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Author Topic: Heathkit HR-10B HELP  (Read 1035 times)
DL3NT
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Posts: 3




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« on: May 15, 2005, 04:33:05 AM »

Hi eHam Community,
I have a Heathkit HR-10 on the bench which gets very hot around the 6EB8 audio amp tube. It starts to smell like heat in about 1 minute. The voltages out of the 6X4 rectifier are also slightly higher than what is shown in the schematic.
C57: 214 instead of 210
C56: 158 instead of 125
C55: 144 instead of 115
The device receives a little and tunes down the bands.
Is this heat normal? The 6EB8 gets much hotter than the others. I only have the schematic and 3 pages of incomplete alignment instructions.
Also, can someone tell me where Lug 1 of terminal strip Q is? This needs to get jumpered for an alignment. Since I don't have a complete manual, I cannot locate or align the device.
Does someone have the possiblity of sending me this info electronically?

Thanks for any replies.
Hans  DL3NT@darc.de
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KA5N
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Posts: 4380




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« Reply #1 on: May 15, 2005, 05:50:51 AM »

The audio output tube comsumes more power than any of the other tubes so it will run hotter.  Check R35 and C36 at the cathode of the 6EB6 as they control the tubes disapation.  Also check C38 the audio coupling capacitor for leakage (if this is a paper cap it is probably a good idea to replace it anyway) as this will cause the grid to run positive and the tube will really heat up.
As a youngster back in the tube era I worked on TV sets and handled so many hot tubes that my fingers became toughtened and calibrated.  If it was too hot to pull out, something was wrong (except for the high voltage tubes which ran just below the melting point of glass or so it seemed).
ALLEN
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DL3NT
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Posts: 3




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« Reply #2 on: May 18, 2005, 12:11:58 PM »

Hi Allen,

Thank you very much for your response. I have checked these parts and they are ok. The tube gets too hot to touch inside of a minute. The others are warm as they would feel normal. Yeah, those tubes back then... They got hot and yes, you get used to it after a while. But, this one...? Well, maybe it's normal. I'm going to try using a variable Xfmr to reduce the input voltage at the mains and see what that does. I'm missing page 33 of the alignment procedure. Do you have this page? Or, maybe someone has this avail and can Tx it to me.
Thanks in advance.

73! Hans DL3NT
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KA5N
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Posts: 4380




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« Reply #3 on: May 18, 2005, 04:30:39 PM »

You can download the manual at

http://bama.edebris.com/manuals/

You may have to download a reader program (djvu) but both are free of charge.

Some tubes just run hot.  If I suspect a problem I turn the gear on and turn the lights off and look for a red glow on the plates.  If there is much color (and you already checked the components I indicated) the screen grid voltage may be too high.  In older units the resistors may have changed resistance either higher or lower.
good luck Allen
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DL3NT
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Posts: 3




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« Reply #4 on: May 21, 2005, 01:09:30 PM »

Hi Allen,

Thanks for the Info. I've got the manual from BAMA already, but it's missing page 33 of the alignment. What's on the page, I have no idea. According to the table of contents, it's the final assembly and connection. But, it also contains the last steps in the alignment procedure. You know, all those resisitor values in question are about 10 to 12 percent higher than they should be. I'll have to replace them and while I'm at it, I'll replace a few caps as well. Still haven't been able to check it with the variable Xfmr though. Was on business this week, so didn't get around to it.

73! Hans
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KA5N
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« Reply #5 on: May 21, 2005, 07:21:27 PM »

Remember that most of the resistors in older Heath stuff are probably 10% tolerance to begin with.  Also the average AC line voltage in the U.S.(called by the English: mains,and the French: sector)was 110 VAC back in the 1950's, 1960's and early 1970's and are now more like 125 VAC in the U.S. so your power supply voltages may well be higher than listed  depending on your input voltages.  
Alignment on simple receivers consists of aligning the IF's so that all stages are peaked at the same(probably 455 kHz) frequency and the local oscillator is adjusted to match the dial indicated frequencies and the RF amplifier stage is peaked for each band.
Good luck Allen
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W9GB
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Posts: 2626




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« Reply #6 on: May 26, 2005, 11:21:32 AM »

The IF for the HR-10B is about 1681 kHz (half lattice crystals are in back (middle).  This was the first receiver that I built in 1972.

w9gb
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