Broken tube/incorrect voltage readings

[apcbhf]

Hi-

After a couple of slow weeks I finally (thought) I finished my crack build and after passing all the resistance checks I plugged it in to start running through the voltage test. Ran into a couple of issues:

• My center tube wasn't lighting up and when I attempted to pull it out the plastic the housed the center pin snapped off. I'm not sure what this tube is supposed to look like but I'm afraid it may be damaged. Picture attached.
• My voltages were universally off for the terminals my incorrect readings were:
• 1 - 214 (90)
• 2- 214 (170)
• 4- 214 (170)
• 7 - 0 (100)
• 9 - 0 (100)
• 13 - 214 (170)
• 15 - 222 (185)
• 21 - 230 (206)

[*] I then moved on to the A terminals where my readings were correct for the first 5 but on testing A6 there was a pop and sparks flew. I can't eyeball any damage but I'm probably not experience enough to find it even if it was there.
[/list]

I don't really want to go any further without consulting this board so I'd love to hear if there's anything that sounds obviously broken or at least a good way to start debugging. Also it would be great to know if my tube is broken (and where to find a replacement) or if I got lucky and that casing isn't too importnat.

Thanks so much

 

[Paul Birkeland]

I bet T1-T5 are all about on (with 2/4 being a little high).

You can test the amp without the 6080 plugged in to confirm this. 

That's unfortunate that the guide broke off, but it doesn't make the tube useless.  Grab a sharpie and mark where the key should be on the metal ring wrapping around the base of the tube.

From the voltage readings you provided, the 6080 isn't working at all, which makes me wonder if it was inserted correctly?

Otherwise, the tube will glow of the run from power transformer terminals 4/5 to B7/B8 is connected.  Since your voltages on T1-T5 were about right, the heater supply is passing through B7/B8 just fine.

So, what I would do is measure T1-T5 again with no 6080 in, then carefully insert the 6080 back in and perform the rest of the checks.

-PB

 

[apcbhf]

Thanks so much for the help Paul. You were 100% right and I had inserted the tube incorrectly. Both are lighting up properly and all of the voltage readings for the terminals are dead on now.

That said I'm still a bit terrified about testing the octal socket because of the spark on my first time through. Is there anything I can do to doublecheck/ensure that I'm being safe before testing those voltages or is that a thing that will just happen from time to time?

Thanks again for you help

 

[apcbhf]

Well never mind then. Decided to just go for it and everything checked out. Thanks so much again for your help and glad this was caused by a stupid mechanical issue and not something fundamentally off.

Appreciate it

 

[Grainger49]

Check this thread, second picture down:

http://www.bottlehead.com/smf/index.php/topic,3145.0.html

Clip one end on the tube pin to be checked, the other end on the red meter lead.  Then the black lead is clipped to ground.  Turn the amp on and read voltages.  It is slow, but very safe and effective.

 

[2wo]

parts Express sells a set of test leads with alligator clips. They are decent quality and are only $2.95.
# 390-125. Very handy to connect to your circuit for hands free measurement. I'll post this in tools as well...John