[Milsurplus] Re: Plastics turning to cheesecake

[Scott Johnson]

The plastic is nylon in the older units, but I have some that appear to have 
Delrin gears, which do not seem to shrink and crack.  I have salvaged 
several 8640's for this reason, and would not advise anyone to invest in an 
8640, due to the geartrain problem, as well as the general unavailability of 
things such as the output hybrids.

Scott
----- Original Message ----- 
From: "Bob Camp" <ham at cq.nu>
To: "Al Parker" <anchor at ec.rr.com>
Cc: <kargo_cult at msn.com>; <milsurplus at mailman.qth.net>
Sent: Sunday, April 17, 2005 6:26 PM
Subject: Re: [Milsurplus] Re: Plastics turning to cheesecake


> Hi
>
> A number of plastics get used in equipment. The band switch drive train on 
> the 8640 looks a lot like nylon to me. Of course I am no expert. Nylon is 
> interesting stuff. It dries out and shrinks over time. I have always 
> assumed you could fix the problem by simply boiling the offending parts 
> for a while.
>
> Take Care
>
> Bob Camp
> KB8TQ
>
>
> On Apr 17, 2005, at 9:17 PM, Al Parker wrote:
>
>> Hi guys,
>>     Hue, maybe you, living out there in the great NW (I think), know
>> something abt this, but I heard it today & was a bit alarmed.  slightly 
>> on
>> the same topic--
>>     I told a friend, at the Raleigh, NC, 'fest today, that I was kinda
>> looking for an HP 8640 sig. gen.  He told me that he'd had a few (he has 
>> a
>> small commercial repair shop) but was steering away from them based on
>> info from knowledgeable sources, and reports he had on failures, that the
>> plastic used for the bandswitching mechanism (a turret?) was reaching the
>> end of it's expected life and they've been failing.  Strictly a 
>> mechanical
>> problem, and difficult, if not impossible, to remedy.
>>     Anybody have more input on this?  BTW, he said the 8654's don't have
>> the problem.  I'm not familiar with the construction of either.
>> 73,
>> Al, W8UT
>> New Bern, NC
>> BoatAnchors appreciated here
>> http://www.thecompendium.net/radio/
>> http://www.hammarlund.info
>>
>>
>> Message: 5
>> Date: Sat, 16 Apr 2005 20:13:20 +1000
>> From: "Brian Clarke" <brianclarke01 at optusnet.com.au>
>> Subject: [Milsurplus] Re: [The WS No.19 Group] Plastics turning to
>> cheesecake
>> To: <Wireless-Set-No19 at yahoogroups.com>, <milsurplus at mailman.qth.net>,
>> "Hue Miller" <kargo_cult at msn.com>
>> Message-ID: <011001c5426c$eb299800$0404a8c0 at brian>
>> Content-Type: text/plain; charset="iso-8859-1"
>>
>> Could be de-polymerisation of the poly-vinyl-chloride. Well-known problem
>> with house wiring = great income earner for electricians.
>> Brian.
>>   You wondered:
>>   I wonder: what is going on here. Is the "plasticizer" which lends
>> flexibility or some softness to plastics based materials, now migrating 
>> to
>> the surface? Or?
>>   Will all plastics based components meet this fate - the still solid 
>> ones
>> just waiting their turn?
>>
>>
>>
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