Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Nov Wed 13, 2019 3:11 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 23 posts ]  Go to page Previous  1, 2
Author Message
 Post subject: Re: Johnson Viking Adventurer Current Meter
PostPosted: Jun Wed 26, 2019 3:35 pm 
Member

Joined: Nov Wed 17, 2010 11:14 pm
Posts: 193
New (Old) meter installed and working well. This meter is the original revised current sensitivity meter. It does measure 13.5 mA FS deflection and the meter resistance required a slight change in meter shunt values. That said, the grid current peaking and plate current readout (meter moved to cathode) are spot on.

The supply is now changed over to solid state and cap bank is now new as well. There is a surge protection R in series with the secondary winding - diode string of 100 ohm/5 W. Now 5 W is on the light side in my opinion. Key down while trying to do tweaking and loading, that R can get pretty warm. So going to 10 W and easy way is to parallel what I have in box. Taking surge R down to 50 ohm.

Before doing that, I wanted to be sure that going to 50 ohm would still provide comfortable surge protection. So I measured the HV supply line winding R terminal to terminal. It comes in at 570 ohm. Seems higher than I would have expected. Other transformers in a similar power class I measured about 100 ohm. I need to measure key down HV. Should be somewhere around 450-500 V. HV key up is ~ 700 V. Correction 650 V and dropping to 500 V. If you really drive the line up you can hit 700 V, not nice.

That said, the Adventurer now works great, keying nice, Pout ~ 25 W max. So can anyone chime in who knows what this little xmfr R sec is nominal? If it is indeed 570 ohm, I am not going to worry about dropping the surge R value.

Tnx, Alan


Top
 Profile  
 
 Post subject: Re: Johnson Viking Adventurer Current Meter
PostPosted: Jun Fri 28, 2019 4:14 pm 
Member

Joined: Jan Fri 27, 2017 8:41 pm
Posts: 120
Location: Springwater, NY
Alan, here is some data from my notes:

R(primary): 2.5 ohms
R(1/2 HV secondary): 270 ohms
R(other 1/2 HV secondary): 284 ohms
R(full secondary): 555 ohms

HV(one side, unloaded, 115VAC): 500VAC
HV(other side, unloaded, 115VAC): 500VAC

HV(5U4GB, key up, 115VAC): 635VDC

555ohms/1000VAC = 0.555, Duguid's graph indicates that the transformer (with capacitor input) should be good for "65ma."

Alternatively, if we allow a subjective 3W to be burned in the winding, I=SQRT(3W/555ohms)=74ma

Is that CCS or ICAS? Is this an illustration of "value engineering?" Novice duty cycle was likely pretty low and the transformer could take its time.

73, Dean, NW2K


Top
 Profile  
 
 Post subject: Re: Johnson Viking Adventurer Current Meter
PostPosted: Jun Fri 28, 2019 7:38 pm 
Member

Joined: Nov Wed 17, 2010 11:14 pm
Posts: 193
All good information Dean. Thanks. Those numbers agree very close to what I measured.

So the unit is done and on its way back to the owner.
Found a nice original meter and works and reads as required.

Key up was running 650-700 V depending on the AC line value. Key down about 500 V at 110 mA. Pout 24-25 W with nice note and keying.

Another Adventurer rides the sky-waves. 73'


Top
 Profile  
 
Post New Topic Post Reply  [ 23 posts ]  Moderator: Sandy Go to page Previous  1, 2

All times are UTC [ DST ]


Who is online

Users browsing this forum: Tom Herman and 4 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB