[Heathkit] Dumb speaker question

[Carl Nord WA1KPD]

Agree. I have found bad ones too. It is as you point out you can pretty well figure the wax are bad so just replace them (besides it could save an IF transformer one day). Ceramics you can default to good unless there are symptoms that indicate otherwise. 


----- Original Message ----- 
From: "Mike McCarty" <Mike.McCarty at sbcglobal.net> 
To: Heathkit at mailman.qth.net 
Sent: Monday, March 1, 2010 3:30:15 PM GMT -05:00 US/Canada Eastern 
Subject: Re: [Heathkit] Dumb speaker question 

Carl Nord wrote: 
> Wayne, 
> 
> In my experience a number of resistors in a radio are isolated. By that I 
> mean do they go to a grid or a capacitor so by looking at the circuit you 
> will find many can be done without touching them 
> 
> Older wax caps or Black Beauty types I just change out period. But something 
> from the SB era is likely to be ceramic disc so should be OK 

Not to argue, as what you say is pretty much right; ceramics 
generally are good, no matter how old. 

However... 

Ceramics also go bad, just not nearly as often. By actual count, 
97% of papers are bad, IME. I've encountered a few bad ceramics, 
and a handful of bad micas, especially in cheaper IFTs. 

I bought a GR-54 inexpensively, and found that it had a shorted 
output plate filter (tone control) cap. It was ceramic, and read 
ZERO ohms. Others I've found have been or become microphonic. 
One of them was used as a line filter, and it had completely 
exploded. I've seen one of them burn before my eyes, while it 
had been in continuous use for months. It was not vintage. 

So, it does happen. 

Mike 
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