I measured 1.1V so it looks like a bad IC. I used the coax tuner chassis box as a ground point. The CRT metal band as a ground gave a lower .8V measurement so I don't think it is a good ground for this test.
Another reply suggested that I check Horizontal Output Transistor. Do you think that is worth looking into at this point? I don't know what to measure for or the designation of the Horizontal Output Transistor. If you feel that the odds are high that IC561is the problem then thats were I will stop.
An expert who has achieved level 3 by getting 1000 points
An expert that got 20 achievements.
An expert that got 10 achievements.
An expert that got 5 achievements.
Re: I measured 1.1V at pin 2 on IC561
Check for +15V from the flyback pin # 9, if that voltage is present; check R541 and D531. If these parts are good you should find +12V at TP98 nearby C539.
If still not voltage found, I would suggest to desolder and isolate IC561 pin 2.
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need. goodluck!
- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
Your TVs vertical output section has the fault. You just open your TV after disconnecting it from the AC mains wall socket, and locate the vertical output section. This section uses an Ic marked as part [IC 401] on the board and its number is LA7840. Just look for any loose soderings around its components legs, and the solderings at the IC legs, which has 7 of them. The IC stated above will be screwed onto a heatsink to radiate heat out of it when it works.
If all soldering point are fine, come towards the IC legs and measure the voltages at each leg. The voltages must be
pin 1= Ground
pin 2= 12.6
pin 3= 24.7
pin 4= 4.4
pin 5= 4.4
pin 6= 24v [vcc]
pin 7= 1.8
All voltages stated above are DC voltages with respect to ground. If any of this voltage is missing, find out the reason for that. If all of them are noted abnormal, IC may be defective, and replace it.
[vcc] stands for main input voltage to the IC.
If you need any more assistance, feel free to contact me through Fixya. Ok.
Get you a metal box about 4 inches X 4 inches. Use 2 female Cb antenna inputs from old Cb radios or Radio Shack. Get a old Am radio tuner out of a AM radio(530-1700 khz.) Buy or scrap up some copper wire; big gauge I used. Wound 8-10 turns about " 1 inch round close tight wound. Solder to AM tuner- C1 it shall say on top of Am tuner. Solder Center of Am tuner to Ground(Metal box). For those who know electronics the Tuner is 0-365pf Am band 530-1700khz types. OK, back to assembly. drill a hole for the Two Female Cb Inputs on both sides of metal box. Attach copper wire inside to center taps of Inputs on both sides. Drill a hole for Am tuner and Screw on its lock nut and place a knob on it. Solder all grounds of Female Antenna inputs and Tuner Ground and all Grounds to metal box. Use a washer and Bolt to lock down Grounds to Box. This is how it operates after you use a Jumper to hook to TX of Cb radio. Antenna to other side. Its just a simple L/C network. The Tx travels through copper wire(coil) inside box and gets shunted to ground by the right level of PF Capacitance. The operator tunes it in to get a close to 1.1 to 1.5 SWR ratio. Its simple, but helps with bad Antennas.
Tuner is lokely the cause or cable box that is hooked up is on mute.
If you have no cable box or sat system the cause would be a bad tuner at coaxe region there is ashort in the connection the brings the adio filtered from the tuner to the control IC AMp witch is part of the tuner assay what this means is bad tuner or bad control ic at coaxe region. Or its one of the causes above a device is on mute. Best of luck to you in your repairs. good feedback and ratings will be expected further in this diagnosis.
The chassis series used in that set was notorious for bad solder connections around its tuner and a few other places. (They used the tuner shield to provide a number of ground connections, and these cracked and went flaky.) These connections would cause a variety of problems including a set that won't turn on.
The fuse is located right near the AC mains cord connections on the board. You will probably find it's good. Not much went wrong on this chassis to blow that fuse unless it was power line troubles or shorted parts on the power supply primary side.
Check for 5 volts at one of the 3 pins on the the remote sensor. If the power is there, you probably have a bad EEPROM IC. Operating parameters and TV settings are stored in that chip, and the bad solder connections I mentioned above can lead to the data getting scrambled and a "dead" set. To repair this, you need to resolder the connections at the tuner shield and a few other locations, then replace the EEPROM.
If you Google "RCA tuner solder problems" or something similar, you should find all kinds of information about where to solder. The replacement EEPROMs are available from MCM (www.mcminone.com) and you order the appropriate IC for the chassis. I'm not home now, but when I get home later I'll check my files for the service bulletin RCA released, and look up the EEPROM you need in case that turns out to be the trouble.
Most TVs today use a "hot-chassis" design and a switch-mode power supply. You should use an isolation transformer when doing any service work on a TV. This helps protect you and your test equipment, and can prevent accidental damage to the TV by grounding parts to the wrong point.
Hot-chassis sets use two different grounds. The power supplies have one ground reference for the primary side (hot ground) and a different point for the secondary (cold ground). The point you pick will depend on what part of the TV you're measuring.
If you are troubleshooting a dead set and working on the primary side of the power supply, use the negative lead of the large electrolytic capacitor you'll find near the AC input connection. There's almost always a bridge rectifier and filter cap (300 to 400 uF range, 180 to 250 volt rating, so physically pretty large) in that area to make the raw DC. That's a guaranteed good hot ground. Sometimes the set will have a labeled hot ground point right on the circuit board for you.
For measurements on the secondary (output) side of the supply, almost any shield can is ground. The tuner cover is a good choice.
I'm pulling up a link while typing; the device is a fixed voltage regulator with some DC input voltage applied, ground (chassis common) and an output of a stable 9 volts DC.These are generally referred to as '3-terminal' regulators.There won't be any significant AC on any pin if operating normally.
You can get the data sheet as a .pdf file here:
You probably have Adobe Reader which you will need to open the file.
The term 'low saturation' refers to the range of DC it requires to regulate as intended; early ICs of this design needed more 'headroom' to enter into the region of stable regulation.
Looking at the marked side, the #1 pin is to the left; #3 to the right.
#2, the center pin is grounded to common (chassis) and if you measure resistance from #2 to any point attached to the broadest traces you can see on the solder-side of the board, it should read close to 0 Ohms (power off for this measurement!).
Measuring resistance on these parts won't yield much unless the part is shorted, a pretty uncommon condition and one that is not as easy to predict as one could with a diode or transistor.
The input lead is #1 and should be well above 9 volts DC if measured to the center pin; the output lead, #3 should have ~9 volts DC referenced as before to the center pin or chassis common.
Any AC you measure on any pin is meaningless, just noise.
I think you will find the part OK since these regulators are quite reliable when used in sensibly designed circuits.
in theses set's there should be a board that has a module that the power chord plugs into this module supllies the motherboard and the componants on it. to be honest it would be best to just let a professional replace any defective chips orboards at this point because i believe it is not just one problem but several and without me beibg hands on it would be difficult to narrow it down to just a simple answer.
The coax connector you describe is called the F connector and the silver box it is attached to is called the tuner. The original F connector or a replacement F connector can be soldered back into the tuner, but the metal frame of the tuner must be straightened out and the center pin must be delicately reattached too. This is quite an easy job but requires some labor, assuming that nothing was jammed into the tuner when the F connector was out and the coils behind the F connector have not been disturbed. I usually charge about $40 to reattach F connectors but if I have to replace the tuner I charge about $50 because it is a lot less labor to replace the tuner and they can be purchased for about $25.
The GE (actually RCA) 35GT690 uses the CTC187 series chassis. The tuner uses the VHF circuits for cable channels lower then 51 and the UHF circuits for the higher channels. This means that the VHF circuits have stopped working in your set. I usually find that this is caused by a defective U7301 IC in the tuner, the SIP IC labeled CXA1594L. This is a very difficult IC to change and all tuner ground solder joints should be resoldered too, so that should be done by someone with experience in the CTC187 chassis.