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HT-45 tuning

Brian
 

Hello all.
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I am excited to have found this group. My callsign is W6BPT. I recently acquired a hallicrafters ht-45 loudenboomer. I did the initial tuning via the downloadable manual and the amp works great. My question to the forum is this:
Is there a writeup only on the tuning of the amp.?
I was hoping for something like this so when I go from 40 meters to 20 to 15 it would be a quick reference for quick tuning.
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Thank you and 73's
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Brian
 

Welcome to the group.
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I am not familiar with the Loudenboomer but, the settings of the amp would have to be determined experimentally since it is not or does not have a tuner or auto-tuner.? The quick reference would have to be made by you as you run low power and adjust the plate and load controls for peak output.? Then you can start an excel of word document to save the settings.? I have attached my setting document for my Ameritron amp to this posting as an example.
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Good luck with it.

K2WH

AL-800 Tune Settings for Voice Frequencies.docx
AL-800 Tune Settings for Voice Frequencies.docx
AL-800H Tune Settings for Digital.docx
AL-800H Tune Settings for Digital.docx

 

Hi Brian,
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Congratulations on your "new" amp!
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I have one of those!? Just tune it using a watt meter for max output!? Drive it with no more than 40-50W so as not to exceed max grid current.?
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You can peak "ballpark" plate and load settings by driving with very low power (5-10w) to get the approx settings, and then finish at (briefly) full output?
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Keep tuning sessions as short as possible when approaching high grid currents "single-tone" .?
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Expect to see color in the tube.? It's quite normal!
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I get around 500-600w out of mine with around 2700V on the plate.
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What are you driving it with?
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--
73/Rick
W7IMM
__________________________________
All posts are created using free and opensource? Linux
Brian
 

Thanks,
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I have a question. I just noticed that when I switch on the "fil" switch the "plate" and "filiments" lights both come on. If I switch the plate to "on" the light still stays on. Is this normal? If not what could be the issue?
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Thank you very much.
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73's and Semper Fi
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Brian (W6BPT)
 

Brian <1codetech@...> wrote
I have a question. I just noticed that when I switch on the "fil" switch the "plate" and "filiments" lights both come on. If I switch the plate to "on" the light still stays on. Is this normal? If not what could be the issue?
Hi, Brian

Does the HV power supply still use 866A or 3B28 rectifier tubes?
If a previous owner had changed to solid state rectifiers,
he would not need the heaters on, but plate voltage off preliminary
warm-up for the rectifier tubes before plate voltage is applied.
Hallicrafters says a 4 minute warm up is needed, Collins in the KWS-1
only used a 30 second warm up. You can ruin the rectifier tubes
if HV is applied immediately, because the mercury within the tube
needs preheating.

Is the DC Voltage still indicated on the HT-45 panel meter when the HV switch is off? If so, that's a problem. The "plate" indicator is a neon
lamp, so even a very high resistance path across the plate switch
contacts would be enough for it to light, without necessarily
passing enough current to turn on the relay in the HV supply.

Does the neon light in the HV power supply stay on when the HV switch is switched off? It should take a few minutes for it to go off completely,
as the bleeder resistors in the HV supply drain the capacitor.

The most likely failure is a that the plate switch of the HT-45 is stuck "on". That switch connects to the relay coil in the power supply,
which applies AC to the primary of the HV transformer.

I don't own an HT-45, I'm just going by the manual downloaded from BAMA.

73,
Ed Knobloch K4PF
Brian
 

Thank you very much for the reply. I will look at the switch. They are old. The original power supply for the HT-45 did not come with the AMP. The power supply that came with the amp has been converted to not use tubes. DC voltage is not present with the "filament" switch turned off but does show 2600 when the "filament" switch is turned on.
The amp does put out 500 watts with 45w from the exciter. I just do not want to damage the 400Z tube.
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Thank you always.
W6BPT
 

Brian,
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If the power supply is wired properly, as Ed indicated, the "PLATE" light will only illuminate when AC is provided to the HV relay.? (I.E. the PLATE switch is ON? and the FIL switch is ON)
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Also, if HV is available, the NE51 on the power supply box will only illuminate if actual HV is present
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The FIL switch provides AC to the Blower and filament transformer and to the HV SWITCH powering the HV relay in the power supply such that HV cannot be switched on unless the FIL switch is on.?
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The operator has to wait after powering the filaments so as to allow time for? mercury vapor rectifiers to heat (use 3B28's and the time is much less....and if you replace with solid state rectifiers, you essentially eliminate the need to wait at all.....the 3-400 like the 4-400 & 3-500 filaments are essentially "instant-ON" (R & L Drake applies FIL and HV simultaneously in the?? L-4/L-4B/L-7 amplfiers)
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But to your question, IF the HV "light" (on the power supply)? is illuminated with the HV switch OFF (after waiting for the filter cap to discharge) .....it would appear the HV switch is either staying closed or the relay contacts are "welded" --ON.?
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Note that the primary power is ALWAYS present at the relay regardless of switch position.? Closing the relay then applies power to the plate transformer.?
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When I rebuilt my power supply using the Drake L-4B transformer, I eliminated the rectifier filament transformer, the original plate transformer, oil cap and choke.? I used? pair of SEMTEC 5000V solid state rectifiers PLUS a (Harbach) filter-cap board for a Heathkit SB220.? I wired the entire mess similar to an L-4B using a voltage doubler.
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I also eliminated the relay and used a pair of solid state relays in each leg of? 240VAC? powering the transformer.
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I did however keep the HV "light" which only illuminates with HV present.? It's a great safety feature.
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Brian <1codetech@...> wrote
I have a question. I just noticed that when I switch on the "fil" switch the "plate" and "filiments" lights both come on. If I switch the plate to "on" the light still stays on. Is this normal? If not what could be the issue?
--
73/Rick
W7IMM
__________________________________
All posts are created using free and opensource? Linux
 

Brian, be careful working on this amp, those voltages in the amp can kill you !
--

K2WH

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