Choosing a Power Transformer for a Class A single-ended amp build

[Dolmetscher007]

I have worked with devices that have a Power Transformer that needed to be replaced. I did not do the replacing myself, but I was able to find a replacement very easily, just by looking at the existing one.

I am working through a DVD tutorial on DIY Tube Guitar Amps, and even though the video(s) are really awesome(!!!), every once and a while, they assume the audience knows things that I just do not. To make matters worse, the author is from Croatia originally, but lives, and has been living in Australia for a long time. So right out of the gate, I start to get the feeling that some of the components he is using are either not available here in the US, they are called something different here, or there are just some concepts that I am not aware of yet.

I have attached a .jpg image that I made... literally just by pausing the DVD and sketching in Adobe Illustrator the rough shape and label values from the transformer they are using. On the same graphic, I used Illustrator to draw up the first section of the power supply schematic. This is my first time drawing a schematic, and again the guy is not from the US, so if there are some weird things that look funny, that may be why. In the DVD, he is sketching the schematic on a dry erase board.

Basically, I have gone to Digi-Key, the Hammond Mfg website, parts-express, and several other amp and vintage electronic supply website, and I cannot find a transformer that matches all of the parameters that their power transformer has. Also, I know how a transformer works, for the most part. AC voltage comes in through a primary coil, induces a voltage into 1, 2, 3, 4... however many secondary coils, which are stronger or weaker based on the number of windings, and can sometimes have a "Center Tap" which can make one secondary coil behave almost like two. I am, however not as knowledgeable about current. In the video he mentions X.X Amps, and/or XX mili-amps. But when I go to one of those above electronic's websites, they all have these long menus that you select parameters, and then filter the results... the current this and current that doesn't seem to make any sense and/or just does not match the label on the transformer in the video.

If any of you guys have a second to take a look at the graphic I've attached, I'd love some tips on what you think. I'm not sure at this point if I have enough information to find one yet.

Thanks guys!

[nosaj]

I have worked with devices that have a Power Transformer that needed to be replaced. I did not do the replacing myself, but I was able to find a replacement very easily, just by looking at the existing one.

I am working through a DVD tutorial on DIY Tube Guitar Amps, and even though the video(s) are really awesome(!!!), every once and a while, they assume the audience knows things that I just do not. To make matters worse, the author is from Croatia originally, but lives, and has been living in Australia for a long time. So right out of the gate, I start to get the feeling that some of the components he is using are either not available here in the US, they are called something different here, or there are just some concepts that I am not aware of yet.

I have attached a .jpg image that I made... literally just by pausing the DVD and sketching in Adobe Illustrator the rough shape and label values from the transformer they are using. On the same graphic, I used Illustrator to draw up the first section of the power supply schematic. This is my first time drawing a schematic, and again the guy is not from the US, so if there are some weird things that look funny, that may be why. In the DVD, he is sketching the schematic on a dry erase board.

Basically, I have gone to Digi-Key, the Hammond Mfg website, parts-express, and several other amp and vintage electronic supply website, and I cannot find a transformer that matches all of the parameters that their power transformer has. Also, I know how a transformer works, for the most part. AC voltage comes in through a primary coil, induces a voltage into 1, 2, 3, 4... however many secondary coils, which are stronger or weaker based on the number of windings, and can sometimes have a "Center Tap" which can make one secondary coil behave almost like two. I am, however not as knowledgeable about current. In the video he mentions X.X Amps, and/or XX mili-amps. But when I go to one of those above electronic's websites, they all have these long menus that you select parameters, and then filter the results... the current this and current that doesn't seem to make any sense and/or just does not match the label on the transformer in the video.

If any of you guys have a second to take a look at the graphic I've attached, I'd love some tips on what you think. I'm not sure at this point if I have enough information to find one yet.

Thanks guys!
[ATTACH=CONFIG]51330[/ATTACH]

This is a much easier site to navigate Unless your outside the US the primaries only need to be 117v/120v.
http://www.classictone.net/
nosaj

[eschertron]

Do you have a list of the specifications that you're looking for? Someone here can help you filter through the choices if we know what we're looking for.

The two drawings that you posted are close, but I'm not sure if they represent the same transformer or not. Some clarification on the "0 N 6.3" taps might be needed. I agree, that's not how I've seen taps identified in the US.

[nosaj]

Do you have a list of the specifications that you're looking for? Someone here can help you filter through the choices if we know what we're looking for.

The two drawings that you posted are close, but I'm not sure if they represent the same transformer or not. Some clarification on the "0 N 6.3" taps might be needed. I agree, that's not how I've seen taps identified in the US.

if you look at the schematic. The rectifier is a 6v, the other 6v tap is for other tubes, you seperate the rectifier filament from the other 6v filaments. Basically 6 n 0 is a 6.v CT.
I was just referring to the primaries.

nosaj

[eschertron]

if you look at the schematic. The rectifier is a 6v, the other 6v tap is for other tubes, you seperate the rectifier filament from the other 6v filaments. Basically 6 n 0 is a 6.v CT.
I was just referring to the primaries.

nosaj

OK. I'd never seen it that way. The other discrepancy between the two drawings is the current rating on the 6.3vac windings. I can see the similarities, but the drawings didn't match up exactly.

Is one drawing from what's in there now, and another from a likely replacement? Where did the numbers come from? Oh, I see, the illustrator drawing is from the actual device, including amp ratings?

[g1]

Like the others mentioned, there are discrepancies between the drawings as far as the current ratings for the two 6V heater windings. (and voltages, 6.3V is often just called 6V)
So one one pic they call out 2A and 1A, on the other, they are more specific with 2.3A and .6A, but both are talking about the same basic thing.

I think the biggest problem is that the design is using a fairly uncommon 6V rectifier tube. Most common tube amps use 5V rectifiers, so most PT's have a 5V winding for the rectifier filament. This is probably what you are seeing on the websites.
Also, lower current secondaries are not always available. Like 1A for the rectifier filament, usually they are 2 or 3A. You can always use a winding that meets or beats the required current, you just can't go lower.

[mikepukmel]

I have worked with devices that have a Power Transformer that needed to be replaced. I did not do the replacing myself, but I was able to find a replacement very easily, just by looking at the existing one.

I am working through a DVD tutorial on DIY Tube Guitar Amps, and even though the video(s) are really awesome(!!!), every once and a while, they assume the audience knows things that I just do not. To make matters worse, the author is from Croatia originally, but lives, and has been living in Australia for a long time. So right out of the gate, I start to get the feeling that some of the components he is using are either not available here in the US, they are called something different here, or there are just some concepts that I am not aware of yet.

I have attached a .jpg image that I made... literally just by pausing the DVD and sketching in Adobe Illustrator the rough shape and label values from the transformer they are using. On the same graphic, I used Illustrator to draw up the first section of the power supply schematic. This is my first time drawing a schematic, and again the guy is not from the US, so if there are some weird things that look funny, that may be why. In the DVD, he is sketching the schematic on a dry erase board.

Basically, I have gone to Digi-Key, the Hammond Mfg website, parts-express, and several other amp and vintage electronic supply website, and I cannot find a transformer that matches all of the parameters that their power transformer has. Also, I know how a transformer works, for the most part. AC voltage comes in through a primary coil, induces a voltage into 1, 2, 3, 4... however many secondary coils, which are stronger or weaker based on the number of windings, and can sometimes have a "Center Tap" which can make one secondary coil behave almost like two. I am, however not as knowledgeable about current. In the video he mentions X.X Amps, and/or XX mili-amps. But when I go to one of those above electronic's websites, they all have these long menus that you select parameters, and then filter the results... the current this and current that doesn't seem to make any sense and/or just does not match the label on the transformer in the video.

If any of you guys have a second to take a look at the graphic I've attached, I'd love some tips on what you think. I'm not sure at this point if I have enough information to find one yet.

Thanks guys!
[ATTACH=CONFIG]51330[/ATTACH]

Maybe there is a more standard 5v heater rectifier tube that would be a good substitute, and hence would be much easier to find a transformer. I don't have the engineering chops to help there, but if you could post the entire schematic, Im sure the gurus here could help.

[nosaj]

Maybe there is a more standard 5v heater rectifier tube that would be a good substitute, and hence would be much easier to find a transformer. I don't have the engineering chops to help there, but if you could post the entire schematic, Im sure the gurus here could help.

If it were me I'd contact classictone with those specs, Other option is to change circuit to a 5y3 which is a 2amp draw compared to the 1amp draw of a 6ca4.
Now going back to the pic the 6v windings The CT one can handle a rectifier, but the other 6v winding .6a What are you going to run with that? barely 2 12ax7's
Might be best if OP gives more real Info..for example the DVD series he's watching and the make and model of the amplifier.

If not this will turn into a 100 page thread of useless meanderings.

nosaj

[mozz]

Marshall 18w uses a 6ca4, draws 1amp. You may look on that website (18watt.com) and see a SE version or just ask the forum members. I have a similiar transformer here out of a piece of test equipment i got cheap. Maybe a vox ac4 uses something close?