[ARC5] BC-221 frequency meter

[Glen Zook]

Looking at the schematic, I don't see how applying too much B+ would damage the crystal.

Of course, it is possible that the crystal always was bad.

However, I really suggest that, before you do anything else, you replace all of the fixed capacitors in the unit including the bathtub capacitors.  There is like a 99% chance that the capacitors are leaky.  There several slightly different versions of the BC-211 and the components can vary somewhat.  However, remember that the "nominal" values of components have changed since the BC-211 was manufactured.

For example, a 0.2 mfd capacitor is now replaced with a 0.22 mfd.  A 0.5 mfd capacitor is now replaced with a 0.47 mfd capacitor, and so forth.  Considering the tolerances of the "olde tyme" capacitors, the new values are generally going to be nearer to the "exact" values than the old ones ever were!
 
Glen, K9STH


Website:  http://k9sth.com



On Wednesday, January 1, 2014 6:11 PM, KG4KGL <kg4kgl at gmail.com> wrote:
 
Alright before I start, you have to promise not to laugh at me. 

I bought this freq. meter and when I powered it up with my Heath PS-4, I read the wrong scale on the meter and applied ~300v B+. Oops. So I saw a little smoke and thought I fried one of the old fixed caps, so I recapped it. 

Now it worked at that high voltage and it works after the recap, but I get nothing out of it when I put it in the Crystal position. Am I right in assuming I have fried the crystal? Everything else works fine. 

Does anyone have a spare xtal they would be willing to sell?

Tnx,

Robert
KG4KGL
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