The fine art of recapping

[iw5ci]

I have a nice Hammarlund SP-600 receiver. It worked fine for my standards , good stability sensivity and selectivity.
I someone asked me about it's performance i said it was a very good performer for for BC bandcruising and also for
Ham traffic (AM an CW and not bad in SSB with proper regulations).

After a problem with the BF, i had to take the radio out of the box and change the 6v6gt tube , meanwhile i read many
infos about SP-600 and the Black beauties BBOD issue. I told me ... well my receiver works great , why i have to bother
about recapping it... it a HUGE work and i have never done a thing like that.
Then i examined the BBOD of my receiver and i saw what i would never had seen... many of them where split in half and
maybe also the other where not in good shape.
So i decided to recap my 600. i have done i 2 steps. At first all except RF deck, and at last RF deck.
I spent 4 evenings and nights in the operation, because it was my first experience in a full recapping. After the first step
i checked the radio and it was working only on some bands. Fortunately it wasn't an error in recapping but a tube had failed
(6c6 tube) after tube exchange the 600 started working a lot better that before. More s/n ratio better sensibility and a better
audio.
When i reworked the RF deck , i was disappointed because the situation of the BBOD was even worse. There where a couple
of completely burned resistors inside the rf deck and all the condensers where in bad shape.
So when i finally ended the recapping and turned the radio on again i was astonished in the great performance increase.
A signal (from the generator) that is inaudible on the Icom 4 conversions receiver i have on the shelf, is perfecly listenable on
the sp-600 . I cannot here any significant difference in performance with my Collins 390.
All the condensers were leaking except for a couple that were open and 4 shorted...

Now the questions:

How it's possible that a receiver can work with all the condensers in that conditions (and it was going really bad)
why this problem is so evident in the SP-600 and not in the many receivers ot it's age?
for example R-390 Superpro 200 uses the same BBOD?

thanks for attention

[KB2WIG]

I hope you saved the BB's..... ebay is waiting.


klc

[KL7OF]

Where do you buy your resistors and capacitors?  Is there a Radio Shack Italia down the street?  Congratulations on fixing the SP 600...That is not an easy job..Ciao  Steve

[w3jn]

The SuperPro 200 uses paper-wax capacitors.  don't forget those hidden inside the IF cans - it's easy enough to remove the IF can covers but the 6 or so in the RF compartment are a bitch.

You'll generally find higher quality Sprague Vitamin Q oil capacitors in the R-390.  They do go bad, but are MUCH more reliable than the Black Beauties.

[iw5ci]

Where do you buy your resistors and capacitors?  Is there a Radio Shack Italia down the street?  Congratulations on fixing the SP 600...That is not an easy job..Ciao  Steve

Fortunately here in Florence we a couple of shops who sell spare components.
Resistors are cheap (1 euro for 25 1/2 W resistors).
Capacitors (i used axial polyester rated at 630V) are quoted 0.15 euros each, so for a sp-600 full recapping less that 8 euros are needed.

[w3jn]

Cheaper than the US!