Condensers ???

[John Holotko]

I've probably asked this question before so please bear with me. I am going to need to re-cap a few radio's  that I have around here and was wondering, what type condensers serve as the best replacement for the old wax coated paper caps commonly found in old gear ? Also, what about those cardboard tube electrolytics ?? Would standard aluminum can electolytics suffice ?? While we're at it, how about those square mica caps commonly used for rf coupling, etc. ?? Any reccomendations on good modern replacements for those ?

[Glenn NY4NC]

Hi John;

You can replace the old wax caps with modern polyester type. Mouser Electronics carrys them. Yes, cardboard electrolytics can be replaced with metal cans. Some "purists" will hollow out the old cardboard tubes and hide modern axial lead electrolytics inside to keep the original "look". I believe you can replace the old domino type mica caps with modern silver mica caps. 

I've probably asked this question before so please bear with me. I am going to need to re-cap a few radio's  that I have around here and was wondering, what type condensers serve as the best replacement for the old wax coated paper caps commonly found in old gear ? Also, what about those cardboard tube electrolytics ?? Would standard aluminum can electolytics suffice ?? While we're at it, how about those square mica caps commonly used for rf coupling, etc. ?? Any reccomendations on good modern replacements for those ?

[Jim, W5JO]

Hi John;

 I believe you can replace the old domino type mica caps with modern silver mica caps. 

Except for some values such as 91 uuf.  Those won't be available nor will many of the old values.  My suggestion is leave the old micas in place unless they need replacement.  Most of the time they won't, but I have had to find and replace some that wicked moisture around the leads. 

Use your judgement on that and if the radio performs properly after alignment you should not need to replace them.  The problem I have had is in the IF transformers,  The cans should have a sharp peak near the middle of the coil.  If it doesn't, you will need to replace the micas.  Other indicators are popping and crackling with no antenna hooked to it.

[Glenn NY4NC]

I've noticed over the years, the subject of replacing caps in old receivers has been a source of heated debate believe it or not!  As Jim mentions, use your own judgement. My opinion has always been, if yer in there going through the trouble of replacing some caps, and there is a good chance others will start to break down or leak in the future, why not replace them all and be done with it? 

Some receivers like the SP600 can be challenging to work on. Some caps are burried deep and may require removing assemblies to reach them. Imagine replacing only the bad one, putting the whole thing back together only to have another one in the same area crap out a month later? Grrrr!!!! 

Two 47pf silver micas in parallel are pretty darn close to the 91pf original.

[W2JBL]

John- i usually just replace the paper bypass and coupling caps, and leave all the micas in th RF section alone. i use ceramics, cause i have them, or ployester (orange drops). the LAST thing i do after is realign the radio. these days you may also need to re- resistor the average set. they go WAY out of tolerance with age. if it has not been "aligned" by HAM BONE, chances are you will not have to touch anything. i have recapped many many receivers and not had to realign unless it was messed with before i got to it. however if it's still numb and realignment does not do it, then it's time to replace caps in RF and IF tuned circuits. for the receivers i know you have there a simple recap is about all you should need. and call me if you need off color stuff like 91 PF micas. i've got it ALL. or go see Tom Hunt, HA!!!!