[Johnson] Old Resistors

[Carl]

There is no one mandatory type to use. I use 1W carbon film for 1/4W to 1W 
since the size is close to the originals and they are cheap enough. I buy in 
100 lots.

Metal film is fine for high gain audio stages where any noise is 
unacceptable.

Ohmite OY series for 1 and 2W parasitic suppressors and generic Xicon MOX 
for others.

Its all at Mouser.

Carl
KM1H



----- Original Message ----- 
From: "David C. Hallam" <dhallam at knology.net>
To: "Carl" <km1h at jeremy.mv.com>
Cc: "Johnson List" <johnson at mailman.qth.net>
Sent: Tuesday, April 03, 2012 8:48 AM
Subject: Re: [Johnson] Old Resistors


> Of the three principal types of resistors available, carbon film, metal 
> film, and metal oxide, which one exhibits the best long term stability, or 
> it more related to the manufacturer?  Given the smaller size of today's 
> components, I generally double the wattage rating when I replace a 
> resistor.
>
> David
> KW4DH
>
> On 4/3/2012 8:31 AM, Carl wrote:
>> Thats common with a few brands of resistors. I see 47K screen resistors 
>> in Nationals well into the megs fairly often as well as 10X-20X changes 
>> in other gear.
>>
>> OTOH a first run after WW2 NC-240D and a last year 1961 Viking II CDC 
>> didnt have a one out of tolerance.
>>
>> Blame it all on the purchasing departments and managements money saving 
>> controls. National changed management shortly after and bought the 
>> cheapest they could find. I remember having to replace many even in the 
>> mid 60's.
>>
>> Carl
>> KM1H
>>
>>
>> ----- Original Message ----- From: "David C. Hallam" 
>> <dhallam at knology.net>
>> To: "Johnson List" <johnson at mailman.qth.net>
>> Sent: Tuesday, April 03, 2012 7:34 AM
>> Subject: [Johnson] Old Resistors
>>
>>
>>> I ran into an interesting situation yesterday.  I was finding multiple
>>> spurious signals when I tried to zero beat a received signal with my
>>> Invader 2000.  I put it on the bench to find out why.  It turned out to
>>> be a carrier oscillator problem.  The unused oscillator was not being
>>> turned off so the carrier frequency was a mix of both the 9001.5 and
>>> 8998.5 KHz frequencies.  The cause was both of the grid dropping
>>> resistors on the 12AU7 oscillator were WAY out of spec and insufficient
>>> bias was applied to cut off the unwanted oscillator.
>>>
>>> The resistors are supposed to be 820K.  One measured 3.2M and the other
>>> 4.1M.  Has any seen old resistors go this high in value?  This makes me
>>> wonder how many other resistors in this thing have a similar problem.
>>>
>>> David
>>> KW4DH
>>>
>>> -- 
>>> There are four boxes to use in defense of Liberty:
>>> SOAP, BALLOT, JURY AND AMMO. Please use in that order.
>>> VOTE for REAL CHANGE in 2012.
>>>
>>> ______________________________________________________________
>>> Johnson mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/johnson
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:Johnson at mailman.qth.net
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>>
>>>
>>> -----
>>> No virus found in this message.
>>> Checked by AVG - www.avg.com
>>> Version: 10.0.1424 / Virus Database: 2113/4910 - Release Date: 04/02/12
>>>
>>
>>
>
>
> -----
> No virus found in this message.
> Checked by AVG - www.avg.com
> Version: 10.0.1424 / Virus Database: 2113/4911 - Release Date: 04/02/12
>