Cr 112 Hum

[clamup1]

hey i got the led to light up but i cant get anything but hum.
http://www.shedradios.com/images/crate_cr-112_04.jpg

at the vcc+ im getting 44 v. almost double the 24 thats supposed to be coming to the IC 2. the only thing before the IC 2 is a 5% 1w R and a led.
ive got 44v going to IC1 also. IC 1 and 2 are supplied by the same trace. could this be a grounding issue? help

[joecool85]

hey i got the led to light up but i cant get anything but hum.
http://www.shedradios.com/images/crate_cr-112_04.jpg

at the vcc+ im getting 44 v. almost double the 24 thats supposed to be coming to the IC 2. the only thing before the IC 2 is a 5% 1w R and a led.
ive got 44v going to IC1 also. IC 1 and 2 are supplied by the same trace. could this be a grounding issue? help

Are you measuring from vcc+ to ground or vcc+ to vcc- ?

[clamup1]

ive got the ground clipped to the heat sink with an aligator clip and the pos on the vcc+. is it different for amps ?

[clamup1]

what i have hooked up is green wire attached to a piece of steel and the board ground attached to the metal face plate that i put on the front of the amp. it still hums

[phatt]

hey i got the led to light up but i cant get anything but hum.
http://www.shedradios.com/images/crate_cr-112_04.jpg

at the vcc+ im getting 44 v. almost double the 24 thats supposed to be coming to the IC 2. the only thing before the IC 2 is a 5% 1w R and a led.
ive got 44v going to IC1 also. IC 1 and 2 are supplied by the same trace. could this be a grounding issue? help

Check you have 24VDC at C37.
If you get 40 VDC there then Zener D4 is likely futt, Replace.
Phil.

[J M Fahey]

green wire attached to a piece of steel

And what is the piece of steel attached to?
Can you post a picture?
Thanks.

[clamup1]

@phatt- ill check it out
@fahey- its screwed into the side of the amp-would the green wire need to be grounded to the same thing the board is grounded too. ie the face plate?

[J M Fahey]

Hi clamup
Unfortunately that doesn't answer my doubt.
Is that "piece of iron" attached to a wooden side?
Does it touch the chassis?
Do you measure any resistance between the green/yellow wire attached to the iron piece and the chassis? How much?
Thanks.

[clamup1]

@fahey- hey there isnt a chassis. the closest thing i have to a chassis is the metal that the pot knobs will stick through when i get this thing working. the green wire gets really hot. i burned the carpet a little.

yes the piece of iron is screwed into the side of a wooden cab

[joecool85]

@fahey- hey there isnt a chassis. the closest thing i have to a chassis is the metal that the pot knobs will stick through when i get this thing working. the green wire gets really hot. i burned the carpet a little.

yes the piece of iron is screwed into the side of a wooden cab

Sounds like you have a short.

[clamup1]

@phatt- at c37, +side 44, at -side 38

@joe- would a futt diode cause a short?

@fahey- i get -2.6mv at the peice of steel. is that the resistance you were talking about?

[joecool85]

@phatt- at c37, +side 44, at -side 38

@joe- would a futt diode cause a short?

@fahey- i get -2.6mv at the peice of steel. is that the resistance you were talking about?

Resistance would be measured in Ohms.  Although if it was grounded you should have 0v, so something is amiss there.

[phatt]

To Clampup,
I Strongly suggest you seek professional advice because the way you are going you will land yourself in the ER.

Put it down and read up until you grasp what the hell you are playing around with. :grr

The green wire is for safety backup it goes to the metal chassis,,, which you do not have :duh

I'm sorry chum but that is flaunting death and stupid. :loco

Yes I can't stop you from flying a *non air worthy* plane without a parachute but at least
you get a warning when the engine conks out,,, but with electricity it's instant,, and often fatal.
Sure you might say but it's only You that gets hurt.  But what if you accidently kill someone you love because you thought you knew what you where doing?
How smart would you look then? 8|

learn the basics (And safety issues) then you will be able to understand the answers you are getting.
Just Google any word you don't grasp and spend some time absorbing how things work.
Magnitisium, Transformers, DC circuits, AC circuits. there's some for you already:)
How stuff works will even be able to help with this.
Good luck. Phil.

[joecool85]

I think Phil has a good point.  I sometimes forget that people don't always have all the basic knowledge needed for this type of stuff just because I know it.  It's not a hard topic to learn either, just take a bit of time, sit down and read.

Here are two good links:

This one for the safety concerns - read section C (you can read the whole thing if you want, but it pertains to tube amps): http://www.ax84.com/safety.html

And this one for electronics theory: http://www.utwired.engr.utexas.edu/rgd1/index.cfm

[J M Fahey]

OK, thanks for taking a sensible position.