Jump to content

What the Hum Is Going On Here?


thebes

Recommended Posts

On 3/27/2020 at 9:29 AM, seti said:

Hey Marty do you have an o-scope? This could help look around and actually see what everything is doing.

 

 

 

Yes I do but I haven't used it in a long time. I've got various probes and stuff but really don't know how to use it in amp testing.

Link to comment
Share on other sites

On 3/27/2020 at 11:44 AM, babadono said:

I just tried calling Jensen Transformer. They are shut down following the mandatory order of Governor of CA and Mayor of LA until Monday 20th of April(at minimum).

Digging out a pair of cheap rca cables right know, and i have 1k resistors so I'll build a set this morning.

Link to comment
Share on other sites

So I built the plugs and used them and other than replicating the lowering of hum I noticed when I plugged a cd player in, no startlingly revelations. However, I have noticed that the hum seems to be coming from the right channel. I swapped all the tubes back and for the in pairs and the hum stayed with the right channel, so I've ruled out the tubes themselves as a source.  It also decreases when I touch the amp, and while pocking around with a plastic probe the hum increases and makes weird science fiction sounds when it's around an area that includes the on/off light/ the power switch, and volume control and the balance pot. I've already disconnected the on/off light with no change, and I've replaced the volume pot with no change.

 

I'm going to get a dental pick and tighten all the points to eliminate that as a problem.  Then I have to troubleshoot the whole right circuit.  What do you think, should I start with preamp or power section? Work from the outputs in, or rectifier out?

Link to comment
Share on other sites

@thebes Marty I believe it is, man I almost forgot about this. Give me a shout @babadono

So you built some dummies, basically 1K center contact to shield and plugged them into a line level input, then selected that input. And you have observed that you have a hum but only in the right channel. Is this correct? Not a "startling" revelation but it determines that in fact the problem is in the integrated itself not further upstream in your system.

So you are going to or did what with a dental pick? Tighten points? Do you mean the tube socket contacts.

Link to comment
Share on other sites

Your recap is correct.  Just to be clear, I've only put this in my two systems to see how bad the hum is.  I already knew the rest of my gear worked properly. I also use test speakers when working on an amp. I'd rather blow them up than my Khorns!  Yes, I'm making sure a poor tube socket contact is not causing a grounding problem.  The dental pics I ordered should be here in a couple of days.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...