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Does anyone know of a mod to clean up the humm (sounds like AC). I have two of these amps. One has the new HV power supply board and the other has an old board. Both amps do very well. I have new tubes in one and the other has full output however there is a low level hum. Any suggestions.

Replace the large filter capacitors

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""""was not thinking of a cber sat with his makita screwdriver winding round the presets untill his meter said s9+60db from a guy on a handheld 15 miles away""""

one has a brand new HV board with new caps.

Check your exciter.
Rich

Every Dentron amp has built-in B.S.

Look at the schematic of the Clipperton. The filament is fed improperly. There isn't any centertap on the filament winding. Half of the filament AC will intermodulate the R.F. drive. That's why there is a hummm.
There are several cures. The one I like most is to add an additional transformer with a certertap and the CORRECT filament voltage, then set the bastard up like any other amplifier with centertapped filament iron.

This will not be noticed on ssb most of the time because of all the system distortion that has to be carefully overcome before a little bit of AC intermod gets noticed.

(Ever wonder why some of those fabulous old thingys aren't around any more? There's one reason. Then again, some of us old thingys just get better with age. A lot of this also has built-in B.S.)

if Im not mistaken those dentron amplifiers dont even have input tuning built in or some didnt anyways. We just talked about this on one of the other bands I was told heathkit was a better choice like the SB 200, SB 220 etc

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""""was not thinking of a cber sat with his makita screwdriver winding round the presets untill his meter said s9+60db from a guy on a handheld 15 miles away""""

Well the Dentron has twice the plate dissipation as an SB-200 and is isn't ugly green. The Dentron has consistent build quality. The Heath could have been built by someone with awful skillz.

The Heath tuned input is sure fine buisness compared to the imaginary one on many Dentrons. Back when the Dentron was designed most hammy hambone rigs had tube finals and would match the other than 50 ohm load. All the tuned input had to offer would have been lower intermodulation distortion. Harldy worth the parts cost in a cheesy machine.

It's all about the Cheeze Whizz.

they did produce a dentron match box - to give you tuned input. It matches the box. I think it is a good box - not going to totally trash it. Good power output. I just dont like the hum. sure it would be good on ssb. Im into audio quality so I have had some issues.

Those Dentron tuned inputs are not easy to find and they go for bug bux.

There are tuned input boards offered by at least one company. Probably better than the original.

I forgot to explain that many of those era Dentrons have waaaay too much filament voltage. Higher line voltages nowadays make it even worse.

An add-on filament transformer with an R.F. Parts CLxx current limiter thermistor in the primary will make yer tOObs live much longer. This will also kill the hummmmmmmm if hooked up properly.