First post tweed twin questions

[tfrost]

Exactly where are you measuring that 484VDC?  Pin 8 of the rectifier tubes and that side of the standby switch. And I bet the stby switch is open. If so, that's fine.  Yes measuring with standby OFF or as you put it OPEN....Correct.  I guess I never thought to check it with the standby in the ON or closed position

Measure the DC voltage on pin 3 of a 6L6 tube. How much? With power ON 406vDC ...Very good.

Measure the DC voltage on pin 4 of a 6L6 tube. How much? With power ON 408vDC ...Very good.

As for the voltages on the filter caps, look at the attached pic and compare to the voltages on the original. It's a perfect match. I'd say all is good. You're done.

What about that odor?  I shot off an email to Jason at Mojotone with a link to that other thread and also to this one...  I am just concerned that if the transformer smokes will they replace it?  And that B+ is still high.  And now after reading that other thread I am concerned about 6 Amps vs. 3 Amp rating on the transformer.... 

Like I said before though the amp sounds spectacular, very impressed! 

Thanks again Sluckey, HotBluesPlate, Willabe, Timbo....  I really appreciate the help!  I hope I can do the same for someone in the future.  As my knowledge increases I will be sure to help others.  I've learned a lot from you guys here.  thank you!

~Tony

[sluckey]

What about that odor?

Probably a combination of hot new smells. If you can touch it without getting a blister I'd say good.

I shot off an email to Jason at Mojotone with a link to that other thread and also to this one...  I am just concerned that if the transformer smokes will they replace it?

Didn't he say he would stand behind it?

And that B+ is still high.

No it's not. It's perfectly normal when the stby switch is open. That little .05µF cap on the stby switch charges to the max peak voltage your rectifier tube puts out. That voltage will be 1.414 x 350 = 495v for your PT. Since there is no discharge path for that little cap whenever the stby switch is OPEN the voltage just sits there. Perfectly normal. Closing the stby switch connects the recto tube to the filter cap and the amp load and that 'hi' B+ will drop down to the level you measured on the first filter cap. So, don't get hung up on a 'hi' B+ voltage when there's no load connected to it.

Prove it to yourself by measuring the voltage on pin 8 of the recto tube with the stby switch closed.

And now after reading that other thread I am concerned about 6 Amps vs. 3 Amp rating on the transformer.... 

Don't be. That rating is for the 5VAC filament winding. If you want to really save on some heat, pull those two 5U4s and plug in a single 5AR4. That single 5AR4 will handle the load for a pair of 6L6s all day long and will run cooler than even a single 5U4.

Like I said before though the amp sounds spectacular, very impressed!

There you go. Quit fretting and enjoy.

[tfrost]

SWEET!!!  Thanks again Sluckey....  Time to rock!

[Willabe]

And that B+ is still high.

No it's not. It's perfectly normal when the stby switch is open. That little .05µF cap on the stby switch charges to the max peak voltage your rectifier tube puts out. That voltage will be 1.414 x 350 = 495v for your PT. Since there is no discharge path for that little cap whenever the stby switch is OPEN the voltage just sits there. Perfectly normal. Closing the stby switch connects the recto tube to the filter cap and the amp load and that 'hi' B+ will drop down to the level you measured on the first filter cap. So, don't get hung up on a 'hi' B+ voltage when there's no load connected to it.

Prove it to yourself by measuring the voltage on pin 8 of the recto tube with the stby switch closed.

I totally missed that.     


           Brad     

[tfrost]

And that B+ is still high.

No it's not. It's perfectly normal when the stby switch is open. That little .05µF cap on the stby switch charges to the max peak voltage your rectifier tube puts out. That voltage will be 1.414 x 350 = 495v for your PT. Since there is no discharge path for that little cap whenever the stby switch is OPEN the voltage just sits there. Perfectly normal. Closing the stby switch connects the recto tube to the filter cap and the amp load and that 'hi' B+ will drop down to the level you measured on the first filter cap. So, don't get hung up on a 'hi' B+ voltage when there's no load connected to it.

Prove it to yourself by measuring the voltage on pin 8 of the recto tube with the stby switch closed.

I totally missed that.     


That's Okay!  I appreciate your help on this as well!!!  Thank you. 

I'm just sorry I was caused a two page thread over nothing!  But hey, at least I learned something from it...

           Brad     

[tfrost]

And that B+ is still high.

No it's not. It's perfectly normal when the stby switch is open. That little .05µF cap on the stby switch charges to the max peak voltage your rectifier tube puts out. That voltage will be 1.414 x 350 = 495v for your PT. Since there is no discharge path for that little cap whenever the stby switch is OPEN the voltage just sits there. Perfectly normal. Closing the stby switch connects the recto tube to the filter cap and the amp load and that 'hi' B+ will drop down to the level you measured on the first filter cap. So, don't get hung up on a 'hi' B+ voltage when there's no load connected to it.

Prove it to yourself by measuring the voltage on pin 8 of the recto tube with the stby switch closed.

Ughhhh okay!  I can't believe I did this.  Anyway, yes standby switch closed = 414vDC!!!  there we go!  That seems better.

[tfrost]

So I was contacted by Mojo promptly the very next day.  They confirmed that all the readings were accurate as you stated Sluckey.  Also, they went onto inform that they had beefed up the secondary filament winding to handle the bigger load of 6 Amps...  He mentioned that the originals had a 4Amp which caused them to get hot.

He also said DO NOT use 5Y3 rectifier tubes...

Anyway the amp sounds great, I can't wait to use it in a live setting.  I think my home made cab adds some depth, some beef, as I made the physical dimensions quite a bit larger than the original, even larger than the original high power twin.  I think this may have a really good affect overall.

Again thanks for all the help you guys!

Happy Holidays!!!

Tony