I recently got a 41-300, as detailed in my introduction forum thread. I replaced all the caps and cleaned the volume/tone pots and it works. However, not at 100%. Reception is still weak: It gets a few strong stations on the upper half of the broadcast band, but the lower half has nothing except a loud hum peaking in the 600-650 kHz range. I also don't get anything from the shortwave bands, though there I know less what to expect. I just learned that that could be dirt or oxidation on the band switch, so I'll have to try that.
This brings me to having to figure out my next steps, and a lot of the online resources that cover beyond the absolute basics of recapping or something seem to assume a level of expertise I don't have. Is there anything out there with some sort of general troubleshooting flow or things I should look at first?
For instance, I'm pretty sure some resistors will need to be replaced but the number and placement makes just replacing them all like the caps pretty daunting. Knowing which parts of the circuitry might relate to my issues can help me focus on what's giving me problems. Or should I just look for what's furthest out of spec first regardless of where it is?
Also, for getting resistors, is there any particular reason not to just get a set of 2W metal film resistors in whatever sizes are on the parts list, or should I be more sophisticated about it?
>>Also, for getting resistors, is there any particular reason not to just get a set of 2W metal film resistors in whatever sizes are on the parts list, or should I be more sophisticated about it?
No, no need. The 2W size is good and universal, has good length and will not care about dissipation in most of the places.
I do look for out of spec resistors. Most you can check in-circuit. If the resistor really much lower, see if the circuit is reponsible.
If much higher, it has to go as it cannot get higher due to the circuitry. 20% is a good benchmark for replacement.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
For a bit of updating I checked resistors and did some extra research. Some of the resistors running high are associated with the XXL tubes (RF amplifier and oscillator I think?) in ways that could explain the symptoms I'm having. So I'll start there, ordered a box of assorted 2W resistors. Also got a new higher power soldering station since my 80W iron is pretty marginal on some of the connections in this chassis.
I think I'm going to need to repair/rebuild all the lamp cables and sockets since they have some rotting rubber cables, but I see there's a guide on that and the parts are all common since the same lamp types are used in just about every pinball machine.
Now I have an apparent typo in the 1941 service yearbook.
The biggest of the three bias resistors, 82B on the diagram, is measuring about 156 ohms. The problem is, the circuit diagram says it's supposed to be 150, which is acceptable, while the parts list says it's 115, which means it needs replacing. It gets all the more complicated since the part number (33-115336) turns up in other manuals as a 1/2 watt 150 ohm, but a 2010 thread here seemed to conclude that 150 ohm, 2W was the right value so I'll assume the parts list is just wrong for now.
That's what I figured once I looked through it, thanks.
I got several of the high ones fixed today, particularly around the XXL tubes that I think are causing my problems and some around the detectors section. There are a few left I'll want to flip the chassis to get at easier but that should wait until I get the 10M that's arriving separately tomorrow. That one drifted up to 15M, which I think is the largest percentage I've seen as well as absolute value. There are others in the 20-35% range, but I'm only getting smaller than that when they're easy to get at right now. I don't have the steadiest hands and some of them I don't want to go after unless I have to.
Partial success! Once my last order arrived (late) I replaced all the resistors that were significantly above spec. Then had a loud hum because I got sloppy on something in the amp section I think but I got that fixed.
Reception is definitely improved on the upper part of the broadcast band, but not getting anything below 900 kHz or so. The relatively nearby stations on that end of the dial aren't as close which might be part of it, but there's a growing hum that peaks a little above the bottom of the dial. Don't get anything on the shortwave band, not that I know what to expect on those bands in 2026. There's at leasta little static here and there that I didn't before. Some hum at the low end there too, but a lot less pronounced than on broadcast.
Any advice on the next natural step of troubleshooting? Is it most likely an alignment thing, a tubes thing, something else?
Also, since I think I would like to add an aux in at some point, where would that insert on this one? I know the switch/input goes near the volume control but I'm not confident where.
Typically you disconnect cap 46 from the volume control with a switch then connect the aux input to the top of the volume control. Now you have the audio source either from the radio or the aux input. Sometimes it isn't that simple. You may have to disable the radio somehow when it's in aux mode.
You could try to align it. This will tell you if you have problems below 900kHz or you simply have nothing to receive.
A scope can tell you if your oscillator is still being an oscillator when your dial is set at 900kHz.
Some other folks like doing it difefrently.
Depends on the equipment you own, your age and the ability to bring a 50lbs generator to your working table
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
RodB: Thanks. I figured it was 46 or 51 but I really didn't know which.
morzh: I don't really have the equipment for alignment right now since this is outside my usual (old computer) tinkering space, but might be worth looking into in the future. But that's good to know.
Also I had more time to toy around with the radio when it wasn't after 1 am. While there's a hum at lower frequencies (peaking around 600 kHz), it seems to be noise rather than just not getting reception since I can still use the AM transmitter there and it displaces the hum. It just doesn't work as well as it does at higher frequencies.
So for now it seems to work as a radio and I can still route an MP3 player through it to get something other than talk and sports.
Edit: Okay, I realized I have a clock radio with AM to compare with and it gets hum at the same range so I guess there's just local interference. Guess it will be on to fixing the pilot lights.
(This post was last modified: 02-23-2026, 02:31 AM by RedRobot.)
Sorry, I should have suggested using another radio to compare reception. You could try to install an external antenna. There is a 3 pin jack on the back of the set. You can connect a ground to screw #3 on the antenna terminal and try connecting a "Long Wire" antenna to either of the 2 end holes of the jack. One of these holes connecs to Screw #4 of the antenna terminal strip. The other connects to the secondary of the antenna transformer. You can leave the internal antenna connected or disconnect, whether gives better reception.
+1 on the Aux input. Either break the connection between Cap #46 and the "end" of the Volume control, or (I think the netter spot), break the connection at the other end of Cap #46, (the junction between Cap #46, Resistor #47 and the Detector output of the IF transformer #42), connect cap #46 to the common terminal of a SPDT Single Pole Double Throw) switch, Resistor #47 and the detector output lead of the 2nd IF transformer #42 to one terminal, and the Aux terminal to the other terminal. See the drawing below:
In the above drawing, the "common" of the switch connects to point labeled "1" in red. This is the 0.01 uF cap # 46. One "leg" of the switch connects to point "2" indicated in red on the drawing, the junction of Resistor # 47 and the lead coming out of the IF transformer that carries the output of the detector. The other "leg" of the switch connects to the Aux Jack.. the other connection of the aux jack is connected to chassis ground.
There can be some blead-through of the radio signal when the aux input is used. To deal with this, either tune the radio to a quiet spot or use a DPDT (Double Pole Double Throw) switch where the output of the detector is shorted to ground when the switch is in the Aux position.
If your AM transmitter can be picked up below 900KHz and the dial of the radio indicates the frequency of the AM transmitter correctly, then the radio is likely mostly functional. There is a motherload of interference to the AM broadcast band from power line noise, CFL and LED lighting, computers, switching power supplies, automatic meter reading, the Internet of Things, etc., etc., etc. This set is supposed to have an internal antenna. If it is rotatable, rotate it to see if the signal is strengthened or noise is reduced. Make sure that you replaced the EMI Caps #85 with the correct safety caps. The hobby community refers to these caps as "Death Caps", as they often short, making the chassis hot, causing a shock or electrocution hazard.
Also check the continuity of the antenna leads, the antenna coil and clean the band switch.
You SHOULD be able to receive shortwave radio. However, such popular shortwave stations such as BBC, Vatican Radio, etc. have shut down their transmission to North America and moved to the internet. I don't know if 80, 40 and 20 meter HAM bands are still popular as opposed to 2 Meter (outside the range of this radio). There are a lot of religious and talk radio stations on shortwave right now, so you should find something. I believe that the WWV (US) and CHU (Canada) frequency and time stations should still be functional
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Thank you for the handy diagram, MrFixr55. Familiar enough spot since I just replaced all those components: I guess I'll just need to order the parts. I already replaced #85 with Y2 safety caps which I think is what's meant for that now.
I should have thought of the antenna idea. If I do a long wire, should it be directly connected to that jack? Looking it up I saw some old posts about how Philco used an antenna coupler that had some internal components (resistor, capacitors) on top of a switch, though the posts were old enough that the images diagramming it got eaten from their original hosting.
Gang, if anyone is following this thread, does anyone know the best way to connect a long wire antenna to this set? It has the 3 hole socket for a specialized Philco antenna, and a terminal strip for a built in antenna. 2 screws do correspond to 2 contacts on the external antenna plug. The 3rd contact does not route to the same spot that the built in antenna routes to. If anyone has info on the Philco external antenna for these sets, please post.
Thanks!!
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Another question is: would reception/clarity on a set like this improve if I replaced the cord (again) with three-prong grounded to the chassis? I should probably add a fuse anyway while I'm doing further tinkering.
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