Loud Buzzing After Using 6SN7 Adapter

[Bottle Rocket]

I have an issue after using a 12au7 adapter for a 6sn7 tube.  After turning my amp on with the adapter and tube in (and with the headphones plugged in), I heard a loud buzzing coming from my headphones.  I turned off the amp and when I turned it on again with just my regular 12au7 tube, the right channel was out and then both sides started buzzing (very loudly).  I checked my headphones separately and they're okay, so I'm guessing I may have blown something in my Crack.  Any ideas what could be wrong?? (My amp is upgraded with speedball and output caps and everything worked fine before trying out the 6sn7 tube with the adapter).

 

[Paul Birkeland]

Post any voltages that don't conform with those in the manual.

 

[Bottle Rocket]

Okay, here are the readings that are off:

Terminal:
1 - 36.35
7 - 153.0
15 - 197.6
21 - 215.8

 

[Chris65]

Where did you get the adapter? And are you certain it is wired correctly?

 

[Paul Birkeland]

Okay, here are the readings that are off:

Terminal:
1 - 36.35
7 - 153.0
15 - 197.6
21 - 215.8

Pull the 6080 and retest terminals 1-5.

 

[Bottle Rocket]

Where did you get the adapter? And are you certain it is wired correctly?

I got the adapter from a reputable dealer on ebay.  I was told it was 6.3V.  Not sure about the wiring, I'll have to double check with seller. 

I pulled the 6080 tube and the voltage readings are:
1 - 37.15
2 - 220.4
3 - 0
4 - 221.5
5 - 74.1

 

[Paul Birkeland]

Do both diodes on the 9 pin socket glow?  Do you have another 12AU7 that you can use to confirm these results?

 

[Bottle Rocket]

Looks like the led connected to A8 is not lighting up.  Double checked with two 12au7 tubes. 

 

[Paul Birkeland]

Try jumpering A8 to A3.  If there's a short in the adapter between pins 8 and 9, that would damage the LED pretty quickly. 

 

[Chris65]

I got the adapter from a reputable dealer on ebay.  I was told it was 6.3V.  Not sure about the wiring, I'll have to double check with seller.

You can easily check the adapter wiring using your multimeter. These are the what the connections should be:
12AU7 Pin  wired to 6SN7 Pin
    1                            2
    2                            1
    3                            3
    4                            7
    5                            No Connection
    6                            5
    7                            4
    8                            6
    9                            8

Remember the pins are numbered clockwise from the gap on the 12AU7, from the keyway on the 6SN7 when looking from below.
So when looking at the top of the adapter, the pins will be No.1 to the right of the keyway & then going anti-clockwise from there.
Put one meter lead in the 6SN7 pin1, check it's connected to pin2 on the 12AU7 pins (no resistance), etc

 

[Bottle Rocket]

Try jumpering A8 to A3.  If there's a short in the adapter between pins 8 and 9, that would damage the LED pretty quickly. 

Okay, so I jumped A8 to A3 and now the voltages are within correct limits.  So I hooked my headphones up and everything seems to be working properly now.  Thanks a lot!  Any issues that I'll run into with this set up or is there anything else I should do?

 

[Paul Birkeland]

Okay, so I jumped A8 to A3 and now the voltages are within correct limits.  So I hooked my headphones up and everything seems to be working properly now.  Thanks a lot! 

Yeah, that makes me suspicious of a short inside the adapter.

Any issues that I'll run into with this set up or is there anything else I should do?

One working LED makes diagnostics tough, though that shouldn't be an issue if the adapter goes in the round file.

-PB

 

[Bottle Rocket]

One working LED makes diagnostics tough, though that shouldn't be an issue if the adapter goes in the round file.

-PB

So, if I wanted to in the future, could I just replace the blown LED with a new one and remove the jumper?

 

[Paul Birkeland]

Yes, just be sure it's an HLMP-6000.

-PB

 

[Bottle Rocket]

Yes, just be sure it's an HLMP-6000.

-PB

Okay, great.  Thanks Paul.