[ARC5] [Milsurplus] BC-348-Q Capacitor Questions

[Glen Zook]

It has been my experience that the "bathtub" oil-filled paper capacitors are starting to go bad in many units.  Although a "pain in the posterior" to replace, I now routinely do replace all of the "bathtub" capacitors.  In most cases I leave the original capacitors mounted on the chassis and then install new capacitors under the chassis.  At least this way, when viewed from the top, the unit still "looks" the same.

It is the same with true mica capacitors.  For some reason a lot of them are now starting to go bad.  Of course the "micamold" capacitors, which are really paper capacitors, have been going bad for some time.

Glen, K9STH

Website:  http://k9sth.com


--- On Sun, 8/22/10, Mark K3MSB <mark.k3msb at gmail.com> wrote:

Interestingly I highlighted the B+ line on the schematics last evening,  so following your suggestions went pretty fast.
 
I never thought to isolate and test a circuit like that;  I typically go for testing groups of resistors in a similar fashion though if they can't be isolated individually.
 
My mantra has always been to replace all paper caps unconditionally,  as they are either bad or will go bad in the future and take something made of "unbotanium " along with them.
 
However, the construction of the 348 is a bit more challenging than the open bottom of most BA's I've worked on.   And,  it's stock, and I'd like to keep it that was as much as possible.    Still, an orange drop as the audio output plate bypass cap will make me sleep easier at night knowing the tranny primary is safe.....