Best wire gauge and type for heater supply

[Mike_J]

My amp will have four EL34s and seven 12A_7s.  In the past I have used stranded 18 gauge Teflon wire for the power tubes and 20 gauge solid core Teflon wire for the preamp tubes.  Unfortunately, in my ODS - HRM - 100 amp build the solid core wire broke from some bending it encountered while I was making some changes to the amp.  The holes in the preamp tube sockets are so small and it is difficult to get stranded wires into the holes without having annoying stragglers.  This is the reason I tried the solid core wire. 

It is obvious to me that solid core wire is not appropriate for the heater supply.  My questions are: 1.  What gauge wires would you recommend for the tube compliment I referenced above?  2.  Does anyone have any secrets for getting stranded core wire through the small holes in the preamp tubes without annoying stragglers?

Thanks
Mike

[sluckey]

I've never used solid conductor wire because of the possible breakage issue. One little nick while stripping is all it takes. Stranded wire is more forgiving during stripping.

I would use 18AWG stranded for four EL34s (20 is fine for two 6L6s) and 20AWG stranded for the little tubes. I use Cinch sockets which will easily accept two 20AWG wires. I always tin the stripped wires before inserting into the sockets.

[Mike_J]

I've never used solid conductor wire because of the possible breakage issue. One little nick while stripping is all it takes. Stranded wire is more forgiving during stripping.

I would use 18AWG stranded for four EL34s (20 is fine for two 6L6s) and 20AWG stranded for the little tubes. I use Cinch sockets which will easily accept two 20AWG wires. I always tin the stripped wires before inserting into the sockets.

Sluckey

Thanks I am ordering the wire today.

Thanks
Mike

[labb]

There are lots of charts available for wire continuous current rating in chassis wiring: typically
18 ga. rated for 16 amps
20 ga. rated for 11 amps
22 ga. rated for 7 amps

[Mike_J]

There are lots of charts available for wire continuous current rating in chassis wiring: typically
18 ga. rated for 16 amps
20 ga. rated for 11 amps
22 ga. rated for 7 amps

Good information.  Thank you for your reply.

Thanks
Mike

[Mike_J]

I've never used solid conductor wire because of the possible breakage issue. One little nick while stripping is all it takes. Stranded wire is more forgiving during stripping.

I would use 18AWG stranded for four EL34s (20 is fine for two 6L6s) and 20AWG stranded for the little tubes. I use Cinch sockets which will easily accept two 20AWG wires. I always tin the stripped wires before inserting into the sockets.

Sluckey

I am in the process of ordering some Cinch sockets.  Do you use tube shields on your preamp tubes?  If so, do you use the separate shield connectors (for lack of another word)?

Thanks
Mike

[sluckey]

I use shields on all preamp tubes, including PI tube. The shielded Cinch sockets I have are high quality NOS milspec with gold plated pins. The shield base is integrated into the socket. If you try to remove it, you will destroy the socket. I also have some non shielded Cinch sockets that I use for power and rectifier tubes.

My sockets look like this...

[eleventeen]

My favorite type of wire is heavily tinned #20 AWG stranded. It was commonly used to wire up record players in the 50's and 60's. The tinning is so thick on the conductors that they act as one solid conductor.


I have some surplus reels of excellent quality #18 AWG Belden stranded wire I got from a surplus sale some years ago. it is excellent wire but you're right, it's very troublesome when it comes to hooking up 9-pin sockets. Always scares me that I will have a straggler strand sticking out that my crappy eyes can't see that will short something out. I tend to use it for B+ wiring, maybe I will do the 6L6 heaters with it and go #20 AWG for the smaller tubes.


The ideal is to find a length of multiconductor cable in #20 AWG. Although that wire is usually rated no better than 300 volts, at least you get your half-dozen or ten colors.


Wire used to be free, right? Now you have to pay for it. Sigh.

[Mike_J]

My favorite type of wire is heavily tinned #20 AWG stranded. It was commonly used to wire up record players in the 50's and 60's. The tinning is so thick on the conductors that they act as one solid conductor.


I have some surplus reels of excellent quality #18 AWG Belden stranded wire I got from a surplus sale some years ago. it is excellent wire but you're right, it's very troublesome when it comes to hooking up 9-pin sockets. Always scares me that I will have a straggler strand sticking out that my crappy eyes can't see that will short something out. I tend to use it for B+ wiring, maybe I will do the 6L6 heaters with it and go #20 AWG for the smaller tubes.


The ideal is to find a length of multiconductor cable in #20 AWG. Although that wire is usually rated no better than 300 volts, at least you get your half-dozen or ten colors.


Wire used to be free, right? Now you have to pay for it. Sigh.

Those stragglers are what really frost me.  I had one once that was touching the chassis.  So small I missed it with a loop like the jewelers use.  Thankfully the PT did not have a center tap for the heaters and the 100 ohm balancing resistors fried.  Ever since then whether my PT's heater supply has a center tap or not I use the 100 ohm resistors until I know there is no problem and then I remove them and connect the center tap.  The 100 ohm resistors are much cheaper than a transformer.

Thanks
Mike

[Mike_J]

I use shields on all preamp tubes, including PI tube. The shielded Cinch sockets I have are high quality NOS milspec with gold plated pins. The shield base is integrated into the socket. If you try to remove it, you will destroy the socket. I also have some non shielded Cinch sockets that I use for power and rectifier tubes.

My sockets look like this...

edit... removed pic from quote...sluckey

I like those sockets.  The sockets I purchased on ebay this am are NOS B9A sockets.  They look like yours but without the shield retainers.  I figured I could buy them separately so I ordered 10 of them.  If they work I will get more.  Thank you for the suggestion.

Thanks
Mike

[sluckey]

Those stragglers are what really frost me.

If you will tin the wires you won't have any stragglers.

See that white can of brown stuff in the following pic? That's rosin paste flux. I also have a small 'eyedropper' bottle of liquid flux. EVERY wire that I strip will be dipped in that rosin and immediately tinned. This is a habit. I don't shortcut this step. Tinning does several things for you. The few seconds it takes is well worth the effort. Not only does tinning hold all the strands together as one solid wire, it also cleans the wire and prepares it to be easily soldered to whatever with a minimum of heat time and additional solder. All the wire on the board in that pic have been cut to length, stripped, and tinned, and the board is now ready to install. Just connect the wires to the sockets and the solder will flow like melted butter on those gold plated Cinch socket pins.

There are times that I cannot dip the end of a freshly stripped wire in the can of rosin. For those times, I will either use a toothpick to take a little paste to the wire or I'll use the 'eyedropper' bottle to put a drop of liquid flux on the wire. Regardless of the method used, I TIN EVERY WIRE. Sure, it takes time. Is it worth it? I think so. So does the Air Force. So does NASA.

[Stankfut]

I also always tin the wire before I solder it, makes it easy. I don't dip in flux, but that's something I will look into. As an added step, I also give the strands a slight twist before tinning. I'm not sure if this is a good practice, since I am completely self taught, but it seems to work well enough to prevent stragglers and helps the wire slide through the hole a little better.

[Mike_J]

I also always tin the wire before I solder it, makes it easy. I don't dip in flux, but that's something I will look into. As an added step, I also give the strands a slight twist before tinning. I'm not sure if this is a good practice, since I am completely self taught, but it seems to work well enough to prevent stragglers and helps the wire slide through the hole a little better.

Sure makes sense to me.  I will do it the same way.  Tin the strand and look for stragglers.  Eliminate them before inserting the wire into the socket.

Thanks
Mike

[Mike_J]

Those stragglers are what really frost me.

If you will tin the wires you won't have any stragglers.

See that white can of brown stuff in the following pic? That's rosin paste flux. I also have a small 'eyedropper' bottle of liquid flux. EVERY wire that I strip will be dipped in that rosin and immediately tinned. This is a habit. I don't shortcut this step. Tinning does several things for you. The few seconds it takes is well worth the effort. Not only does tinning hold all the strands together as one solid wire, it also cleans the wire and prepares it to be easily soldered to whatever with a minimum of heat time and additional solder. All the wire on the board in that pic have been cut to length, stripped, and tinned, and the board is now ready to install. Just connect the wires to the sockets and the solder will flow like melted butter on those gold plated Cinch socket pins.

There are times that I cannot dip the end of a freshly stripped wire in the can of rosin. For those times, I will either use a toothpick to take a little paste to the wire or I'll use the 'eyedropper' bottle to put a drop of liquid flux on the wire. Regardless of the method used, I TIN EVERY WIRE. Sure, it takes time. Is it worth it? I think so. So does the Air Force. So does NASA.

edit... removed pic from quote...sluckey

Sluckey

Is there a special name for the flux?  I think I have heard of rosin flux somewhere.  Do you think I could get some from Sears or Radio Shack?  Does the liquid flux come in the eyedropper bottle and do you think I could get it at the aforementioned places?

I just read about flux on Wikipedia.  They basically said what you do.  They said oxidation can form at high temperatures which reduces the bond of the solder.  Whereas with the flux the oxidation does not form and also flux by its very nature allows for the easier flow of the solder.  All good things.

Really appreciate the suggestions.  I am confident these suggestions will improve the quality of my connections.

Thanks
Mike

[eleventeen]

"Sears or Radio Shack"


maybe...I'm thinking not.


Fry's Electronics I know has those more exotic "electronic chemicals"


Whatever you do, and forgive me for repeating it if you already know, don't come anywhere near acid flux or let it near your build(s)!

[EL34]

I like 20 gauge solid core on the 9 pin sockets and 18 gauge stranded on the power tubes.

Just my personal preference for heater wire

[labb]

That is what I do too, EL34

[sluckey]

My paste flux came from work. If you build ten amps per year that can I have will only last about 30 years. 

My liquid flux came from eBay. eBay probably has a good selection of rosin paste also. DO NOT BUY ANYTHING FROM THE PLUMBING AISLE!

[Mike_J]

I like 20 gauge solid core on the 9 pin sockets and 18 gauge stranded on the power tubes.

Just my personal preference for heater wire

Thank you for the reply. 

That is how I have always done my amps too with no problems except in one instance where I was making numerous changes to an amp and bending the heater wires back and forth in order to make changes to the wires going to the PI socket.  The wire broke but of course  I couldn't see where it was broken. 

After a few hours of starring at preamp tubes with no lit heaters it finally clicked that there must be a problem with voltage getting to the heaters.  The way I was measuring each socket showed 3.15 volt on each side.  I believe it was Sluckey that suggested that I take the measurement across the tube which made it obvious that there was no voltage present.  A gentle poke with a chopstick quickly found the break.  I place the heater wires over the sockets.  I think a stranded wire in my case would reduce the likelihood of a recurrence of the wire breaking again.

My guess is anyone that does their wiring where they lay the heater wires flush against the chassis behind the sockets would probably never have a problem like the one I had.  So how you wire your heater wires probably would be contributory to the decision as to whether to use solid core or stranded wires on the preamp sockets.

Thanks
Mike

[Mike_J]

My paste flux came from work. If you build ten amps per year that can I have will only last about 30 years. 

My liquid flux came from eBay. eBay probably has a good selection of rosin paste also. DO NOT BUY ANYTHING FROM THE PLUMBING AISLE!

Thanks again Sluckey

Mike