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Title: Heathkit HR-10B Help Post by: wa3qns on February 13, 2016, 12:02:12 AM I Recently Picked up a pretty clean Heathkit HR-10B and believe it would be
a reasonable improvement to replace the 6X4 with diodes. Maybe it would reduce the drift and at a minimum it will reduce the xformer load a bit. Not being a very good tech type even though I have built lots of kits I would appreciate if someone would modify the schematic so that I know exactly how to get those diodes in the right place. The next step would be adding a VR tube but one small step at a time. Tnx Joe Title: Re: Heathkit HR-10B Help Post by: KA2DZT on February 13, 2016, 12:34:39 AM Joe,
Each diode is connected to the cathode (pin 7) The cathode on the SS diode is the end with the line. So, you have one diode connected from pin 1 to pin 7 and the second diode connected from pin 6 to pin 7. Again, the ends that are connected to pin 7 are the ends with the line on the body of the diode. Adding a VR tube will be more involved. Which of the three voltages do you want the VR tube. VR tubes come in 150 volts, 105 volts and 75 volts. I have to recheck the voltages, not sure about the 105 volt type. Problem with VR tubes is that you can not add one in your filter circuit. A VR tube has to have a series dropping resistor off some higher voltage source. The value of the dropping resistor is somewhat critical. After the VR tube you can not have any filter caps. Usually the max capacitance on the VR tube is only about .05ufd. So you can see why you can not add one in the filter circuit chain. Fred Title: Re: Heathkit HR-10B Help Post by: wa3qns on February 13, 2016, 12:52:09 AM Thanks Fred but I just read this because I do not
have a compelling reason to do this, it is not worth the trouble AND possible consequences. Joe http://www.dairiki.org/HammondWiki/SolidStateRectifiers Title: Re: Heathkit HR-10B Help Post by: K4RT on February 13, 2016, 07:37:01 AM Joe, how long does it take the VFO to stabilize? Is your HR-10B paired with a particular transmitter?
That article contains good advice. I also use the "compelling reason" standard in considering design changes. Title: Re: Heathkit HR-10B Help Post by: VE3LYX on February 13, 2016, 08:18:03 AM I doubt that would be an improvement. I can't for the life of me imagine what you would gain. And it might be noisier as SS rectifiers often can be. I have a HR10B used with my DX60B. VFO drift is not a problem however it is not a receiver I am in love with. I own it because it matches. No other reason.
donVE3LYX Title: Re: Heathkit HR-10B Help Post by: w4bfs on February 13, 2016, 04:04:09 PM I don't like 6X4 rectumblasters ! .... very often the oxide fails between the filament and cathode and it shorts .... if you have an unprotected power supply, you often lose the power transformer .... if you must use, be certain about protection !!! (sounds like gi training film)
Title: Re: Heathkit HR-10B Help Post by: KZ5A on February 16, 2016, 04:21:41 PM I've done something like this before. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
Replacing the 6X4 with silicon diodes is just the start. The rest of the mod is to reuse the 6X4's socket to support a 0A2 (150V) regulator tube and dropping resistor. Feed everything except the audio amp from the regulated B+. This easy mod resolves a number of problems with the HR-10B. It's been a while and I don't remember the value of the dropping R but seems like it was around 2K at 5W. 73 Jack KZ5A |