Help, voltage problem!

[Paul Joppa]

It might harm the 'phones, if the computer puts out any transients (typically turn-on or turn-off but sometimes when switching sources).

It will probably damage the resolution, since digital level control usually involves a loss of digital resolution.

But what do I know? Nothing, when it comes to current digital practice!

[smallmany]

Interesting info
Is there a way to improve crossfeed in the crack? I have noticed a lot of channel separation and left/right panning, and it's starting to get fatiguing..
Only happens during crack use 

[Paul Birkeland]

Crossfeed should be relatively easy to implement on the digital side (on your computer).

[smallmany]

Idk if this affects the sound, but the screw between the 9 pin socket and terminals 1-5 stick out more than the other side.
And there is the #6 lockwasher, I was only able to use 1 out of the 2. The second one is in my drawer, was I supposed to use both?

Also even with daily usage, the sound has yet to reach full dynamic range on the left side. I've rewetted every joint and it is all smooth and shiny, resistance and voltages all check out. What is wrong with my amp

Any suggestions are welcome zzz

Can provide pictures if it will help resolve my issue
thanks

[Paul Birkeland]

Idk if this affects the sound, but the screw between the 9 pin socket and terminals 1-5 stick out more than the other side.
And there is the #6 lockwasher, I was only able to use 1 out of the 2. The second one is in my drawer, was I supposed to use both?

The front screw is supposed to be shorter, as part of the Speedball mounts to a longer standoff on the rear screw.  Did you have an extra #6 lock washer included with your kit, or did you intentionally leave one out?

Also even with daily usage, the sound has yet to reach full dynamic range on the left side. I've rewetted every joint and it is all smooth and shiny, resistance and voltages all check out. What is wrong with my amp

I would still guess that it is a solder joint, or that there may be an issue with one of the RCA jacks.  What resistance do you get from pin to shell on each RCA jack?  (This measurement will be between 90 and 110K, if one side is 90K and one side is 110K, this is meaningless and should be ignored)

If none of that helps, I have another test in mind that should be helpful for you.

-PB

[smallmany]

When i received the package, there were 2 #6 lockwashers, but to my knowledge from the manual, it is only used once. RCA pins read 98-97k for both jacks
I would love to try your test, I am willing to try anything.

Just curious, when you mention the measurements, are you implying reading the meter while moving the tester probes across the wire and jack? because I do get wild reading when I slide the probe around as I try to read it. I get a constant reading of 97-98k if i keep it still.

[Paul Birkeland]

Yes, both #6 lock washers go on the 9 pin socket to keep the nuts in place.

OK, the next step of diagnosis is to download a 60 Hz tone, then play it through your Crack while taking voltage measurements.

You will want to measure AC volts between the chassis and:

Outer top pot lug
Outer bottom pot lug
Middle top pot lug (turn the control all the way up)
Middle bottom pot lug (turn the control all the way up)
If you have the grounding mod on the headphone jack, turn the level control about half way down, then plug headphones in and measure:
Terminal 6
Terminal 10
If you do not have the grounding mod on the headphone jack, you can perform this measurement with nothing plugged in.

These voltages will be in the tenths of a volt to several volts, so adjust your meter scale accordingly. 

-PB

[smallmany]

I am getting absolutely nothing.. Uh ohh..

This is without that grounding mod you spoke of, all the tests were done without anything plugged in the headphone jack.

[Paul Birkeland]

You can try measuring the 60Hz tone with your meter at the interconnect.  It might help to really crank the level coming out of your PC.

[smallmany]

I forgot to connect the pc to the amp 
The pot reads 1.61-1.62v
Terminal 6 reads 14.6v
Terminal 10 reads 1.83v

[Paul Birkeland]

I forgot to connect the pc to the amp 
The pot reads 1.61-1.62v
Terminal 6 reads 14.6v
Terminal 10 reads 1.83v

Woah, yeah, there's a problem there!

So all four terminals on the pot gave ~1.62V?  That's a good sign.

Can you very carefully repeat the measurements, but this time measure the AC voltage at T1 and T5?  Most meters should still pick up on the 60 Hz AC component and block the DC.  If you see something like 12V AC, that's a valid measurement.  If you see something a lot higher, then let me know and we can tweak things to get your measurements. 

[smallmany]

T1=177.6v
T5=176.9v

Terminal 6 and 10, I must have read wrong, after doing numerous tests, T6 is on average is only 2-3 times larger than T10. i.e: T6=2v    T10=.7v

Also, at maximum volume, T6 and T10 both have a reasonably close value of 15.3v.

[Paul Birkeland]

Well, while those voltages are sort of meter nonsense, they would suggest that the 60Hz signal is getting into the 12AU7 and being amplified properly. 

This would leave a funky 6080 (which may have been damaged when run with the missing wire from B2 to 2L), or a bad solder joint on the 6080 tube, specifically the wiring to and from T9 and T10, as well as the feed from T5 to B4.

-PB

[smallmany]

Is there a way to test if the 6080 tube is in fact damaged?

[Paul Birkeland]

The easiest way would be to pop in a different 6080 and see if you get the same results. 

I'd really go over those specific solder joints first.