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My HT-45 HP-45 project.

 
Edited

I mentioned this in Rick's thread about his new power supply. /g/HallicraftersRadios/topic/ht45_loudenboomer_working_now/106322290

So far I've:
Replaced a resistor in and verified PS operation, with ~24 V on the transformer primary and 110k load, makes ~750 V. This translated to 3750 V with 120 V input.When connected to the amp and with the tube drawing 120 mA per design, modeling, with the Duncan Amps PUS Designer II, shows the specified ~3000 V.
Replaced the open Ig and Ip metering resistors.
Added a protection diode for the meter.

Hopeful for today.
Get it dusted out. Gotta buy a new dust brush. Grandkids made off with mine.
Temporarily wire RF deck AC separately to run heater and blower.??
Run HV off a variac with the tube biased to conduct at low voltage and run the anode red-orange for a while.

In time, I'll hook the nano VNA up and see how input and output look over 3.5-30 MHz range. It will be nice to learn if the amp is OK for any of the WARC bands.?

Photos: I have all the covers, screws, etc.
Note the Jones plug on the RF deck power cable. 3 kV @ 330 mA goes through this connector. Pins are on the cold end.
 
Edited

Looks great. Did you add the heat sinks to the transformer? It's a nice job.

Nice looking amp!
John

On Wed, Jun 26, 2024, 1:04 PM Bob ah7i via <katz.ajamas=[email protected]> wrote:
I mentioned this in Rick's thread about his new power supply. /g/HallicraftersRadios/topic/ht45_loudenboomer_working_now/106322290

So far I've:
Replaced a resistor in and verified PS operation, with ~24 V on the transformer primary and 110k load, makes ~750 V. This translated to 3750 V with 120 V input.When connected to the amp and with the tube drawing 120 mA per design, modeling, with the Duncan Amps PUS Designer II, shows the specified ~3000 V.
Replaced the open Ig and Ip metering resistors.
Added a protection diode for the meter.

Hopeful for today.
Get it dusted out. Gotta buy a new dust brush. Grandkids made off with mine.
Temporarily wire RF deck AC separately to run heater and blower.??
Run HV off a variac with the tube biased to conduct at low voltage and run the anode red-orange for a while.

In time, I'll hook the nano VNA up and see how input and output look over 3.5-30 MHz range. It will be nice to learn if the amp is OK for any of the WARC bands.?

Photos: I have all the covers, screws, etc.
Note the Jones plug on the RF deck power cable. 3 kV @ 330 mA goes through this connector. Pins are on the cold end.
 
Edited

Hi John.

That's the factory supply and original transformer. It came with fins! You can see them in the manual photos.
Somewhere along the line, the 866As were replaced by a pair of solid state rectifiers.

I fired it up today. Initially ran 120V to 240V wired HV transformer. No smoke or bang. Swapped wires and still no smoke or bang.
With grid grounded, there's a pleasant glow from the anode.? Meter reads ~2800 V and ~85 mA. Misplaced my HV probe so
verification will have to wait a bit until it's found.?

Will apply drive later today or Saturday. Have to clear space on the bench first :-)

You can just make out some red glow from the anode.?
 
Edited

Hi Bob,

You've got it well down the road at this point.? It really looks like a nice example from what, 60 yrs ago or so?? Can't be too many that are in better shape than that.

While the Jones connector wouldn't seem a natural first choice for HV+ , I suspect the guys in the lab did a lot of HiPot testing before they let that be the connector of choice .? As long as there's no other conductors in that plug it's feasible (especially since it seems to work!) but the metal shell becoming grounded somehow might be a concern.

It would be neat to know what that actual (core?) temp drop those fins on the transformer housing deliver.? Given the "10 deg C drop doubles the life of the electrical component" axiom, it seems like a great idea (and one that could be used in other designs).

I can't remember which transmitter I was working on years ago (32V2?) when I noticed that the power trans (black) was about a half inch away from a large envelope tube with a toasty filament in the chassis. I put a thin piece of aluminum between the (black) transformer housing and the tube, as tubes are << expensive than power transformers? and every bit helps.

Thanks for sharing the pictures of the project.

You're almost done!

John K5MO


On Fri, Jun 28, 2024 at 5:45?PM Bob ah7i via <katz.ajamas=[email protected]> wrote:
Hi John.

That's the factory supply and original transformer. It came with fins! You can see them in the manual photos.
Somewhere along the line, the 866As were replaced by a pair of solid state rectifiers.

I fired it up today. Initially ran 120V to 240V wired HV transformer. No smoke or bang. Swapped wires and still no smoke or bang.
With grid grounded, there's a pleasant glow from the anode.? Meter reads ~2800 V and ~85 mA. Misplaced my HV probe so
verification will have to wait a bit until it's found.?

Will apply drive later today or Saturday. Have to clear space on the bench first :-)

You can just make out some red glow from the anode.?
 

It's looking pretty good!? 2800V should easily get you about 600W or more? if it doesn't drop too much under load!

Running 3KV through an octal plug is very scary though!? You might want to consider using the HV connector for that purpose.

85mA seems a little high.? Someone might have changed that resistor across the terminal in the back.

With the terminal open, I think it should be somewhere around 50ma.....that coupled with the current due to the 210K bleeder is supposed to be enough to "swing" the choke.

Mine with 2600V did about 600W output with 45-50w drive.




--
73/Rick
W4XA
__________________________________
All posts are created using OpenSuSE Leap 15.5 x64 Linux
 

Thanks Rick!

With 40W drive it's making ~500W per the drake meter and a dummy load. Meter is within about ~10% of reality.
I'm happy. Just need to get the relays set up for RF and bias switching.?

73, -bob ah7i
 

That's right in the "zone"

I measured mine with a Bird 43 at the input (250W slug )? and one on the output (1000W slug) into a Bird 500W load.

With the power supply wired for 120, it did about 500W and wired for 240, it did around 600W



Now onto the HT33 (Mark-I)? power supply!?

I have another Drake L-4PS transformer + Harbach L-4B board that I will install in it removing the old (110 only) transformer, swinging choke and oil cap.


There's nothing wrong with the old PS except that I cannot pick up the amp @ 125lbs! ?(I'll save all the old parts and I will not drill any new holes!)?

I expect about a 50lb reduction in weight!! (and an increase in plate voltage from 2100V-2600V)

Cheers,?? Rick


On Tue, Jul 2, 2024 at 09:33 AM, Bob ah7i wrote:
ah7i

?
--
73/Rick
W4XA
__________________________________
All posts are created using OpenSuSE Leap 15.5 x64 Linux

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