OT noise - need some help

[YMI5150?]

hey guys,

working the final bugs out and could use your ears and experience.

the amp measures good (see data), and plays well at low volumes. Attached are noises heard when the guitar is not plugged in and can be heard through the cabinet while playing.

noise on the normal channel is triggered at 9 on the volume pot. its not progressive. on or off.

the noise on the bright channel is more like squelch. it ramps up at volume of about 4 and varies in pitch. i thought it was coming from the tubes because if you wiggle them the noise varies a bit. i tried swapping tubes with no luck.

normal channel OT noise.mp3

(110.03 KiB) Downloaded 346 times

bright channel noise.mp3

(114.88 KiB) Downloaded 388 times

startup voltages 4.4.12.pdf

(50.2 KiB) Downloaded 201 times

Thanks for the help.

[YMI5150?]

anyone??

it seems that because everything checks out and plays well at low volumes, that something is failing when current goes up, either exceeding its rating, a cold solder joint, or a bad ground.

side note - can someone explain to my why the postive and negative leads are shunted on the input jacks (zig zag buss wire)? I'm not following why it doesnt look more like the output jack wiring.

[jerrydyer]

check all your work for wires crossed. and of course do some tube swapping etc.
turn it on put it at the edge of making noise then poke around with a stick and try to find a location (source)

[Strat78]

Those PI grid resistors look like they are 1/3 or 1/4w, they might be a little noisy. Make sure the NFB wire (purple) is isolated. Perhaps a ground wire is missing somewhere?

[YMI5150?]

Thanks guys. Will poke around when I get home. Easter road trip.

The odd thing is each channel acts differently. Makes me think it's something in the first two stages. Might try making a shielded input like junkie did.

[YMI5150?]

all fixed. Bad ground from the preamp can. I think it would be helpful to add this to its own thread for future builders when troubleshooting. those sound files will be helpful. basically good functionality at low volumes, high end squelch from all volume and tone pots on the bright channel when the volume is increased.

[vanhalen5150]

How was it bad?

[YMI5150?]

cold joint, high resistance. i read some swapped the split turret boards for Georges due to frequency of cold solders. i just added a lot more to each joint and got a better connection.

[vanhalen5150]

I have those similar turrets in my 2204 build. Not split but, they are the huge high buggers, that look like the chess castle piece. Still doesn't work. I get a "rrrrrrrrrrrr" when the guitar is plugged in and gets louder with increasing the LarMar.

[YMI5150?]

if things test out well, check all your grounds. does it make any noise when the guitar is not plugged in and the pots are moved with volume cranked?

those turrets have a fair amount of thermal mass and take more heat to get solder to flow through than Georges.

[vanhalen5150]

if things test out well, check all your grounds. does it make any noise when the guitar is not plugged in and the pots are moved with volume cranked?

those turrets have a fair amount of thermal mass and take more heat to get solder to flow through than Georges.

No noise with the guitar unplugged. Plug in and turn up "rrrrrrrrrr".

[YMI5150?]

sounds like an issue with the input jacks. how are they grounded? can you post a pic of the input jack wiring?

[vanhalen5150]

sounds like an issue with the input jacks. how are they grounded? can you post a pic of the input jack wiring?

I'll post one tomorrow. It's a 2204 with a larMar. I went by the SDM for the wiring of the inputs. The shielded cable connections seem bizarre to me. I'm pretty sure I have the LarMar correct but.....

[Strat78]

I still can't get used to those split turrets, nothing but grief for me. George's turrets give you a nice clean canvas and after repeated mods, they stay pretty tidy. I've probably cooked a couple of resistors just waiting for those split turrets to stop drawing off the heat before the solder can flow.

[vanhalen5150]

Yup. On some of them that have 3-4 components, I had to really jack up the digital iron I have to get a melting point.