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 Post subject: How's My Grid Gonna Leak?
PostPosted: Mar Sat 03, 2007 8:56 pm 
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I am working on a FADA C75A Neutrodyne and cannot find the grid leak.

Not only is it not there but there is no place that it may have been visible on this factory built 5 tube 3 dialer.

Did they ever make these radios minus the grid leak resistor?

Ed Kraushar.


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 Post subject:
PostPosted: Mar Sat 03, 2007 9:06 pm 
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Ed, I couldn't find the model listed on Nostalgiaair, so I'm thinking this is a Canadian model?

Can you point us to a schematic?

Doug


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 Post subject:
PostPosted: Mar Sat 03, 2007 9:07 pm 
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Is it the same as a Fada 175A? Ryders 1-28.


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 Post subject: Re: How's My Grid Gonna Leak?
PostPosted: Mar Sat 03, 2007 9:19 pm 
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efkcfd wrote:

Did they ever make these radios minus the grid leak resistor?

Ed Kraushar.


Yes, its fairly common. They count on leakage to do the function. See if you don't have about 8-10 Megs of leakage. It'll work!

-Bill


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 Post subject:
PostPosted: Mar Sat 03, 2007 10:59 pm 
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dcriner wrote:
Ed, I couldn't find the model listed on Nostalgiaair, so I'm thinking this is a Canadian model?

Can you point us to a schematic?

Doug


Yes it is a Canadian model made in Toronto. No schematic, too early for RCC.

Ed.


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 Post subject: Re: How's My Grid Gonna Leak?
PostPosted: Mar Sat 03, 2007 11:02 pm 
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ElectricBill wrote:

Yes, its fairly common. They count on leakage to do the function. See if you don't have about 8-10 Megs of leakage. It'll work!

-Bill


I will try it soon, just finishing rebuilding two tube sockets and need to replace 3 bypass caps.

I will try to get chassis pictures up soon.

Ed.


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 Post subject:
PostPosted: Mar Sat 03, 2007 11:45 pm 
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Canadian FADA C 75A pictures.

Cabinet needs a lot of work, panel is not cleaned yet. Engraving does not show up on this photo.

Image

Chassis top view, and not fully cleaned yet. Brass tube bases are two I just made, the originals were missing.

Image

Chassis under side. Notice the milled channels for the tube contacts. The tube holders are set into the bakelite chassis rather than using separate socket islands.

Image

Ed.


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 Post subject:
PostPosted: Mar Sat 03, 2007 11:52 pm 
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Nice lookin rig. That cap on the left, does it have a couple tabs for holding a grid leak?


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 Post subject:
PostPosted: Mar Sun 04, 2007 1:08 am 
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Lou deGonzague wrote:
Nice lookin rig. That cap on the left, does it have a couple tabs for holding a grid leak?


No.

Ed.


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 Post subject:
PostPosted: Mar Sun 04, 2007 2:19 am 
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Ed: One of those mica caps should be connected to the detector grid, correct? Just for grins, measure the resistance (grid leakage) across that cap.

Once you get the set working, you can try temporarily hanging a fixed resistor, say 2-meg to start with, across that cap to see if it improves performance. If you find that a particular resistance value improves performance, you can solder it in so that it doesn't show.

OT - I see those two "slider" neutrodyne caps. Don't adjust them unless you need to.

Overall, an attractive layout. I wonder why the tube sockets are different - two appear to be brass and three nickel?

Doug


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 Post subject:
PostPosted: Mar Sun 04, 2007 4:45 am 
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I have a FADA 160. It doesn't have a cap or leak in the detector grid circuit. Grid connects directly to the RF coil secondary. It actually works quite well.

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 Post subject:
PostPosted: Mar Sun 04, 2007 3:13 pm 
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It should be close to the 192A
I have the 175A, which looks exactly like yours. One of the audio transformers was bad.


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 Post subject:
PostPosted: Mar Mon 05, 2007 7:01 pm 
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I have been away for a day and have got back to working on this radio.

I had to replace three caps that appeared to be about 1 mfd that were leaking badly. It is playing quite well, no grid leak resistor.

I can reply to a couple of the comments now.

Ed.


Last edited by Ed Kraushar on Mar Mon 05, 2007 7:21 pm, edited 1 time in total.

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 Post subject:
PostPosted: Mar Mon 05, 2007 7:12 pm 
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dcriner wrote:
Ed: One of those mica caps should be connected to the detector grid, correct? Just for grins, measure the resistance (grid leakage) across that cap.

Once you get the set working, you can try temporarily hanging a fixed resistor, say 2-meg to start with, across that cap to see if it improves performance. If you find that a particular resistance value improves performance, you can solder it in so that it doesn't show.


OT - I see those two "slider" neutrodyne caps. Don't adjust them unless you need to.

Overall, an attractive layout. I wonder why the tube sockets are different - two appear to be brass and three nickel?

Doug


I tried several grid leak resistors, no effect on performance.

These "Neutrodons" are a little diferent than those I have seen before. The internal sliders have two positions with detents and are marked "D" and "S". The "D" position gives louder reception.

As mentioned in the pictures two of the tube holders were missing. I had to make up the brass ones.

Thanks,

Ed.


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 Post subject:
PostPosted: Mar Mon 05, 2007 7:19 pm 
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DeathRex wrote:
It should be close to the 192A
I have the 175A, which looks exactly like yours. One of the audio transformers was bad.


It looks quite close to the 175A.

Ed.


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 Post subject: Re: How's My Grid Gonna Leak?
PostPosted: Jun Wed 19, 2019 11:31 pm 
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Hi.a buddie of mine just gave me this radio never worked on a radio this old.im looking for info on this gear if anybody can help.thanks,RonL

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