[Hammarlund] HQ-180 hum in CW mode

[Charles Ochs]

Sounds to me that you are "closing in" on the problem. A failing filter cap will often be more audible as the 60 HZ content of the B+ will beat against the steady tone of a CW signal.Troubleshooting should ALWAYS start with the power supply. Can capacitors should ALWAYS be considered "suspects" and must be carefully eliminated before proceeding onward to other things. Without a healthy power supply, the radio can not be expected to operate properly.Given the age of the HQ-180, it should be assumed that if these caps are not bad now, they will be shortly--so just replace them. The preferred method--used by all "professional" re-builders, is to remove the can, and re-stuff it with individual electrolytics. This is tricky surgery but will result in a receiver that both works properly, as well as preserving original under-chassis appearance.If you don't care about appearance, or future resale value, you can always cobble in some clutter of terminal strips and individual electrolytics. This is up to you. In either case, you will have eliminated one of the main trouble spots.