#124 "T4" Transformer

[lgehrig4]

Hello, I need help choosing the correct T4 transformer for this build. I''m not sure what this it is technically referred to.

The schematic shows 6.3V PT, but the layout shows 3V. The BOM I'm using lists a 12.6V CT transformer, but assume CT is a different measurement.

Layout ---> SEC 3-D-3V 0.45A Radioshack
Schematic ---> 6.3V PT

I found a photo of another members build where they use this one below. I was going to pick up one of these but I wanted to confirm that it would be ideal first.

Hammond 166F12B (photo)
Power Rating (VA) 3.6
Primary VAC 115V 60 Hz.
Secondary (RMS) VAC 12 C.T.

#124 Schematic_1988_Skyliner [marked up_2].pdf

Dec-19-2011.png

124 BOM Joost 1.2 AMPGARAGE.xls

[sluckey]

The schematic shows 6.3V PT, but the layout shows 3V.

The schematic shows 6.3V with CT which is 6v end to end.

The layout shows 3-0-3 (not 3-D-3) which is 6v end to end.

It's just two ways of expressing the same PT rating. These two PTs are identical.

[GAStan]

You are correct, those are two different transformers; a 6.3 in the build documents and 12.6 on the BOM..

#124 was built with a 6.3vac secondary xfmr with a voltage doubler/rectifier. If you are keeping true to #124 this is the way to go, both the schematic and layout in your post show this style 12vdc power supply.

I purchased a set of boards to make my #124. The included 12vdc rectifier board did not use a doubler so I needed a 12.6 vac xfmr, that is what is listed in most BOMs I've seen.

The xfmr you need depends on which of the above you will use in your build. The 166F12B transformer you list does have 12vac secondary.

To be clear i am not contradicting Sluckey in the previous post, he is absolutely correct.

[mensur87]

If you're sticking to the original #124 design, go with a 6.3V secondary transformer since it uses a voltage doubler. The 166F12B you mentioned is 12V, so it depends on whether your build follows the original power supply setup or a different BOM. Just make sure your rectifier setup matches.

[lgehrig4]

Thank you for the feeback!

I received the 166F12B. To be clear I'm not 100% dead set on making it exact. I want to be as close as I can without going nuts finding the exact parts.

I received the transformer. Unlike the layout, this has 3 secondaries, green - green/yellow - green.

If I understand correctly, I can connect the two solid green for 12V or one solid green and the green/yellow for 6V. Am I off here?

Attached is a photo of the ODS relay boad. I'm using Amplified Nation's, which is different from the layout.

IMG_3359.jpg

[martin manning]

Your board is configured as a full wave bridge rectifier, so it will need to be supplied with 12VAC for 12V relays. .

[lgehrig4]

Your board is configured as a full wave bridge rectifier, so it will need to be supplied with 12VAC for 12V relays. .

Thank you Martin!

[martin manning]

PS the Amp Nation boards were copied from the eyelet board .pdf in the D files section, so you can refer to that document for component placement and options. https://ampgarage.com/forum/viewtopic.p ... 08#p365408

Also, the best practice is to keep all inquiries related to a particular build in a single thread.

[lgehrig4]

PS the Amp Nation boards were copied from the eyelet board .pdf in the D files section, so you can refer to that document for component placement and options. https://ampgarage.com/forum/viewtopic.p ... 08#p365408

Also, the best practice is to keep all inquiries related to a particular build in a single thread.

Thank you for letting me know! I will do that going forward

[lgehrig4]

Please help me to understand the ground from from the power amp/pre amp ground. The skyliner schematic just shows them goingto ground(which makes sense) but the layout shows this black wire running under the board and connecting to the 0.1uf cap.

I'm not looking to build an exact copy so I would be fine just sending these to ground on their side of the chassis, but I'm guessing there is more to this.

Screenshot 2025-03-20 at 8.51.48 AM.png

Screenshot 2025-03-20 at 8.52.21 AM.png

[martin manning]

Do you mean the black wire from the 1.0 uF cap to the send jack sleeve lug? That is the PI ground and it should be grounded at the loop jacks.

[GAStan]

There is much more to it. Definitely something to look into, there is plenty of discussion on grounding. For now my suggestion is follow the original as closely as you can.

[lgehrig4]

Do you mean the black wire from the 1.0 uF cap to the send jack sleeve lug? That is the PI ground and it should be grounded at the loop jacks.

Yes, that is what I mean.

I just realized my error in thinking. The sleeve is already grounded to the chassis directly. This is the ground for the PI, not the jack sleeve specifically. Thank you for pointing that out

[lgehrig4]

I noticed the layout/schematic has a 1/2 power slide switch, which I am not incorporating into my build. Can I just solder pins 8 of V5/V7 to the nearest ground like V4/V6, or do I need to run this up to the ground near the voltage doubler like the switch does?

[martin manning]

The half power switch either grounds the cathodes of two of the power tubes to the solder lugs between the left and right pairs of tubes sockets or takes each through a 10k resistor and then through a single LED to the nearest solder lug. If you’re not doing the 1/2 power switch, ground the cathodes through 1 Ohm 1 Watt resistors to the solder lugs between the left and right pairs of tubes. You can then run a wire from each cathode pin to a test jack for measuring DC voltage (numerically equivalent to current in Amps) to set the bias.