Partial horizontal collapse. Nu-tec Model NTT-829A
I have replaced IC Tda3654. I have replaced all electrolytic capacitors in high voltage circuitry and som of the non polarized cap's. High wattage resistor 436 on pc board measures 4.6k ohms but cannot determine what the actual resistance is supposed to be as the colors are totally discolored due to the heat the resistor dissapates. Do you know where I can get a circuit diagram or do you have any ideas to rectify problem?
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All chargers with sophisticated circuitry for regulation and timing have a number of capacitors inside. The more intelligent the charger the more sophisticated the circuity and generally the more capacitors are included.
The capacitors are of two types, electrolytic and none-electrolytic of which there are many types. The electrolytic capacitors are generally of high capacity (many microfarads) with a low voltage tolerance and are polarity conscious and the other types are generally of small fractions of a microfarad but tolerant of much higher voltages and are not polarity conscious.
The former type are mostly used to help regulation and smooth lower frequency ripples and the second type helps remove or suppress transients and component-created noise and suchlike that occur in any mains electric supply and apparatus where rapid switching takes place.
Capacitors rarely fail, unlike resistors and semiconductors though electrolytics sometimes do, especially when they grow old. Almost without exception the capacitors and other discrete components used in such circuitry are standardised items and can be sourced form a multitude of mail-order outlets, constructor stores and the local electronics repair shop.
There may be more than one and when they fail due to service in the high frequency section of the supply, I find room to add multilayer ceramic capacitors parallel to each replaced electrolytic cap with a value of .01 to .047 uFd. Voltage of these are in the range of 50 volts or less and adequate to bypass and replaced capacitor with that or less voltage rating.
This will bypass the electrolytic capacitor for high frequencies and potentially extend their life by decades.
The chemical in electrolytic capacitors breaks down nearly always creating internal gas pressure that shows itself by turning the flat tops into domes and reducing the capacitance and increasing the losses by orders of magnitude.
The capacitor determines the cutoff frequency of the filter used to either block or pass frequencies above or below the intended design point. Generally, electrolytic capacitors are used for this, due to their capacity for a given size. electrolytic capacitors are manufactured with two foil plates separated by a gauze soaked in electrolyte compound. This electrolyte compound forms a one molecule thick insulation layer. If this electrolyte dries up, the cap will tend to fail, either short or open, usually short. Because the insulation so thn, it is very much affected by the applied voltage (usually DC). Most electrolytic capacitors are used to block DC. these capacitors are usually pretty sensitive to the applied voltage. Most electrolytic capacitors have a WVDC rating, which stands for Woirking Voltage Direct Current. The higher the WVDC rating, the largewr the capacitor for a given capacitance. Also, these capacitors have a very wide tolerance because of this. Typically, this tolerance is +10%/-80%. This rating would indicate that at close to the WVDC rating, the capacitor will be within 10% of its rating. If the capacitor is used in a circuit where the WVDC rating is much higher than the circuit voltage, their will not be enough bias voltage to form the one molecule thick dielectric (insulation) needed for the rated capacitance. So, if the capacitor is rated for 100WVDC and is used in a circuit that only has 40 volts, the effective capacitance will be much lower, and therefor, the crossover frequency would be affected. If the crossover filter is a high pass, then you would risk damage by allowing too much low frequency content to get to the mid/high frequency driver(s). For a low pass configuration, too much high frequency material would get to the woofer, which might affect imaging, but should not damage the driver. Also, electrolytic capacitors come in many varieties. Almost all of them are polarized, meaning that the terminals are marked plus and minus. Capacitors for crossovers are not typically polarized. Here is a link to some non polarized electrolytic caps: http://www.parts-express.com/term/crossover-caps?c=293,1385
Most audio enthusiasts prefer the sound of polypropylene, polycarbonate or polystyrene capacitors over aluminum electrolytic caps, which also have the advantage of not drying out over time, so they last longer. Also, aluminum electrolytics tend to fail if they do not have a bias voltage applied for a long time. Here is a link to some film cpas for crossovers: http://www.parts-express.com/term/crossover-caps?c=294,1382
Best bet is to replace all of the electrolytic capacitors in the power supply one by one, noting original capacitance values, and voltages (capacitance values are marked in µF as well as their voltage on their jackets), uprating the value/voltage where necessary, and observing polarity (the negative pole is marked by a stripe down one side of the cap, and replacements should have this opposite the + symbol on the board) when fitting new ones in the PSU.
It may also require replacement of IC1, a 12V 5 pin IC regulator, since this may have been partially damaged by the increased output voltage of the failing electrolytic caps in close proximity to it. This device has its type number (prefixed by STR) on its face, and should be available from Panasonic. Make sure if you order a replacement, that it is for THIS MODEL only, and that it is for the power supply in this unit.
Before you go out and buy a whole bunch of new electrolytic capacitors (available from most electronics stores including Radio Shack etc), take a visual look at the power supply (unplug unit from power point, and carefully remove the power board.) Examine it carefully, and note each capacitor that you can the value/voltage of - write it down, and obtain the closest replacements of each. Don't panic if you can't get a 20V 680µF, use a 25V 1000µF instead.
The total cost depends on how many electrolytic capacitors require replacing, but it is best to replace ALL of them one by one, to ensure reliability of the circuit they are in, in this case, the power supply. Don't worry about the IC regulator or any other parts just yet, do the caps first, as these are not terribly expensive, before taking any further action.
I am not sure exactly what you mean here; do you mean the whole unit is dead? no functions? no front LED? If it is dead, the 'blown circuit' after replacing the fuse would be the power supply. Chances are, there may be several short-circuit/leaky components within this area.
IC regulators, power/chopper transistors, diodes (may be leaky or shorted), resistors (fusible and standard colour-coded types) may be open-circuit, and of course a whole lot of electrolytic capacitors may have leaked/failed. In other words, it could be an expensive repair job if you were to take it to a workshop and had them fix it. The most likely culprits in this instance would be the electrolytics; these capacitors may be poorly engineered. so they leak or burst their vents (the impressions in the tops of the caps split open and electrolyte comes out). When these caps fail, the subsequent result is increased DC voltage being passed through the lower output rails (due to decreased DC filtering) and they often take several other parts with them. Electrolyte is highly corrosive, so if any gets on to the copper side of a PCB, it will eat the track; which could render the entire board U/S. Let's hope that is not the case here, and hope the surface mounted components on that side are not affected in any way. It might be something simple, which a competent technician with adequate facilities and equipment can ascertain.
BUT - you can submit it to a service centre/workshop, and obtain a quote on the likely repair/parts cost first, this way you can make a decision as to whether it is economical/worthwhile repairing or not.
Or if you have some technical knowledge of basic circuits, you could probably opt to replace ALL the electrolytic capacitors (uprate their working voltages and values where necessary, whilst observing their polarity) and perhaps change the IC regulator(s) as required (assuming you can obtain the correct type and voltage rating of these). Don't forget to check the resistors and diodes for leakage (out of circuit if possible).
I have yet to find a power supply in any appliance manufactured recently with high quality low failure rated components on it.
If when you get the workshop quote on possible repair(s) for this unit, and you find it a tad high, consider cutting your losses and perhaps buy a new DVD player (or a recorder if you want one) with extended warranty - if you do; but only as a last resort.
Of course, all this is entirely up to you. The power supply is the main problem in this unit.
1) I have to assume that you installed the caps in the correct direction, observing the polarity. Otherwise they would explode. I should state 'probably' because I have never installed a cap backwards. Do not know if they explode every time, or not.
Point is if they do not explode every time if installed backwards, then see if you have installed them correctly. Line the Negative polarity marking on the cap, to the Negative polarity marking on the mobo. (MOtherBOard)
How close did you get to the stated uf, (Microfarads), and voltage?
2) As I am sure you are aware, it is the Electrolytic paste going bad inside, and forming a gas, (Hydrogen Gas), that expands, and swells the cap's case. Sometimes though, there are no visual signs of failure, as the paste just dries up inside.
3) Capacitors are used as Filters or Voltage Regulators.
Ones in the general area around the CPU, are part of the motherboard voltage regulator circuit, and this part of the motherboard voltage regulator circuit is for the CPU. (However read on) These caps are in a Series circuit. Just takes one cap to be bad, and the circuit fails.
The caps around the expansion slots, and ram slots are in a Parallel circuit. Takes more than one going bad to mess things up.
However, just to add confusion to the matter, the motherboard will Not have the motherboard voltage regulator circuit capacitors, that handles each specific hardware component, IN it's general area.
For example, the part of the motherboard voltage regulator circuit that handles voltage regulation for the CPU, may have capacitors located across the board from the CPU, plus the one's that surround, or are in close proximity to the CPU.
There may be a cap that regulates voltage for the CPU, and it could be clear over on the other side of the ram slots, or down next to an expansion slot.
The motherboard voltage regulator circuit, has a high ratio of being what fails, when a motherboard goes bad.
The motherboard voltage regulator circuit is composed of Chokes, Transformers, and Electrolytic Capacitors. The Electrolytic Capacitor, (Radial Aluminum Electrolytic Capacitor), is the Weakest link.
Especially when the world market was flooded with a deluge of bad Electrolytic Capacitors, and they are still cropping up today in all kinds of electronic components. Not just computers.
Point? You may want to follow the above link, and see if you can figure out the voltage regulator circuit caps, and replace all of those that didn't get replaced, or replace every cap on the motherboard.
Sounds extreme, huh? Understandable.
But how much do those caps cost? How much does a replacement board cost of equal value. (About the same as all of the caps, probably)
Is this just to see if you can do it?
[ I'm a computer geek, and I probably would. In fact I have, but not to the extreme of replacing all the caps. It could be the motherboard chipset next, (Northbridge/Southbridge chipset), so you have to keep things in perspective. You won't be replacing the motherboard chipset. But if you do, WE ARE FRIENDS! lol!]
Video processor being what? The Nvidia GeForce 6100, Northbridge chip? Under the 'Meat tenderizer' heatsink. Large one on the side towards the I/O ports?
Are YOU sure the PSU is good? No doubt in your mind what-so-ever. A PSU with a weak voltage power rail will light LED lights, maybe spin fans, but will not have enough power to turn the Processor on. No Processor, no video signal.
Just stating in case you pulled a PSU out of your parts pile, to see if you had those mobo's fixed.
Without checking components associated with the TDA3653, the exact cause is impossible to say.
This IC has extensive built in protection circuitry that should protect it from overloads caused by such things as shorted turns in the vertical deflection coil, or from faults with any associated components, e.g. open/shorted resistors/diodes/capacitors.
The following data sheet describes this IC in detail: http://www.datasheetcatalog.org/datasheet/philips/TDA3653.pdf
Therefore as the IC keeps failing at switch on, and if no other components are failing or suffering damage, suspicion must fall on the supply voltage delivered to Pin 9 and Pin 6 being excessively high (or spiked) and thus causing a rapid demise of the IC. As most LV (low voltage) supply voltages in TVs are derived from a common regulated source, this would imply that the power supply circuitry itself may be faulty - dried out electrolytic capacitors being prime suspects.
However, as with any fault in complex circuitry such as this, there may be other causes including less logical ones such as dry joints or shorts in wiring or between PCB tracks.
Either the capacitors in the power supply are bad, or the caps on the main board. You can test them with a capacitor tester or ohmmeter. It is common, especially in newer devices.
Replacement Parts: Replace the original four (4) 1000µF, 16V, 85ºC capacitors on the DM Module with Radial Polarized, 1000µF, 35V, 105ºC Capacitors. Description: Computer Grade Electrolytic Capacitors or High Temp Electrolytic Capacitors; Capacitance = 1000µF; Voltage = 35 V; Operating Temperature Range = - 20º C to + 105º C; Termination Style =
Radial, Operating Hours = 10,000 Life Hours. The original DM capacitors
are rated at 1000µF, 16V, 85ºC. Do not use capacitors with
this rating to repair your Mitsubishi television, or else the same
issue will reappear in 1-2 years.
The capacitors are available from several on-line electronics stores and possibly from a local television repair
shop. I recommend that you use ONLY
high temp Capacitors rated at 105º C, with a voltage rating of 35
V. Refer to the "General Information" section below for additional
information about purchasing the capacitors from a online website.