Bottlehead crack voltage measurements

[mpasanthosh]

Dear all,

I have just finished assembly of the bottlehead crack and currently face issues with voltage measurements at the below two points.

Terminal 1:158 volts
Terminal 7: 158 volts

Please let me know your inputs to proceed further .
The other terminal voltages measure ok.

Thanks a lot for your time and support .

Regards
Santhosh

 

[mpasanthosh]

I would also like to add that the led between pin 9 and the pin a8 is not glowing .
The emitter resistors are running hot and the 6080 tube is hot to touch.

 

[Paul Birkeland]

Can you carefully measure the DC voltage at pin A8?

 

[mpasanthosh]

Can you carefully measure the DC voltage at pin A8?

I measured the voltages at pin A8 to 13.3 volts.
I used two ground points one is the Center of the tube socket and the other ground point is 12U.
With both the ground points I get a voltage of 13.3 volts at the pin A8.

Please let me know if you need more inputs from my side.
Thanks for helping .

 

[Paul Birkeland]

Connect a wire jumper from pin A3 to A8.

The LED at A8 is damaged (potentially cracked in half, overheated from soldering, or reheated by solder after sitting for a few years).

 

[mpasanthosh]

Connect a wire jumper from pin A3 to A8.

The LED at A8 is damaged (potentially cracked in half, overheated from soldering, or reheated by solder after sitting for a few years).

Hello Paul,

I have shorted the pin a8 to ground and the voltages across terminals 1 and terminals 7 have dropped to 87V(terminal 1) 115V(terminals 7).

Below is the list of voltages I have measured again.
1. 50-100 (87V)
2. 170V (201V)
3. 0V (0V)
4. 170V (202V)
5. 50-100V (88V)
6. 0V (0V)
7. 90-115V (115V)
8. 0V (0V)
9. 90-115V (122V)
10. 0V (0V)

The voltages in brackets are the measured values in test points.
The emitter resistors are still running hot .

Can you confirm if the above voltages are fine ?
The voltages across points 2 and 4 are above the 10% deviation and I am quite worried about it.
Please let me know your inputs .

Thanks again for helping me out .

 

[Paul Birkeland]

I have shorted the pin a8 to ground

This will cause some problems, but based on your voltages, I would say that you've correctly jumpered A3 and A8.

When you say the emitter resistors are getting hot, can you clarify what you mean?  Are you referring to the R1 resistors on the PC board?  How hot are they getting?  How are you measuring the temperatures?

 

[mpasanthosh]

This will cause some problems, but based on your voltages, I would say that you've correctly jumpered A3 and A8.

When you say the emitter resistors are getting hot, can you clarify what you mean?  Are you referring to the R1 resistors on the PC board?  How hot are they getting?  How are you measuring the temperatures?

Sorry and yes I meant A3 and A8.
By emitters I meant the 3k 10watt wirewound resistors.
They are supposed to run a bit hot I suppose .
I just touched them and felt them to be a bit on the hotter side .

Please confirm if this is fine .

 

[Paul Birkeland]

Yes, don't touch those resistors.  They are running within their thermal limits.