[R-390] R-390 6082 Question

[Jacques Fortin]

Mark, have you changed the capacitors ?
At 280V out, R625 and R626 should look toasted by now..
Hard to tell what's going on there If no other measurements than the output
can be taken.
Not sure the problem is the 6082 if they test good on a tube tester.
Not good either to have the supply connected to the rest of the radio during
the debug process !
Even if it's output is disconnected, the supply output have to be close to
180V.
If not, try to measure the pin 5 of the 6BH6 to understand what's happening.
The voltage there should be low enough to put the 6082 almost at cut-off,
like 100 to 120V (60 V below the output or lower).
Other possibility is that R616 have opened, or raised in value badly: V607
cannot control the 6082 grids (drawing current to GND) if there is not a
high enough positive voltage at pin 6 (screen grid).


73, Jacques, VE2JFE

-----Message d'origine-----
De : r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net] De
la part de hackmohr at myfairpoint.net
Envoyé : 30 mai 2017 10:21
À : r-390 at mailman.qth.net
Objet : [R-390] R-390 6082 Question

Hello All,

A question if you please. Is it likely (or even possible) for a tested good
6082 to still fail in the R-390 voltage regulator circuit? While working on
RF and IF alignments the voltage has suddenly gone high to 280V. I've
checked all 14 resistors in the VR circuit and they are all good. I've
swapped out both 5651 reference tubes and the 6BH6 amplifier tube with no
difference. I even moved all the tubes to a spare audio unit and it shows
the same high voltage. The only thing I haven't replaced is the 6082's which
both test good in the Hickok tester. I've ordered new ones but I feel like
I'm missing something. Any other possibiliites?

Mark WA2FXM
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