Hallicrafters T-54 HV transformer
 

I'm looking for a HV transformer for a '49 Hallicrafters T-54/505.
Used in many of the 7" sets of the period that used a 6c4 Horz osc tube.
I will be at the ETF convention and have many pre-'50 parts I can trade.
thanks.

Most all are prone to sagging voltage after a few minutes on...They are like the rubber masks on the moto VT-71 maybe 6 good ones exist the rest are doomed, get a modern equivalent (HV power supply) and save your self a goose chase for hen's teeth.

Indeed, something like an EMCO F40, which can usually be found on eBay for 55 bucks will do a fine job of providing the HV for the Hallicrafters. Here a F40 (rated at 4kV full load) is producing about 5.6 kV, to a Hallicrafters.

https://live.staticflickr.com/4446/3...5f66b7_z_d.jpg

However, the F40 requires 15 volts at around an amp to power it, so that must be fabricated, as well.

EMCO info: http://www.eie-ic.com/Images/EMCO/EMCO/fseries.pdf

jr

The EMCO F40 looks like an interesting little project, and I have a 505 that would probably benefit from it. If you have done a permanent installation, would you like to share how you came up with the 15V supply?

Regards,

Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html

I am considering just mounting a cheap wall wart or power block inside the hv cage along with the EMCO, rather than scratch building a 15 volt supply. :scratch2:
In the photo, it was powered from a variable bench supply.

perhaps something like this:

https://www.amazon.com/Power-Supply-...%2C232&sr=8-19

not affiliated,

jr

Not all Hallicrafters T54s have HV problems. Mine, using the transformer it came with,
works just fine, for well over an hour. I've never tried it longer. The transformer
did not work when I got it, but that was just a bad solder job attaching one of the thin
wires to its terminal. I had no problem finding a replacement, I forget where ... they are not unobtainium.

I cooled it better by raising the lid over the HV enclosure 1/2 inch on standoffs.

I have two of these, one to be donated to the ETF. This spring both worked fine for over an hour.
measurd to have very little sag.. Yesterday both drooped to 2.5 kV in about 15 minutes.

Today I am running one with the HV rectifier unplugged. After an
hour it has begun to slowly recover. (The AC measured on a scope.)
I do have a NIB one .. but not two. If its humidity it should eventually
recover.

What to do?

Edit: after another hour its back up from 50% normal to 80%. Note: That's still no rectifier.

2nd Edit: after another 30 minutes it was up to where it was at turnon. I reinstalled the rectifier
and the voltage went UP ... as expected since it was not resonating properly with no rectifier.
After yet another hour the DC voltage was 5 kV.

Tomorrow will tell more.

3rd update: the next day (the 4th) the set turned on and worked fine, never having drooped in HV in 45 minutes.

I think these sets merely need to be used regularly.

Can't disagree with that...

I tried my 2nd T54 chassis. It was not as bad a dip, but took like three hours to recover.

Not about the transformer, but why would they design this set with exactly zero remote cutoff pentodes in the RF and IF? Why not 6BA6s in the IF and a suitable remote cutoff
tube in the RF? AGC performance is abysmal.

Do you have/know of any 7 inch electrostatic sets with better operating AGC? :scratch2:

jr

No ... My Emerson 639 is bad too

I finally found a suitable fan. Its a Sunon 120 mmx38mm 220 volt [sic] one,
model DP203A 2123LBL.GN but its running on 122 VAC. This slows it down to
inaudibility but it still moves enough air.

Its a pain to mount, however, as I had to drill new holes to get it away from
the HV rectifier cap.