Hallicrafters shortwave receiver

[Shadow7212]

I have a hallicrafters transistor (ca 1972) that only faintly receives strong signals throughout 120 to 11 meter bands. I suspect the rf transistor is damaged. Antenna coils seem ok, at least full continuity. Can anyone assist in tracking down the rf amplification circuitry. I have no schematics and have had no success finding any. Thanks

 

[K7MEM]

Specifically, what is the radio model number? Hallicrafters made a lot of different radios over the years. Depending on the model, your radio may, or may not, have a RF stage. Low cost radios didn't have a RF stage and fed the antenna directly into the first mixer. This usually makes for poor reception on any band higher than 40 Meters (7.0 MHz). Even radios with RF stages often had difficulty receiving anything near 11 Meters (27.0 MHz).

The fact that it receives something means that it is partially working and may have nothing to do with the RF stage. Part value drift over the years could mean that it's just badly misaligned. Shot gunning the parts isn't a good way of finding the problem.

 

[Shadow7212]

Specifically, what is the radio model number? Hallicrafters made a lot of different radios over the years. Depending on the model, your radio may, or may not, have a RF stage. Low cost radios didn't have a RF stage and fed the antenna directly into the first mixer. This usually makes for poor reception on any band higher than 40 Meters (7.0 MHz). Even radios with RF stages often had difficulty receiving anything near 11 Meters (27.0 MHz).

The fact that it receives something means that it is partially working and may have nothing to do with the RF stage. Part value drift over the years could mean that it's just badly misaligned. Shot gunning the parts isn't a good way of finding the problem.

This is an s-240. I used to pull in stations well with this radio, but I didn't mention that I'd direct connected a battery am transmitter kit directly to the antenna when I was a kid; never received well after that. I assume I burnt out something in the gain circuitry. I agree that shotgunning is not the best, but I do need to track this down. If I can't, is there an alternative such as a stand alone rf stage I could buy or build? Thanks

 

[K7MEM]

An external RF stage would be a bad idea. All that would do is overload you RF input circuitry. The S-240 seems to be sensitive to overload.

If you are really interested in making it all work again, you might was to get a copy of the S-240 Manual. It's about half way down the page and it's only $14. There is no guarantee that it will include a schematic. However, if you get it working well and decide to sell it, having a manual could increase it's value.

At this page there are a couple of YouTube videos on the S-240. I didn't go through them in detail but the owner of the videos may have a copy of the schematic he can send you.

Here are a couple of reviews for the S-240. The reviews set the production date to 1967 to 1971 (ham license: 1965; graduated HS:1967), which is a bit older than you thought. While the radio is entry level, it does get a pretty good review. I find it interesting that the reviews warn against a antenna that is longer then 10 feet. But that's only an issue when using the BFO.

It took a little hunting around but I did find a schematic for the S-240 at the RadioMuseum.org. I uploaded it to my web site so I could share it with you. The schematic appears to be nice and clear and has lots of voltage test points. Make sure you use a high impedance volt meter (e.g. VTVM) There are two other pages available that include a parts list, layout, and alignment instructions, but you should be able to get them yourself and maybe they are included in the $14 manual.

Looking over the schematic a bit shows me that there is a 2-transistor preamp (Q1 & Q2) built in, but it is for FM only. The short wave circuitry bypasses the preamp and goes directly into the mixer (Q3). If this transistor was damaged, you wouldn't hear anything.

But this brings up a possibility. Clean all of the switching with contact cleaner. Over the years, there can be lots of oxidation on the band switch. The oxidation can cause quite a lot of signal loss. And, the S-240 has a pretty sizable band switch. I use some cleaner that I got at Radio Shack many years ago, but you should be able to find some on Amazon. Like this WD-40 Specialist Contact Cleaner Spray. Someone my have a suggestion for an other type of cleaner.

Next, I would take a careful look at all the polarized capacitors (electrolytics). These capacitors tend to leak over time. The base of the electrolytic, where the leads come out, should be clean. If you see any type of buildup, replace it.

One thing you need to consider is the demise of short wave broadcasting. The short wave bands are not the same as they were in the 60s, 70s, and 80s. Most of the big signal short wave stations are gone. As a Novice ham our 40 Meter band allocations were shared with the international broadcast stations. So we had to operate alongside some pretty powerful stations, and not cause any interference. Things would get pretty crowded in the evening. But now, international broadcast stations are pretty scarce.

Overall, restoring a radio to like-new condition, takes a lot of work, time, and sometimes money. Good luck with your radio.

 

[Shadow7212]

An external RF stage would be a bad idea. All that would do is overload you RF input circuitry. The S-240 seems to be sensitive to overload.

If you are really interested in making it all work again, you might was to get a copy of the S-240 Manual. It's about half way down the page and it's only $14. There is no guarantee that it will include a schematic. However, if you get it working well and decide to sell it, having a manual could increase it's value.

At this page there are a couple of YouTube videos on the S-240. I didn't go through them in detail but the owner of the videos may have a copy of the schematic he can send you.

Here are a couple of reviews for the S-240. The reviews set the production date to 1967 to 1971 (ham license: 1965; graduated HS:1967), which is a bit older than you thought. While the radio is entry level, it does get a pretty good review. I find it interesting that the reviews warn against a antenna that is longer then 10 feet. But that's only an issue when using the BFO.

It took a little hunting around but I did find a schematic for the S-240 at the RadioMuseum.org. I uploaded it to my web site so I could share it with you. The schematic appears to be nice and clear and has lots of voltage test points. Make sure you use a high impedance volt meter (e.g. VTVM) There are two other pages available that include a parts list, layout, and alignment instructions, but you should be able to get them yourself and maybe they are included in the $14 manual.

Looking over the schematic a bit shows me that there is a 2-transistor preamp (Q1 & Q2) built in, but it is for FM only. The short wave circuitry bypasses the preamp and goes directly into the mixer (Q3). If this transistor was damaged, you wouldn't hear anything.

But this brings up a possibility. Clean all of the switching with contact cleaner. Over the years, there can be lots of oxidation on the band switch. The oxidation can cause quite a lot of signal loss. And, the S-240 has a pretty sizable band switch. I use some cleaner that I got at Radio Shack many years ago, but you should be able to find some on Amazon. Like this WD-40 Specialist Contact Cleaner Spray. Someone my have a suggestion for an other type of cleaner.

Next, I would take a careful look at all the polarized capacitors (electrolytics). These capacitors tend to leak over time. The base of the electrolytic, where the leads come out, should be clean. If you see any type of buildup, replace it.

One thing you need to consider is the demise of short wave broadcasting. The short wave bands are not the same as they were in the 60s, 70s, and 80s. Most of the big signal short wave stations are gone. As a Novice ham our 40 Meter band allocations were shared with the international broadcast stations. So we had to operate alongside some pretty powerful stations, and not cause any interference. Things would get pretty crowded in the evening. But now, international broadcast stations are pretty scarce.

Overall, restoring a radio to like-new condition, takes a lot of work, time, and sometimes money. Good luck with your radio.

Thank you for your helpful response. I fully understand the external RF amplification point regarding overpowering. I am a novice at circuit troubleshooting and repair, so your information is a blessing. I will start with your cleaning recommendatios and obtaining schematics. I am committed to doing whatever I can to repairing my radio, not just for nostalgic reasons but my pushback on the profusion of throwaway devices these days. I will follow up on the schematics and see what I can figure out. Probably the main challenge I face is determining what electrical values to expect for each component. Again, thank you for your interest in this project and your valuable advice!

 

[K7MEM]

I am committed to doing whatever I can to repairing my radio, not just for nostalgic reasons but my pushback on the profusion of throwaway devices these days.

I am partially with you on that. I don't think I have anything that is newer than 40 years old. I still have most of the equipment that I started with in 1965. In ham slang, the old stuff is referred to as "boat anchors". Although, most of the really old stuff just sits on a shelf. Probably my newest radio is a Icom IC-735. It's a simple all band (160 to 10 Meters), all mode (AM, FM, SSB, CW), 100 Watt output transceiver. As an antenna I have a 43' vertical with 16 - 32' radials, which is also good for 160 to 10 Meters.

Pushing back on the profusion of throwaway devices only goes so far. The problem with trying to fix the really old stuff is that most of the parts become unobtanium. You will find that out when you try to source the transistors for the S-240. Often, the original purpose of the equipment has disappeared. For example, I started with a Lafayette HE-30 receiver. To get on 2 Meters, I added a 2 Meter Nuvistor converter and used the transmit section of a Heathkit Twoer. I still have everything, but it was intended for "AM" operation. Since then, FM repeaters have taken over 2 Meters. It's hard enough to find any activity these days, let alone another AM station. But at the time, I had a great time and made hundreds of contacts.

Probably the main challenge I face is determining what electrical values to expect for each component.

If you look at the schematic, the expected voltages on all the transistors is listed. And, as I said before, be sure to use a high impedance volt meter, like a VTVM. Low impedance VOMs can load the circuit and cause incorrect readings. Of course, a oscilloscope would be preferred. It would also be beneficial to have a stable signal generator. But, you use whatever you have on hand. I still have the first VOM I ever bought. It only cost $5, new. It is only 1,000 Ohms/Volt, but it got me through the early days. Today, for only $7, you can go to Harbor Freight and get a Cen Tech 7-Function Digital Multimeter. Buy two, they're cheap.

Note that, the schematic says, all voltages are "negative" with respect to ground. So even though there is no negative sign on the schematic voltages, they will be negative with respect to ground. It is common for older transistor equipment to have the power supply "positive" output referenced to ground. You just have to adjust your thinking accordingly.

 

[Token]

Often, the original purpose of the equipment has disappeared. For example, I started with a Lafayette HE-30 receiver. To get on 2 Meters, I added a 2 Meter Nuvistor converter and used the transmit section of a Heathkit Twoer. I still have everything, but it was intended for "AM" operation. Since then, FM repeaters have taken over 2 Meters. It's hard enough to find any activity these days, let alone another AM station.

I still have an HE-30, and I have an unbuilt, NIB, Twoer. A few years back we used to do a regular AM roundtable on 2M here locally.

T!

 

[K7MEM]

For me, there is no such thing as "unbuilt" or "NIB". I built my Twoer when I was 17 years old, in 1968. I also have a first year Sixer (before they switched to the 8 MHz crystals). I was surprised that many of my contacts were teenagers just like me. Man, that was a long time ago.

A regular AM roundtable is great, but not enough activity for me to justify the whole setup any more. Back in the day (1968), the repeaters were not in the way and we ran on any frequency between 145 MHz and 146 MHz. I had a crystal for my Twoer that put me right on 146 MHz. It was the only crystal that I could afford. On the Twoer, I disabled receive by unplugging the receiver tube. I made a antenna switch over relay (RX/TX) and then connected the 2 Meter converter to the HE-30. I tapped into the Twoer's RX/TX switch to run the relay. The relay also muted the HE-30 during TX.

Yea, I still have my original HE-30. Plus, a parts doner without the case. They are actually two different versions of the HE-30. One has a VR tube and the other does not. When I was experimenting one time, I added a low voltage power supply and then replaced the RF Amp, Mixer, and HFO tubes with FETs. But I couldn't get the Q- Multiplier/BFO working with a FET, so I stopped there. I was surprised at how well it worked with the FETs.

 

[Token]

For me, there is no such thing as "unbuilt" or "NIB". I built my Twoer when I was 17 years old, in 1968. I also have a first year Sixer (before they switched to the 8 MHz crystals). I was surprised that many of my contacts were teenagers just like me. Man, that was a long time ago.

I have my original Twoer and Sixer, both of which I built in either the very late 60's or very early 70's. However this unbuilt Twoer is one I stumbled on at a garage sale a few years back. I have found a number of unbuilt Heathkit kits over the recent years, and I decided to acquire any I come across (assuming a reasonable price), adding them to my collection. I have a dozen or so unbuilt Heathkits, but they only remain unbuilt if I already have a built version of the same thing.

T!

 

[WA8ZTZ]

Still have my 1968 vintage Twoer... had been a SWL up until that time so it was my first ham rig.
Lots of local 2M AM activity around the Detroit area in the pre-FM days... made lots of contacts with it feeding a Halo antenna
on a tripod on the roof..
There was a guy a mile or two away supposedly running a KW with IIRC a 100' tower (any tower on a city lot looked 100'). When he transmitted, my Twoer heard him on all 4mc of the dial.
The solution was an Ameco converter kit that down converted 144-148 to 7-11 so as to be heard on my Heath GR-54 SWL RX.
So, fast forward a few years until after the Navy and everything had gone to FM. All that remains is the Twoer in a box around here
somewhere.

Anyway, good luck to the OP on the restoration of the Hallicrafters.