PT & OT Parallel

[The New Steve H]

I made, well, a tiny booboo while putting my new amp together today. It has two OTs, and after I drilled everything, I realized one of them has laminates coplanar with the PT. Sometimes I get a little too close to the work, and something like this happens.

I figure I might as well fire it up and see what happens before redrilling. I can leave enough slack in the wires to move it. Is there any hope it will be okay?

[The New Steve H]

Not sure which ways the bobbin axes point.

[Zippy]

Read the posts regarding the "headphone trick" to learn how to evaluate how profound a boo boo you may have made.

[The New Steve H]

Thanks. Guess I'll try that when I get back to work.

[xtian]

Read the posts regarding the "headphone trick" to learn how to evaluate how profound a boo boo you may have made.

+1. Been doing that with my recent Rocket and 18watt builds. Doesn't take much effort, and is fantastic at making the invisible audibly obvious.

[The New Steve H]

If you guys are so smart, explain this.

I did the headphone test on both OTs. I heard absolutely nothing. I was afraid I wasn't picking up the sound, so I got out the oscilloscope. Again, nothing, although I did confirm that AC was going through the PT. I checked the heater voltage, and it was clearly visible.

Here's the weird part. When I had the probe across the OTs, with one on one OT and one on the other, I got a grainy, weak AC trace. I noticed this while I was switching from one to the other. I had one wire from each OT connected to the probe.

As soon as I connected either OT, by itself, I got nothing. In fact, I got a little trace when the probe was in the air NEAR the amp, but connecting it to the OTs killed it.

????????

Anyway, I guess the OT placement is not a problem.

[renshen1957]

If you guys are so smart, explain this.

I did the headphone test on both OTs. I heard absolutely nothing. I was afraid I wasn't picking up the sound, so I got out the oscilloscope. Again, nothing, although I did confirm that AC was going through the PT. I checked the heater voltage, and it was clearly visible.

Here's the weird part. When I had the probe across the OTs, with one on one OT and one on the other, I got a grainy, weak AC trace. I noticed this while I was switching from one to the other. I had one wire from each OT connected to the probe.

As soon as I connected either OT, by itself, I got nothing. In fact, I got a little trace when the probe was in the air NEAR the amp, but connecting it to the OTs killed it.

????????

Anyway, I guess the OT placement is not a problem.

Hi New Steve,

If this becomes an issue, you could try Mu-Metal as a shield between the OT and PT.

Steve

[The New Steve H]

I think I'm okay, since there was no AC in the actual signal path. I'm wondering if the trace I picked up came from the overhead lights.

[Structo]

Did you have your scope on the OT secondaries?

Supposed to be easier to hear if you use the highest impedance taps.