Hi Matt,

If you suspect that the supply and take-up reels on your tape deck are  
acting as a Van De Graph generator as Richard Hess reports, 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 holes 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. Play the tape using  
metal reels and see if you notice a difference. If it helps, the  
aluminum foil can be replaced with copper. Use the thinnest foil  
possible to avoid affecting the reel height.

The use of conductive paint:
Grounding the heads with conductive paint (in addition to the factory  
connections) can help. I?ve done this with conductive silver paint on  
modified AMPEX 351?s and MCI decks.
Start the whole process by using an ohmmeter to check the connection  
from the heads to the chassis. 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 is good but dirt, corrosion over time, etc.  
can change the ground between the head block and chassis. If you can  
measure capacitance, do that as well. You?ll want a reading of NO  
capacitance.

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.

Conductive silver paint is expensive, about $30.00 US for an ounce!

Conductive silver paint is expensive (about $30.00 US for an ounce)

Another chemical that can help both electrical and metal-to-metal  
connections is Stabilant 22A

Both and can be found on the internet.


Cheers!

Corey
Corey Bailey Audio Engineering


Quoting Matt Sohn <[log in to unmask]>:
> I had a terrible problem with this last year (on an A-80RC), which  
> got progressively worse. I figured it was a problem with the head,  
> so I tried replacing the caps on the headblock and the wires from  
> it. Didn't help. I finally took it to Tony at IEM  
> (http://www.iemmag.com/About_Us.html). He determined that the ground  
> to one channel of the playback head was faulty, and used some kind  
> of conductive paste to fix it. This almost totally eliminated the  
> problem, but not entirely. I still get random spikes on either  
> channel, perhaps two or three in a 30min reel, where there were  
> dozens before.
> I have found that Wavelab is great for repairing those spikes. I use  
> the global analysis (error tab) to identify them, and the Waveform  
> Restorer to zap 'em.
> The reel-grounding idea seems interesting, but how do you ground a  
> plastic reel?
> -Matt Sohn
>

>> I have identified this as the reel being part of a Van de Graff  
>> generator. When the voltage exceeds the breakdown of the air gap,  
>> tick, there is a spark. The trick is to ground the reels. Some reel  
>> tables are painted with an insulating coating. I have used a  
>> variety of tricks to ground the reels.
>>
>> I recall seeing this on ReVox A77s and Studer A807s, but I can't  
>> recall seeing this on a Studer A80 or A810, nor a Sony APR-5000.
>>
>> Cheers,
>>
>> Richard

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