Presonus TubePre

premiumdan · Post by **premiumdan** » Wed Feb 25, 2009 6:15 am

FixOp:

A friend gave me his Presonus TubePre to mess with;
It was not working when he gave it to me;
The VU doesn't move nor lights up;
Running a guitar in/out of the 1/4's, the sound is barely there;
Sounds the same with the gain and drive knobs at 0 and 10;
The 80Hz roll-off is the only thing that changes the sound;
He installed a new GrooveTube 12AX7, but the original may not have been bad;

Any ideas?

Oh, the red LED under the tube lights up to show that it's "working".

Thanks.

-Dan

vorian · Post by **vorian** » Wed Feb 25, 2009 7:16 am

The first thing I'd check is the tube. Can you get the one it came with from him (or another known good 12AX7)?

I hate even asking this since it's way too obvious a thing, but it's something I actually did myself once.. Do you have the leads patched into the wrong jacks?

suppositron · Post by **suppositron** » Wed Feb 25, 2009 9:40 am

The tube doesn't explain why the backlight for the meter isn't lighting up. I'd check the power supply first. Because it is a wall wort they get damaged quite often.

casey campbell · Post by **casey campbell** » Tue Mar 03, 2009 2:57 pm

the tube pre is mostly fet with a tube blend in it. it should work whether the tube is bad or good.....

i have had 3 presonus wall warts go out on me in the 2 years ive owned them...

just a hint....

premiumdan · Post by **premiumdan** » Thu Mar 05, 2009 5:16 am

Checked the wall-wart with my unscientific Radio Shack multimeter:

Aggressively pegs the needle on the 15VAC setting;
Showing 100VAC on the next setting;
Wall-wart output-rating is 16VAC;

Checking on the Radio Shack www for photos of the scales now because
100VAC doesn't make me think that I'm reading it properly...

OR, over-active wall-wart blew out the VU and its owner's hopes of my fixing
it, maybe?

-Dan

suppositron · Post by **suppositron** » Thu Mar 05, 2009 7:40 am

I'd say the primary shorted to the secondary and the wall voltage isn't getting stepped down anymore. Buy a new supply. And, yeah, most likely there are components damaged inside the pre because of that.

Bro Shark · Post by **Bro Shark** » Thu Mar 05, 2009 4:00 pm

Try the Presonus forums at all? I haven't dealt with them directly but I remember browsing their message board and seeing a lot of individual attention being dealt by folks there.

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