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Author Topic: Johnson Viking Adventurer HV filter caps?  (Read 45453 times)
KC2VDM
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Posts: 145




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« Reply #15 on: October 06, 2011, 05:35:31 AM »

Right now there's a 3 amp fuse in it. I'll toss in a 2 amp one tonight.  Thanks for the tip!
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W1BR
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Posts: 4188




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« Reply #16 on: October 07, 2011, 09:43:12 AM »

The meter in the Adventurer is an iron vane type (very very cheap) and unlike D'Arsonval movements which are damped the needle or pointer wags back and forth across the meter face.  Many folks replaced these meters since it is difficult to see what you are doing when you tune up.

Allen

If the meter is good, I would leave it. Too many vintage radios have been hot rodded, and there are few
original examples left to enjoy.

Pete
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KC2VDM
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Posts: 145




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« Reply #17 on: October 12, 2011, 10:25:52 PM »

It lives! It Lives! After putting in the new caps and figuring out a mess by the Ext. socket, The transmitter lives. The only problem is i can't find a dip (as indicated by the meter). I can tune the radio by using an external wattmeter or lightbulb, but the 0-10 mA needle is pegged all the way through. At this point, I;m just glad to see signs of life.

Thanks for all the help guys!
-Alex
KC2VDM
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N4NYY
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« Reply #18 on: October 13, 2011, 06:06:54 AM »

There are a ton of milliamp meters on ebay. Do a search for "10 ma meter" .
« Last Edit: October 13, 2011, 06:20:07 AM by N4NYY » Logged
G3RZP
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Posts: 1265




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« Reply #19 on: October 13, 2011, 08:15:36 AM »

Is the meter shunted to read something like 100mA? Or was the original moving iron meter a 100mA or so?
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N2EY
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« Reply #20 on: October 13, 2011, 08:22:16 AM »

The only problem is i can't find a dip (as indicated by the meter). I can tune the radio by using an external wattmeter or lightbulb, but the 0-10 mA needle is pegged all the way through.

Does it read grid current correctly?

The Adventurer reads grid and plate current by connecting the meter across resistors in the plate and grid circuits. If those resistors change value, the meter won't read correctly. Since the meter is not original, the shunts are almost certainly the wrong value.

Easily fixed, though, if you have another meter of known accuracy, a battery, and some resistors.

73 de Jim, N2EY
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AC5UP
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Posts: 4546




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« Reply #21 on: October 13, 2011, 08:44:12 AM »

...and if you were to temporarily connect a regular VOM or DMM across the pegged meter you'd probably see a normal dip in the transmitter tuning. Which would tend to confirm it's the meter circuit that needs a little TLC.

BTW: This winter I plan to refurb a Farnsworth N4 chassis (1949 AM / FM / Phono pulled from a console) and just for grins took a look at the Rider's to see if the junque box can handle the parts list....... Yes, but, the schizmatic and parts list includes several 470 MEG 1/2 watt carbon resistors. No Joke, No Typo. I have never seen a resistor with a value that high and a web search tells me 22 megs is the upper limit from the usual sources. Best I have in the 'box is 220 meg metal film in 1/4 watt and I have a hunch that's close enough.

Do a little Ohms Law with 470,000,000 for the R and I gets real close to zero unless E is lightning........  Wink
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G3RZP
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« Reply #22 on: October 13, 2011, 09:49:20 AM »

The original RCA AR88 circuit uses 'm' e.g.250m for 250 kohms. it's not one of those, is it?
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AC5UP
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« Reply #23 on: October 13, 2011, 10:09:49 AM »

Bingo!

Went back and looked at the schizmatic with both eyes open... http://www.nostalgiaair.org/Resources/view.asp?FN=\M0005988.pdf and sure enough, there are NO resistors with a K after the value! Anything below a thousand is the straight number, like 470 (omega), and I've never seen a chassis where the resistor values are all above a million or below a thousand with nothing between.........

I would have caught that once I had the chassis on the bench, but thanks for mentioning that as it has been a long time since I've seen an 'm' used for thousands. The other oddity about this radio is that the FM dial scale is marked by FCC channel, 200 through 300, and not frequency.

Which is why I'm keeping it.  Wink

BTW: Another project that might happen this winter is a Stromberg-Carlson AM / FM / FM console chassis that not only has the US pre-war and post-war FM bands, but is all permeability tuned. Love those odd ducks.
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KA5N
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Posts: 4380




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« Reply #24 on: October 13, 2011, 10:19:16 AM »

Extremely high value resistors were used in electrometers and were glass encapsulated.
These were made using egg white as a cement to keep the resistance material on the
internal structure.  This technology is way out of date today and examples of the resistors
might be found in old nuclear instrumentation. 
Just for what it's worth.
Allen
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W8JI
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Posts: 9748


WWW

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« Reply #25 on: October 13, 2011, 12:50:11 PM »

Bingo!

Went back and looked at the schizmatic with both eyes open... http://www.nostalgiaair.org/Resources/view.asp?FN=\M0005988.pdf and sure enough, there are NO resistors with a K after the value! Anything below a thousand is the straight number, like 470 (omega), and I've never seen a chassis where the resistor values are all above a million or below a thousand with nothing between.........

I would have caught that once I had the chassis on the bench, but thanks for mentioning that as it has been a long time since I've seen an 'm' used for thousands. The other oddity about this radio is that the FM dial scale is marked by FCC channel, 200 through 300, and not frequency.

Which is why I'm keeping it.  Wink

BTW: Another project that might happen this winter is a Stromberg-Carlson AM / FM / FM console chassis that not only has the US pre-war and post-war FM bands, but is all permeability tuned. Love those odd ducks.


M is still used for thousands in things like hardware. It isn't that unusual. It is, after all, the Roman numeral for 1000

Even Sears uses it:

http://www.sears.com/shc/s/p_10153_12605_SPM246725291?mml=MMLxGIDxsearsProductDetails#desc


When we order 5M screws or nuts, we expect 5,000.

There are cases were MM means millions, and M means thousands, and M means mega.
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KC2VDM
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Posts: 145




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« Reply #26 on: October 13, 2011, 01:28:23 PM »

The radio has a 10mA meter in it. There are no shunt resistors. Right now i'll go check a few resistors and try to find a dip (using my Simpson 260).

In the grid position, It reads a nominal 4-6mA with a 8125 kHz XTal (all I have right now, Its going into a dummy load)

Something odd that might be causing it, R11 (20K 10 Watt) has been replaced by a 12.5 K 10 watt resistor. I think this is for the 807's grid leak? The thing is, I temporarily replaced it with a 22k, 1/2W resistor, and the meter is still pegged.

-Alex
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KC2VDM
Member

Posts: 145




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« Reply #27 on: October 13, 2011, 02:12:46 PM »

Alright, well I checked r5, the 10 ohm resistor for the plate mA and it was 14 ohms. not bad, but i replaced it with a 10 ohm anyway.

Taking readings from the meter terminals (I didn't disconnect the meter) I got:

30mA dip with the PA tuning at about 80, loading at 0

55mA undipped.

50 mA dip/full power out/ loading at 10
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N2EY
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Posts: 5079




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« Reply #28 on: October 13, 2011, 02:26:03 PM »

R11 (20K 10 Watt) has been replaced by a 12.5 K 10 watt resistor. I think this is for the 807's grid leak?

No. R3, a 15 K resistor, is the 807 grid leak. R11 is the screen dropping resistor, and should be a 20K 10 watt or a combination that adds up to that value.

Reducting the screen resistor value increases the screen voltage, which is not a good idea.


 The thing is, I temporarily replaced it with a 22k, 1/2W resistor, and the meter is still pegged.

The half-watter won't last long there. You need 20K at 10 watts or so.

73 de Jim, N2EY
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KC2VDM
Member

Posts: 145




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« Reply #29 on: October 13, 2011, 02:41:07 PM »

-Jim

Right now there is a 12.5k 10W resistor for the screen drop. That's how the rig came. I had a feeling that wasn't right! Do you think that could be the cause of the off scale readings? I'll have to see if I have enough resistors to gang up! The half-watter was just for a quick test.

-Alex
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