If you're a 1970s-vintage ham, there's a good chance you got your start on HF with a Heathkit HW-16 novice rig. WBBVGE not only stokes the fires of your memory, he shows you how to restore one of these classics to put on the air today.

Keeping the Green Flame Burning

BY MIKE BRYCE, WB8VGE
955 Manchester Avenue South
North Lawrence, OH 44666

e-mail: <prosolar@sssnet.com>

Part I - Restoring an HW-16.

Heathkit. The name alone triggers smiles and sparks memories. When Heathkit was producing electronic kits, many hams got their start in amateur radio via Heathkit gear. Even today, it's hard to find a ham who has never owned or operated a piece of Heathkit equipment. In occasional articles over the next several months, I'll take a close look at some of the classic Heathkit radios. I'll show you some simple repairs and a few modifications along the way. In the process, I hope this series will inspire youto take a closer look at ham radio's living legend-Heathkit. We will start out with one of the most popular transceivers ever sold to get new Novices on the air - the famous Heathkit HW-16.

The Heathkit HW-16 is a handsome table top unit that was very easy to build and simple to operate. The transceiver was designed with the Novice ham operator in mind, but could easily be updated when you got your General class license. The HW-16 is a CW-only rig, designed to operate on crystal-control transmit, although you could add the matching HG-10B VFO. This reflected the license privileges of the time. Novice stations could operate only CW, at no more than 75 watts, and had to be crystal-controlled! Only after you got your General class or higher license were you allowed to have a VFO and/or use phone.



Likewise, the HW-16 operated only on 80, 40, and 15 meters, the three most popular Novice bands (the only other Novice allocation at the time was on 10 meters).

The HW-16 transmitter uses 80 meter crystals for the 80 and 40 meter bands and 40 meter crystals for the 40 and 15 meter bands. Input power to the final amplifier is adjustable from 50 to 90 watts, with a mark on the meter face that represents the maximum Novice input power of 75 watts. The transmitter uses grid-block keying, and all three stages of the transmitter are keyed. Designed with simplicity in mind, the only control you need to tune is a single knob that sets both the transmitter and receiver.

The receiver is based on a superhet design, is VFO controlled, and covers the lower 250 kHz of the 80, 40, and 15 meter bands. High selectivity is possible due to the 500 Hz crystal filter. The receiver will easily drive a speaker to room-filling volume. Receiver sensitivity is excellent.

The receiver is automatically muted each time the key is depressed, providing full break-in operation. Think about that. The HW-16 uses full QSK! I find this amazing, considering the age of the rig. The QSK is silent and works perfectly. There's no need for an external antenna relay. The HW-16 also provides its own sidetone.

The HW-16 came out just as solid-state technology was beginning to work its way into amateur equipment, and it contains one -just one- transistor. A complement of nine electron tubes rounds out the HW-16. The final PA (power amplifier) tube is a 6GE5 Compactron. An internal high-voltage supply provides all the necessary voltages. A new HW-16 ran about $150 in the early 1970s. It was discontinued by Heathkit in the mid-70s.

An HW-16 is by no means a rare find. They are everywhere. Any good-size hamfest should produce a handful of them, many with the matching HG-10B VFO. Plus, on any given day on the internet, E-Bay has several up for bid. Depending on condition and whether the rig has any accessories, plan on spending anywhere from $35 to about $100 for an HW-16. The HG-10B VFO should run you another $45 to $150 or so, again depending on condition and whether the unit comes with the manuals.

Having manuals is very important, as it's highly unlikely that you'll find an HW- 16, as is, in perfect operating condition. Repairing a radio as old as some of these Heathkits often requires hunting down the manuals and schematics. There are several individuals and companies that offer manuals for discontinued radios (I'll try to list them in the next installment.), but believe it or not, you can still get manuals and schematics for the HW-16 from Heathkit! Just call the number listed in "Resources" and they will supply you with a condensed manual consisting of alignment and schematics for not only the HW-16, but for just about any piece of gear Heathkit ever made.

In today'sworld of microprocessors and surface-mount components, working on a vintage Heathkit has an odd feel as you work with vacuum tubes and discrete components.



First of all, you'll need to arm yourself with a different set of tools than you normally would use. Most of the components in this vintage gear are mounted to tie strips. To remove them, you'll need at least a 45 watt soldering iron. A soldering "gun" will also work. Along with the soldering iron, you'll need some desoldering braid. Get the widest width you can. A wide braid will suck up much more solder than the thinner stuff. This is important, because the less time you spend on the connections, the less likely it will be that the components are damaged by excess heat.

You'll also need a pair of long needlenose pliers and a few rubber bands, to be used as a heatsink. The rubber bands hold the pliers together. Clip this onto the leads of components you are removing from a tie strip. This pliers will soak up the heat, preventing damage to the part. Pick up a good VTVM (Vacuum Tube Volt Meter)-a Heathkit, of course-to use in troubleshooting. While the digital ones are slick, many of the alignment steps require peaking a signal for maximum reading on a VTVM. Of course, your digital meter will work, but I find using the analog VTVM much easier.

My HW-16 is kind of rare. I purchased it from a gentleman whose dad had built the rig. Well, dad lost interest and the HW-16 was never completed! It sat unfinished on a basement shelf for nearly 30 years. To say that the front and case were "mint' would be an understatement. On the other hand, because the radio had been sitting in storage for so long, the odds of it working were kind of slim.

On a radio this old, it's good practice to use a Variac transformer and slowly increase the supply voltage. That way, you can get the capacitors in the power supply to reform slowly. It also reduces the initial shock of having full power applied after sitting dormant all these years. But, alas, I did not use the Variac this time. I plugged the power cord directly into the 110 VAC socket. I flipped the switch and the soft glow of the tubes greeted me-at least for a few seconds.

After a few minutes I could smell the distinct odor of frying capacitors. A moment later and I was greeted with fingers of white smoke venting from one of the large twist-lock electrolytic capacitors. Now any sane person would have yanked out the power cord or at least flipped oft the power switch. Nope, not me. I was a driven man! It had been a long time since I'd smelled capacitor smoke, so I just sat and watched until the smoke stopped. A few seconds later the smoke detector in the house tripped!

The HW-16 is an unusual radio to work on. It's a mix of point-to-point wiring with chassis-mounted tubes and a large printed-circuit board thrown in for good measure. The entire receiver, including the receiver's VFO, is mounted on the PC board. However, the transmitter section is all point-to-point wiring. The HW-16 has a high-voltage power supply that runs the tubes as well as a bias supply for the transmitter. There's also low- voltage AC for the tube filaments. The power supply is all solid state and is located in the lower part of the chassis. It too is wired point-to-point. The high-voltage section of the power supply uses a string of voltage dividers to generate the necessary voltages required by the receiver and transmitter. High-wattage, low-ohm resistors make up these dividers.

The capacitor that failed (remember the smoke?) was in the power supply. That's simple enough. The cap was not formed or had simply dried out. Now, finding a replacement capacitor for a radio that is 30 years old is not so simple. In fact, I could not find one anywhere. (Later on I did find a supply of twist electrolytic caps. They are available from Surplus Sales of Nebraska, contact info in "Resources." The going price for one is about $24.) Thus, I chose an NEC replacement part instead. The only trouble was that the new part was not a drop-in replacement for the old cap. The old cap was about the size of a tube; the new part was one tenth the size. Luckily, the old cap was a twist mount, which mounted to a tube socket. (NØJMY note: the author says "tube" socket, but really means "twist-lock wafer"). The new cap, while much smaller, fit right on the socket and was held in place by a glob of RTV cement.

After the new part was installed, it was time to try the smoke test once more. This time, no smoke, but the capacitor I had just installed got very hot and started making noise. Now I studied "broke" in high school, and I knew that resistors get hot; capacitors do not. The new capacitor was 40 mF at 450 volts DC. The old one had a rating of 43 mF at 350 volts (NØJMY note: actually 50 mF at 350 v.d.c., with some originals actually stamped 400 v.d.c.) . With my DVM, I found 680 volts on the capacitor. Well, that explained the smoke.

Clearly, the high voltage was, in fact, too high. I also noticed, before my replacement cap got too hot, that there was no B+ voltage on the receiver. Both of these voltages are generated by a voltage divider. These resistors generate the necessary voltages for the various stages of the rig. With the plate voltage for the transmitter way too high and the receiver B+ non-existent, I deduced one of the resistors in the voltage divider must be open or way out of spec.

Here's why the old cap smoked: Resistor R205 (if you happen to have an HW-16 schematic handy) had changed its value from 330 ohms to over 100K. In effect, there was no voltage divider at work. Result: Too much voltage was sent to the capacitor, and virtually none was sent to the receiver. That's why there was no B+ there. The fix is simple enough-replace the resistor. But instead of just replacing the 5 watt resistor, I put in a 7 watt device. Mouser Electronics (see "Resources' handles high-wattage, low-value resistors. I ordered a few extra, just for my junk box. As it turned out, after talking with other hams using the HW-16, that resistor seems to go bad quite often. It's a good place to look for trouble if you're working on an HW-16.

While you have the covers off the radio you might as well check all the resistors in the high-voltage power supply. Also, while you're at it, check the 22k resistor between location "G" on the PC board and lug 2 of L3. This resistor tends to overheat. Replace with a high wattage resistor of the same value.

Tube sockets, especially the ones on the PC board, have a tendency to corrode. Pop out each tube and clean the sockets with a toothbrush dipped in a bit of alcohol. Don't use WD40 or any other solvent that contains oil. This stuff will come back and bite you later on.

If your HW-16 has been in storage a while, check to see if all the tubes are in fact in their correct locations. Sometimes the tubes fall out and are put back into whatever socket they fit. Also check to see if the electrolytic capacitors in the power supply have a powderlike fuzz on their bottoms. If they do, then the caps will have to be replaced. Check the electrolytic capacitors on the PC board, too. If they're growing hair, then replace them.

Today you just can't drive to the local drug store and get your tubes tested. I don't have a tube tester either, so I swap out suspect tubes with known good ones. If you are going to be working on vintage tube gear, you'd better start collecting spare tubes. I find hamfests are a good source. If you can't make the hamfests, then Surplus Sales of Nebraska has tubes, as does Antique Electronic Supply.

Check for B+ at the plates of all the tubes. Often, resistors on the PC board feeding one or more tubes may be open. Also, check for open cathode resistors if you have oscillation in the first mixer.

If the receiver breaks into oscillation at audio frequencies, check the two wires coming from the audio output transformer. Make sure the wires are pressed down against the chassis as tightly as possible. Never operate the HW-16 without a speaker connected. Doing so may damage the output transformer or audio driver tube.

While the HW-16 is called a transceiver, it is really a transmitter/receiver. The only thing in common between the two is the power supply and T/R switching (NØJMY note: and the pi-network output/input) If the receiver is working, but the transmitter is dead, there's no need to

dig into the receiver PC board.

Once you have everything working, the HW-16 is very simple to use. If you are going to use crystal control, you plug your favorite crystal into one of the two sockets on the front panel. A peak of the "tune" control adjusts the final tuning as well as the receiver front end. Key the rig, and you're on the air!

The HW-16 is really at home on 80 and 40 meters. It can hold its own on those bands even today. On 15 meters, the receiver is not as sensitive as some of the state-of-the art radios we have today. Generally, though, if you can hear a signal on 15, you will be able to work the station. The transmitter produces up to 45 watts output on 80 meters. On 15 the power is lower. The Compactron sweep tube in the final is quite robust. With the output resonant, the tube will last a long time.

I hope you have enjoyed this look at the HW-16. If you do, please let me know. If you would like to see a specific Heathkit featured in this series, by all means contact me, too. If it's doable,we'll give it a shot. Next time we meet, I'll take on one of the most popular single-sideband radios ever made in kit form-the Heathkit HW-101, or as it was known to a generation of hams, the "Hot Water 101."

73, and keep the green flame burning!

Resources

For a schematic and alignment instructions for the HW-16, call Heathkit at(616) 925-5899.
Replacement parts for this and other vintage radios are available from the following:
Antique Electronic Supply, 6221 S. Maple Ave., Tempe, AZ 85283 (phone 800- 706-6789; fax 602-820-4643).
Mouser Electronics, 958 N. Main St., Mansfield, TX 76063 (phone 800- 346-6873; fax 817-483-7011; e-mail: <sales@mouser. com>; web: <www.mouser.com> .
Surplus Sales of Nebraska, 1502 Jones St., Omaha, NE 68102 (phone 402-346-4750;
fax 402-346-2939).

December2000 . CQ