# wiring for 5Y3 or 6X5 to be plug-in interchangable



## keeperofthegood

Hey oh

Ok, there are a multitude of rectifier tubes out there. I have the ability to get the 6X5 tube relatively low priced and definetly better priced than the 5Y3.

The main differences between the two are, the 5Y3 can flow twice the current and has twice the inverse voltage rating and has a 50 volt drop compared to a 10 volt drop at max current for the 6X5.

There are a couple other differences. One being the 6X5 has an indirect cathode and the 5Y3 is direct. Also, the 5Y3 uses 5 volts at 2 amps while the 6X5 uses 6.3 volts at 0.6 amps.

The pin outs of these two are also different. But maybe this can be a good thing? I do not know. I drew up this image here of how I would envision I would wire a socket only there is a piece of information I do not know. Can the 6X5 work with the cathode voltage dropped 1.3 volts from the filament in this fashion?

The red lines represent the different pin-out of the 5Y3 over the 6X5. There is no red line to the cathode segment as there is none in the 5Y3, the 6X5 cathode goes to pin 8, the 5Y3 filament goes to pin 8.


----------



## nonreverb

I doubt that it will work well. That's a significant drop in voltage. Plus you won't know how it will affect the loading on the 6.3 volt supply either.


----------



## John Bartley

KOTG,

6X5's have a reputation in the antique radio community for being "transformer killers". If I recall correctly, they tend to short between the heater and cathode. If your heater string uses (as is common) the chassis as the return side of the heater wiring, then a heater to cathode short circuit will have the result of also shorting the HV winding to the chassis. For the extra few dollars, I'd be buying the 5Y3's. 

cheers

John

EDIT :: a better sub would be a 5Y4. It has the same ratings as a 5Y3, sells for half the price or less, and by soldering in three jumpers on the tube socket (pin 3 to 4, pin 5 to 6 and pin 2 to 7), you can put in either tube without worry.


----------



## WCGill

Keeps, you're always thinking, that's really awesome. Don't ever stop doing that, it's the only way forward. If you do wire the socket to take both rectifiers, remember that you'll have B+ on pin 2, as well as pin 7 and 8 and it may not be healthy for the other tubes that only want to see 6.3 volts on their heaters. I'm assuming you're using the common filament winding. If you do use an auxiliary transformer, it would have to be rated for this type of service.


----------



## keeperofthegood

Thanks for that heads up on that John :O

If you know where I can bulk purchase the 5Y4 I am all ears 

The deal for us is, we need 15 to 25 tubes at one purchase (our participant range). We can do the 6X5's at 2 dollars each, this keeps the costs within a reasonable budget, the idea of the "either or" is actually so that people could upgrade to better tubes at a later time thus taking off that "up front" money pressure. I was looking to do this with a minimum of re-wiring, or in fact no rewiring. I am also working to avoid the use of a 5 volt winding. I can get a 200VA transformer with a 350v x2 winding and 6.3v x2 for 35US, where-as the other manufacturers that include the 5 volt winding have units beginning at 100+ dollars (going into the unreasoned land quickly).

Hmm.... more drawing table work for us then 

Thank you


----------



## keeperofthegood

WCGill said:


> Keeps, you're always thinking, that's really awesome. Don't ever stop doing that, it's the only way forward. If you do wire the socket to take both rectifiers, remember that you'll have B+ on pin 2, as well as pin 7 and 8 and it may not be healthy for the other tubes that only want to see 6.3 volts on their heaters. I'm assuming you're using the common filament winding. If you do use an auxiliary transformer, it would have to be rated for this type of service.


 My late grandfather used to do crosswords. Did them every single day. Used to say, if he couldn't think through a crossword he would be dead. Pretty much worked out that way for him too, he was unable during the last few weeks of his cancer to do crosswords. For me that translated to "always thinking" as a leisure activity to stay sharp and alert. Last few years have been hard but hey 

Hmm.... I sure don't want B+ all over the place. I also do not want a 5 volt winding on the transformer. Cost control. Hmm... lots more for the drawing board


----------



## Paul Babiak

keeperofthegood said:


> Thanks for that heads up on that John :O
> 
> I am also working to avoid the use of a 5 volt winding. I can get a 200VA transformer with a 350v x2 winding and 6.3v x2 for 35US, where-as the other manufacturers that include the 5 volt winding have units beginning at 100+ dollars (going into the unreasoned land quickly).


Have you checked this site for transformers? You might be able to get exactly what you need custom-wound, for reasonable $$$.

http://www.musicalpowersupplies.com/4.html

Paul


----------



## keeperofthegood

Paul Babiak said:


> Have you checked this site for transformers? You might be able to get exactly what you need custom-wound, for reasonable $$$.
> 
> http://www.musicalpowersupplies.com/4.html
> 
> Paul



I am going to have to do that, or use an LM### voltage regulator. I had a bit of a brain fart on this. When the tube is cold, the standard is to consider it a short circuit. That means if I use a 0.65 ohm voltage dropping resistor, until the tube heats it has the full 6.3 volts across it. Using a bit of Ohms and Watts laws, 6.3/0.65 = just about 10, and 10 * 10 is really 100 and 100 * 0.65 is close enough to 70 WATTS! OMG!

Not to mention what it would do to a 6.3v winding that has 2 amps as its working max >.<

OK! Back to the drawing board!


----------



## John Bartley

keeperofthegood said:


> When the tube is cold, the standard is to consider it a short circuit.



Ummm ..........I've never used that as a standard...

If you measure the cold resistance of the filament on your tube, "that" is the resistance across which the startup current is measured. Also, the warmup time for the filament (unlike the time to emission) is very, very short and won't pose any hazard to your transformer. All you have to do is make sure that the "operating" specs are ok, and give your self a reasonable amount of margin over and above that. This is not quite the same as the calculations for things like startup current for electric motors. 

cheers

John


----------



## keeperofthegood

John Bartley said:


> Ummm ..........I've never used that as a standard...
> 
> If you measure the cold resistance of the filament on your tube, "that" is the resistance across which the startup current is measured. Also, the warmup time for the filament (unlike the time to emission) is very, very short and won't pose any hazard to your transformer. All you have to do is make sure that the "operating" specs are ok, and give your self a reasonable amount of margin over and above that. This is not quite the same as the calculations for things like startup current for electric motors.
> 
> cheers
> 
> John



 I remember losing the field on the gen in high-school electronics class, that was a heck of a rush...

I have been reading on restoring AA5's (I have one in progress right now) and a fair number of sites have said this, to concider tube cold resistance as zero. Doing so, is mathematically intimidating @[email protected] as you can see with the maths.

The ONLY 0.65 ohm resistor (yes, I had a dyslexic moment on my diagram) that is available from Mouser is a 5watt model wire wound. Do you think this would suffice or is this going to have to be a "try it and see if it works" deal?


----------



## Wild Bill

keeperofthegood said:


> I remember losing the field on the gen in high-school electronics class, that was a heck of a rush...
> 
> I have been reading on restoring AA5's (I have one in progress right now) and a fair number of sites have said this, to concider tube cold resistance as zero. Doing so, is mathematically intimidating @[email protected] as you can see with the maths.
> 
> The ONLY 0.65 ohm resistor (yes, I had a dyslexic moment on my diagram) that is available from Mouser is a 5watt model wire wound. Do you think this would suffice or is this going to have to be a "try it and see if it works" deal?


Don't worry, Keeps! Think of a power resistor as a toaster! It may have a maximum operating power level but when it first starts up it looks like a zero resistance. Within a half second or so it has a few ohms resistance and this quickly climbs higher and higher.

So it takes TIME to get hot enough to start toasting bread! It's not an instantaneous thing. That's why some devices in startup applications also have a startup spec. Filter caps might be rated at 600 volts for a quick initial instant, like a half cycle of 60hz. That immediately falls to a working voltage of maybe 450 volts. The cap can handle the big peak when it first starts charging but it's understood that very quickly things in the circuit will warm up and start drawing current, pulling that peak voltage down towards the working level.

I'd be much more worried about the current draw on that 6X5! It's only rated for 70 ma. or so. That's enough for a single 6V6 Champ style amp. If you want to run a pair in pushpull you're asking for trouble.


----------



## keeperofthegood

Wild Bill said:


> Don't worry, Keeps! Think of a power resistor as a toaster! It may have a maximum operating power level but when it first starts up it looks like a zero resistance. Within a half second or so it has a few ohms resistance and this quickly climbs higher and higher.
> 
> So it takes TIME to get hot enough to start toasting bread! It's not an instantaneous thing. That's why some devices in startup applications also have a startup spec. Filter caps might be rated at 600 volts for a quick initial instant, like a half cycle of 60hz. That immediately falls to a working voltage of maybe 450 volts. The cap can handle the big peak when it first starts charging but it's understood that very quickly things in the circuit will warm up and start drawing current, pulling that peak voltage down towards the working level.
> 
> I'd be much more worried about the current draw on that 6X5! It's only rated for 70 ma. or so. That's enough for a single 6V6 Champ style amp. If you want to run a pair in pushpull you're asking for trouble.


Well, it is like building a ladder. One rung at a time. 

The transformer I have been basing this on so far has 2 separate primary windings 120v each, and 2 separate secondary 350 volt windings at more than 0.5 amps and 2 separate secondary windings of 6.3 volts 2Amps each. So, the rectifier would not be sharing the same 6.3 winding as the rest of the amp. 

The 5Y3 and company tubes seem to be selling from 10 to 20 dollars about the net. The 6X5 is selling for 2 to 3 dollars. However, what can be done is going SS simply to get the build done at a reasonable cost, while at the same time building in for the tube (as the socket is only 1 dollar, and users can add their own 5Y3 later) the intention at this juncture is to have a tube rectifier that works "out the door" for people at a reasonable cost, and the 6X5 I felt provided that. 

The base design is the 5C1; it is a nice amp with a very straight forward circuit, and does provide that "room to grow". I have read that the pentode pre-amp also gives a tone very different from the later tridoes used in pre-amps in amplifiers, and I think that would be interesting to present as well. On the upgrade, there is for instance a 'tone' cap in the 5C1, that can be essentially removed and replaced with the 12AX7 + tone stack ala Fender (or whom evers design the user would wish, but Fender made that little block, 1/2 12AX7, tone stack, 1/2 12AX7 and simply repeated it across a lot of amp models, it looks to be a cookie cutter circuit). Or a tremolo circuit can be added or reverb + tank, etc all these have been made as modules over time. 

For sure, with any of these additions the 6X5 would not do, more current would be needed but yes, the idea was a working simple, straight forward 5C1 that was true enough to the original that people would have a general idea what to expect up front while keeping costs down and adding in some safety and use features to begin the road of expansion (integrated capacitor discharging without using resistors, and using three wire plugs, and the stand-by switch).


----------



## John Bartley

keeperofthegood said:


> . However, what can be done is going SS simply to get the build done at a reasonable cost, while at the same time building in for the tube (as the socket is only 1 dollar, and users can add their own 5Y3 later) the intention at this juncture is to have a tube rectifier that works "out the door" for people at a reasonable cost, and the 6X5 I felt provided that.


One way of accomplishing this (above) is to design the build as if the amp was going to be "tube only", and have the solid state rectifier system built on top of an eight pin plug salvaged from an old tube base. Given the size of solid state components today, the SS rectifier and voltage regulator shouldn't be much larger than the tube it's replacing. If you go ahead with this idea and are in need of tube bases, I'm sure I can provide what you need at no charge. I have many octal TV tubes that I'd be happy to sacrifice for the project.

cheers

John


----------

