[Hammarlund] Capacitor replacement

Thu Mar 10 22:03:41 EST 2022

    The SP-600 lists 42 paper caps but I've never seen a list of 
the bathtub electrolytics. The Sprague Black Beauty caps are all 
to be replaced. I am not sure all BB caps of all ages were bad 
but the ones used in the SP-600 had short time failures and the 
cases tend to crack. The oil filled ones leak the oil. At the age 
these receivers are now the electolytic caps should also be 
replaced. I don't like restuffing the cans, others prefer it. I 
used terminal strips and mounted high quality electrolytics on 
them. Easier and works fine. Its a good idea to mount the 
terminals with external tooth lock washers since they insure good 
ground connection for the grounded terminals.
    It is not too difficult to remove the side panels and it may 
make it easier to change some of the capacitors.
    Some capacitors are located inside the IF cans. Not that 
difficult to get at but a right angle solder iron may make life 
easier.
    As is usual the mica caps are nearly always good.
    Also note, there are paper bypass caps on the modules on the 
RF (forgot a word, the barrel with the modules on it). Don't 
forget them. Also, there was a special tool for working the clips 
that hold the modules in place. They can be removed and returned 
without the tool but it takes care and is a bit difficult.
     If you remove the RF component from the top of the tuning 
unit be extremely careful to set the band switch in a mid way 
position. If its left on any band it will mutilate the contacts. 
They are virtually unrepairable (although I've done it).
     Also, NEVER bend any plates on the tuning capacitor. They 
should be completely flat and parallel. Sometimes they get out of 
alignment. They can be centered without damaging but DON'T bend 
them to try to compensate for their being decentered.
    Be extremely careful of the spring coupling. Try wrapping a 
little fine solder around it to keep it from flying. Mostly this 
stuff does not have to be done but you should be aware of it.
     Some receivers have uneven sensitivity. That can be due to 
bad capacitors or a weak double conversion crystal.
    Since you are going to be doing open heart surgery on this 
thing also watch out for out of tollerance resistors. Resistors 
tend to go up in value (but not always) and I've found that 
values of 100K and above are especially likely to have drifted. 
Modern film capacitors simply do not drift and will likely last 
forever. Same for modern plastic film caps.
    The old mod for the receiver used ceramic caps but probably 
using polypropylene plastic caps is better.
    Enough. when these things are correctly rebuilt and aligned 
they are very fine receivers.

On 3/1/2022 1:42 PM, Joe Connor via Hammarlund wrote:
>   Victor, it's described in the SP-600 Anthology as C-102, a .022 BBOD, and it's located on the single-conversion switch. With the help of the manual for your particular model, you should be able to find it. If I remember correctly, it's not one of the hidden ones.
>                             Joe Connor
>      On Tuesday, March 1, 2022, 04:35:37 PM EST, V R <n4vic at live.com> wrote:
>   
>   Joe,
> I’ve somehow missed the cap warning you referenced. Can you provide any more detail? Of course I’m still reading and gathering data so I shud eventually come across the warning. Tnx
> Victor
> 
>> On Mar 1, 2022, at 15:57, Joe Connor via Hammarlund <hammarlund at mailman.qth.net> wrote:
>>
>>  Just a few more things:
>> 1. Al Parker's write-ups on http://www.boatachors.org  are well worth reading. They're informative and entertaining.
>> 2. WARNING: the SP-600 Anthology points to one easy-to-access cap that should be replaced immediately. If it shorts, it can take out the filter chokes.
>>                          Joe Connor
>>
>>      On Tuesday, March 1, 2022, 03:09:12 PM EST, Al Parker <anchor at ec.rr.com> wrote:
>>
>> Hi Folks,
>>      Even tho' it's a bit crippled right now, the Hammarlund Historian
>> website is still there, and has a very detailed article by Ray Vasek,
>> W2EC, on the topic of refurbishing the SP-600's.  It includes a list of
>> the capacitors (BBOD's) to be replaced.  Note that the factory realized
>> 2 things during the long run of SP-600's: first you don't need to use
>> .022's, use .01's in their place, and second, due to reports of early
>> failure, the few SP-600's after sn ~17,500 used disc ceramic caps
>> instead of BBOD's.  I have been thru a cupla dozen SP-6700's in the last
>> 25 yrs, and have only seen 1 that had all discs from the factory.
>>      Some of my  work on them may be seen on the <www.boatanchors.org> website.
>>      Note that there are many model designations of the SP-600, and some
>> have different no.s of capacitors in them.
>> 73,
>>
>> Al, W8UT
>> www.boatanchors.org
>> www.hammarlund.info
>>
>> "There is nothing -- absolutely nothing -- half so much
>> worth doing as simply messing about in boats"
>> Ratty, to Mole
>>
>>> On 3/1/2022 12:17 PM, Joe Connor via Hammarlund wrote:
>>>    I'm with Wes and Loren on the clipping.
>>> 1. With the bathtubs, I didn't use a heat gun. I cut off the back of the cans with a Dremel cutting wheel, and the innards came out pretty easily. It looked good because the back of the cans are hidden by the chassis when the cans are reinstalled.
>>> 2. The most difficult part of the job is removing and reinstalling the RF deck. Both the SP-600 Anthology and the Radio Boulevard site give detailed instructions, but that might be something you'd want to ask about on here because I'll bet some of the guys in here have figured out some useful short-cuts.
>>> 3. The biggest pain was one isolated cap located in a pod by the RF deck. That one cap took an awful lot of work to get to.
>>>
>>>
>>>                                  Joe Connor
>> <snip>
>>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL