12xxx Series Build w/Marstran T2562 PT

[Robocop101985]

Hey Guys,

Hoping for some help. I just started a 12xxx series build based off of EVH specs, however when I opened my package from Marstran... I noticed the PT from my original '68 12xxx amp I bought from Metro has a different orientation than the PT I bought from Marstran. I did contact Marstran before I placed the order to make sure I was indeed buying a PT that would work with the build I had in mind and I was assured by Marstran that I was buying a PT that would work. So what I could help with is how do I connect the Marstan PT (T2562) into the 12xxx series build. I've been sitting on this kit and parts for about 6 months due to my work schedule and I just unpacked the package from Marstran and noticed this difference. I've been using "nightowls" Metro 12xxx build journal as a reference and I've very early on in the build. I'm just trying to get ahead of any problems I may run into later on with the build. I've attached the Metro PT along with the Marstran PT I bought with their Wiring Diagram. Any help would be appreciated. Thank you!

[Tazin]

If the Marstran PT (T2562) is the laydown version then it would be correct for a '68 12xxx series build. The standup/upright version, Dagnall T2623, would be for a '69 build.

[Robocop101985]

If the Marstran PT (T2562) is the laydown version then it would be correct for a '68 12xxx series build. The standup/upright version, Dagnall T2623, would be for a '69 build.

Yes, it is the T2562. I'm following the build journal that's including the Virtual Variac, which I will not be using in this build, so my PT is different than the one in the journal. So essentially, I just want to know if I'm properly connecting the PT in my build.

I'm trying to upload pictures but the forum keeps giving me the error message " the board attachment quota has been reached" on one file that's only 435 kb.

[Tazin]

Unfortunately, you can no longer upload photos to this board's server. You have to use a third party photo hosting site.
Marstrans site has the wiring diagram for his T2562 so check there.

[Robocop101985]

So I'm hoping to get a paint by numbers approach if I can get the help. I can't find the wiring diagram for the current PT that is in my Metro '68, I believe it's the Metro 1203-80-ML Power Transformer. The building journal is using that Metro PT and that's where I'm getting thrown off. Also, my metro has been modded so the three green wires that are being connected in the journal as shown in the journal picture, one of them in my metro is taped off and isn't being used. I just want to make sure I'm not goofing up at one of the initial steps right at the start. I will attach images:

Marstran PT
https://imgur.com/pTtp3e4

Marstran Wiring Diagram
https://imgur.com/SyNkn8z

My Metro Amp PT
https://imgur.com/NYJhKLm

Build Instructions Picture
https://imgur.com/a/DBGZvZm


This is the step in the journal:

Step 5 - Connect Heater Wires and Ground

Parts:

• (1) 1” piece 18 gauge buss wire
• (4) 1-ohm metal oxide resistors (small blue resistors with brown-black-gold-gold bands)
• (1) 4” piece black wire

This is similar to Step 5 in the basic 100w kit instructions, other than how the F1 capacitor polarity is marked and placed.

a. Tightly and evenly twist together the two solid green wires from the PT and solder them to pins 2 and 7 of the V7 power tube socket after cutting them to length. It doesn’t matter which wire goes to which pin.

b. Solder the green wire with the yellow stripe to one of the ground lugs by the capacitor in F1 after cutting it to length. One of the F1 capacitor terminals has a red dot on it. Do not use the ground lug by that terminal - use the other ground lug.

c. Take one of the two blue wires from the PT bias circuit and solder it to the same ground lug that was used in Step b above.

d. Solder 1” of 18 gauge buss wire from the negative terminal of the capacitor in F1 (the one without the red dot) to the second ground lug by F1. Trim closely.

e. Install one of the 1-ohm resistors on each power tube socket. One leg goes to the ground lug by each socket. The other leg goes through pin 8 then pin 1. Solder and trim closely.

f. Cut a 4” piece of black wire and strip 1/4” from both ends. Solder one end to the ground lug of V5 (second power tube socket from the PI). Let it stick straight up, out of the way for now.

Pictures 7 and 8 show this step.

[Tazin]

It looks like Brian at Marstran may have changed the wire colors slightly compared to the wiring diagram so I would drop Brain a message to see if he has an updated wiring diagram available or see if he can clarify the current wire colors used. Typically, all the primary wires exit from one side of the transformer and the secondary wires from the other end. So, the orange, brown, red, gray, blue and violet wires should be the primaries.

[ValveStorm]

Looks like the Marstran PT pic matches the associated wiring diagram for it. The primary is on one side, the secondary on the other. You can use an ohmmeter to figure out what is what.
6.3v Heaters: The Yellow/Green striped wire will have a connection to two of the green wires (likely the thickest ones).
100v Bias: The white wire will have connection to one of the remaining green wires.
HT: Should be the remaining green, yellow and black wires all showing connection to each other.

For the primaries: Orange is common/neutral, red is 120v mains.

[Tazin]

Looks like the Marstran PT pic matches the associated wiring diagram for it. The primary is on one side, the secondary on the other. You can use an ohmmeter to figure out what is what.
6.3v Heaters: The Yellow/Green striped wire will have a connection to two of the green wires (likely the thickest ones).
100v Bias: The white wire will have connection to one of the remaining green wires.
HT: Should be the remaining green, yellow and black wires all showing connection to each other.

For the primaries: Orange is common/neutral, red is 120v mains.

I don't know why these guys who make reproduction T2562's don't adhere to the original wire colors & layout for the sake of clarity. It would make life so much easier and eliminate the guess work.

[Robocop101985]

I just appreciate everyone taking the time to help me along. I’m sure I’m over thinking all this. All my tube amp books explain what a transformer is and how it operates. They don’t explain anything with a wiring diagram to show me which wires connect to what.

[Tazin]

Were you able to sort out the wires on the Marstran PT?

[Robocop101985]

Let’s say I’m getting a better understanding of things overall. Valvestorm was able to help confirm what I thought were the wires being used for the heaters.

My main problem right now is the build journal only refers to the colors of the wires, it doesn’t tell me what the wires and their values are from the PT that are being connected. So that’s where my extra homework is coming into play and trying to understand.

In order to test them, do I connect a power cord from the neutral side to the common (orange wire) and the hot side to the 120v?

[Tazin]

Let’s say I’m getting a better understanding of things overall. Valvestorm was able to help confirm what I thought were the wires being used for the heaters.

My main problem right now is the build journal only refers to the colors of the wires, it doesn’t tell me what the wires and their values are from the PT that are being connected. So that’s where my extra homework is coming into play and trying to understand.

In order to test them, do I connect a power cord from the neutral side to the common (orange wire) and the hot side to the 120v?

NO! I would not put 120v through the transformer to test/sort out the wires. I highly recommend you contact Marstran for the proper wiring diagram. In the mean time, you can use your multimeter set to Ohms to check for continuity between the secondary wires like Valvestorm mentioned earlier. So, for example, the black wire, yellow wire and one of the green wires (could be the green w/ yellow stripe) should all have continuity between any combination of two wires....This would be for the H.T. secondary winding. Same thing should hold true for the two thicker green wires and one of the green wires...This would be for the Heater winding. The white wire and the thin walled light green wires should have continuity between them and they would be for the bias winding.

[Robocop101985]

Let’s say I’m getting a better understanding of things overall. Valvestorm was able to help confirm what I thought were the wires being used for the heaters.

My main problem right now is the build journal only refers to the colors of the wires, it doesn’t tell me what the wires and their values are from the PT that are being connected. So that’s where my extra homework is coming into play and trying to understand.

In order to test them, do I connect a power cord from the neutral side to the common (orange wire) and the hot side to the 120v?

NO! I would not put 120v through the transformer to test/sort out the wires. I highly recommend you contact Marstran for the proper wiring diagram. In the mean time, you can use your multimeter set to Ohms to check for continuity between the secondary wires like Valvestorm mentioned earlier. So, for example, the black wire, yellow wire and one of the green wires (could be the green w/ yellow stripe) should all have continuity between any combination of two wires....This would be for the H.T. secondary winding. Same thing should hold true for the two thicker green wires and one of the green wires...This would be for the Heater winding. The white wire and the thin walled light green wires should have continuity between them and they would be for the bias winding.

Appreciate the reply. I watched a video regarding this but it doesn't state how to hook it up properly. Another guy who replied to a post on a tube amp facebook page said the same thing but again didn't tell me how to hook it up. So I'm staying away from that for now.

[Robocop101985]

Here are my readings with the multimeter.

Green and Yellow/Green
https://imgur.com/Vsd5tNo

Other Green (same gauge) and Yellow Green
https://imgur.com/w6XcSjg

Green and Green (same gauge)
https://imgur.com/z2Huf5R

Black and Yellow
https://imgur.com/8Cs5EWy

Green and Yellow
https://imgur.com/bG2JD0S

Green and Black
https://imgur.com/98fzcYC

White and Light Green
https://imgur.com/koqaGIZ

When taking the readings I noticed the different size gauges being used, I'm assuming that they go together accordingly. I wasn't getting any readings when I swapped them around.

I'm assuming these are the group that's "sleeved" on the diagram
https://imgur.com/Gi3e37N

22 GA (maybe)
https://imgur.com/IZiFqo5

Thinwall
https://imgur.com/YZj0o0H

So am I suppose to get readings for the other wires? Like the black and Yellow, is there going to be a reading for those or should that be 0 and so on for the other readings?

[Tazin]

The secondary of the PT is made up of three independent windings which are wound on top of each other. Therefore, the three heavy gaged wires (18 gage?) which are Green, Green and Green w/Yellow stripe should all have continuity between any combination of wire pairs. They should NOT have continuity with any of the other wires (i.e. Black, Yellow, White, Green (thinwall), and the Green (22 gage).

The same should hold true for the 22 gage Black, Yellow and Green wires....They should NOT have continuity with any of the other wires (i.e. Green (18 ga.), Green (18 ga.), Green w/Yellow stripe (18 ga.), White, Green (thinwall)).

Ditto for the White and Green (thinwall) wires...They should NOT have continuity with any of the other wires (i.e. Black, Yellow, Green (22 ga.), Green (18 ga.), Green (18 ga.), Green w/Yellow stripe (18 ga.).

Once you've sorted out which wires are grouped together via continuity label them if necessary. Now you need to sort out which wire is the center-tap for the Heater winding and also for the H.T. winding. Assuming the H.T. winding is comprised of the 22 gage Black, Yellow, and Green wires, you should have an Ohm's reading of approximately half the value between the Yellow and the Black wires compared to the reading between the Black and Green wires. For example, the Ohm's value across the Black and the Green wires is 12 ohm's verse the reading across the Black and Yellow wire which is 6 ohm's. The same example should hold true when comparing the Black and Green wires Ohm's value to the Green and Yellow wires value. So, the above example would show that the 22 gage Yellow wire is the H.T. center-tap.

The Heater winding is more difficult since the wire has basically no resistance value due to its large diameter coupled with the fact that it's a small winding (very little turns of wire). Here you can use a couple of resistors of equal value (i.e. 10K) and temporarily clip them on the ends of the two heavy gage (18 ga.) Green wires. Here you'd measure across the free ends of the resistors on the two Green wires and you should see a value of 20K on the multimeter. Then you'd measure between one of the Green wires with the 10K resistor (the free end of the resistor again) and the heavy gaged (18 ga.) Green w/Yellow stripe wire (which has no 10K resistor) and your meter should read only 10K. Perform the same reading across the other Green wire with the 10K resistor and the resistor less Green W/Yellow stripe wire and it should also show 10K on your meter. In this example it would show that the heavy gaged Green w/Yellow stripe wire is the Heater center-tap.

Again, once you've sorted out the center-tap wires for the Heater winding & H.T. winding label them.