Schem wiring question

[C Moore]

The schem is below.
Electrically it all looks like the same connection to me, but it still looks wrong. Because of the close proximity, I ran the OT center tap straight to the 5V winding of the PT. It just feels like I did something wrong, but the schem implies it is all the same electrical connection. OT is on the left, CT has pink shrink on it.
Am I OK to wire it this way.?
Thank You
http://www.webphix.com/schematic%20heav ... 12_6v6.pdf

[tubeswell]

Hiya hired hand - when I go to click on those links, a message comes up saying the selected attachment don't exist anymore?

[C Moore]

Don't know how the double post happened, sorry about that.
Then I screwed up the pictures somehow.
Do I have it working now.....?
Thanks

[Firestorm]

Never seen it done that way, but a wire is a wire is a wire. Just don't hang your caps off Pin 2. Move that connection over to Pin 8.

[Phil_S]

Okey dokey, you've got some fixing up to do there.
Remove all the cross connects between the two transformers. Never do that.

All the center taps from the PT go to the same ground lug.

I see a black wire on one of the 6.3v taps. Remove that.

I'd rework that splice from pin 8 of the rectifier to the blue cap. You have the room for a proper Western Union splice (Google for it), solder and cover with heat shrink. While you are at it, remember to add a wire from that 1st cap to the OT primary center tap or you will be doing it over again. (Sorry, not sure which lug this is.) I don't like the proximity to the chassis and this will offer good protection. The ground splice and the + on the other cap are sloppy too. I am sure you can do better. Please try. Neatness counts, not for looks but for dependability.

Your HV secondary (light brown cloth wire) is poorly dressed. Route it on the other side of the transformer bolt where you have the ground wires. Keep them from resting on the transformer.

The ground wires: don't use a transformer bolt -- this is a last resort. Use a dedicated stud through the chassis. Using the orientation of the pictures, draw a center line between the rectifier socket and the one next to it, and find a spot halfway between the upper edge of the tube sockets and the PT to drill a hole for a dedicated circuit ground bolt.

The signal input from the PI to the power tubes (yellow pair) runs under a blue 100u 50v. Route this away from that cap.

On that same 100u 50v cap, there is a red wire looped around. Rework and run along the terminal strip.

You must choose on the PT to connect either the 125 or 117 tap, but not both, so one of those wires has got to be removed. The other primary connection is marked "C" for common, next to the 117. Using the 117 tap will result in higher secondary voltage than the 125.

To determine the best primary tap, I'd wire up the filament harness to all the sockets (normally the first thing to do anyway), put the tubes in the sockets, and find out which one gives you closest to 6.3V. Make sure nothing is connected to the high voltage secondary when you do this.

The 5v winding connects to the last tube socket, pins 8 and 2 -- looks like this is done OK.

Whew, I'm out of breath. I feel certain this needs more attention, but this is a plate full. It is what I would do if it were mine. I suggest you do some fixing up and post a new picture. Maybe someone else will chime in?

Also, what are those wires on the left side that go through the grommet to the outside of the chassis? Same for the orange wires. Is there going to be a separate perpendicular panel for mounting the pots? If so, this would be OK.

Just trying to help, so you will learn something in the process. I think you can get this done with a little help. You did the right thing by stopping to ask.

[tubeswell]

So you should still get 5VAC between the two ends of the 5V winding even if one side is grounded, but it seems odd that it is then connected to the 4R secondary tap? (intuition tells me, if anything, it would be 'normal' to connect to the 0V tap on the OT secondary as one way of grounding that winding - I guess it probably doesn't matter because if the 0V tap is floating and the 4R tap is grounded, you will still get a voltage swing on the secondary to drive the speaker with (and reflect a load to the OT primary) - so maybe its got something to do with the phase of the secondary winding? (but I can't see why that would matter, since you only have one secondary winding is use?) Who knows. maybe they wired it in a seemingly confusing way to throw would-be copycats off the trail?

What do others say?

[Phil_S]

Are you guys looking at the same schematic as me? What I see is conventional wiring: 5v to the rectifier, pin 8 take off to the first filter cap. I don't see any cross connect between the PT and OT. Where's this coming from?

[tubeswell]

The gut-shot(s)

[Phil_S]

Yeah, I saw it in the pix. It looks wrong to me. I figure the 60Hz alone will mess up the sound and have no idea what the 5v will do.

[C Moore]

Let me start by saying that A Lot of what you see is temporary, some of this stiff is not even soldered. I was at the point where I had to terminate wires to keep them out of the way. Not that what I have completed is all correct, I am sure some of it will be wrong, and I appreciate being told so.
Back to Phils advice.....
1. Maybe I do no understand what a "cross connect" is. The only wire that goes from one tranny to the other is the OT center tap, to the PT 5VAC winding.
2. I am "saving" the heaters for last. I do not have a black wire, or any other color wire connected to the heater supply. Again, this stuff is pretty new to me, so I may not understand your advice. Sorry about that....
3. I will take your advice about trying a different/better splice for the first filter cap. As far as the OT CT....that was what my original post is all about. It is connected to the PT 5VAC winding. Electrically, it all looks like the same connection to me.
4. The HV wires are not connected to anything, they are just twisted and run through some holes on the rectifier to keep them out of the way. Again. I am nowhere near done with this. I am doing the best I can to make things fit, and have had/will have to keep changing things as I go.
5. Will take you advice about the feed from the PI to power rubes and avoid the blue by-pass cap the best I can. That was definitely a "finished" connection.
6. On the same 100/50 cap, I do not see the red wire looped around you are talking about. Sorry if I am missing it.
7. "You must choose on the PT to connect either the 125 or 117 tap, but not both, so one of those wires has got to be removed. The other primary connection is marked "C" for common, next to the 117. Using the 117 tap will result in higher secondary voltage than the 125".
I do not even have a power cord installed yet, so I do not have anything connected to the PT primary. Again, if I am missing the intent of your advice, I apologize. You will just have to chalk it up to my inexperience.
8. When I tested the transformers, I did just what you are saying. My wall voltage is pretty much 121-122 VAC, so I am going with the 125 tap.
9. The orange and other assorted wire through grommets are just leads that will be connected to the front panel pots. That panel is not even on the amp yet. I am just trying to keep those out of the way for now. I am having to work on the amp while it is up-side-down. So anything like a panel just makes it very hard to deal with at this point.
I appreciate all of you suggestions. Some of your help will make for an easier fix now than later.
Thank You

[Phil_S]

1. Maybe I do no understand what a "cross connect" is. The only wire that goes from one tranny to the other is the OT center tap, to the PT 5VAC winding.

I'm saying there is nothing on the schematic connecting that 5V tap to the OT. Remove it. The CT on the OT goes to the + on the first filter cap.

2. I am "saving" the heaters for last. I do not have a black wire, or any other color wire connected to the heater supply. Again, this stuff is pretty new to me, so I may not understand your advice. Sorry about that....

Your choice on that. Everyone's style is different. I see that you have not wired it yet. I was mistaken about the black wire. What I see is the end of the winding coming from the transformer to the terminal. Please leave that alone!

3. I will take your advice about trying a different/better splice for the first filter cap. As far as the OT CT....that was what my original post is all about. It is connected to the PT 5VAC winding. Electrically, it all looks like the same connection to me.

Um, no. See #2 above. Take a good look at the schematic. The CT on the OT goes to filter cap #1. I can see where you think it goes to the rectifier pin 8, but it's not generally done that way. Now I understand the comments from the other guys. I suppose it would work, but very unconventional. I suggest sticking with what's conventional. You are not looking for the 5V supply, you are looking for the high voltage, which I always see tapped at the filter cap.

4. The HV wires are not connected to anything, they are just twisted and run through some holes on the rectifier to keep them out of the way. Again. I am nowhere near done with this. I am doing the best I can to make things fit, and have had/will have to keep changing things as I go.

Well, OK.

5. Will take you advice about the feed from the PI to power rubes and avoid the blue by-pass cap the best I can. That was definitely a "finished" connection.

Likely to hum that way, better to rework. That's what I think. YMMV.

6. On the same 100/50 cap, I do not see the red wire looped around you are talking about. Sorry if I am missing it.

It is a long loop around the tube sockets, all the way to V1 cathodes. I think it is PVC wire -- the color in the pic is a bit more red-orange. This sort of long run is begging for trouble.

7. "You must choose on the PT to connect either the 125 or 117 tap, but not both, so one of those wires has got to be removed. The other primary connection is marked "C" for common, next to the 117. Using the 117 tap will result in higher secondary voltage than the 125".
I do not even have a power cord installed yet, so I do not have anything connected to the PT primary. Again, if I am missing the intent of your advice, I apologize. You will just have to chalk it up to my inexperience.

It is always better to ask than to assume. I think you will be fine on either tap at 121, which is right in the middle. If your don't like the result, you can always change to the other tap. This isn't that big a deal. I was concerned seeing wires on both taps when you can only choose one.

8. When I tested the transformers, I did just what you are saying. My wall voltage is pretty much 121-122 VAC, so I am going with the 125 tap.

See #7.

9. The orange and other assorted wire through grommets are just leads that will be connected to the front panel pots. That panel is not even on the amp yet. I am just trying to keep those out of the way for now. I am having to work on the amp while it is up-side-down. So anything like a panel just makes it very hard to deal with at this point.
I appreciate all of you suggestions. Some of your help will make for an easier fix now than later.

Yup, just making sure.

Thank You

I didn't do much, but am glad to try to be helpful.

[C Moore]

Regarding #6....
Yeah OK, I was taking you a bit too literally, sorry about that. I thought you were seeing a Red Wire some where on the term strip.
That Long Orange Wire......I kind of new that was going to be trouble. I do not have any layout to go by, and I am just trying to make things fit the best I can. So, if I move that, I am probably going to have a long lead somewhere else.
If it comes down to a choice, is it "better" to have a long lead for a plate to grid connection than it is for a cathode." If that long orange wire were from a plate to grid, would you be as concerned.?
Thanks

[C Moore]

Regarding #3....
I am not stuck in the mud about having the CT go straight to the 5V lead on the tranny. I am really just curious if it matters. Like I say, on the schematic, it is all the same wire. So, in reality, does it make any difference if the CT connects to the 5V lead, or if it connects to the first filter cap.?
The reason the CT lead is so short, is that was how the original PA Head was wired. At first, I could not figure out why it was like that. It is not often you see an OT in such close proximity to a PT, where the wiring is concerned. But then when you look at the schem, you see it is all the same connection.
If it is better to add length to the CT lead and run it over to the first filter, I am happy to do it.
Thanks Again

[Firestorm]

Regarding #3....
I am not stuck in the mud about having the CT go straight to the 5V lead on the tranny. I am really just curious if it matters. Like I say, on the schematic, it is all the same wire. So, in reality, does it make any difference if the CT connects to the 5V lead, or if it connects to the first filter cap.?
The reason the CT lead is so short, is that was how the original PA Head was wired. At first, I could not figure out why it was like that. It is not often you see an OT in such close proximity to a PT, where the wiring is concerned. But then when you look at the schem, you see it is all the same connection.
If it is better to add length to the CT lead and run it over to the first filter, I am happy to do it.
Thanks Again

Everything connected to Pin 8 of the rectifier is the same point electrically, so it should not matter if you run a separate wire or if you tie to the lead on Pin 8 at the PT end. It does matter, though, that the filter cap be connected on Pin 8, too. Two reasons: by putting the cap on Pin 2, you have it on the other side of the tube filament. And, although the 5Y3 is a directly heated filament tube (meaning that the filament and cathode are the same and Pin 8 and Pin 2 are both the cathode), an indirectly heated cathode rectifer like a 5AR4, 5V4, etc. has its cathode only on Pin 8 so the B+ should always be connected there.

[C Moore]

OK.....Thanks
I see the difference you are talking about regarding rectifiers (GZ34 for example). So it is just a good habit to be in, connecting the B+ to Pin 8. There is never anything to think about when you do it that way.
Thank You