bobine

[bobb12 Profil YIM]

HELLO TO BOTH

This evening i took voltage reading on the 6F6, hear are the reading i obtained.

pin 3 the plate 170 dc
jontion of r27 and r28 265 v dc .
at point x and r37 150 vdc should be 102 volts
cathode 2.1 v dc
at pin 5 first grid varies from 3volts to 5 volts -dc

r27 measures 2000 ohms r 28 4700

Would like to have your opinion on this and why the bulbs does not shut down .

Thanks again for all your help.

bob

[bobb12 Profil YIM]

hello again

Ichange the 1 meg the .1 at the grid of 6f6 still the same problem with the lights but the light is dimmer.

Could it be cause by the open antenna the singnal is not strong enough to cause the light to go out .

I reread daniel post he also mention this .

I have done everything i could think of doing ,i am at a dead end.
I have no news from daniel maybe i should go back writing in french i might have upset him ,i am sorry if i did

bob

[Daniel Profil]

Hello Bob, I am not that susceptible, we can continue in spanish or italian if you wish.

The capacitor you changed C40 is not a 0.1 µf it is a 1µf, big difference, it takes the audio and filter it to polarize the 6F6 grid. You can find it at Digikey canada, they deliver by mail in 24 hours http://dkc3.digikey.com/PDF/CA2010/1636-1638.pdf

Now we see that the model Champlain has only one lamp and the second one is replaced by a 400 ohms resistor, so we can assume that the resistance of the 2 lamps is equivalent to 800 ohms.

So you have 800 ohms between point K and point Y. I cannot explain perfectly how this bridge works put it is a question of balance between grid and cathodepotential that makes the current flow trought the lamps instead of trought R 27. So I think you realy need to replace C40 by 1 µf.

Another thing since you don't have a signal at the antenna the lamps light wich is normal. Try injecting a signal with a generator.

Also it would be interesting to put a miliamp meter in serial with the lamps to see what kind of current it is pulling.

Daniel

[bobb12 Profil YIM]

salut daniel

I check the diagram it indicate .1 tuburlor 6oo volts for C40,like you mention earlier it ma be cause by the antenna .

The antenna should arrive by the end of the week .

thanks for your help ,iwill let you know .

bob

[Ken Profil]

Hi Bob,

Did you measure current through tuning lamps? alternatively you can measure voltage, which is easier since you don't have to open the circuit. Connect your test leads on points K & Y then tune a station in then out, you should observe a voltage increase when off station and a decrease when on station. Inform me of readings you obtain.

Ken

[bobb12 Profil YIM]

hello ken

The voltage taken at point X AND Y 23 volts on or of station, at the screen of the 6f7 should be 92 volts i get 140 volts dc ,i would like to mention that all the dc voltage are higher about 35 volts maybe because the main tranformeris a 115 primary now running at 120 ac.

THE VOLTAGE AT THE GRID OF THE 6F6 SWINGS FROM 3 TO 7 VOLTS.
Do you know the cut off point of this tube at cut off point the tube cease to conduct and the light should blankoff.

thanks for your help

bob

[bobb12 Profil YIM]

DANIEL

Thanks for the effort for what you are doing its very kind of you, i did stop working on the set untill i install the antenna ,i will check the lamp if they are all m typt ,the 2 f6 audio output and the preamp. tube are glass typt ,if i remeber well all others are m typt.

thanks again

bob

[Daniel Profil]

Hello Bob

To help preserve antique radios and the knowledge associated to its conception and repair is the goal of our association. There will be an article on this type of tuning lamp on Northern Electric in the february edition of our newsletter.

Its only $40 a year to become member of the association, to receive the newsletter and benefit from our archives and activities.

If you are interested just print the form under ''Devenez membre''.

But anyway will be there for you.

Daniel

[bobb12 Profil YIM]

HELLO DANIEL AND KEN

Check tubes both 88m where change and they are glass tubes , look it up on the internet and are direct replacement.

many thanks


bob

[Daniel Profil]

Hello Bob

As commented in Rogers replacement tube manual that they published when Philips the new owner discontinued the metal spray tube, the 88M should be replaced by a 6K7 or 6K7G with a shield kit, but later on came the metal 6K7M with metal envelope, that should be a good replacement.

Daniel

[bobb12 Profil YIM]

hello daniel

I took reading on the 6fm6 grid on a very strong station,read-14 volts and this not affect the bulb brightness, but the voltage swings from 5 to 14 volts ,just wondering if this swing is normal should it be a steady -dc voltage at this grid .

With such a swing it will never cause the tube at cut off, at cut of the tube would stop to conduct and the bulbs would turn off .

That how i under stand the circuit.

I am not to good in reading manual charts always had trouble understanding these curves. If someone out there knows the cut off voltage ,please step in.

thanks again

bob

[Daniel Profil]

Hello Bob

I think the voltage seing on the grid is normal as the voltage comes from the filtered audio signal. As for the cut off I don't know.

I would try to replace R27 and R28 by potentiometers and try to balance them in order to extinguish the lamps, then you could measure the pots and replace the resistors with the proper values.

Daniel

[bobb12 Profil YIM]

HELLO DANIEL

At last good news, res. at the plate R27 INCREASE TO 15K I HAVE MEASURED THIS RESISTANCE maybe 5 times , iinterminted problem, if i heat it with the solder gun for few second ,the res value jumped to 30k and slowy goes down to 15k ,the next day it read 2200 ,

The first time i ever encountered such a problem, enough to go crazy.

EXPECT THE UNEXPECTED.

BOB WITH MANY THANKS