there is
probably
> no drive at the Gate of Q500. Is this circuitry operational?
>
> YES
> NO
>
> Now that we have determined that the horizontal oscillator and driver are
> operational, this leaves the Horizontal Output circuit to troubleshoot.
> Start with static checks with an ohmmeter. There should be continuity
> between the 135V source and Q503-C. Also the resistance between the Base
of
> Q503 and chassis ground should be less than 1 ohm.
>
> Bob Waterman, CET® #RI-28
> Master Technician License #9109
> Service Manager / Parts Manager
> Gemini Computer, TV, & Security Alarms
> (508)695-7302
> (508)695-7769 FAX
> geminitv@xxxxxxxxxxxxxxxx
> geminitv@xxxxxxx
> www.geminicomputertvsecurityalarms.com
>
>
> ----- Original Message -----
> From: "Larry Poffen" <lpoffen@xxxxxxx>
> To: <techassist@xxxxxxxxxxxxx>
> Sent: Sunday, January 25, 2004 5:37 PM
> Subject: [TechAssist] Philips Model 35R502 R5 chassis
>
>
> > Need some advise on this Philips R5 chassis. The customer said pix went
> out , then sound, now all that will happen on turn on is a slight power
kick
> & relay click. have 130V & is stable. Have 5 V stby for the micro, but
the
> 9 & 13V is missing, Q465 does not turn on & stay on. It will try to come
on
> but goes right back off. The micro will reset pin 17 momentary & then go
> hi. Have followed procedure for a dead set in the force program, but this
> set really isn`t dead (totally) Either there is a load on the set or the
> power supply has a problem. like I said everything tries to start up but
> won`t come up. Have isolated the vertical load, horiz load & audio.
any
> Philips guys have any ideas???? Larry
> > Larrys TV Service
> > Broken Arrow OK 74011
> > phone 918-455-1041
> > Fax 918-451-4485
> > e-mail lpoffen@xxxxxxx
>
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