potentially reversed OT primaries? Now Express trouble shooting

[aceofbones]

Here is my voltage check on the preamp tubes. It looks way better!

IMG_8006.JPG

I'll try swapping primaries next, but I'd like to be clear on the sound that occurs normally when primaries are reversed. Will it occur with no volume or does volume need to be up? Do power tubes need to be in or can it occur without? I'm just not sure on the type of noise or under what conditions it occurs. There really needs to be an audio library in the files section with a bunch of the common messed up sounds for newbies to reference, haha.

I will bypass the VVR as well, that's not a big deal to reverse.

As for moving the grounds, the black ground wire is easy enough to replace but the PT centre tap may not be long enough to reach the alternate location. I've measured and it will be very close so I'll give it a try.

[sluckey]

I'll try swapping primaries next

Earlier you said...

There was a pretty high pitch sound the whole time. I thought this was because of swapping primaries, so I swapped them back. That made it wayyyy worse, so I've swapped them back, again.

No need to swap anymore. You've already done that and the issue should be settled.

the PT centre tap may not be long enough to reach the alternate location.

This is important. Splice it if not long enough. That center tap contains all the B+ current flowing in your amp. And the high current in the power tube circuit is very dirty. It's important to connect the center tap directly to your reservoir caps to contain their dirty current in a small loop, minimizing this dirty current flowing into sensitive circuits.

Your main AC safety ground wire is currently sharing the same ground point as your PT center tap. There are also a couple more wires sharing this same ground lug. I'm guessing one may be the heater center tap. No idea about the other. But, modern practices say the main AC safety ground wire should be on it's own dedicated ground lug and should not share. Correcting this will not fix any of your problems or make your amp sound any better, but you may feel a little better.

[aceofbones]

I'll try swapping primaries next

Earlier you said...

There was a pretty high pitch sound the whole time. I thought this was because of swapping primaries, so I swapped them back. That made it wayyyy worse, so I've swapped them back, again.

No need to swap anymore. You've already done that and the issue should be settled.

the PT centre tap may not be long enough to reach the alternate location.

This is important. Splice it if not long enough. That center tap contains all the B+ current flowing in your amp. And the high current in the power tube circuit is very dirty. It's important to connect the center tap directly to your reservoir caps to contain their dirty current in a small loop, minimizing this dirty current flowing into sensitive circuits.

Your main AC safety ground wire is currently sharing the same ground point as your PT center tap. There are also a couple more wires sharing this same ground lug. I'm guessing one may be the heater center tap. No idea about the other. But, modern practices say the main AC safety ground wire should be on it's own dedicated ground lug and should not share. Correcting this will not fix any of your problems or make your amp sound any better, but you may feel a little better.

Didn't see this in time, and have already swapped primaries. But guess what?? Noise is gone!! The amp hisses some but I expected that, but I could actually plug a guitar in and make real noise! Holy sh*t are my neighbours going to hate me!!

So, it seems the grounding issue was causing my weird noise. My primaries are now back to how I originally started with in my first post. Other than grounding the buss bar, I haven't moved any other wires yet.

Yes, sluckey, the PT CT and heater CT are on one side of that ground, and the AC ground and black wire from the caps before the bias pot are on the other lugs of it.

You guys are the best!! Thanks so much for your help!!

When I have a guitar plugged in and touch the strings a small fizzy noise goes away. Is that me grounding something? Another gremlin to track down?

[Phil_S]

This is important. The AC ground should not be mixed with the audio circuit ground.The AC ground needs to be separate from all the others and near the point where it penetrates the chassis. If the power supply should get pulled out, you want that ground to be the last thing that goes, so it can and should have some slack. So, please dill a hole for a #10 screw, solder a ring lug on the end of the ground wire, and anchor it on that #10. Make that change. It won't affect the audio at all.

Congratulations on getting the amp fixed!

[Stevem]

Your fizzy noise when not touching the strings is normal for Amps that are safe from shocks due to no longer having a ground reverse switch.

[aceofbones]

This is important. The AC ground should not be mixed with the audio circuit ground.The AC ground needs to be separate from all the others and near the point where it penetrates the chassis. If the power supply should get pulled out, you want that ground to be the last thing that goes, so it can and should have some slack. So, please dill a hole for a #10 screw, solder a ring lug on the end of the ground wire, and anchor it on that #10. Make that change. It won't affect the audio at all.

Congratulations on getting the amp fixed!

Thanks Phil_S.

So just to clarify, does it matter where I drill the new hole or can it be right beside the existing location as long as it's anchored alone?

My power supply cable is plugged into the IEC connector, so if it got pulled out wouldn't it just come out of the connector that's screwed to the chassis, or am I misunderstanding what you're referring to?

[aceofbones]

Your fizzy noise when not touching the strings is normal for Amps that are safe from shocks due to no longer having a ground reverse switch.

OK, so I have nothing to worry about changing in the amp because of this then?

Thanks very much, for all your help Stevem!

[aceofbones]

voltages

Hey sluckey, I figured I'd post my full voltage chart with all tubes in and everything working. Does everything look acceptable?

IMG_8009.JPG

[sluckey]

yes

[aceofbones]

yes

Excellent.

Thanks very much for taking the time to help me get my amp sorted out sluckey. It’s greatly appreciated!
I’m still going to sort out the PT CT ground and the AC ground like you’ve suggested.

Cheers.