|
A common problem with LED type peak meter displays is failure of the individual LEDs (light emitting diodes). It is seen above happening to the SL-HF300. The cause for these failures is difficult to pin down. It could be a combination of vibration, mechanical impacts or age. These displays are no longer available new. Replacing their individual diodes is a challenge because they are very tiny and the replacements are difficult to work with. Here is why they can fail and two methods for reclaiming these displays. The component illustration lower left shows the type of LED assembly used in the manufacture of the SL-HF300, SL-HF500 and SL-HF750 meter boards. The individual diodes are printed onto a circuit board along with other surface mounted components. The diodes construction consists of a conductive anode pot (reflector) and an ultra thin cathode wire. The compound in the pot is called the semiconductor (diode). Semi because it only becomes active when the right DC current is applied going the right direction. When correctly energized it emits colored light. In the circuit the reflector pot is bonded to a thin layer of copper called a trace. It is what remains from an etched copper-coated fiberboard sheet. This is the printed circuit board of the meter assembly. There is another trace next to the pot that has the wire coming from it and protruding into the semiconductor pot. The bowel of the pot is parabolic shaped for the best reflection and protected from contamination by a protective gel. Under certain circumstances the gel separates from the pot and wire comes out of the compound. The LED stops lighting up. The evidence of this is seen in the peak level meter display of the SL-HF300 above. Sometimes these meters can be repaired. Click on the picture and the display assembly is shown removed from the VCR. Click on it again and the repair method is illustrated. Seen here in the upper left are two dead LED sites. Notice the traces and the pot mounted on those tiny square areas. The replacement LED in the center is shown laying on a penny next to Lincoln's nose. This is to illustrate its size and the complexity of making this repair. Notice it has the epoxy resin covering its diode instead of the gel. Upper right is the repair with the one of the tiny LEDs soldered in place. Click the picture again and the front of the SL-HF300 is seen with the six LEDs replaced and all are now illuminated. Another Beta that has this same problem is the SL-HF750. Click on the picture and it is shown with having several failed LEDs. The graphic in the upper left is the same as the one earlier and is for your reference. Click the picture again and here is the assembly being removed from the SL-HF750 linear shutting assembly (cassette loading tray). This LED assembly is almost always non-repairable. I have had good success in the past but the main problem is the repair doesn't replace the remaining LEDs of the meter. They are subject to the same vibration of the originals and probably will fail sometime in the future. It was the only way for a long while but a better solution needed to be found. The best repair would be to replace the meter with one that has the LEDs protected by the hard resin. They are virtually indestructible. Since no new Betahi-fi VCRs are being made and no new parts are therefor available. Any replacement would have to come from a parts unit that is very common and has the same unit spacing as the SL-HF750. It seems that there are several models that fit that requirement. Harvesting these from damaged VCRs has allowed a workaround to be created. The assemblies had to be modified to mount inside the SL-HF750 and the size and spacing was right. The meter drive circuit in the VCR had to be modified drive this dependable replacement. It is shown being fabricated in the upper left and mounted in the loading trays faceplate (from the back). The next photo shows the meter in operation. To return to the previous page click here. ©Misterßetamax
go to homepage |