[R-390] R390 B+ Current?

[Jacques Fortin]

Hello John,

6082: same as 6080 for testing, but 26.5V filament you can use 25 V for
filament if available on your tester and same other settings for a 6080 if
your tester have it.

Do not rely on check for C608: You need a leakage tester to know it is good
or not. Otherwise, just shot-gun it. Any modern 0.22µF / 250V cap will do.
A leakage tester is easy to assemble if you have a variable DC supply, but
talk about that later...

Measuring leakage on the B+ 180V line.
1_ Do not power the filaments.
2_ Use a mA meter in series with your variable supply (you have one, it
seems).
3_ Connect the 180V DC supply with the mA meter in series to the 180V test
point.
4_ Power on the supply, let the current value stabilize and read the value,
if it does not balance across 0, this is not good: something draw current
and should not.
5_ Disconnect the power to every module in turn to see which one draw
current.
6_ Suspect supply decoupling capacitors first. The Sprague Vitamin Q should
still be very good for the age they have, but from experience, not all of
them....

Check that first, then came back to me please.

73, Jacques, VE2JFE

-----Message d'origine-----
De : jgedde at optonline.net <jgedde at optonline.net> 
Envoyé : 24 mai 2019 17:10
À : 'Jacques Fortin' <jacques.f at videotron.ca>; 'r390a'
<r-390 at mailman.qth.net>
Objet : RE: [R-390] R390 B+ Current?

Hi Jacques,

The state of the 6082's were new in box but I am suspecting they failed.  My
tube tester (NRI Model 70) doesn't have a listing for the test settings for
the 6082.

I will check C608 but I think I did already.  R615 is spot on.  I've also
replaced the four 47 ohm resistors since they were burned, as well as R625
and R626 which were charred beyond recognition.  After doing all that, the
receiver worked for a few days, B+ was normal, no hum.  The resistors I
replaced are still good.  Also, the resistors for the 6BH6 are good also.

I may rig up a test setup to measure the Gm of my stock on 6082's to test
them.

I'd like to measure the leakage on my B+ like you suggest.  How is that
done?

Thanks!
John

-----Original Message-----
From: Jacques Fortin <jacques.f at videotron.ca>
Sent: Friday, May 24, 2019 8:58 AM
To: jgedde at optonline.net; 'r390a' <r-390 at mailman.qth.net>
Subject: RE: [R-390] R390 B+ Current?
Importance: High

Hi John,

What is the state of the 6082s ?
Have you a tube tester to test those ?
Whatever the output voltage you got, the plate of the 6BH6 (V607) normally
have to be a few volts BELOW the output.
If C608 is leaky, this will reduce the output voltage for sure because it
will make the 6BH6 grid raising higher than it should.
Expect it to be leaky anyways: I do not see any original one that was
faultless.
Check also R615: I once found one that was measuring almost 1 meg. Replace
it by a 1W part.
When all is in order, you should get 180V out ± 3V and the Hum Balance
should work (provide a minimum output hum setiing).
BTW, it is easier to debug when it give you lower than expected voltage than
the reverse !

170mA is within the spec: the transformer is rated at 200mA DC !
But if there was no leakage test done on the B+ rail, to detect any leaky
cap., it can be that you draw more current than the designed value.

Any other question, just ask !

73, Jacques, VE2JFE

-----Message d'origine-----
De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De la
part de jgedde at optonline.net Envoyé : 24 mai 2019 07:49 À : 'r390a'
<r-390 at mailman.qth.net> Objet : [R-390] R390 B+ Current?

I'm still having trouble with the voltage regulator.  Low B+ and a hum.
There's plenty of input voltage available, but the output isn't right.
Right now I have a 180V bench supply feeding the radio through the B+ test
point and all is working but the current is seemingly high.  I see about 170
mA.  Does this sound right?  It may well be, but I want to make sure I'm not
trying to fix the wrong thing.

 

John

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