No joy with Crack voltage tests

[hardisondan]

Hello,

I've checked and re-soldered everything I can think of.

Most of the voltage tests are in the ball park, although some vary by slightly more than the 10-15% mentioned in the manual.

But the real problem is 7 & 9 (and B3 & B6 respectively). The manual says I should be getting 100V and I am only getting around 6V.

Does anyone have any suggestions?

Is there a chance something is damaged (i.e. a capacitor or tube)?

Failing any breakthroughs here, are there any successful Crack builders in Melbourne, Australia? I would like to get someone more experienced than me to look at it and give me an opinion.

Cheers
Dan

[fullheadofnothing]

What are the resistances at these terminals?

Is your 6080 lighting up?

[hardisondan]

Hi Joshua,

The resistance tests for 7, 9, B3 & B6 are all spot on, i.e. 2.94 K ohms.

The 6080 does glow. Sparks sort of go up and down the filament, then it glows a steady purple. I don't know if that's a normal colour? I thought tubes normally glowed orange-ish.

Dan

[Paul Birkeland]

Can you pop up a photo of what you see? 

[hardisondan]

Can you pop up a photo of what you see?

I'm trying but the website seems to be having issues. Attachments folder is read-only?
Dan

[Paul Birkeland]

I'm trying but the website seems to be having issues. Attachments folder is read-only?
Dan

I'll be sure the web guys are informed.

In the mean time, something like Image Shack or Photo Bucket could be used for linking to an image.

-PB

[hardisondan]

Hi Paul,

See if you can click on this link...

https://drive.google.com/folderview?id=0Bwul9J-9kItHT19CeHRudlN5akE&usp=sharing

Dan

[hardisondan]

I'll be sure the web guys are informed.

In the mean time, something like Image Shack or Photo Bucket could be used for linking to an image.

-PB

Hey Paul,
Were you able to see the photos in the link I shared?
Dan

[Doc B.]

Either your tube is shorted or the socket is miswired. Double check that each wire is connected to the correct terminal on the 6080 socket.

[hardisondan]

Either your tube is shorted or the socket is miswired. Double check that each wire is connected to the correct terminal on the 6080 socket.

Thanks Doc,
So are you basing that on the colour? Or the voltage tests? I will check the wiring, but is there a way to check if a tube is shorted?
Cheers
Dan

[Doc B.]

Both,

if you are reading 6V where you should see 100V and possibly you haven't measured the pins that should read 6VAC across them because we don't have you measure them for ACV, then it could be a miswire or two wires shorted together that shouldn't be. Or it could be due to an internal short in the tube. One way or another it looks like the tube is getting the wrong voltages on the wrong parts inside. A tube tester will usually have a pretty reliable short test. You can also try to test the tube for shorts with a meter but it's not always reliable. Pull the tube and measure the resistance between each possible pairing of pins. You should only see continuity between two heater pins, B7 and B8. All other combos should read open. But even if it tests good the short could be there and just not active unless it sees a higher voltage than your meter battery can provide.

If you don't measure a short with your meter and the wiring is all good, testing by putting a known good 6080 in would be the most expeditious way to determine what is going on. If you would like to exchange the tube we would be happy to do so.

[i luvmusic 2]

Actually those blue lighted tubes looks pretty it's too bad that if they light up in blue something is wrong.

[hardisondan]

Pull the tube and measure the resistance between each possible pairing of pins. You should only see continuity between two heater pins, B7 and B8. All other combos should read open. But even if it tests good the short could be there and just not active unless it sees a higher voltage than your meter battery can provide.

If you don't measure a short with your meter and the wiring is all good, testing by putting a known good 6080 in would be the most expeditious way to determine what is going on. If you would like to exchange the tube we would be happy to do so.

Thanks Doc,
I did the resistance check on the tube and it seems OK. But as you say, it could still be bad. It does have a bit of a rattle when you shake it (gently ;-), although I read on some old posts here that that isn't necessarily a problem. So I'm getting a cheap 6080 to try, just to eliminate that. I won't return the Sovtek 6AS7 unless I confirm that its the problem.
Cheers
Dan

[hardisondan]

Both,

if you are reading 6V where you should see 100V and possibly you haven't measured the pins that should read 6VAC across them because we don't have you measure them for ACV, then it could be a miswire or two wires shorted together that shouldn't be. Or it could be due to an internal short in the tube. One way or another it looks like the tube is getting the wrong voltages on the wrong parts inside. A tube tester will usually have a pretty reliable short test. You can also try to test the tube for shorts with a meter but it's not always reliable. Pull the tube and measure the resistance between each possible pairing of pins. You should only see continuity between two heater pins, B7 and B8. All other combos should read open. But even if it tests good the short could be there and just not active unless it sees a higher voltage than your meter battery can provide.

If you don't measure a short with your meter and the wiring is all good, testing by putting a known good 6080 in would be the most expeditious way to determine what is going on. If you would like to exchange the tube we would be happy to do so.

After waiting what felt like an eternity, my 6080 from tubedepot.com arrived today. And presto... works a charm. I am listening to it now and it is every bit as good as I hoped. At least I know all my solder joints are ok since I checked and re-checked them a million times.  ;-)

So is it OK if I return the original tube Doc?

Thanks for everyone's assistance in the trouble shooting.

Dan

[Doc B.]

We would be happy to send a replacement for the bad tube to you. Just contact [email protected] and request a replacement 6080 per Doc.