[TechAssist] Re: Philips Model 35R502 R5 chassis
- From: "Gemini Computer & TV" <geminitv@xxxxxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Mon, 26 Jan 2004 07:23:47 -0500
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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