Guide to fix up a Cmoy 2

[johanjr 0]

Ok, change them back to the original and short the 2 input cap. That should give no bass roll-off.

i've put it back to gain 6 and after awhile realised what was the prob.

the cable attached to the croc clips were loose with only a few strand attached.wondered why it didn't come off completely.anyway its in the hammond box already until i reliased that the i/o stereo conn is to big for the box.so i'll have to wait till weekend for a trip to slt.

[johanjr 0]

Finish off the cmoy2 but getting problem with oscillation.

Reading the thread i've found that starushz and alvin 2038 also having the same problem.

I'm using opa2228 also. ordered opa2134 to test whether its the ic thats having the prob.

Funny thing is unless i on off/plug out HP, the cmoy2 sounds great. Put it back and i'll get hissing, occillation and a bunch of other noise

Edited August 28, 2005 by johanjr

[xchagg 0]

The OPA2228 is a fast IC, so that might be causing the oscillation problem. The OPA2134s are slower, so if it's the 2228s causing the oscillation than your problem is solved.

 

Also, have you tried removing the LM6171 and shorting pins 2 & 3 to see if the oscillation is still present? Just a shot in the dark haha, but that's one of the things I tried when troubleshooting my CMOY2. Turned out I snipped off the ground pin on the audio jacks by mistake so my IG and OG signals were going nowhere lol.

[johanjr 0]

hi guys

 

opa2134 - lm6171 = no distortion....but occil abit then fades off...the sound continues nicely

opa2134 + lm6171 = distortion

opa2228 - lm6171 = distortion

opa2228 left side = ok

opa2228 right side = ok

opa2228 + lm6171 = distortion

opa2228 left side + lm6171= ok

opa2228 right side + lm6171 = ok

 

will double check the soldering tomorrow..sigh

[skyskraper 0]

have u tried swapping out the lm6171? id like to help more but after many requests it seems they don't want to post the schematic. ahhh the spirit of diy! i am sure once that is posted there will be more people who would be able to help you out.

[heady 0]

johanjr, if you have digicam, take pics of both sides of board. That helps a lot for the people who knows to help you. I think you have a solder join somewhere as I use OPA2134 and LM6171 with no problems.

[jasonhanjk 0]

Oops...

 

Posted at the first page liao, forget to update here....

 

[mormegil 0]

anyone knows whether this amp is suitable for the er6i?

[monsieuroctagon 0]

I'm interested in doing this project. When can I get the PCB?

[1bit 0]

hi monsieuroctagon,

you can buy the pcb from tropicalrips for S$11 each.

i just bought one from him myself last week, and currently doing the project

you can contact him through PM

 

btw, guys can you tell me what is the value for the potentiometer?

is it 10k or 50 k? how does it make a difference?

[monsieuroctagon 0]

can someone make this a little easier and post a compiled list of all of the parts to order from farnell or mouser?

 

also, does the potentiometer already have a switch built in, or do I need to put on on the battery circuit?

[heady 0]

also, does the potentiometer already have a switch built in, or do I need to put on on the battery circuit?

I used a pot with built-in switch to minimise usage of the panel real estate. The panel of the recommended casing is very limited in space. If you get the switched pot, you cannot solder it to the PCB as it is intended for only the non-switched pot.

 

[monsieuroctagon 0]

is there a case large enough that will accommodate the switch and dial at the front, the battery, and two 1/4 inch jacks in the back? If that's not going to fit, I suppose I could have the two cables hanging off the back.

[magicpocket 0]

Is the recommended pot 10k logarithmic or linear? Thanks in advance.

[jasonhanjk 0]

The case that is recommended is at the first page. I recommend mounting the led, volume knob and switch at the front panel, the in and out stereo jack will be at the side. Near the LM6171 IC.

 

The pot is 50k log.