From the Eham web site -

The HW-16 is not a transciever except in name only.
It is a separate transmitter and receiver housed in a single cabinet which happens to use the same power supply.
Which leads to another note... the HW-16 uses an integral power supply on the chassis.
You don't need to possess or go looking for one of the HP supplies to run it.
The HW-16 accomodated a grid-keyed VFO via connectors on the rear panel. Heathkit recommended the HG-10 VFO, which was "rig ready" for the HW-16, DX-60 and others. You could also use the older Heath VF-1 VFO (from the AT-1 transmitter days) after converting it from cathode-keying to grid-block keying. If you hear a VFO-equipped HW-16 on the air today, it's almost always going to be one of these two VFO's that are powering it.
If you get a run-of-the-mill HW-16 today, you've got some work to do in order to get on the air, and you need to be savvy with electronic repair, or have a good friend who is.

First, the filter capactitors are almost certainly on the brink of destruction. You may get some hum in the receiver... you will get a LOT of hum on the transmitted tone. And, if you keep the rig powered up without replacing the capacitors right away one will do the Pop'n Smoke Boogey right in your face. It may take a few hours after powerup, but it will happen and leave a very oily mess to clean up to say nothing of the stink and the wife's nagging.

There are three "cans", an aluminum one and two black "cardboard" ones. The first one to go "POP" is the cardboard one nearest the front panel. The other paper capacitor will follow in time. So, you've got to replace these three capacitors as a minimum.

Get the construction manual and do whatever voltage/resistance checks you can. You'll have some resistors which have changed value and which must be replaced, any you may find a leaky AC cap here or there.

Of course check the tubes. If you can't check 'em, then do substitution checks. If you plan on keeping and using the HW-16 you'll need to stock up on some replacement tubes.

Sidetone. The HW-16 uses the infamous neon relaxation sidetone oscillator. It growls rather than beep when you key the transmitter... some rigs more than others. One cure - the one I use - is to snip out the neon bulb and partially unmute the receiver during transmit. This allows you to hear your transmitted signal as well. If you want to keep the thing original, there's a wealth of information on the Web about Heathkit's idea of a sidetone.

Replacing the filter capacitors should eliminate any hum in your signal, and it may/may not eliminate the chirp. I would expect a small amount of chirp in this HW-16's signal anyway. Some HW-16's have more chirp than others and despite much discussion on the subject I still don't know exactly why.

There are some modifications on the Internet which claim to eliminate chirp by powering the oscillator from the receiver's share of the power supply instead of the higher powered transmit side, and/or using an 0A2/0B2 voltage regulator tube on the power line.

There are a load of mods for this rig. Be careful when using them. I've tried them all. Some mods don't work at all, others work/don't work and induce entirely new problems.

No SSB RX due to the CW filter only. The side tone was disgusting. The neon relaxation oscillator was horrid. It did not have a loading control in the pi network so impedance matching was limited to 50 ohms.

For modern use there are also several things not so good about it. The compactron tv sweep tube in the final must be hard to find now. It was Xtal controlled so you need a VFO for modern use.