5E3 power transformer wiring leads color help (Missing Data Sheet)

[martin manning]

What happens if I still keep on the 2x 100Ohms on the pilot light, will that compromise anything or will that have a neutral effect.
I am asking to understand the logical beyond this. So in my understanding I can still put the 100Ohms and that will still be fine, correct?

Do one or the other, but not both, which will likely result in some unwanted ground current flow.

[pompeiisneaks]

You can ground the black heater center tap, but you don't have to. See my post above.

I would clip any exposed conductors and bundle the unused leads out of the way for now.

Yes the concept of (the heater center tap) is clear for both (the heater center tap) and (the HV center tap) basically if I ground both I can spare the 2x 100Ohms because ground will compensate.

Question

What happens if I still keep on the 2x 100Ohms on the pilot light, will that compromise anything or will that have a neutral effect.

I am asking to understand the logical beyond this. So in my understanding I can still put the 100Ohms and that will still be fine, correct?

My understanding is that you only do one, or the other. The 2x100 ohm is a 'virtual center tap' when you don't have one. I've heard both sides of the coin, but I use whichever is easiest, i.e. if the transformer has a CT I use it, if not, I create the virtual one. Some do say that the virtual one is often quieter with less 60hz hum, I'm not sure, haven't built enough to know... another common tool is a 250 or 500 ohm pot and set the two sides into 1 and 3 pins and have the 2 (wiper) to ground for a hum balance pot.

~Phil

[johnnyreece]

Yeah, Phil, I think some prefer the resistor to the CT because often, then CT isn't located in the exact center so it's not as quiet as it could be. Personally, I don't care much about a little hum at idle, so I'm kinda with you; just use what's easier. If I was building it for someone else and they wanted the trim pot? More power to 'em. Just pay for the parts.

[Mojojtm]

Hey all

Thanks for all the info

so I will use the 2x 100Ohm resistors, therefore I can cut short that black and isolate it with heat shrink tube together with the other unused leads such the blue ones and few others right?

Thanks

[Phil_S]

Yeah, Phil, I think some prefer the resistor to the CT because often, then CT isn't located in the exact center so it's not as quiet as it could be. Personally, I don't care much about a little hum at idle, so I'm kinda with you; just use what's easier. If I was building it for someone else and they wanted the trim pot? More power to 'em. Just pay for the parts.

I know, I'm the other Phil, not the one you answered. I wanted to point out something about the real "center" on a CT lead. Remember the length of the outer winding is greater than the length of the inner winding. If the there are 20 turns and the CT is placed at the exact location between turn #10 and turn #11, it is, indeed, exactly in the center. If you try to prove this with your ohm meter, you will not get equal readings due to the length of each half of the winding. Whether it hums or not is another question. I'm just saying, don't be fooled by a meter reading.

I suggest, if you run test voltage on the PT, and check each outer lead to the CT, then you will know if it is off center or not.

[martin manning]

I will use the 2x 100Ohm resistors, therefore I can cut short that black and isolate it with heat shrink tube together with the other unused leads such the blue ones and few others right?

If you're confident you have identified the leads correctly, sure. I would do a voltage check, either at low voltage as suggested above or, if you're comfortable doing so, connect it to mains voltage and measure it. If you do the latter, it's a good idea to secure the leads to your bench with tape to prevent accidental shorting.

[johnnyreece]

Yeah, Phil, I think some prefer the resistor to the CT because often, then CT isn't located in the exact center so it's not as quiet as it could be. Personally, I don't care much about a little hum at idle, so I'm kinda with you; just use what's easier. If I was building it for someone else and they wanted the trim pot? More power to 'em. Just pay for the parts.

I know, I'm the other Phil, not the one you answered. I wanted to point out something about the real "center" on a CT lead. Remember the length of the outer winding is greater than the length of the inner winding. If the there are 20 turns and the CT is placed at the exact location between turn #10 and turn #11, it is, indeed, exactly in the center. If you try to prove this with your ohm meter, you will not get equal readings due to the length of each half of the winding. Whether it hums or not is another question. I'm just saying, don't be fooled by a meter reading.

I suggest, if you run test voltage on the PT, and check each outer lead to the CT, then you will know if it is off center or not.

Excellent point, other Phil! Sorry, I should have been a bit more thorough with my answer.

[Mojojtm]

So the leads are correct and thanks Martin initially and everyone else for suggestions and advises, while building this Amp this time I am taking opportunity to do some study since I bought "Designing Valve Preamps for Guitar and Bass" book very interesting stuff.

My soldering is going a lot better after building the 2 18 watts I have improved but I was already soldering in the past building pedals.

Once the Amp is finish I will post some photos, the same way how i succeeded for the 5F1 i hope to succeed for this one, that is the 5F1 with Cabinet combo:

Again thank you all!

[Stovemananon]

I have the same power transformer!

Did you end up putting the black wire (0v) for the 5v circuit on pin 2 and the white wire (5v) for the 5v circuit on pin 8?

[martin manning]

Yes, the OP has the rectifier and HV supply working correctly.