My name is Dave and I am new to this forum and vintage radio restoration. I recently picked up a 37-604 and recapped it and replaced the resistors. However, when I powered it up I only got a slightly audible hum from the speaker. I touched the middle tab on the volume control with a screw driver and got a little louder hum. The BC resistor, which is rated at 133 ohms and 15 ohms, got incredibly hot just after a few seconds. I replaced it with a 20 ohm and 180 ohm power resistor on a terminal strip and that, too, got incredibly hot very quickly. I poked around but did not see any broken or otherwise bad wires and that's were my lack of knowledge and experience left me stumped.
Does anyone have any advice they can share with this newbie?
Hi Dave, Welcome to the Phorum. I'm probably not the guy to help diagnose your problem but there are some pretty knowledgeable folks on here who can help. When asking for help on a radio it helps to post a link to the schematic. Unfortunately I see the 37-604 does not show up in the Nostalgiaair schematics. Do you have a schematic and if so I suggest posting a link to it or including it as a picture image in a post. That's a neat looking radio!
If you don't have a schematic then you can get some good clear copies from Chuck Schwark for only a few bucks.
Thanks for the replies. Yes, it is a neet radio and I hope to get it working. I'll check the schematics I got and see if I wired it up correctly. Maybe I have the wrong resistor ohms and am dropping too much voltage some where along the line which is why I only get a slight hum from the speaker. When I first recapped it and added new resistors, I put a couple in series rather than parallel and was able to get a couple stations. When I fixed them, the radio went silent. That's one reason I thought the bc resistor was bad or went bad.
As for the value, you should be dropping 51V at 120VAC input or 46V at 115V AC which is easily calculated by dividing these values by 0.3A which gives you 153 Ohm (about 140-145 in the sch considering the lamps) at 115V or 170 Ohm at 120V.
Here's a dumb question. How do I meaure the plate and screen voltages on tubes 6A8G and 6K7G? Also, I carelessly broke one of the lugs on the brodcast antenna transformer. I think I am able to rewind it if this is something that's repirable or, better yet, can I get a replacement part number 32-2141?
I don't believe anyone makes a replacement for your transformer. The transformers in old radios are often referred to as unobtainium. Always be careful when working around one.
You can try to get a replacement off of eBay, or by posting an ad in the "Wanted Ads" section of the Phorum. You might also search for a donor chassis of the same type in order to retrieve the part you need.
It might also be possible to repair your transformer by replacing the broken lug. Might not look perfect, but if you can make it work electrically, you're probably good to go.
Hi Dave
B- on your set would be at the off/on switch.
Connect the - lead to it and the + to the pin
that is to be measured. With modern meters
the measured voltage will read a bit higher
than what is listed. They don't load the
circuit down as much as the older ones.
As my neighbor Jon said be really carefully
working on these old guys this isn't 1938
anymore and the the 604/37-604 are kinda
rare/collectable because of there unusual
styling so finding a parts set may be difficult
and expensive. Last one I saw in good shape
was about $200.
I've got a 37-604 that I picked up on Epay
a while back. Great playing set with good
sensitivity on both BC and SW bands. The
only problem I have with it is I don't have
enough time to listen to it as much as I'd like!
Love the dial pointer.
GL w/it
Terry
Got it working and refinished the wood but it still needs a new dial and grommets. It might need a new antenna wire, too, because it only gets a few stations but those it does get come in nice and loud.
I'm not quite sure what the problem was. I went back and put in another set of capacitors and 1 watt resistors and it worked. The antenna transformer had a broken wire that was soldered to the mounting lug so I soldered a new wire from the broken part to the lug which seemed to fix the a lot of the reception.
One last question about the antenna. What type of wire is good to use and how long should it be (without running it up a tree in my yard)?
Thanks to all of you for your help and I look forward to working on another.
Congrats on getting the set working. There is nothing special about an antenna. The longer and higher you get it (within limits), the better your reception will be. Also, the wire should be oriented horizontally.
I listen to most of my radios in an upstairs bedroom of my house. Last year I strung a wire up to the attic. About 40 to 50 feet total (30-35 of which is horizontal). Get good reception with it. I also have about a 15 foot antenna that I use in my basement workshop. Reception is decent with just that.
What you will probably end up with really depends on whether you (or your wife) wants a wire strung through the house;)
Also, be extremely careful if you intend to string an antenna outside. Such an antenna can be a hazard for a couple of reasons (lightning, and if it comes in contact with power company wires).
Good luck,
Jon
(This post was last modified: 11-21-2014, 10:51 AM by PAradiogeek.)
