Old Tube TV Keeps Changing Channel to Channel 2: Hitachi CT

Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

 

[Sjouke Burry]

On 29-6-2017 23:02, jeff.panasuk@cfl.rr.com wrote:

Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

Spurious interference from modern light source?
Some cheap ones produce a lot of garbage besides light.

 

[John-Del]

On Thursday, June 29, 2017 at 5:03:35 PM UTC-4, jeff.p...@cfl.rr.com wrote:

Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

Did you try disabling the keyboard?

 

[John-Del]

On Thursday, June 29, 2017 at 5:03:35 PM UTC-4, jeff.p...@cfl.rr.com wrote:
> Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent.

Wow, haven't seen one of these in decades.

If this model has a manual on/off switch, check the reset circuit for the micro.

 

[rickman]

jeff.panasuk@cfl.rr.com wrote on 6/29/2017 5:02 PM:
> Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

A friend had one of those big console TVs that would work, but there was
something wrong with the controls, I don't recall just what exactly. I
suggested he unplug the set for a while to let the caps drain off and the
processor reset. It worked sure enough! I expect a power spike of some
sort glitched the processor and it was working, but some variable was hosed
messing up the operation. A clean reset got everything working right again.

I guess that's not your problem.

--

Rick C

 

[Jon Elson]

jeff.panasuk@cfl.rr.com wrote:

Back in February or March of 2010 the TV began changing from any channel
to channel 2 intermittently. Sometimes very frequent. Other times more
intermittent but it would not go more than a few hours without the problem
popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection
Ckt but no help. Remote control IR circuit not the problem as I disabled
it. Over time have replaced some bad unrelated hw (burnt resistor, Caps).
Have schematics and service manual but can't isolate the problem. Nice
picture and everything else works fine. Unit in storage but every 4
months or so, when I see it and think about it, I fire it up. Hate to
trash this old tv. Kind of part of the family now. Has anyone ever heard
of this before?

Does it have channel up and channel down buttons on the panel? Since
channel 2 is the lowest channel, if the channel down button was occasionally
acting like it was pressed, it might end up at channel 2. I had a computer
LCD monitor that had a soda splashed on the panel, and it got into the front
panel button board, and it would work for months or days and then start
flashing through the menus. Severe cleaning of the board with the buttons
fixed it.

Jon

 

On Thursday, 29 June 2017 22:03:35 UTC+1, jeff.p...@cfl.rr.com wrote:
> Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

Yes from neon channel selector sets, touch selectors & older pushbutton bar tuning sets. Show us the circuit.


NT

 

[John-Del]

On Friday, June 30, 2017 at 2:51:21 AM UTC-4, tabb...@gmail.com wrote:

On Thursday, 29 June 2017 22:03:35 UTC+1, jeff.p...@cfl.rr.com wrote:
Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

Yes from neon channel selector sets, touch selectors & older pushbutton bar tuning sets. Show us the circuit.


NT

Hmmm... you're drudging up long forgotten memories. Back in the late 70s Zenith used a varactor tuned electronic tuner that used neons as indicators for the pre-set push button selector, and sometimes those neons were the cause of the TV jumping channels or refusing to engage a selected channel.

By 1984 I would think that all manufacturers would be using a true digital selector system for anything no using a mechanical tuner.

Unfortunately, OP didn't say if the TV would scan downward to channel 2 or jump to it. He also didn't say if the TV normally defaulted to channel 2 when the TV was powered off or when the AC was lost.

There were a lot of TVs then that used a digital keypad, but were not remote control and used a mechanical AC switch and volume control. In this case, it's possible that the uPc is only used for channel functions and his problem could be on the micro's reset line.

 

On Friday, 30 June 2017 12:29:30 UTC+1, John-Del wrote:

On Friday, June 30, 2017 at 2:51:21 AM UTC-4, tabby wrote:
On Thursday, 29 June 2017 22:03:35 UTC+1, jeff.p...@cfl.rr.com wrote:

Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

Yes from neon channel selector sets, touch selectors & older pushbutton bar tuning sets. Show us the circuit.


NT

Hmmm... you're drudging up long forgotten memories. Back in the late 70s Zenith used a varactor tuned electronic tuner that used neons as indicators for the pre-set push button selector, and sometimes those neons were the cause of the TV jumping channels or refusing to engage a selected channel.

By 1984 I would think that all manufacturers would be using a true digital selector system for anything no using a mechanical tuner.

Unfortunately, OP didn't say if the TV would scan downward to channel 2 or jump to it. He also didn't say if the TV normally defaulted to channel 2 when the TV was powered off or when the AC was lost.

There were a lot of TVs then that used a digital keypad, but were not remote control and used a mechanical AC switch and volume control. In this case, it's possible that the uPc is only used for channel functions and his problem could be on the micro's reset line.

Until the OP tells us what the technology is we have really no way to advise usefully. 1984 could be a few things, switched linear pots with varicap is likely, or touch sensors maybe. There were also old technologies used in some sets, so can't completely rule out a mechanical selector device operating a tuning bar.


NT

 

[pfjw@aol.com]

http://diagramasde.com/page/2118

Might be something usable here.

My S.W.A.G. guess based on similar-vintage technology failing-to-default is a weak capacitor that does not hold the charge necessary to 'latch' to the chosen channel.

Peter Wieck
Melrose Park, PA

 

Most likely it is going into reset. Does it hold your settings, like color, brightness and whatever ? Probably not. They are likely all going to factory reset.

That would mean you are losing power to the micro or maybe the memory IC, or the memory IC is defective. Ir it has a memory IC it is probably an eight pin EEPROM. Look at the board and see if it has a supercapacitor or whatever, or a battery. Those could well be failing. That is actually more likely than an IC failing.

Keeping this old shit running is a good thing because all the new stuff is junk. My Ma watches an old CRT based Toshiba which works just fine. I do not have a TV hooked up because the programing is all junk. The scene changes so fast you cannot see anything. PUT THE IMAC DOWN ! Anything I want to watch is old.

One question here - does it return to channel 2 as you are watching it ? If so, that means there is a temporary interruption in the power supply, probably the standby supply. That would make me suspect a bad connection, or maybe one inside of a device like a regulator or something.

It can also be caused by low supply voltage to whatever holds the memory. I would be headed for the power supply.

 

[Chuck]

On Thu, 29 Jun 2017 14:02:39 -0700 (PDT), jeff.panasuk@cfl.rr.com
wrote:

>Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?
I ran the television service department in the corporate headquarters
for the largest seller of Hitachi sets at that time in the U.S. so I
might be able to help you. First disconnect pin 17 and 18 of IC0102
and see if the problem disappears. If so, then it is likely the
channel tact switches. If not, take freeze spray and a hair dryer to
the tuner. The two main failures in this model, when there were tuner
problems, were the ic you replaced and the tuner itself. The band
switch IC IC0104 occasionally would fail and any 2SC458s in the
circuitry can cause problems. If these checks don't work, post again
and we'll go deeper in depth. Chuck

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[Chuck]

On Fri, 30 Jun 2017 08:44:00 -0500, Chuck <chuck@mydeja.net> wrote:

On Thu, 29 Jun 2017 14:02:39 -0700 (PDT), jeff.panasuk@cfl.rr.com
wrote:

Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?
I ran the television service department in the corporate headquarters
for the largest seller of Hitachi sets at that time in the U.S. so I
might be able to help you. First disconnect pin 17 and 18 of IC0102
and see if the problem disappears. If so, then it is likely the
channel tact switches. If not, take freeze spray and a hair dryer to
the tuner. The two main failures in this model, when there were tuner
problems, were the ic you replaced and the tuner itself. The band
switch IC IC0104 occasionally would fail and any 2SC458s in the
circuitry can cause problems. If these checks don't work, post again
and we'll go deeper in depth. Chuck

---
This email has been checked for viruses by Avast antivirus software.
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Also replace C703 and R703 (off the flyback) if the previous hints
don't work.

 

[Chuck]

On Fri, 30 Jun 2017 09:04:44 -0500, Chuck <chuck@mydeja.net> wrote:

On Fri, 30 Jun 2017 08:44:00 -0500, Chuck <chuck@mydeja.net> wrote:

On Thu, 29 Jun 2017 14:02:39 -0700 (PDT), jeff.panasuk@cfl.rr.com
wrote:

Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?
I ran the television service department in the corporate headquarters
for the largest seller of Hitachi sets at that time in the U.S. so I
might be able to help you. First disconnect pin 17 and 18 of IC0102
and see if the problem disappears. If so, then it is likely the
channel tact switches. If not, take freeze spray and a hair dryer to
the tuner. The two main failures in this model, when there were tuner
problems, were the ic you replaced and the tuner itself. The band
switch IC IC0104 occasionally would fail and any 2SC458s in the
circuitry can cause problems. If these checks don't work, post again
and we'll go deeper in depth. Chuck

---
This email has been checked for viruses by Avast antivirus software.
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Also replace C703 and R703 (off the flyback) if the previous hints
don't work.

Ignore my last post; I followed a wire incorrectly. These parts are
in the XRay shutdown circuit and do not pertain to your problem.

 

On Thursday, June 29, 2017 at 5:03:35 PM UTC-4, jeff.p...@cfl.rr.com wrote:
> Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

----------------------------------------

I want to thank all of you for your time and comments. Here is some feedback to you:

Ultimately I would be fine if the only two channels I can get are 3 or 4 for my direct tv cable. Can’t live with channel 2 though.

The tv will go to the channel you select using the key pad or remote (before I disabled the remote). As you watch your chosen channel it will instantly change to channel 2 and not scroll to it.

I can’t imagine a light source being the problem. The IR receiver works but was disabled to rule this out. While it was disabled the tv would still change to channel 2. No suspect rf sources in vicinity either. Problem happens in any room. The most exotic rf source I have are is my computer, monitor and microwave. No “new” technology stuff and problem happens with computer and monitors off. No supercapacitor or battery for backup and not listed in parts. I don’t see any central microprocessor in the schematics or parts list that applies to this model and chassis. The CT1957 model has a Channel Selection memory IC IC0103 (MN1228) but this model CT1955 does not. The circuit board has an empty spot for this 18 pin IC.

Unit has buttons for channel/volume up/down and power. All the picture/video controls are adjusted using potentiometers located behind a flip down panel at the bottom center of the front of the unit. No mechanical selectors other than the video pots.

Your feedback was excellent so I power up the unit for the first time in months and it defaulted to channel 2. I set up some tests.

Test #1 Sequences:
• Power on change to channel 5 and set volume to 15
• Power off button when not having problem. Power back on channel is at 5 and volume at 15
• Power off button, when not having problem, and remove power cord from ac: Plug back in and power up: Channel = 2 and volume = 21. I think this is normal.
• Power on and set to CH5 / Vol=15.
• While not having issue I pulled power cord without depressing power off button: Plug back in and power up: Channel = 2 and volume = 21


Test #2 Rear Switch Settings (S1 3-Way Switch): My default settings are CH=5 / Vol=15

S1= Either CATV1 or CATV2: Monitoring TV unit CH=5 / Vol = 15. Within 2 hours of power on the problem occurred and then it started occurring frequently. The tv Changed to channel 2 from 5 instantly and the volume stayed at 15. It did not change to 21 as what happens when ac is removed from the unit.

S1 = “Normal” (VHF/UHF) : Problem does not happen. Switching back to CATV1 or 2 problem happens within minutes. Put Switch in “Normal” mode. No problem for next hour+, up to the point of posting these notes. If this holds I’m good. I will leave S1 in “Normal” mode and powered on for hour or days until I have confidence in . . . . ….. something.

Tried freezing and heating the tuner and components but no impact. I thought I ruled out the keypad but can’t swear to it. Will check. No neon’s.

From my last troubleshooting notes:

6/9/16 Per T/S flow chart ordered and replaced items below including an incoming power electrolytic 22uF/250v. Not related to problem but has a domed top. :

• IC0102 MN14834HH High hopes…. Big letdown……

• Socket for above

• Q102 2sc458 B/C/d 2sc1740Q/R

• Q0103 2sk105 E/F

• Q0104 2sc1213A

• IC0104 LA7910 Band Drive Ordered and have part but did not replace

• ZD0101 Measured OK: RD33EB1 ZD HZ6(C)1


If problem happens with S1 in “Normal” mode I will replace IC0104 (Band Drive) and get to the remaining 2SC458’s later. There is a 5v Regulator powering IC0102 I’ll try to get that monitored also

Just looked at original receipt. Purchased in 1986 not 1984 $356.

 

[Chuck H.]

On Mon, 3 Jul 2017 14:54:30 -0700 (PDT), jeff.panasuk@cfl.rr.com
wrote:

On Thursday, June 29, 2017 at 5:03:35 PM UTC-4, jeff.p...@cfl.rr.com wrote:
Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

----------------------------------------

I want to thank all of you for your time and comments. Here is some feedback to you:

Ultimately I would be fine if the only two channels I can get are 3 or 4 for my direct tv cable. Can’t live with channel 2 though.

The tv will go to the channel you select using the key pad or remote (before I disabled the remote). As you watch your chosen channel it will instantly change to channel 2 and not scroll to it.

I can’t imagine a light source being the problem. The IR receiver works but was disabled to rule this out. While it was disabled the tv would still change to channel 2. No suspect rf sources in vicinity either. Problem happens in any room. The most exotic rf source I have are is my computer, monitor and microwave. No “new” technology stuff and problem happens with computer and monitors off. No supercapacitor or battery for backup and not listed in parts. I don’t see any central microprocessor in the schematics or parts list that applies to this model and chassis. The CT1957 model has a Channel Selection memory IC IC0103 (MN1228) but this model CT1955 does not. The circuit board has an empty spot for this 18 pin IC.

Unit has buttons for channel/volume up/down and power. All the picture/video controls are adjusted using potentiometers located behind a flip down panel at the bottom center of the front of the unit. No mechanical selectors other than the video pots.

Your feedback was excellent so I power up the unit for the first time in months and it defaulted to channel 2. I set up some tests.

Test #1 Sequences:
• Power on change to channel 5 and set volume to 15
• Power off button when not having problem. Power back on channel is at 5 and volume at 15
• Power off button, when not having problem, and remove power cord from ac: Plug back in and power up: Channel = 2 and volume = 21. I think this is normal.
• Power on and set to CH5 / Vol=15.
• While not having issue I pulled power cord without depressing power off button: Plug back in and power up: Channel = 2 and volume = 21


Test #2 Rear Switch Settings (S1 3-Way Switch): My default settings are CH=5 / Vol=15

S1= Either CATV1 or CATV2: Monitoring TV unit CH=5 / Vol = 15. Within 2 hours of power on the problem occurred and then it started occurring frequently. The tv Changed to channel 2 from 5 instantly and the volume stayed at 15. It did not change to 21 as what happens when ac is removed from the unit.

S1 = “Normal” (VHF/UHF) : Problem does not happen. Switching back to CATV1 or 2 problem happens within minutes. Put Switch in “Normal” mode. No problem for next hour+, up to the point of posting these notes. If this holds I’m good. I will leave S1 in “Normal” mode and powered on for hour or days until I have confidence in . . . . ….. something.

Tried freezing and heating the tuner and components but no impact. I thought I ruled out the keypad but can’t swear to it. Will check. No neon’s.

From my last troubleshooting notes:

6/9/16 Per T/S flow chart ordered and replaced items below including an incoming power electrolytic 22uF/250v. Not related to problem but has a domed top. :

• IC0102 MN14834HH High hopes…. Big letdown……

• Socket for above

• Q102 2sc458 B/C/d 2sc1740Q/R

• Q0103 2sk105 E/F

• Q0104 2sc1213A

• IC0104 LA7910 Band Drive Ordered and have part but did not replace

• ZD0101 Measured OK: RD33EB1 ZD HZ6(C)1


If problem happens with S1 in “Normal” mode I will replace IC0104 (Band Drive) and get to the remaining 2SC458’s later. There is a 5v Regulator powering IC0102 I’ll try to get that monitored also

Just looked at original receipt. Purchased in 1986 not 1984 $356.

The set didn't come on the market in the U.S. until 1985. If all you
need is channel 3 and it doesn't do it with the switch in the normal
mode, I'd just leave it be unless you are just curious to know the
solution. I don't have the schematic in front of me because I am on
vacation but doesn't that normal - cable switch also have a HRC
position? I'd be curious if it goes to 2 in that position. If it
doesn't I'd clean the switch, it possibly could be the problem. Chuck

 

On Thursday, June 29, 2017 at 5:03:35 PM UTC-4, jeff.p...@cfl.rr.com wrote:
> Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

No STD, IRC or HRC position switch or other type of such options. Just the single 3-position switch: CATV1, CATV2 or Normal. TV has been running for more than 24 straight hours in the “Normal” switch position mode and has not changed to channel 2.

Moving 3-way switch to position:

CATV1 TV switched to channel 2 in a few seconds
CATV2 Waited a few minutes but it did not change this time
Normal Steady

When switch is moved to one of the three positions the tv defaults to CH2/Vol=21. I cleaned the switch and all is stable while I type these notes. Will monitor and report out.

 

[megamusic]

<jeff.panasuk@cfl.rr.com> wrote in message
news:45234dd2-55fe-4efa-a90d-39a920cf2af9@googlegroups.com...
On Thursday, June 29, 2017 at 5:03:35 PM UTC-4, jeff.p...@cfl.rr.com wrote:

Back in February or March of 2010 the TV began changing from any channel
to channel 2 intermittently. Sometimes very frequent. Other times more
intermittent but it would not go more than a few hours without the problem
popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel
Selection Ckt but no help. Remote control IR circuit not the problem as I
disabled it. Over time have replaced some bad unrelated hw (burnt
resistor, >Caps). Have schematics and service manual but can't isolate
the problem. Nice picture and everything else works fine. Unit in
storage but every 4 months or so, when I see it and think about it, I fire
it up. Hate to trash this old tv. >Kind of part of the family now. Has
anyone ever heard of this before?

MN14834HH is processor, check oscillator (pins 36/37) and reset voltage
(pin 39).
Replace resistor RO125 and DO110 (on pin 6).

 

On Thursday, June 29, 2017 at 5:03:35 PM UTC-4, jeff.p...@cfl.rr.com wrote:
> Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

Thanks for the info. I'll add it to my troubleshooting short list. I cleaned the switch S0125 on 7/3 and the TV has been running solid through today 7/7. This has been the longest period without the problem since it first popped up in 2010. The TV is now back in action on its shelf in the kitchen area.

 

On Thursday, June 29, 2017 at 5:03:35 PM UTC-4, jeff.p...@cfl.rr.com wrote:
> Back in February or March of 2010 the TV began changing from any channel to channel 2 intermittently. Sometimes very frequent. Other times more intermittent but it would not go more than a few hours without the problem popping up. Replaced IC0102 (MN14834HH) Main IC for the Channel Selection Ckt but no help. Remote control IR circuit not the problem as I disabled it. Over time have replaced some bad unrelated hw (burnt resistor, Caps). Have schematics and service manual but can't isolate the problem. Nice picture and everything else works fine. Unit in storage but every 4 months or so, when I see it and think about it, I fire it up. Hate to trash this old tv. Kind of part of the family now. Has anyone ever heard of this before?

8/26/2017 One final note. It's been over 6 weeks now and the tv has worked fine since cleaning the 3-way switch. I guess it's fixed. Thanks for all your help guys.