Detrola 436----No "B plus"

7/2/2007 9:58:40 AMJob Goudie

This Detrola was working but for some reason it quit on me and now I can't get any voltage except the filaments which give correct readings for all the tubes. I am also not receiving any voltage from the switch to the cathode of 35z5. All resistors appear to be ok plus capacitors have been replaced. Just can't figure this one out and neither can I find the correct schematic for this chassis.The tubes used are as follows:12SA7, 12SK7, 12SQ7, 50L6, 35Z5 ...HELP..
Regards

Job

7/2/2007 10:32:28 AMrickd

If this is one of the field coil sets, any chance the field coil went open? Not usually too much in the B+ circuit. Good luck, let us know what ya find.

:This Detrola was working but for some reason it quit on me and now I can't get any voltage except the filaments which give correct readings for all the tubes. I am also not receiving any voltage from the switch to the cathode of 35z5. All resistors appear to be ok plus capacitors have been replaced. Just can't figure this one out and neither can I find the correct schematic for this chassis.The tubes used are as follows:12SA7, 12SK7, 12SQ7, 50L6, 35Z5 ...HELP..
:Regards
:
:Job

7/2/2007 11:10:48 AMRadiodoc

Job,

Check for AC voltage on pin 5 (plate) of the 35Z5.

Radiodoc
***********

:This Detrola was working but for some reason it quit on me and now I can't get any voltage except the filaments which give correct readings for all the tubes. I am also not receiving any voltage from the switch to the cathode of 35z5. All resistors appear to be ok plus capacitors have been replaced. Just can't figure this one out and neither can I find the correct schematic for this chassis.The tubes used are as follows:12SA7, 12SK7, 12SQ7, 50L6, 35Z5 ...HELP..
:Regards
:
:Job

7/2/2007 11:16:46 AMEdd

The filament string powering up should suggest of the integrity of the tap off from the 35Z5 to feed

raw AC to its plate.

The first thing that you might try is to have the set in a discharged... no power condition and make
an initial voltage check

from the 35Z5 cathode to ground...just for meter safety in the next step.
THEN test from the cathode to the ground in the
ohmmeter mode and see that the B+
line is not at
a low resistance value. No miswires / low level loading / or direct shorts...but the warm up action of
the 35Z5
should have shown you that, by it displaying no pyrotechnics....

Then you might go back to the DC voltage function of metering and clip in its NEG lead to B- ground
and the POS lead to
the positive lead of that sets 40 ufd input filter capacitor. Then, If no B+voltage
is being produced after initial filament warm
up. Power down and take one of your collection of
1N4007's diodes that were sent to you and take another clip / test lead
and connect the cathode
(banded) marked lead of the diode to the mentioned + 40 ufd input filter cap and the diode neg
lead
is connected to yet another test lead which has its other end connectred to an ~100 1/2-1 W ohm
current inrush limiting
resistor.

Reiterating.....plate of 35Z5 to anode of 1N4007, its cathode goes to current inrush limiting / dropping
resistor, with the
outside end of resistor being free.

Warm up the sets filament string, observe your metering that is clipped into place, and take the resistor
lead and then initiate a
single brief "scratching / striking" action with the free end of the resistor to the
+40 ufd electrolytic connection junction .....much
in the order of striking a match.....in its duration.
If you show a partial developed B+ level for that short charge duration, looks like
a new 35Z5 tube is in
order.

If the developed B+ level is not excessive, and the series C/L does not overheat , you could try out the
set for a bit longer duration.

73's de Edd

:Job,
:
:Check for AC voltage on pin 5 (plate) of the 35Z5.
:
:Radiodoc
:***********
:
::This Detrola was working but for some reason it quit on me and now I can't get any voltage except the filaments which give correct readings for all the tubes. I am also not receiving any voltage from the switch to the cathode of 35z5. All resistors appear to be ok plus capacitors have been replaced. Just can't figure this one out and neither can I find the correct schematic for this chassis.The tubes used are as follows:12SA7, 12SK7, 12SQ7, 50L6, 35Z5 ...HELP..
::Regards
::
::Job

7/2/2007 11:20:40 AMLewis Linson

:This Detrola was working but for some reason it quit on me and now I can't get any voltage except the filaments which give correct readings for all the tubes. I am also not receiving any voltage from the switch to the cathode of 35z5. All resistors appear to be ok plus capacitors have been replaced. Just can't figure this one out and neither can I find the correct schematic for this chassis.The tubes used are as follows:12SA7, 12SK7, 12SQ7, 50L6, 35Z5 ...HELP..
:Regards
:
:Job

Just about any schematic you xcan find with that tube line up will be more or less exactly like yours. The differences in AA5s were very small among different radios, makers, etc.

Lewis

7/2/2007 2:55:07 PMJob

I feel so darn foolish. After doing some of the test as per instructions I decided to replace the 35Z5 tube with one of a half dozen I had just received from ebay. I almost flipped out when I checked the filament voltage and found that I was getting full line voltage. Needless to say I yanked that one out fast and then checked the continuity of the heaters for the other tubes. When I put another 35Z5 tube in I imediately heard static when proceeding to take voltage readings, and then audio came. So,it looks as if the original rectifier tube was bad although the filament readings were O.K....This will certainly teach me a leason, and that is to take nothing for granted.
Thanks a lot fellows... You guys are just great.

Job

::This Detrola was working but for some reason it quit on me and now I can't get any voltage except the filaments which give correct readings for all the tubes. I am also not receiving any voltage from the switch to the cathode of 35z5. All resistors appear to be ok plus capacitors have been replaced. Just can't figure this one out and neither can I find the correct schematic for this chassis.The tubes used are as follows:12SA7, 12SK7, 12SQ7, 50L6, 35Z5 ...HELP..
::Regards
::
::Job
:
:
:Just about any schematic you xcan find with that tube line up will be more or less exactly like yours. The differences in AA5s were very small among different radios, makers, etc.
:
:Lewis