Solid state tube replacements for the 5R4GT and 6AX5-GT

[Knightt150]

Dose anyone know where I can get a plug in solid state replacement's for the 5R4-GT and 6AX5-GT high and low voltage recitifers for my RANGER II.

I don't want to get 4 diodes and some resistors and come up with the same thing. I just want to plug them in or pull them out at will.

John W9BFO

[Jim, W5JO]

Ifn you don't want to build them search for Webber Copper Top rectifiers.

[Opcom]

for FAA-certified 5R4 replacements, try magnetosphere.net
6AX5 replacements are not very common.

[Pete, WA2CWA]

Here's the Weber site: http://www.webervst.com/ccap.html

I still like using the base of a discarded octal tube, a couple of 1N5408's, and maybe an upside down  empty pill bottle or equivalent, or a small pvc cap, etc., to enclose it. Diodes are roughly 10 to 15 cents each. I like functionality and less expense rather then functionality, pretty, and expensive.

[Bill, KD0HG]

OK, here's what you do, if you don't want to increase the rig's B+ voltages...And nearly approximate the voltage drop across the hollow state rectifiers..

Get some chunks of perfboard..Put a bunch of 4001-4006-series diodes in series on the board. The rated voltage drop of a 6AX5 is  50 volts. So that would be the 83 x .6 volt diode drop. So buy a bag of diodes from Mouser  for a few bucks and solder 83 of them in series on the perfboard per rectifier section.

Same for the 5R4, which has a 67 volt drop. That would require maybe 100 silicon diodes in series. But they're cheap!

Of course, the diode stacks will get warm, Make them maybe 1" wide x whatever height you can fit into the box. Zig-zag the diodes into several rows.

You can use #4-40 machine screws to plug into octal rectifier sockets like the 5R4.
.
I've done this on my R-390A to replace the expensive 26Z5 rectifiers, which have a 22 volt DC voltage drop. Used 50 1N4006 in series to replace per rectifier section.

Bill

[Opcom]

The Weber ones seem to be very well thought out. $22 each is more than some but you get a lot.

In some tube manuals, the voltage drop is given (as stated above) or may be expressed as a curve. If possible, measure your B+ or take the known B+ and then tune the dropping resistor by experiment. I prefer a resistor but one may also use a Zener diode on a small heatsink if there is little concern over distortion of the rectified wave. 67V@200mA is 13W, a decent size heatsink. It could certainly be made of a metal tube that fits the octal base. Drilling a series of small holes around the circumference of the metal tube near the base will help the convection airflow to also pass across the inside surface.

For inrush limiting, if an NTC has not already been put in series with each power transformer, an NTC may be put in series with the voltage dropping device. It should not be too big a deal considering the high-ish impedance of the typical power transformers used in sets that also use 5R4 and smaller rectifiers.

The Ametherm MiniAmp line offers selections from 3 to 250mA and 5-220 Ohms.
http://www.ametherm.com/
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=570-1087-ND

Although parts required to make a plug-in might cost only a little, the time required to make it is significant but it is as pleasant a pastime for an evening as any.

[KA2DZT]

Just solder a couple of 1N5408s on a base from an old tube. You can add some small amount of resistance if you are worry about the higher voltage.  The added resistor will help limit any inrush current.

I replace all my tube rectifiers with 1N5408s without any added resistance and never had any problems.

For the 5R4 I would use at least two diodes in each leg.  One diode probably will not have a high enough PIV.

Don't turn a simple improvement into a major project.

Fred

[ke7trp]

He does not want to make anything or cobble some junk together. 

On ebay there is a man who sells the 5ar4/5r4 plug ins for $5.99.  Email him and ask him to also send you one for the 6ax5.  He will do it. Its just two diodes and a plastic case. 

Search ebay for 5ar4 solid state and he will come up.

When Peter Dahl was around he stocked the 6ax4 and 5r4 plug ins. I have some in my ranger.  Seemed to work fine.

C

[Knightt150]

Thanks again guys for all your info I will pursue some of your ideas.

I wonder is is the 5R4 the same as a 5AR4. I can find these on ebay.

John W9BFO

[ke7trp]

As for the plug is ss, yes they are the same.

[Pete, WA2CWA]

Thanks again guys for all your info I will pursue some of your ideas.

I wonder is is the 5R4 the same as a 5AR4. I can find these on ebay.

John W9BFO

mouse over and click:
5AR4

5R4

[Knightt150]

Thanks again guys I have just put my order into weber.

Maybe that RANGER will run cooler, and use less power.

John W9BFO

[ke7trp]

Has anyone here ran back to back tests for power supply ripple with a tube and then SS rectifier?

I noticed something the other day that has be baffled.  I am seeing a larger amount of ripple  on the DC supply with the SS rectifiers.  I am wondering why that would be. I did not use my scope, I wish I had.  I wonder if the cylce i sharp with the diode vs smooth with the Tube rectifier?

Anyone?

C

[W4NEQ]

Has anyone here ran back to back tests for power supply ripple with a tube and then SS rectifier? ...

I would venture to say that, assuming you have enough series R to produce the original B+ that the ripple should be similar? 

While we're on this subject, it seems to me a minor extension of this concept would be to add a shunt HV FET just after the series R with the idea of regulation and ripple tracking.  I wouldn't think it would be too involved but would require some heat sinking.  Could be built into a cylindrical enclosure with a tube base ... or do away with the R and use a series FET ... might be as simple as a zener and some voltage dividing resistors ...

[ke7trp]

So the increased ripple is because the voltge increased?   That makes sense.  The Voltage does increase. I wish I took better measurements so I could put that into a percentage.  I could run the test on an receiver here very easy.  The SX42 uses 5r4 so I can swap that, Then measure back to back.  But the ripple sure is higher with SS

[W7TFO]

All this hegemony just leaves more rectifier tubes for me !

BWAHAAAAA !!

73DG

[ke7trp]

Damn.  The results are in.  Using SS rectifiers have SIGNIFICANT increase in ripple.

Its not the increased voltage either.  Even if you resist the volts down, The SS recitifer has way more ripple. They also can have noise from the switching.
The Tube rectifiers are slow and smooth the output. The Diodes are fast and have spikes. 

I needed to add in 47UF to stop the ripple from the SS rectifiers.  This is fine if you want to add the cap.  If not, If this is used in a bias supply, you could be shotgunning crap into the grids of the tubes creating hum and noise.

Moral,  If you go to SS, Add 47+ UF cap on that supply.   You will end up with a very quiet supply then.  ALmost no ripple.  But if you just use the tube rectifier, you dont need the cap. 

You cant/should not use huge caps behind the tube rectifiers. Otherwise, you draw alot of current on them. (depends on alot of factors here)

Dennis, I think I am starting to sway your direction on this.  Its probably best to just leave the rectifiers alone.  I always solid stated everything here. In my eyes, Why would you want that heat in the rig if you dont have too? You also get some more plate volts there which on some rigs really helps, The valiant is one for example.

Keep in mind, this probably does not matter in some situations.  Do your own tests and see what you think.  That hum master,  T368 is full of SS replacements.  In fact, ALL  of the 5r4s, and the 3b28s are replaced with SS plugins,  I have to wonder if that change made me chase my tail for a week tracking down that damn hum. 

C

[Knightt150]

Hello again: I have on order the 5R4 and 6AX5 plus the 6AL5 and the OA2 SS replacements for my RANGER II, has anyone done this before and checked the ripple before and after.

John W9BFO

[ke7trp]

Put your ranger on its side and measure the ripple.  Put your Neg lead on chassis. Then the pos lead on plate pin.  You can probe around and find the B+ DC volts if you dont know the pin.  Then, Switch the meter to AC.  Read the AC voltage.  Then swap the rectifier and measure again.  Write it down and let us know. 

My feeling is you wont have any trouble.  I ran SS on my rangers for years and nobody complained of hum.  On a Bias supply for a String of tubes, You could need some extra capacitance.

Listen to the rig BEFORE and after each tube install.

 

[kb3ouk]

A solid state diode has a more abrupt action than a tube diode does. I remember hearing a recording of Timtron once where he was talking about negative peak limiters, and saying how he preferred using tube diodes because they had a smoother action. Every mention of solid state vs tube diodes I've seen, not matter what kind of circuit they are in, says the same thing: solid state diodes act faster and more abruptly than tube diodes.

[Opcom]

Damn.  The results are in.  Using SS rectifiers have SIGNIFICANT increase in ripple.

Its not the increased voltage either.  Even if you resist the volts down, The SS recitifer has way more ripple. They also can have noise from the switching.
The Tube rectifiers are slow and smooth the output. The Diodes are fast and have spikes. 

I needed to add in 47UF to stop the ripple from the SS rectifiers.  This is fine if you want to add the cap.  If not, If this is used in a bias supply, you could be shotgunning crap into the grids of the tubes creating hum and noise.

Moral,  If you go to SS, Add 47+ UF cap on that supply.   You will end up with a very quiet supply then.  ALmost no ripple.  But if you just use the tube rectifier, you dont need the cap. 

You cant/should not use huge caps behind the tube rectifiers. Otherwise, you draw alot of current on them. (depends on alot of factors here)

Dennis, I think I am starting to sway your direction on this.  Its probably best to just leave the rectifiers alone.  I always solid stated everything here. In my eyes, Why would you want that heat in the rig if you dont have too? You also get some more plate volts there which on some rigs really helps, The valiant is one for example.

Keep in mind, this probably does not matter in some situations.  Do your own tests and see what you think.  That hum master,  T368 is full of SS replacements.  In fact, ALL  of the 5r4s, and the 3b28s are replaced with SS plugins,  I have to wonder if that change made me chase my tail for a week tracking down that damn hum. 

C

I would not be satisifed if I had paid a lot of $ and got those results and then had to waste time and do mods. Are those modules that you can return or did you use individual rectifiers and find these issues?

If they are modules, could it be that there is a zener diode inside for the voltage drop (rather than a resistor) and that is causing issues in the rectified wave? I ask because I tried that scheme making it from parts before and was unhappy that the bottom edge of the fullwave rectified waveform was 'cut off', making the series of half-sines into "pulses" that didn't touch at the 'zero' line.

[ke7trp]

The diode stacks I used where the 2637s and the plug in replacements used in collins S line gear. Those are the FAA approved solid state plug its for the 5ar4 and 5r4.  I think they just diodes. They work great, You just need to add a 47 UF cap on the bottom or to the supply. Otherwise, You will have ripple.  Its a nasty fast switching noise on the supply as seen on the scope.
C

[Opcom]

That is odd. I have not had any problems using those type units. I guess every set is different.

[ke7trp]

Its not about problems.

The point was that the AC ripple goes way way up with SS diodes.  So if you have a circuit that you dont want ripple in, You should add a cap to the supply to further filter it. 


C

[Jim, W5JO]

Clark, could something else be affecting the circuit?  I use those plug in diodes and have not seen an increase in ripple.