[GreenKeys] AN/UGC 74A and 74B

[Bruce Gentry]

Bruce Gentry wrote:
> Jeffrey Angus wrote:
>> On 11/29/2010 9:57 PM, Don Robert House wrote:
>>  
>>> I have not figured out exactly what happens but I believe
>>> it is a combination of the type of lubricant, the type of
>>> ink in the ribbon, plus heat and the composition of the
>>> platen.
>>>     
>> I suspect it is the material itself.
>> Some time in the '70s, the Japanese seem to have gone crazy
>> experimenting with "How to make cheap rubber" for drive
>> belts and phono idler wheels.
>>
>> These things turn to black goo. Damned ugly to try and clean  up.
>>
>> Partly I think the problem was partly nobody fully understood
>> that the stuff would polymerize and turn to crap.
>>
>> And of course, if it was cheaper, by all means use it.
>>
>> Took 15-20 years for it to happen, and by then, well, it was
>> everywhere.
>>
>> Jeff-1.0
>> wa6fwi
>>
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>>   
> I am fairly certain the decomposing parts are polyurethane. In the 
> early 1970s, it was considered a miracle material and used for an 
> incredible number of applications. It worked very well, but no one 
> apparently know of it's instability. The best recording tapes of that 
> day used it in the binder  to hold the oxide coating to the base,  
> these tapes are totally unusable about 95% of the time today. I have 
> cleaned the gook out of a couple UGC-74s and substituted rubber tubing 
> for the covering. The decomposition is greatly accelerated by heat and 
> humidity, and tends to occur without warning over a short time. 
> "Gumout" brand choke and carburetor cleaner did a good job getting the 
> goo off everything. It won't dissolve it immediately all the time, but 
> loosens it's grip on surfaces so it can be peeled off. It is one of 
> the nastiest things you can imagine to get off skin and it stains 
> clothing permanently. Do it outdoors away from any ignition sources, 
> and wear old clothing and gloves.
> Bruce Gentry     KA2IVY
>