High Voltage on T2, T4, T9 & Generally Voltages on the High Side [resolved]

[mr_wilton]

Hello all,

Like many here, I've just finished assembling and soldering my Crack Amp (Stock).
During the voltage check, I noticed a few voltages outside the tolerance as written in the manual. See values below.

But first, my Powerline Voltage Test gave me a voltage of 134-137V AC, so I configured my transformer per page 25 "Voltage greater than 115V AC and less than 130V AC", since, well no other option.
I am using the Crack 1.1 Manual (09-20-16) and I am located in Los Angeles, California.
I am also using the BH Power Cord Kit.

All resistances are within tolerance per page 47.

Both halves of each tube (6080 and 12AU7) glow during glow test and both LEDs light up.

T1 - 99V
T2 - 213V (outside 10% of 170V requirement, i.e. 187V)
T3 - 0V
T4 - 213V (outside 10% of 170V requirement, i.e. 187V)
T5 - 103V (within 10% of 100V requirement, i.e. 110V)

T6 - 0V
T7 - 125V (barely within 10% of 115V requirement, i.e. 126.5V)
T8 - 0V
T9 - 130V (outside 10% of 115V requirement, i.e. 126.5V)
T10 - 0V

I've seen the following 2 threads, but it wasn't quite like my readings.
https://bottlehead.com/smf/index.php?topic=9781.0
https://bottlehead.com/smf/index.php?topic=11197.msg101923#msg101923

Thank you in advance!

Sincerely,
Wilton

[Paul Birkeland]

Hello Wilton,

I would strongly suggest calling your power company and reporting your line voltage.  That is way, way too high and can cause issues with many appliances you would otherwise expect to be totally reliable (incandescent light bulbs will also be very short lived).

If your power company ignores you, I would suggest getting a 120:110 step-down transformer around 200VA and using it to reduce the line voltage going into your Crack.  A Hammond 168B could be used to accomplish this without spending a whole ton of money.  If you have more components in your system, it would probably be worth going with a bigger transformer/autoformer to put between your components and the wall.

-PB

PS - as far as the Crack goes, yes, you're going to have high voltages.  Your tubes will have moderately diminished lifetimes, but otherwise the kit should still work just fine.

[mr_wilton]

Hello Paul,

Thank you for the super quick reply!!!
You are awesome!

Woah, ok! Thanks for the heads-up. It did seem high to me too, but I simply thought, well, that's what it is.
I'll get a line voltage checker and measure the rest of my house and then report to the power company.
We did have an LED ceiling light fail on us after moving in, but I thought it was faulty, but now ... who knows, maybe the high line voltage.

Thanks for the power transformer recommendation. The Hammond 168B indeed seems reasonable in price and I can build my own little power box for the Crack and my DAC.

Great, thanks for the confirmation that the Crack will work/I didn't screw it up. I was worried.

May I ask if you have any recommendations on some reading material, etc to get into some electronics understanding? I am a mechanical engineer and as the majority of us, mechanical engineers and electronics is almost like oil and water; it's almost a mystery to me, but I'd like to learn.

Thank you again!

Regards,
Wilton

[Paul Birkeland]

If you're an ME, an easy-ish option is to do a few community college classes.  Lots of folks recommend the NEETS course that you can just download online for free.

[mr_wilton]

Paul,

Thanks! Time is my only issue with having to go to classes.
With NEETS, did you mean the "Navy Electricity and Electronics Training Series"?

Do you/Bottlehead run workshops, etc?

Thanks again!

Regards,
Wilton

[Deke609]

I once got similar voltage readings from my mains power and it turned out to be a problem of weak batteries in my meter. With fresh batteries, voltages dropped to around 120 VAC.  So check your batteries!

[Deke609]

See my post on this topic here: https://bottlehead.com/smf/index.php?topic=11103.msg101047#msg101047

[mr_wilton]

Derek,

I'm going to try that tonight!
Thanks for the suggestion.

I've had that meter for more than 15 years and never once changed the batteries on it .....

Regards,
Wilton

[mr_wilton]

Derek,

You were right.
I've changed out the batteries in my meter (the date stamp was Nov 1996 on them) and voila, my Powerline Voltage is now 119/120V AC.

Derek, Paul, thanks for all the help!

Just to close out this thread, my voltages are now all within tolerance.

T1 - 83V
T2 - 177V
T3 - 0V
T4 - 176V
T5 - 86V

T6 - 0V
T7 - 105V
T8 - 0V
T9 - 108V
T10 - 0V

Have a nice Memorial weekend, everybody!

Regards,
Wilton