[TechAssist] Re: RCA F35751MB 169BG5 pops in speaker at start-up/shutdown
- From: "Gemini Computer & TV" <geminitv@xxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Thu, 30 Jun 2005 15:52:12 -0400
*Audio pop*. The *Audio level* could not be adjusted. The volume was at
normal level. The -10V supply was missing from U1402 pin 11. The voltage
was positive. Q1401 was defective. Replacing Q1401 repaired the set.
*Cycles on and off*. Traced the fault to the audio PCB. The set would stay
on when defeating the DC sense IC (IC1903). At turn on there was an *Audio
pop*. Traced the problem to Q1601. Transistor Q1601 was defetive and not
muting at turn on. The pop from the audio output IC was causing the set to
cycle on and off. Replacing Q1601 repaired the set.
*Audio hum* when the set is turned off. This set uses the 10 watt analog
system. The mute transistor, Q1901, was not turning on with the set off.
The base voltage did not go high. There was not any 16.7VA on R1902 to
supply this voltage. The 16.7VA source was present on U1901 pin 2, but was
down to 14 volts. Connecting a jumper between these two points eliminated
the hum and also increased the 16.7VA source to 17 volts. Because the
location of R1902 was near filter capacitor C1918, C1918 was not getting the
voltage either. Repaired the open trace to R1902 and C1918 repaired the
set.
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@xxxxxxxxxxx
----- Original Message -----
From: "Larry E" <videotech@xxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Thursday, June 30, 2005 3:19 PM
Subject: [TechAssist] RCA F35751MB 169BG5 pops in speaker at
start-up/shutdown
Hi Guys, this 35" RCA makes a fairly loud pop sound through the speakers
when
you turn it off, not as loud when turning it on, set was brought in for a
shorted HOT,
replaced the HOT, no other parts found bad, set runs fine with good audio
but I`ve
never heard one pop through the speakers like this one, any ideas? tia,
Larry E
Larry Eastman
American TV & Electronics
Crystal River, Fl. 34428
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