1940 Montgomery Wards Model 04BR-729A Issues

[vortalexfan]

Hello, recently I had acquired a 1940 Montgomery Wards Model 04BR-729A AM/SW Radio with a dedicated phono input on the back.

It was pretty much virgin when I got it except for one tube being replaced in it, other than that all of the original capacitors were still intact in the bottom, and all four chassis mounting screws were still intact yet, which is why I suspected that the chassis had never been removed from the case before (because usually if it had been removed previously you're usually missing a screw or two.)

Also the preset buttons had never been set before because there were no station call letter inserts installed in the buttons and when you press the preset buttons the tuner pointer doesn't move with the preset buttons.

I replaced all of the capacitors in the radio (except for the main filter can caps because those were still good yet surprisingly enough) and before I replaced the caps the radio tuner worked pretty well except for the lower portion of the AM Band-spread which I suspected was due to a bad capacitor.

After I replaced all of the caps the radio doesn't want to work at all anymore not in AM or SW band, but yet the phono mode works fine, and I double checked my work against the Rider's Schematic and it seems like everything is where it should be but yet I've got a dead tuner section, and I'm kind of stumped and there weren't very many capacitors in this unit, there's 20 capacitors all together in this unit, and only 10 of them were of the paper variety, the rest were mica capacitors, and adjustable capacitors and 2 electrolytics (the main filter cap.)

Also the volume control knob broke on me when I was trying to remove it from the radio so I could remove the chassis from the cabinet so I could service the radio chassis, and the volume control knob is kind of unique to this model of Montgomery Wards unit because of the fact that it has a wider than normal knob shaft so it can fit into the dial bezel. Does anyone on here have a spare knob for this radio laying around that I could have?

Thanks for your help.

[vortalexfan]

UPDATE: I figured out that it was a bad rectifier tube, causing the radio to not function correctly because as soon as I swapped out the rectifier tube it started working correctly.

But that still leaves me with needing to source a new volume control knob for the radio...

[vortalexfan]

Another Update: The radio is still dead beginning at around the 760 KC mark on the tuner dial on the AM Band and the Shortwave band is completely dead, not even any tuner hiss.

The weird thing about the AM Band's dead spot is that it seems to travel, meaning that when you're tuning down the AM Band going from the top of the dial (1560 KC on down) the dead spot starts around 760 KC, but then when you start tuning up the dial from the bottom of the dial (560 KC on up) the the dead spot stops at around 900 KC and the reception starts again there.

I had thought at first that the issue had happened due to a failed capacitor (because I ran it a little bit with the original paper caps in place yet) but its still doing it even with the new caps in place.

I was thinking maybe it needs an alignment but if the radio hadn't really been electrically touched much in its life, then I'm thinking that might not be the issue.

Also I forgot to add, that there was a thunderstorm going on outside when I first started working on this unit where there were some pretty close lightning strikes, but I don't think that a close lightning strike would affect the radio's tuner in that way unless it was hooked to an outdoor antenna which it wasn't.

Any ideas as to what might be going on here?

[Alex KL-1]

Various things to check, but 2 crossed my mind: variable capacitor bent, or maybe weak oscillator tube, if all SW is out (or cap/ resistor near this section)(if this perhpas have 2 issues at same time).

[Phil]

I sounds like for some reason the oscillator is just barely working. As Alex said you might check for a bent vane on the variable capacitor, although that should result in the dead spot staying at the same place and be accompanied by a loud, scratchy noise when it shorts. A weak osc. tube is possible and probably most likely a resistor is way out of tolerance.

[vortalexfan]

I was thinking resistors as well as a possibility but wasn't sure and I was checking a few last night and some of them seemed to check almost 5%-10% above the rated 10%-20% tolerance that the resistors were rated for but I wasn't sure where in the circuit those resistors were because while I could see where they were on the Rider's Schematic it was kind of hard for me to trace where they were in the overalll circuit because the schematic was drawn out just small enough that I had a hard time seeing the lines and where they went (I can usually read small print but there's a limit for me, especially when the print quality isn't that great to begin with, and the ink starts smudging when you touch it with your fingers.)

Also I did check the tuner section tubes (SK7, SQ7, etc.) and they seemed to test ok (one of the tubes tested just a little above the "?" mark on the tube tester but I wasn't sure if that would affect things or not because I've worked on radios in the past that had tubes in them that were in the "?" zone that still worked fine (albeit it was a single band 4 tube series string set.)

I'll double check the resistors again and the tubes again.

This radio by the way uses all dogbone resistors (BED type) so I wonder if that might be something that might be worth taking into consideration when testing them...

[jr_tech]

Originally Posted by Phil

I sounds like for some reason the oscillator is just barely working.

Perhaps b+ is low

jr

[old_coot88]

Originally Posted by vortalexfan

Also I did check the tuner section tubes (SK7, SQ7, etc.)

Unless I'm mistaken, there should be another tube containing the osc./mixer function, something like 6SA7.

[vortalexfan]

Originally Posted by old_coot88

Unless I'm mistaken, there should be another tube containing the osc./mixer function, something like 6SA7.

There is, I was just listing the tubes as an example type thing, also at the time I was writing my message I couldn't think of the tube number which yes it was SA7 I was thinking of but I couldn't think of it at the time.

[vortalexfan]

Originally Posted by jr_tech

Perhaps b+ is low

jr

That's what I was thinking at first, so when I took voltage measurements the B+ was actually higher than listed in the Rider's, it showed that the B+ voltages were listed at 260V and 290V in the Rider's and I was measuring 320V and 350V which I chalked that up to being due to higher line voltages than were around at the time the radio was made, (which when the radio was made line voltages were usually between 110V-115V AC, whereas now it isn't unheard of for us to have line voltages between 120V-125V AC.)

[vortalexfan]

UPDATE: I got it fixed, I tested all of the old Dog Bone Style Resistors in this radio and they were all well outside of tolerance so I replaced them with 1/2 Watt carbon-film resistors (in place of the original 1/3 Watt resistors) and the two 1W resistors just stayed 1 Watt resistors, and it works fine now.

The only issue I've noticed is that the dial light acts like it has a short in it (it has two dial lights in it and the one on the right side of the dial will flicker on and off and or dim in and out every once in a while and the left side bulb is unaffected), I was thinking possibly the bulb was trying to burn out or fail but I would of thought that the bulb would of just burned out and not did some weird dimming and flickering stuff.

Also I had to replace the original tone control because it was broken but the closest control I could find was one that had a slightly shorter shaft than the original, and I was wondering if there's a way to extend that shaft so that the original knob could still be used?