Re: HT-37 CW Break-In Modification
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Sorry for so long on the reply but a lot going on here.
Went back through all my notes on my HT-37 build (yes, did build one, another story). My only problem with my build occurred with original power supply problems which had increased the voltages to the VOX circuitry. After correcting those problems, the regular VOX worked as planned.
I did not have a need to try the breakin mod tho knew someone who I believe did with no problems.
Only suspect component I can see is C85, the .22 mfd. If it has gone leaky it would definitely shorten the circuit TC. Be sure your plate voltages meet spec as I have found at least here that Edison is closer to 130 which definitely raise transformer supplies.
Hope this helps, let me know.
73 ... Ed, WA9GQK
On Thursday, March 20, 2025 at 07:05:14 PM CDT, Alan via groups.io <alancgut@...> wrote:
Hi,
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I recently did the modification for break-in keying as shown in the Hallicrafters Information Bulletin.
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I used a separate 10M pot and mounted it in the 3/8” empty hole in the back of the chassis. I installed the 4.7M fixed resistor in series and I did remove the .005mf cap from pin #8 of SO8.
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The break-in function works as advertised - counterclockwise for shorter delays.
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However, I do have one issue in that the break-in function is always on. I can not return to normal manual CW operation by turning the pot maximum clockwise as stated.
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My 10M pot actually measured 8.6M so I tried going up to a 6.8M fixed resistor and that didn’t fix the issue. I also tried a 10M fixed resistor and still had the same issue.
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I also tried substituting the V14A VOX diode 6AL5 with 3 other spares that I had here and still had the issue.
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The copy of the bulletin that I have here has a sketch that shows someone using a fixed 22M resistor in place of the normal components resulting in a 2 second delay. I find that interesting in that 22M resistance is certainly beyond the factory’s full clockwise “return to normal manual CW operation” resistance.
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Has anyone here successfully performed this modification and had if perform as described in the bulletin? Maybe I’m missing something, so I thought I’d ask here.
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Regards, Alan, W9CG
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