Hammarlund HQ-100 tubes aglow

The HQ-100 has some new Class X2/Y1 capacitors across the AC input, a polarized two-prong power cord, a new multi-section can capacitor from Hayseed Hamfest, and now three “new” tubes.

After spending a few days checking over things, I put the front panel and knobs back on, plugged the radio in and was greeted with some warm glowing lights.

The two lamps behind the frequency dial indicator both came on, and a nice warm red glow was coming from most of the tubes. Three of them (a 12AX7 and two 6BA6s) were dark though. Fortunately I had acquired all the tubes I needed for the HQ-100 at past hamfests. After replacing the three tube and applying power again, all the tubes were lighting up!

Replacement tubes lighting up

Next step will be to attach a speaker and antenna and see how well, if at all, the radio receives.

Hammarlund HQ-100

At long last, the Hammarlund HQ-100 I picked up a few years ago is finally getting some time and attention on the workbench.

Hammarlund HQ-100 receiver
Hammarlund HQ-100 receiver

After a bit of cleaning outside, it was time to dig in and see what was going on. Removing the knobs and four slightly rusty screws let me remove the front panel to see if the band spread tuning dial could be fixed.

Exposed tuning frequency indicator dials after removing the Hammarlund HQ-100 face plate
Exposed tuning frequency indicator dials after removing the Hammarlund HQ-100 face plate

Turns out the frequency indicator dials (the large white disks) are connected to the tuning dial knob by friction fit. Turning the knob makes the indicator dials turn, and the shaft those dials are attached to are connected to the variable capacitors that do the tuning. The band spread dial was free-spinning because there wasn’t enough friction between the indicator dial and the tuning knob. While I was trying to figure out how to fix it, I discovered the nut at the back end of the tuning shaft was loose, and tightening that up made the tuning knob work again.

The other big issue I came across while looking around was a burnt capacitor across the AC input.

Not a good thing to see. I clipped the toasted capacitor out as well as the old two-prong non-polarized plug. I’ll see about wiring in a new three-prong plug and maybe a fuse as well.

Haven’t seen any other obvious component issues yet. There’s a multi-section electrolytic can capacitor that probably should be replaced, but there aren’t any signs of leakage.