Wiring Question (Answered)

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DH166
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Re: Wiring Question (Answered)

Post by DH166 »

Bieworm wrote:
Sun 09/05/21 11:35 am
You can perfectly follow the Trinity guide. Stephen knows his stuff very well!
I also test the power supply when wired. Don't forget to add the DC from the rectifier to the filter cap.. or you can not test the B+. Be aware these are "unloaded" voltages, thus higher than the eventually wired up amp.
The rectifier measuring points are the 2 HV AC wires going in and the B+ at the
conjunction of the outcoming DC voltage.
So, that's the part I'm asking about. Remember, first time builder here. I didn't catch most of that. The 2 HV AC wires going in. Is that here?
Screen Shot 2021-09-05 at 5.49.58 PM.png
And the B+ at the conjunction of the outcoming. Is that here?
Screen Shot 2021-09-05 at 6.04.36 PM.png
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Re: Wiring Question (Answered)

Post by JMPGuitars »

Looks like you did catch that. ;)

Either side of that 10W resistor could be measured as your B+ DC voltage. That resistor is there for sag, to simulate a tube rectifier.
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Re: Wiring Question (Answered)

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Got it. Thanks! Next question. My PT came prewired and has leads for 5V on one side and 240 on the other that aren't used in this build. What do I do with those? Do I just roll them up or clip them short and get them out of the way? Are they carrying either of those voltages away from the transformer? I clearly don't want 240V flopping around in the chassis. Do I need to tape up and heat shrink the ends of them closed?

Side note: In a previous post, I stated I was building the Modern Classic. Actually, it's the Tremolo TMB.
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Re: Wiring Question (Answered)

Post by JMPGuitars »

DH166 wrote:
Sun 09/05/21 6:32 pm
Got it. Thanks! Next question. My PT came prewired and has leads for 5V on one side and 240 on the other that aren't used in this build. What do I do with those? Do I just roll them up or clip them short and get them out of the way? Are they carrying either of those voltages away from the transformer? I clearly don't want 240V flopping around in the chassis. Do I need to tape up and heat shrink the ends of them closed?

Side note: In a previous post, I stated I was building the Modern Classic. Actually, it's the Tremolo TMB.
You got it. Clip the ends, heat shrink the ends with extra heat shrink hanging off, and tie them off.

I'm glad you've been taking the advice about lead dress, with the Tremolo TMB build you want to make sure it's all as good as it can be.

Thanks,
Josh
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Re: Wiring Question (Answered)

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Ok. I've never been accused of being the world's smartest man, but I am intelligent enough to realize I need to know EXACTLY how to measure and test voltages, so as not to fry my amp or myself. I searched this forum, as well as youtube for 'measuring power supply voltages in a guitar amp', a search string I thought would generate lots of useful results, but found very little. Can you point me to a good tutorial?
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Re: Wiring Question (Answered)

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Perhaps you can read what Paul Ruby states in his powering up an amp guide?

https://paulrubyamps.com/info.html#FirstPowerUp
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Re: Wiring Question (Answered)

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Alright. Been a few weeks since I got to work on the build. Next question. I wired up the output jacks as shown on the layout (pics below), and when I test for ground, I'm grounded not only on the lugs on the outer side of the jacks (those connected to the black wire from the OT and the gray wire to the star ground, which is yellow in my pic because I didn't have gray) but also on the innermost lugs, those attached by the blue wire to the output selector. That doesn't seem right to me. The jacks themselves are insulated. I tested them and they don't ground out. Am I just mistaken, or doesn't this mean that the signal coming from the OT will ground out before it reaches the jacks?
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Re: Wiring Question (Answered)

Post by JMPGuitars »

If you test your OT secondaries with no connections to anything, you'll get a continuity beep when it's not powered on. Never test continuity with the amp powered on. If you disconnect the ground connection, you will still get continuity between the secondary connections to the negative (black) wire, but no longer to ground.

Most of the wire colors in my drawings are to keep things clear, you can use whatever you like.

Thanks,
Josh
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Re: Wiring Question (Answered)

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Ok, thanks. So, it sounds like you're saying everything is as it should be. Just to clarify, I was measuring continuity (with power off) between the lugs on the jacks and the chassis ground, and likewise between the lugs on the selector and chassis ground, and getting a beep on all of them. So, that's right? In terms of signal, then, how does it get from the OT to the speakers without grounding out?
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Re: Wiring Question (Answered)

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Because there is no connection to ground from the selector switch. The speaker will be the resistive path to ground.. otherwise there would be a short, and that's a no-no!!!
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Re: Wiring Question (Answered)

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Ok. Thanks. So now at this point I'm ready to start putting the passives on the turret board. A question on that. How do I find the outside foil end of my caps? I don't have an oscilloscope and I tried the fuzz pedal method and didn't get any difference in hum level. This build is my first tube amp. I just have a Fender modeler and I'm guessing its software is made to eliminate hum from pedals in the first place. Ideas for figuring this out?
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Re: Wiring Question (Answered)

Post by Bieworm »

There are some methods using a disassembled instrument cable.. use Google for the details. But you could buy the sozo caps when you don't have a scope to do this. Sozos have the outside foil side truly marked with a stripe
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Re: Wiring Question (Answered)

Post by TriodeLuvr »

Not all caps have outer foil. Depends on the construction method. Maybe try a few different types to see if any of them respond to the method you're using.

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Re: Wiring Question (Answered)

Post by JMPGuitars »

Jack and Bjorn make good points. If you don't want to invest in an oscilloscope, the easiest thing is to just get SoZo caps. They're great caps, especially after being broken in.
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Re: Wiring Question (Answered)

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Alright. October was a busy month but I'm back at it. Bought a second hand old Tektronix and got the caps figured out. Next question: I'm about to wire up the input jack. I recall reading about how to hook it up with the shielded wire, but I can't find the article I read. Does the shielding get soldered to the ground lug? Does it just get clipped off and heat-shrunk out of the way? On the layout, it just shows the shielded wire going to the tip side lug and a separate wire going from the sleeve side lug to ground. So, the follow-up question would be likewise for the other shielded wire coming off of V1 and V2. How do they hook up? Thanks
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Re: Wiring Question (Answered)

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The shielding of the shielded wire has to be soldered on one side only. The other side should be clipped off and sealed with heat shrink. If you solder the hot wire (core) to the hot/tip side of the input it's best to solder the shielding to another ground reference than input ground. You might add a terminal at V1 where you can solder the other end of that hot wire from input. Connect your 10k grid stopper between that terminal and V1 pin 2. Solder the shielding on the center of that terminal, where it's bolted to the chassis.
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Re: Wiring Question (Answered)

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So, the end of the wire that connects with the input shouldn't have the shielding connected to anything at all? Just clipped and sealed? Connect the shielded portion of the other end to the grounded terminal adjacent to V1? Is that correct?
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Re: Wiring Question (Answered)

Post by JMPGuitars »

DH166 wrote:
Sat 11/13/21 5:43 pm
So, the end of the wire that connects with the input shouldn't have the shielding connected to anything at all? Just clipped and sealed? Connect the shielded portion of the other end to the grounded terminal adjacent to V1? Is that correct?
Yes, only one end. I don't know if it really matters which end you use. I've read opinions that shielding should have independent connections to ground, and others say it should connect to the preamp ground bus. I've connected either way without issue. 🤷

This is how I wired the input jacks on my latest builds:
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Re: Wiring Question (Answered)

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Ok, thanks. Two more questions:
1. The shielded wire from V2 would probably be similar, since it likewise goes through a grounded terminal, but what about the shielded wires coming from pins 1 and 6 of V1? They go straight from the pins to the board. Does the shielding on those ground anywhere?
2. After wiring up the input and wiring it to the terminal that connects it via the 10k resistor to V1, I tested my connections for continuity. I got a beep when I probed across the core wire and shield wire attached to either of the two lugs on the terminal. Is that right? Shouldn't those be isolated from each other, both by the separation in the wire jackets and by the fact that the terminal is insulated between the lugs? I tested the lugs with the wires removed and they're isolated, and I tested the core wire against the shielding to make sure I didn't tear through the inner jacket when I stripped it but it's also good. The only thing I can think of is that I already wired up all the connections on the input jack, including its ground. Would the signal the multimeter is sending up the core wire go through the input jack and to ground, thereby completing the circuit when I touch the other probe to the grounded lug on the terminal?
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Re: Wiring Question (Answered)

Post by JMPGuitars »

DH166 wrote:
Sat 11/13/21 6:22 pm
Ok, thanks. Two more questions:
1. The shielded wire from V2 would probably be similar, since it likewise goes through a grounded terminal, but what about the shielded wires coming from pins 1 and 6 of V1? They go straight from the pins to the board. Does the shielding on those ground anywhere?
2. After wiring up the input and wiring it to the terminal that connects it via the 10k resistor to V1, I tested my connections for continuity. I got a beep when I probed across the core wire and shield wire attached to either of the two lugs on the terminal. Is that right? Shouldn't those be isolated from each other, both by the separation in the wire jackets and by the fact that the terminal is insulated between the lugs? I tested the lugs with the wires removed and they're isolated, and I tested the core wire against the shielding to make sure I didn't tear through the inner jacket when I stripped it but it's also good. The only thing I can think of is that I already wired up all the connections on the input jack, including its ground. Would the signal the multimeter is sending up the core wire go through the input jack and to ground, thereby completing the circuit when I touch the other probe to the grounded lug on the terminal?
1. If one end of the shielding isn't connected, it's not shielding. Some people mount a terminal strip or use a ground lead to connect the shielding near the socket. On my Tremolo TMB PCB, I have a shield plane they connect to on the PCB.

2. If the jack is fully wired, then the hot will be grounded out without a plug connected. Insert an instrument cable, and you should no longer get continuity between the shield and the hot lead.

Thanks,
Josh
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