Hamarlund Comet Pro Caps

[Carl WA1KPD]

Just checking against another set of minds. I am restoring a Comet Pro purchased at Nearfest. The IF section has several "caps in a can" that look like the first picture. The enclosed caps are outlined in yellow Comet Caps.jpg
 I am keeping the cans on top and replacing them. It makes sense that they should be done like the Comet Caps after .jpg, but welcome another set of eyes.

Thanks
Carl
/KPD

[Joe Connor]

Carl, I'm not sure I fully understand your question but here goes. The common connection for those three caps is the cathode, not ground. You can install replacements under the chassis because there is plenty of room under there. When I restored mine, I spent a fair amount of time studying the schematic to confirm how those caps were connected. In mine, they were all leaky so replacing them improved performance considerably. I believe that three of those cans contain three 0.1 mfd caps each but one contains only one cap (0.5 mfd).

The Comet Pro has a couple of bathtub caps that are easy to restuff. They don't have metal backs so you can simply heat them with a hair dryer or heat gun and the insides come out fairly easily.

When fully restored, the Comet Pro is a very good receiver. However, it takes a little while to get used to the tuning system. You have to remember that the people who used these sets when they were new had cut their teeth on the three-dial TRF receivers from the '20s so this tuning system wasn't foreign to them.

[Carl WA1KPD]

The common connection for those three caps is the cathode, not ground. 

When fully restored, the Comet Pro is a very good receiver. However, it takes a little while to get used to the tuning system. You have to remember that the people who used these sets when they were new had cut their teeth on the three-dial TRF receivers from the '20s so this tuning system wasn't foreign to them.

Hi Joe,
Thanks- You captured in words quite well and that is what I have done.  This has been an interesting restoration as it appears the radio was tinkered with when dog bone resistors were still around. There are wiring errors and wrong values all over the place. I don't mean the resistors have drifted up, I mean the resistors based on time appropriate color coding is off, and then usually drifted higher then the color code.
In addition things are just tacked togther, using solder ass glue. Now hI have seent htat in a Hammarlund HQ-120 I did so it may have been the practice.

Have restored and played with TRF's before so I am looking forward to this. It has been one of the bucket list radios I have always wanted.

The first PS choke is toast so I will replace that under the chassis with something appropriate and I need to locate a better match for the audio output. I may just use a 4K to 8 ohm transformer and leave the original as is. I am intriqued taht there is no volume control, just IF gain.
So far I have the audio amp, BFO and Osc all working. BFO turned into a real project as the variable cap inside the can was ruined so I had to replace that. But now I hear a good strong VFO signal in another reviver. Ditto for the Osc.

Speaker would be nice but I have never seen one for sle. It actually looks like a fairly easy one to HB

Thanks for the response and I will let you know how it all works out.
73
Carl
/KPD

[Joe Connor]

One solution for the audio-output issue is a Hallicrafters PM-23 speaker, which has a built-in 5,000/8 matching transformer. That works very well.

[Carl WA1KPD]

One solution for the audio-output issue is a Hallicrafters PM-23 speaker, which has a built-in 5,000/8 matching transformer. That works very well.

Sadly, I have owned about 4 of those over the years.. Current stock of course is zero..
Carl