Corey Bailey

Audio Engineering

USEFUL INFORMATION

USING CONDUCTIVE PAINT ON TAPE RECORDER HEADS If you suspect that the supply or take-up reels on your reel-to-reel tape deck are acting as a Van de Graaff generator, you can try a simple test: Cut a piece if aluminum foil to the diameter of the turntables on your tape deck. Instead of making a hole in the center, simply cut an ‘X’ and slip the foil over the reel spindles making sure that the foil is making a decent connection to the reel spindles. Using a metal take up reel, play a tape that you don’t care about (a blank tape is preferred) and see if you notice a difference. If you have the stock, try the test with back coated and non back coated tape to see if there is a difference. Metal reels are important because of their ability to conduct electricity. You can use copper or brass shim stock as well. Any metal that conducts electricity well will do. Use the thinnest metal possible to avoid affecting the reel height. If the foil method causes any static electricity, you probably have a grounding problem. Use an ohmmeter to check the connection from the heads to the chassis with all cables connected and disconnected. With an ohmmeter, you’ll want a reading of no resistance. Take a close look at the wiring, connectors, etc. Measure the conductivity of the head cables themselves. Make sure the head block is well grounded. Sometimes the head-to-block connection or the head block to chassis checks good, but oils, dirt and corrosion over time can change the ground connection between the head block and chassis so, clean everything. Use anti corrosion chemicals if you think they will help, but make sure they are cleaned off the head connections thoroughly before reassembly. Take the measurements again to see if anything has improved. If you can measure capacitance, do that as well. You’ll want a reading of zero (no) capacitance. The use of conductive paint: Grounding the heads with conductive silver paint can sometimes help. I’ve done this with conductive paint on modified AMPEX 300 Series and early models of MCI tape decks. If it comes down to painting the heads with conductive paint, then paint stripes down the side of the heads grounding them to the head block, while avoiding the pole pieces. Do not use conductive glue of any kind. I have not tried the printed circuit repair instruments that are now available although, I have used them and silver paint (even conductive glue) to repair circuit boards. Know that using conductive paint is a ‘band-aid’ for tape decks that haven’t been modified. Conductive silver paint is expensive and usually comes in 10 gram quantities or more. Water base conductive silver paint is usually more expensive. A chemical that can help both electrical and metal-to-metal connections is Stabilant 22A. Both and can be found on the internet. While I avoid using anything between the heads and the head block or the head block and the chassis, a chemical to enhance the cable connections is OK. Please contact me with any questions or ideas. Return to TOP of page © Corey Bailey Audio Engineering

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