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An exact replacement remote will be easiest to use but may do significant harm to your bank account. For example, you cannot add or remove channels from a typical Sony TV using the common universal remotes. (From: Ed Ellers (edellers@delphi.com)). Universal Electronics' "One For All" remote controls can reproduce these codes, and any others on any Sony TV (among others). Typically you'd press [MAGIC] and then 1-9-4 to add a channel or 1-9-0 to erase one; to start the auto program mode you'd press [MAGIC] and then 1-2-4.
Loudspeakers incorporate powerful magnets - the larger the speaker, the larger the magnet. However, anyone who goes ballistic when the mention is made of a loudspeaker near a TV or monitor, should take their Vallium. The fringe fields outside the speaker box will not be that great. They may affect the picture perhaps to the point of requiring degauss. The normal degauss activated at power-on will usually clear up any color purity problems (assuming the loudspeakers have been moved away). At worst, manual degauss will be needed. The CRT will not be damaged. The maximum field - inaccessible at the voice coil - is quite strong. However, even for non-shielded loudspeakers, the magnetic field decays rapidly with distance especially since the core structure is designed to concentrate as much of the field as possible in the gap where the voice coil travels. However, keeping speakers away from CRTs is a good idea. Now, you really should keep your superconducting magnetic resonance imager magnet at least in the next room.....
When a bad capacitor is found in a TV, the question of course arises as to the likelihood of other capacitors going bad in short order. It might be worth checking (other) caps in the power supply or hot (temperature) areas but you could spend you whole life replacing **all** the electrolytics in your older equipment!
Always confirm the customer's complaints first!! Then verify that everything else works or you will never know if your efforts have affected something unrelated. (Original request from rogerj@apex.com): >A sweet little old lady has duped me into repairing her old G.E. 13" color >TV. Wanted me fix bad volume pot..... "oh it has such a good picture"... >she says. >Stupidly w/o even turning it on, (big mistake) I begin to open the set. >After 15-20 min. of travail, I discover that a previous "repairman" has glued >the case shut! >Now w/ set open, I turn it on and this picture is LOUSY. Bad color, and very >poor convergence. But I don't know if I'm to blame for banging it around >trying to open it up. Also, no horizontal or vertical hold. (fixed that >wiht a few caps). This thing has probably been sitting around for a few >years. Well, you certainly did not kill the caps. Anything that sits for a few years - probably in a damp unheated attic - is suspect. Did you find the adjustments on the yoke assembly tight? If so, you probably did not move anything very much either. She may remember the good picture it produced before being stuffed away in the attic. > Anyway after going through all the adjustments, the convergence at the sides > is still bad and the horizontal size is a tad insufficient (w/no adjustment > available) Could be that the convergence (including pincushion) circuits are still faulty - not just misadjusted. Other things that can effect horizontal size while still giving you a complete picture: 1. Voltage to horizontal output transistor low. Is there a voltage regulator in your set? The one I have has none. I assume your line voltage is ok. 2. Increased resistance or inductance of the yoke windings. For all you know, the yoke may have been replaced with the wrong part. 3. Yoke improperly positioned on tube neck. 4. Excessive high Voltage. This is usually not adjustable. I bet the thing hasn't worked properly in 10 years.
(Portions of the following from a video engineer at Philips.) Why is there a splotch of colored light at the center of the CRT after I kill power to my TV? Why does this not happen if the plug is pulled instead? It seems to last for hours (well maybe minutes at least). A broad diffused glow (not a distinct spot in the middle of the screen) that lasts for a few seconds to minutes is called 'afterglow' and may be considered 'normal' for your model. The warm CRT cathodes continue to emit electrons due to the high voltage that is still present even though the signal circuits may have ceased to operate. For more sharply defined spots there are two phenomena: 1. Thermal emission from a cathode that has not yet cooled off (and this could take several minutes) gives a more or less circular spot near the centre. It is actually 3 spots from the 3 cathodes, we at Philips call them 'Christmas balls'. 2. Field emission from sharp whiskers on any electron gun part gives a much sharper spot, sometimes with a moon-shaped halo around it. Even with the filament off, there may be some electron emission from these sharp points on the cold cathode(s) due to the strong high voltage (HV) electric fields in the electron gun. I do not know how likely this is or why this is so. The shape of the spot is an inverted image of the shape of the emitting area(s) on the electron guns cathodes. The visibility of both effects depends in the same way on the decay time of the high voltage (HV/EHT) on the anode. When turned off with the remote or front panel button, you are not actually killing AC power but are probably switching off the deflection and signal circuits. This leaves the HV to decay over a few minutes or longer as it is drained by the current needed to feed the phantom spot or blob. When you pull the plug, however, you are killing AC input and all the voltages decay together and in particular, the video signal may be present for long enough to keep the brightness (and beam current) up and drain the HV quickly. Whether this actually happens depends on many factors - often not dealt with by the designers of the set. A proper design (who knows, yours may simply have been broken from day 1 or simply be typical of your model) would ensure that the HV is drained quickly or that the other bias voltages on the CRT are clamped to values that would blank the CRT once the set is off. If the problem developed suddenly, then this circuitry may have failed. On the other hand, if it has been gradually getting more pronounced, then the characteristics of the CRT or other circuitry may have changed with age. In most sets it is left to chance whether the picture tube capacitance will be discharged by beam current at switch-off. It may simply be due to the behaviour of the video control IC when its supply voltage drops that causes the cathodes to be driven to white and this may not be formally specified by the manufacturer of the IC. Some of of the latest sets have an explicit circuit to discharge the EHT at shutdown. As noted in the section: "Safety guidelines" the HV charge on the CRT capacitance can be present for a long time. A service technician should be very aware of that before touching HV parts! Interestingly, most sets for the Asian Pacific market have a bleeder resistor built in that will discharge the EHT without the need for a white flash at switch-off. These will in fact drive the beam to black at switch-off via a negative voltage to the CRT G1 electrode. The AP market is very sensitive to proper set behaviour, they don't like a white flash. In short, it all depends on the demands of the particular market, the chance of the picture tube producing a spot/blob, and the mood of the designer. So, it may not be worth doing anything to 'fix' this unless the splotch is so bright (more so than normal video and for an extended time) that CRT phosphor damage could result. This is usually not a problem with direct view TVs but would definitely be a concern with high intensity projection tubes. On the other hand, your phantom blob may provide for some interesting conversation at your next party!
I don't know what the law says, but for safety, here is my recommendation: Treat the CRT with respect - the implosion hazard should not be minimized. A large CRT will have over 10 tons of air pressure attempting to crush it. Wear eye protection whenever dealing with the CRT. Handle the CRT by the front - not the neck or thin funnel shaped envelope. Don't just toss it in the garbage - it is a significant hazard. The vacuum can be safely released (Let out? Sucked in? What does one do with an unwanted vacuum?) without spectacular effects by breaking the glass seal in the center of the CRT socket (may be hidden by the indexing plastic of the socket). Cover the entire CRT with a heavy blanket when doing this for additional protection. Once the vacuum is gone, it is just a big glass bottle though there may be some moderately hazardous materials in the phosphor coatings and of course, the glass and shadow mask will have many sharp edges if it is broken. In addition, there could be a nice surprise awaiting anyone disconnecting the high voltage wire - that CRT capacitance can hold a charge for quite a while. Since it is being scrapped, a screwdriver under the suction cap HV connector should suffice. The main power supply filter caps should have discharged on their own after any reasonable length of time (measured in terms of minutes, not days or years). Of course around here, TVs are just tossed intact which is fortunate for scavengers like me who would not be happy at all with pre-safed TVs!
TVs with hot chassis - where signal ground is actually line connected and at some intermediate (and dangerous) voltage - will have an isolation block in between the tuner and antenna/cable connections. TVs with isolated power supplies may have some bypass capacitors between the power supply and signal grounds (including the A/V shields if there are A/V connectors). It is possible for a failure to result in a serious safety hazard where the RF (antenna/cable) or A/V connectors become electrically live. However, a tingle or small spark might be normal. RFI bypass caps between the AC input and shield on the connector could result in some leakage - 50 V or more might be indicated using a high impedance multimeter. This is harmless. Reversing the plug in the AC socket (if it is not polarized or if you are using an unpolarized extension cord) might eliminate or greatly reduce the effect. Nonetheless, it should be checked out. Measure the resistance between each side of the AC plug and the RF and AV connector shields. It should be 1 M ohm or more. Test for voltage between the cable (or other device) connector and earth ground. If there is anything significant, test the resistance on the device between its shield and its power plug as above - other devices may have RFI bypass caps or be defective as well.
(From: Jeroen H. Stessen (Jeroen.Stessen@ehv.ce.philips.com)). JVC owns the patent for VHS. JVC has made a deal with Macrovision that from a certain date in the past *no* VHS recorder licenced by JVC shall be able to record any video signal that contains Macrovision's copy protection pulses. Any video recorder from before that date (VHS or other) might well work OK on the altered video signal ! The copy protection pulses upset the video-AGC and H-sync. TV's usually don't have a video-AGC. The stabilizer box removes the extra pulses and makes it into a normal video signal again. No VCR should ever know the difference, so they should all record properly again. At the same time, all TV's are required to ignore the copy protection pulses. As a TV-designer I can tell you that this is sometimes far from trivial. Not in the least because in the beginning we were not included in "the deal". There may be TV's around whose brightness and/or sync will be disturbed by the Macrovision pulses. Officially, this is the reason for existance of the stabilizer boxes: to view better, not to copy better. Unofficially, they are sold for copying, of course. The next step will be that digital-TV decoders will output an analog TV signal with Macrovision copy-protection pulses so that you may watch but not record your pay-per-view program. Same problem, same solution ... And I thought that PAL/Secam/NTSC were *standards*, sigh ... Whether they like it or not (and from personal experience I can tell you that we don't like it) it is the responsibility of the TV set-maker (in your case Sony) to build a TV that takes the Macrovision copy protection pulses without showing any side effects on the screen. Seems like they didn't do a good job on your TV :-). But they will have to fix this, your complaint is valid. I think in this case it may be the dealer's responsibility too, maybe you can trade it for a different brand ? And do try it out first ... Sadly, more complex TV's seem to suffer more than the simpler, old-fashioned, designs. Unfortunately, Macrovision seems to be satisfied when their pulses do not affect the majority of (mostly older) TV's. In your Sony TV, the clamping circuit seems to be affected by some ultra-black pulses in the signal. Maybe an anti-Macrovision decoder can help you, officially they are designed for *this* purpose.
(From: Jeroen H. Stessen (Jeroen.Stessen@ehv.ce.philips.com)). 1. RF-AGC which compensates for different signal strength at the aerial, it measures RF amplitude and is *not* sensitive to video contents because with negative modulation the sync is the peak and is constant, this AGC will not work on CVBS (baseband video) inputs. 2. Video-AGC which normalizes baseband signals which enter *after* the tuner-IF. A.o. this compensates for different signal strengths when you connect two VCRs together. It measures peak-white, so it *is* sensitive to video content and thus to the Macrovision pulses. And: a television does NOT have a video-AGC, unless you want to call the beam current limiter circuits an AGC. (Exception: the Secam-L system with positive modulation requires an RF-AGC which measures peak-white instead of peak-sync.) The RF-AGC does not see the peak-white of the anti-copy pulses. If you connect the VCR to the TV via the CVBS (baseband) input, then the RF-AGC is not even in the path. Still, it may be disturbed. But the sync separator may see the extra inserted Hsync pulses, and due to the phase disturbance the video clamping may be disturbed too.
You will need the Sams' Photofact for the set. If the clock reference is power line derived, noisy power can sometimes result in erratic timekeeping though running fast is probably more common than running slow. This could be a result of a lamp dimmer or compact fluorescent on the same circuit. If it has a separate crystal for the time keeping, that could be faulty. Now think about it: Do you absolutely need the TV's clock??? After all, there are probably a half dozen other clocks in the same room!
(From: Ren Tescher (ren@rap.ucar.edu)). My Christmas repair story wasn't so happy. I worked as TV repairman for an appliance store. On a very cold (20 below zero Fahrenheit) evening a man bought a new 25" console for the family. As we loaded it into the back of their pickup truck, we *told* them. "Do not plug this in until it warms back up to room temperature." They nodded and said "uh-huh, okay". They lived about 15 minutes away. 25 minutes later we get a telephone call... "Hey! that TV you sold us don't work!" So we ended up loading another TV into our delivery van, drove out to their place. Unloaded it, and WAITED until the thing was warm enough to plug in. Needless to say, I got home late that Christmas Eve and had brand new TV console waiting for my repair back at the shop.
Older GE TVs used double sided circuit boards with poor-man's vias - rivets soldered to the traces top and bottom. These have been called 'Rivlets' and 'Griplets'. Unfortunately, whoever did the design didn't realize that (1) the the rivets did not heat adequately during soldering and (2) the expansion coefficients of the rivets and circuit board were not qutie identical. Thus, erratic problems are almost a certainty with these TVs. Normal logical troubleshooting is useless. The only solution is to repair every !@#$ Griplet on all circuit boards in the TV. I have repaired these with a high power soldering gun used on both sides with liberal application of solder and flux. However, I do not recommend this shortcut unless you are willing to redo the repair every couple of years. (From: Mr. Caldwell (jcaldwel@iquest.net)). There are two methods of repair. * Method 1: Clean the paint from around each griplet on both sides of the board to expose the surrounding copper pad. Apply liquid solder flux to the cleaned copper. Solder so as to bridge the griplet to the cleaned copper. * Method 2: Do the above but desolder the griplet and place a wire through it so that the wire extends beyond the griplet to the copper foil and solder the wire on both sides (this was the final fix GE used in this chassis). If done carefully Method 1 works and is reliable. I would normally do this prior to any troubleshooting, it repairs most problems in this chassis. While you have the board out working on it be sure to also clean and resolder high temperature components and connections that look bad. These griplets can be on all boards, even the tuner control board.
Problems with bad solder connections, mostly in and around the tuner are very
common with several series of late model (e.g., CTC175/176/177 chassis)
RCA/GE/Proscan TVs. Ignoring these erratic and intermittent problems can lead
to serious damage including failure of the EEPROM and possibly other expensive
ICs. Therefore, it is essential to deal with the solder connections as soon
as these symptoms appear. The repairs are straightforward though perhaps
tedious. Thompson may reimburse for reasonable cost of repairs.
Some of the common symptoms include:
* Random power cycling. It may come on in the middle of the night!
* Picture shifts or changes size vertically or horizontally.
* Picture turns to snow or shows other reception problems.
* Picture turns to random display of time or other data.
* Noisy or muted sound, volume buttons have no effect.
* Remote has no or unexpected effect.
See the document: "RCA/GE CTC175/176/177 Tuner Repair" for additional
information on these types problems including repair procedures and
approaches to getting coverage from Thompson Electronics.
Check the resistor supplying initial base current to the horizontal driver (not HOT) transistor. On many chassis, it is R502, 47 K. It opens for not good reason. Why it fails is a mystery as its power rating should be adequate.
Symptoms are that the TV or monitor will shut down possibly after a warmpup period. There can be other causes but failure of the Hstat module HV sense wire is quite likely on many Sony models. (From: Mr. Beanz (slin01@mail.orion.org)). If you've determined that the HV is fine, and the H-STAT is shutting down for no reason, it's possible to bypass. There is a little brown wire coming out the bottom of the H-STAT which goes to a 3-pin connector. Two wires have a jumper, and the brown wire goes to the other. Snip the brown wire at the H-STAT and the TV will continue to function normally. Measuring the regulated B+ to the flyback will give you a pretty good indication of the condition of the HV output. If it remains steady at rated voltage (I forget what it was, 130V or 135V) then HV is A-OK. If it slowly creeps up or is too high to begin with, you have a problem. The voltage will normally jump to 150V or so after HV shutdown is tripped. Ideally, you should replace the H-STAT in this case. Although taking the poor man's route will WORK, you lose any protection in the event that the HV circuitry should malfunction.
(From: Shawn Lin (slin01@mail.orion.org or lin@science.smsu.edu)). The H-STAT is a plastic box that sits mounted to the picture tube's shield. It's red in color (for every SONY TV that I have owned) and has a single knob on it. The flyback's HV output wire goes into the H-STAT and another HV wire exists the H-STAT and connects to the anode cap on the picture tube. It has a dual purpose, horizontal static convergence (the control adjusts this) and HV overvoltage shutdown protection. Chances are, your HV is within spec and the H-STAT is bad, but you should make sure the regulated voltage to the flyback is steady and doesn't fluctuate before assuming the H-STAT is bad. H-STAT is expensive, and may not be worth replacing. My KV-1952RS is old and as a whole, not worth the cost of a new H-STAT, so I just bypassed it and didn't bother replacing it. The TV's been working great for over a year and the picture is still excellent. Note: On some models, the sense wires need to be connected during startup or else it will never come on. CAUTION: On some monitors (like the Sony CPD1302), the sense signal may be used for actual HV regulation. Thus, if the sense wire is disconnected, (or the divider inside the Hstat block fails open) there is no feedback and it is possible for the high voltage (and probably B+) to increase until the HOT (and possible other components) blow. I do not know if this applies to Sony built TVs as well.
(The following is from: Marty). Most of the old tube type color TV sets used a shunt HV regulator tube, usually a 6BK4. If it failed, or some component in the HV circuit failed, the high voltage, normally 25KV, could go up to 35KV or more, causing some X-Ray leakage from the CRT. In the early 70s when news of this radiation scare was first announced, there was a public outcry to immediately fix the problem. The feds hastily imposed a requirement on manufacturers of TV sets to somehow render a TV set "unwatchable" if the HV exceeded rated limits. The manufacturers first response was to follow the letter of the law and the first "HEW" circuit simply blanked the video when the HV exceeded a setpoint to make the set "unwatchable". It was quickly noticed that the HV was not turned off with this circuit and the CRT still could emit some radiation. Many TV sets with this feature were left on so the consumer could listen to the sound, so the feds tightened the requirement. By this time new TV sets were all solid state and some manufacturers experimented with HV shutdown circuits, but most of these circuits were poorly designed and not reliable. Zenith thought they had the answer by regulating the HV with a bank of 5 capacitors across the horizontal output transistor to "hold down" the HV to 25KV. If one capacitor opened, the HV would only rise about 2KV, not a dangerous situation. This wasn't good enough for the feds. The "fix" that Zenith finally came out with, was a "4 legged capacitor. Two legs were the emitter return for the horizontal output transistor, & two legs were the HV holddown capacitor (the equivalent value of the bank of 5 caps). This "fix" was accepted by HEW and millions of TVs were produced. It worked so well, that other manufacturers soon followed the lead (Magnavox, GE, etc.). Then the worst happened! The 4 legged monsters started failing in a large numbers. Not opening completely & not shorting out. They sometimes allowed the HV to skyrocket to over 50KV. Some of them even cut the necks off of the CRTs. Zenith issued a recall on those models with the problem (more than one entire model year). After several "improved" versions of the capacitor, the problem was fixed but that recall almost bankrupted the company. Other companies had failures too, but usually not as dramatic as Zenith's. Magnavox used the HV holddown capacitor, both single & 4 leg version in several 70s era TV sets and is a good candidate for fireworks as well.
That goop is probably glue and generally harmless - it is there to hold down the components aganst vibration. I have heard of it sometimes decomposing and shorting stuff out but I doubt you have that problem. Therefore, unless you find a bad cap in the focus or related circuit, we are still looking at a flyback problem.
The typical flyback or Line OutPut Transformer (LOPT) consists of two parts: 1. A special transformer which in conjunction with the horizontal output transistor/deflection circuits boosts the B+ (120 V typical for a TV) of the low voltage power supply to the 20 to 30 KV for the CRT as well as provide various secondary lower voltages for other circuits. A HV rectifier turns the high voltage pulses into DC and the CRT capacitance smooths it. The HV may be developed from a single winding with many many turns of wire or a lower voltage winding and a diode-capacitor voltage multiplier. The various secondary voltages power the logic, tuner, video signal, vertical deflection circuits, and CRT filament. In fact, with many TV designs, the only power not derived from the flyback is for the keep-alive circuitry needed to maintain channel memory and provide startup drive to the horizontal deflection/high voltage system. 2. A voltage divider that provides the focus and screen supplies. The pots are in this divider network - and these things fail resulting poor focus, uncontrolled brightness, or fluctuating focus and/or brightness. A total short could also result in failure of other components like the horizontal output transistor. In some TVs, the focus and screen divider and/or controls are external to the flyback and susceptible to dust and problems particularly on humid days. The resistance of these circuits is so high that dirt or other contamination can easily provide a bypass path to ground especially when slightly damp.
While flyback transformers can on occasion be blown due to a failure elsewhere in the TV or monitor's power supply or deflection circuits, in most cases, they simply expire on their own. Why? Flybacks are wound with many layers of really really fine wire with really really thin insulation. This entire assembly is potted with an Epoxy resin which is poured in and allowed to cure. In some ways, these are just short circuits waiting to happen. Flybacks get hot during use and this leads to deterioration of the insulation. Any imperfections, nicks, scratches, etc. in the insulation contributes to failure. Temperature cycles and manufacturing defects result in fine cracks in the Epoxy potting material reducing the insulation breakdown particularly in the area of the high voltage windings, rectifiers, and focus/screen divider network. It is amazing they last as long as they do with the stress they are under. They also physically vibrate to some extent. A whole bunch of other factors are also no doubt important.
For a TV with no blown fuses that will not start, here are two quicky checks to see if the HOT is good and has power and drive: * HOT tests - check across each pair of pins for shorts (preferably removed from the circuit board). No junction should measure less than 50 ohms or so. Lower readings almost certainly indicate a bad HOT. If in-circuit, however, the reading between base and emitter will be near zero due to the secondary of the driver transformer. See the document: "Testing Diodes and Bipolar Transistors with a DMM or VOM". Don't be confused by internal damper diodes and B-E resistors. * Power - measure across the collector to emitter with a multimeter (with the HOT removed or if there is no deflection, this is safe with it in place). There should be solid B+ - typically about 100 to 160 V (115 VAC sets - possibly higher for 220 VAC sets). If this is missing, iether there is a problem with the power supply or the emitter fusable resistor has blown (probably in addition to the HOT) and there is no return. * Drive: put an oscilloscope on the base - there should be pulses around .7 V for most of the scan (~50 microseconds) and probably going negative a couple volts at least for retrace (~12 microseconds). If drive is weak or missing, determine how startup is implemented as there may be a problem in the startup power supply or deflection IC. WARNING: use an isolation transformer for the oscilloscope tests (and whenever you are probing a TV in general)!!! This part of the circuit, in particular, is usually line connected. See the sections on safety.
Where one or more electron guns in the CRT have deteriorated due to wear and tear, it is sometimes possible to give them a new, but possibly, temporary lease on life through rejuvenation using a special piece of CRT service equipment. (From: Gary Klechowitz (klechowi@execpc.com)). When I rejuvenate a tube I inform the customer that there is no warranty on the job. Rejuvenating a CRT is like when Clatuu was brought back to life by Gort in "The Day The Earth Stood Still". When asked "How long will you live"? he replied: "no one knows". I use a Sencore Beam Builder. If your tube is just moderately dim and blurry but still shows good cut off threshold, I would just use the auto restore mode on the beam builder rather than using the restore button. If the tube is really bad with little or no cutoff threshold, then the rejuvenator is needed but that has less than a 50% chance of fixing the tube and in many cases the tube gets worse to trashed in the process.
(From: Mark Zenier (mzenier@eskimo.com or mzenier@netcom.com)). Actually, they are EEPROMs. A modern TV has integrated the circuitry so that the microprocessor that controls it also sets the various adjustments like vertical height and other characteristics. The same memory that knows what channels are valid and what the brightness and other user adjustable settings are is used for factory adjustments that are set when the TV is first turned on. It's a lot cheaper to use the remote control signals that are already there than add a handful of trimmer resistors. For service purposes there is often a magic key sequence used with your remote control to access a service page in the on screen display than can change these. Since you can easily set something that could fry the various high power deflection circuits, getting a little too curious can void your warranty, and toast your set.
A separate video input or tuner provides the PIP baseband signal which is then resized and stored in a frame buffer large enough to hold the X and Y dimensions of the PIP image. Readout is timed to place the PIP image in the selected area of the screen and it is substituted for the main video. What could be simpler?!Go to [Next] segment
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