6080 not lighting

[purpleymok]

I've reached the end of my troubleshooting abilities and could use some help - I built a stock Crack and ran through initial resistance and voltage checks which were all within tolerance, then immediately added the Speedball - I'm now seeing the following symptoms:

1. 6080 not lighting
2. LEDs on the "big" speedball board aren't lighting (all others are)
3. some voltages are off:
    terminal 7: 0V (expected per manual: 100)
    terminal 9: 0V (expected per manual: 100)
    terminal 13: 210V (expected per manual: 185)

Any suggestions?  Thanks!

[Paul Birkeland]

Is the 12AU7 glowing?

It would be odd for the 12AU7 to glow and not the 6080, but it's possible.

-PB

[purpleymok]

Yes, the 12AU7 glows.
Edit: or at least the middle "rods" (heaters/cathodes?) of it do, assuming that's all that's expected.

[Paul Birkeland]

That's so very odd.

The twisted pair of red/black wires that leave power transformer terminals 4 and 5 are what make the tubes glow, and they stop off at B7/B8 first, then go up to A4,5/A9.

If the 6080 isn't lighting, maybe there's a loose wire on the octal socket at B7/B8.  It's also possible that a pin isn't making good contact.

In either case, there's no reason to focus on the Speedball boards when troubleshooting this issue for the moment.

-PB

[Paul Joppa]

Also possible the socket is rotated so the wrong pins are connected. Or the heater is dead (check DCR pins B7 to pin B8, with 12AU7 removed).

[purpleymok]

With 12AU7 removed and 6080 in, resistance between B7 and B8 is reading as 0.  So I desoldered transfo terminal 5 and it looks like transformer 5 is going to ground without anything connected to that terminal - is that expected?

----

I buffed the pins and they seem to be making good contact as far as I can tell.  As far as I know the orientation and heater supply seem correct - here are some pictures:

Heater wiring: transformer 4/5 -> B7/B8 (-> A4,5/A9):
http://i.imgur.com/PDbc3Qk.jpg

Socket orientation:
http://i.imgur.com/AgRGKqQ.jpg

[Paul Birkeland]

Power transformer terminals 4 and 5 have a red and black twisted pair of wires attached to them that run to B7/B8.

PB

[mcandmar]

Suggestion, try measuring the resistance of the heater pins on the tube itself, just incase its broken internally.

[purpleymok]

Power transformer terminals 4 and 5 have a red and black twisted pair of wires attached to them that run to B7/B8.

Yep - they definitely have good connections.  I verified good electrical connections between transformer terminal 4->B8 socket, terminal 5->B7 socket.

I just meant that transformer terminal 5 seems to be grounded even when it didn't have anything connected to it, which I didn't expect since pin 4 is also tied to ground in the directions and it seems like that would short things... but maybe that's expected?

Suggestion, try measuring the resistance of the heater pins on the tube itself, just incase its broken internally.

With the tube disconnected?  The resistance between the heater pins (pins 7/8) is reading as infinite.

[Paul Birkeland]

I just meant that transformer terminal 5 seems to be grounded even when it didn't have anything connected to it, which I didn't expect since pin 4 is also tied to ground in the directions and it seems like that would short things... but maybe that's expected?

The winding inside the power transformer between those terminals is just a long piece of wire wrapped around the bobbin, so this isn't too surprising.

With the tube disconnected?  The resistance between the heater pins (pins 7/8) is reading as infinite.

That's an open filament, a different 6080 is in order.  You can also try reheating the actual pins themselves on the tube base to reflow the solder joints in pins 7 and 8, there may just be a loose connection that was never properly soldered from the factory.

-PB

[purpleymok]

I reheated pins 7/8 but there still seems to be no connection between them.  That's assumedly the issue then. 

It's the 6080 that came with the kit.  I'll see if I can get another one somewhere.  Thanks for all the help!

[Doc B.]

Yes if pins 7 and 8 on the 6080 read open it's a bad tube. We are happy to send a replacement. Best way to get the proper info to us for a speedy delivery is to email replacement parts at bottlehead dot com.

[purpleymok]

With the replacement tube everything is working great.  Thanks!