I'm picking up a 120hz hum on both channels. Working the board input to output, I'm picking up the hum on both R414 and 415 (2.2M). I replaced the pair because the left channel value was grossly over spec (2.6 ish) while the right was just a bit out of spec. Used metal film resistors, that was the only change. Been chasing this down for a while and it's getting pretty annoying. I have been going over the power supply and grounds, a couple of cracked solder joints, so most of the issues are gone, just this remaining. Both channels are now at the same level of buzz, the left was by far louder. I've fixed dozens of phono stages (h/k, Yamaha, Sansui, etc), this is only my 3rd Marantz and I'm 2 for 3. Want this thing off of my bench. Any ideas appreciated.
Marantz 2440B Phono Stage noise
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I wish you good luck in figuring this out. It seems that threads about hum problems are tough to gain any traction with around here. Understandably of course! They are tough nuts to crack! (Along with Channel bleed over) I myself have two units with one or both problems. So far I’ve gotten no where. I’ve gotten a lot of help with other sorts of issues don’t get me wrong!
But that said, I do wish that someone could come forward with some kind of best practices or methodology for tracking these issues down. There is of course the standard rule of thumb that states basically that 120hz hum is a power supply problem and 60hz hum is a grounding problem. But that too has gotten me nowhere. So again, good luck!
Cheers………………….Todd
But that said, I do wish that someone could come forward with some kind of best practices or methodology for tracking these issues down. There is of course the standard rule of thumb that states basically that 120hz hum is a power supply problem and 60hz hum is a grounding problem. But that too has gotten me nowhere. So again, good luck!
Cheers………………….Todd
Do you have hum with AUX/CDP input? expect it to be significantly lower level but present.
Possibly a problem (c-e short?) with a voltage regulator letting through ripple. This may happen if pre and phono use the same power rail (often the case), could not find the sm to confirm. A health check on power supply rails would not hurt, looking for symmetry between +/- rails.
Possibly a problem (c-e short?) with a voltage regulator letting through ripple. This may happen if pre and phono use the same power rail (often the case), could not find the sm to confirm. A health check on power supply rails would not hurt, looking for symmetry between +/- rails.
Have you ruled out the turn table? Or are you by chance testing it with no turn table?
I've hooked it up to my reverse RIAA and with nothing, and with blockers in the inputs. Got no room on the bench to fit a table. Still end up at the same place. Just finished a 2220B and that was textbook.
How did you determine 120Hz? Assume you are working with a scope.
Pix of the hum may be helpful, is it 120Hz ripple or pure sine or somewhere between
Can't find 2440B sm, working off 2240B, this sm shows phono psu shared with psu to front end of power amp.
Post pix of trace at phono P400 pin J406
Apart from the hum, does the phono stage appear to work normally.
Pre-out/Main ins fitted?
Try using the 2440B as a preamp, hum still present at power amp?
So when you’re looking for symmetry are you meaning equal but opposite dc voltage or a/c ripple or both? A/C ripple if any should look the same but opposite phase? How much of either do you find is permissible? Do you find that your x1 probe or x10 is better suited for these checks? Thanks for the tips!
Yeah I’m not finding anything on a Marantz 2440B. Only a 2440 Quadradial 4 adapter. I too suspect he meant 2240B but just guessing.
Cheers………………..Todd
Equal and opposite dc voltages.
If a regulator has failed c-e short then it will pass the unregulated supply through, while this supply has higher ripple (120Hz) it will also be several volts (4-10Vdc??) higher, eg -50V/+58Vdc would be a trigger for further investigation especially for 120Hz hum/Buzz.
Varies greatly. Ripple on unregulated supply to output transistors of class A amp could get close to 1Vp-p. Same amp operating in AB (again unregulated) maybe 50mVp-p. Regulated supply is even "harder", hopefully less than a few mVp-p
I mostly use x10 to minimize effects to the signal as force of habit though for ripple either would be ok since you are looking at the Vp-p