USING CONDUCTIVE PAINT ON TAPE RECORDER HEADS
f you suspect that the supply or take-up reels on your analog 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 metal reels, 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 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. 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 (plate) 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.
Another 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.
© Corey Bailey Audio Engineering
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