[R-390] OT: Need advice regarding Blaupunkt tube radio

[bavarianradio at comcast.net]

Hi Barry, The reason the B+ is low is not because of the filter caps, although you should replace them, You need to replace the selenium bridge rectifier with a silicon bridge and a 100 ohm 10 watt resistor(in series with the+ lead)  Be sure that you disassembled one of the 460 cans and not one of the 10.7 mHz cans.  You really should replace ALL of the paper caps as well. Although Blaupunkt used better papers than Grundig and Telefunken, they do still fail unexpectedly. Also, replace the small electrolytics  as well, pay particular attention to polarity as one of the electrolytics has + connected to ground. (agc stabilizer) Keep us posted!! Ross
----- "Barry" <n4buq at knology.net> wrote:

Hi Ross,
I did remove the cover from the first IF transformer, mainly because the
lower ferrite core was difficult to turn.  Thinking it was made more
like some of the transformers I've worked on (e.g. R39i0A), I thought I
might be just twisting the insides; however, once I removed the can, it
was apparent that wasn't the case.  These are made quire well and I
wasn't twisting the windings after all.
If I'm not mistaken, the caps are not the "sandwich" type like I've seen
before, but they are very small diameter, quite long tubular caps that
run vertically inside two of the corners.  I don't know if these are as
prone to the silver disease as the sandwich styles.
The B+ is indeed off and I assume I do need to replace the main filter
caps.  There's slight hum on the output, but I don't hear it at low
levels so the AC on the B+ isn't very bad.
Hmmm, still not sure where to go from here.  There are some other
electrolytics that I figure should be replaced; however, other than
that, shotgunning the caps doesn't seem to be a need here.  This model
used very high quality components, at least for the day.
Thanks again,
Barry - N4BUQ