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 Post subject: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 1:26 am 
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Joined: Mar Sun 22, 2009 5:50 am
Posts: 1133
Location: California
I know this has been talked about before but I'm wondering the correct way to replace the two 6X5's with solid state parts in a Zenith chassis.
I've used two 1N007 diodes and a resistor on other sets with one tube and different transformer leads attached to the plates but the plates and cathodes are connected differently. I'm guessing I would wire them the same way but I can put the diodes together on either pins 3 or 5 as the plates are connected. What would be the best way to make it solid state, adding the parts underneath and still leave the tubes lit in the sockets? I can see where the power transformer had been replaced at one time and don't want it to happen again.

http://www.nostalgiaair.org/PagesByMode ... 024743.pdf


Last edited by shutterdialradio on Jun Tue 05, 2012 5:01 am, edited 1 time in total.

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 Post subject: Re: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 3:37 am 
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Location: Albuquerque, NM 87123
I would disconnect the cathodes (pin 8) of both tubes so they are not in the circuit. You can move the wiring to pin 1 and use it as a tie point.


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 Post subject: Re: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 4:29 am 
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Location: California
Thank you Johnnysan. I'm guessing the voltage willbe increased by using diodes so can I use one 10 watt resistor right off the cathodes to drop the voltage? As I can't find any voltages on the schematic, what would be a good voltage after the resistor and into the first filter cap?


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 Post subject: Re: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 4:53 am 
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Location: Albuquerque, NM 87123
I would check the voltage at the cathodes of the tubes before replacing them with solid state rectifiers, then calculate what resistance value is needed to reduce it to the proper level. Be careful, as you may have a voltage higher than the filter caps are rated.


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 Post subject: Re: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 5:03 am 
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Joined: Jan Tue 03, 2012 10:38 pm
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This old thread shows a perfect diagram to do what you want.
viewtopic.php?f=1&t=190810&hilit=6x5+rectifier
Just ignore the pin 8 reference solder to the other pin suggested or to a terminal strip

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 Post subject: Re: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 5:08 am 
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Location: Haledon, NJ, usa
If you want it to look original and have the original voltage drop but still have the benefit of the solid state diodes (1n4007)... Then you could connect the two diodes to the plates of the rectifier tube (on the AC side).
That way the diodes will be doing the REAL rectifying first ...and you'll be feeding DC to the rectifier-tube and therefore it will not need to do much work anymore.... and it will still drop the same voltage as previously.

Now as far as the dangers of certain tubes like the 6x5 where most folks seem to be worried about internal shorts or whatever... that aspect/liability will still exist.

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 Post subject: Re: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 5:39 am 
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Joined: Mar Sun 22, 2009 5:50 am
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Location: California
Thank you all for the great advice :D
I've checked the voltage off the 6X5 cathodes and will install a resistor to match it. I'm now deciding weather to put diodes/resistors in tube sockets or everything underneath. If in sockets it would be easy for anyone to just replug 6X5's back in the set if they wanted to.


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 Post subject: Re: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 5:50 am 
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Joined: Mar Sun 22, 2009 5:50 am
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Location: California
Pbpix wrote:
If you want it to look original and have the original voltage drop but still have the benefit of the solid state diodes (1n4007)... Then you could connect the two diodes to the plates of the rectifier tube (on the AC side).
That way the diodes will be doing the REAL rectifying first ...and you'll be feeding DC to the rectifier-tube and therefore it will not need to do much work anymore.... and it will still drop the same voltage as previously.

Now as far as the dangers of certain tubes like the 6x5 where most folks seem to be worried about internal shorts or whatever... that aspect/liability will still exist.


Still a little nervous about the tubes shorting as they did before in this radio. But that's a great way to do it :D


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 Post subject: Re: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 3:48 pm 
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Location: Livermore, CA
We talk about adding a diode in series with plates of 6X5's but that still leaves a problem. Cathode of the 6X5 has full DC voltage while filament is grounded. Some 6X5's short cathode to filament.

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 Post subject: Re: 6X5 tube replacement
PostPosted: Jun Sun 03, 2012 3:58 pm 
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Location: Detroit, MI USA
If I were going to do this, I would remove all wires from both 6X5 sockets except for the filaments. Run those leads to a new terminal strip you will install under the chassis, and add the 1N4007's and dropping resistor on that strip.

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