NC-183D B+ Current draw

[W5QWX]

Does anyone know what the normal B+ current draw should be through the 7 Henry choke?
I am measuring 170 mils of current from the choke output to the filter cap, which I think
is too high but have nothing to compare against. The transformer is showing oil leakage, even when the AC line voltage is brought down with a variac to 115 vac. The DC input to the choke measure 352 vdc and the output measures 254 vdc which is a heck of a drop across the choke.
This unit was recapped about 10 years ago along with some of the out of tolerance resistors, mostly in the screen circuits.
Anyone have any ideas on what the current draw should be ??

Dave de W5QWX

[w4bfs]

Does anyone know what the normal B+ current draw should be through the 7 Henry choke?
I am measuring 170 mils of current from the choke output to the filter cap, which I think
is too high but have nothing to compare against. The transformer is showing oil leakage, even when the AC line voltage is brought down with a variac to 115 vac. The DC input to the choke measure 352 vdc and the output measures 254 vdc which is a heck of a drop across the choke.
This unit was recapped about 10 years ago along with some of the out of tolerance resistors, mostly in the screen circuits.
Anyone have any ideas on what the current draw should be ??

Dave de W5QWX

I agree that 170 mA seems high ....hmmm thats a push pull 6v6 pair in class A .... thats the high current user .... cathode biased, I believe .... should be around 20V.... take a close look here first

how warm are the xfmr and choke getting ?

[KA0HCP]

The transformers in NC-173's and 183's have a tendency to die.  Mine was replaced sometime in it's prior life.

[KA2DZT]

Biggest problem with the 183D is heat inside the cabinet.  I completely redesigned the power supply in my 183.  I solid stated the rectifiers and removed the 5U4 (too much heat near the xfmr).  I removed the stock choke and added two different chokes.  I have a choke input filter using a better 7hy 200ma choke (lower DC resistance to reduce the voltage drop) and a 6hy 125ma choke. LCLC filter.  I run the audio output stage (6V6s) off the first choke and the rest of the circuits off the second choke.  The temperature inside the cabinet probably dropped 50 degrees.  The receiver runs much cooler, before you could fry eggs on it.  With the choke input filter the xfmr is running much cooler, before you could burn your fingers if you touch it.  Removing the 5U4 also reduces the load on the xfmr.

I also redesigned the RF and IF screen circuits.  I added a 105 volt VR tube (large 40ma type) in the 5U4 socket and run the screens off the regulated supply line.  All the screen resistors go up in value so I replaced all of them but left them disconnected.  I added 2K isolation resistors with .01mfd bypass caps to each screen.  The whole receiver works better including the S meter readings.

I also run the receiver off a variac at 115vac.  Don't run the radio off todays much higher line voltages.

Fred

[Jim, W5JO]

Your measurement of 170 mils is probably close.  The current specs for the HV secondary of that transformer is 250 ma.  The early ones had some problems and, if you don't watch, that cap on the input to the choke can become leaky which pulls more current than it should from the transformer.  Also be sure to replace the capacitor on the center tap of the HV winding which, as you know, is above ground.  They use that voltage for AGC and it is the filter for it, and don't go too large with it.  Your best bet is just replace all the electrolytic capacitors.  Keep all the electrolytic capacitance values very close so the current is as low as possible during turn on.

Transformers in earlier versions had problems and were prone to burn out.  However later in the build they put in upgraded transformers which solved the problem  I am told that the upgraded transformers are marked SA 461 on them.

The receiver does run hot so if you want to keep it original then be sure the air can circulate up from the louvers on the bottom plate and leave at least 3inches space between the back and whatever is behind it.

Just for grins I put a piece of heat shrink tubing around the main can capacitor to keep from accidentally shorting it to ground and causing troubles.

[W5QWX]

Thanks for the reply Jim,
I have ordered replacement caps for all of them. I am pretty sure the canned cap was
replaced about 10+ years ago and this beast was in storage for about as long, so they
could have started leaking again. I had and used one as my first store bought RX back in
57, and really liked it for AM and even CW was pretty good copy compared to other RX's
of the day.
The cap at the center tap of the transformer does not appear to have ever been changed.
That may be the one cause the choke to get so hot.
The transformer is the 461 in this unit. The S/N starts as 436-XXXX so, puts it at about 1952-3.
My original was a 1951-2 model.
The AC switch on the audio gain pot broke yesterday. I took it apart but the back of the pot
is broken and the switch was seized up. Trying to find a replacement.
Again thanks for the input.

73,
Dave de W5QWX

[Jim, W5JO]

I hope this link works

http://www.radiodaze.com/single-section/

$3 from Radio Daze.

500K audio w/switch

[W5QWX]

Link works FB Jim, Thanks. I hadn't thought about Daze and why don't know... I bought a ton of stuff from them when restored my old Viking 1, hi hi.
The only thing about that pot & switch is the shaft being so long, but can handle that, NP.
Thanks again,

73 Dave de W5QWX