• Re: help with ella hum - tokyofist 18:40:04 03/27/06 (0)
  In Reply to: help with ella hum posted by tokyofist on March 15, 2006 at 18:42:23:

  i'd like to thank everyone for taking the time to share their advice. unfortunately, the coming week or so is a busy one, so i won't have a chance to try any of your suggestions until next weekend at the earliest. it kills me to have my ella just sitting idle on my desk, as it sounded so great when i had it up and running previously. i'll be sure to post an update - hopefully no more questions :) - when i get a chance to sit down and do some troubleshooting.

  thanks again,
  dave
  
  

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• One step at a time. - PeterP 16:16:09 03/27/06 (12)
  In Reply to: help with ella hum posted by tokyofist on March 15, 2006 at 18:42:23:

  You need to find out what stage is causing the hum.
  Is this the point-to-point wiring or PC board type Ella?
  In any case you should follow a method. You need to find out what stage is causing the hum.

  1. Isolate the drive to the power stage.
  .....disconnect the drive. IIRC you can lift the coupling caps from the amp/driver board. Still have hum? It's in the power stage. Tubes, bias, B+, system ground, something. No hum? go to step 2.

  2. Reconnect the coupling caps. Verify that the hum is still present. Disconnect the signal input to the board and short those two inputs. (If this is point-to-point, then disconnect the signal input wires at the input tube.) Still hums? It's in the amp section or power/ground to the board/amp section. No hum? go to step 3.

  3. Bypass the volume control. Connect the inputs directly to the input.

  Could be a bad tube, solder connection, mechanical connection to chassis, etc. etc.

  That's just a rough outline. In no way is it complete, but I hope it gives you some idea as to how to go about finding the problem.

  Keep at it. Ella sounds great and should be just fine on your speakers.

  Take care.

  Pete.
  
  
  

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  • Re: One step at a time. - tokyofist 18:23:14 04/02/06 (11)
    In Reply to: One step at a time. posted by PeterP on March 27, 2006 at 16:16:09:

    Hi Peter:

    I've made some progress using this approach.

    I disconnected the coupling caps (both the 4 .1uF caps from the bias pcbs and the 2 .47uF caps to ground, correct?). MOST of the noise dissappeared, however I still have some low hum, prob. 60hz, present.

    Reconnected coupling caps. Noise present, loudest in left channel. However, it will occasionally drop out, and things are relatively quiet. I suspect I have a loose connection in that channel somewhere, I just haven't been able to track it down yet.

    I did some further tests with the volume control. Starting from lowest position, I can raise the volume pot quite a ways without any increase in noise. Then I reach a point where the noise decreases dramatically to where it is almost inaudible. With any additional turn of the pot, the noise increases rapidly and is very, very loud.

    In conclusion, I think it's clear that I am looking for 2 sources of noise. The first is in the power stage, the second is ?? A final question: When shorting the signal inputs (step 2, previous post), should I short them to ground, or connect them to one another?

    dv
    
    

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    • Re: One step at a time. - PeterP 17:51:44 04/08/06 (0)
      In Reply to: Re: One step at a time. posted by tokyofist on April 2, 2006 at 18:23:14:

      IIRC the .47uF caps are part of the phase splitter. All you need to do is to remove the (4) 0.1uF caps. That is as low as you should expect the hum to be. This hum could be due to a couple of things such as: the output tubes, the tube socket connections, ripple on the B+, heater voltage connections, etc. But from what I'm hearing from you, it seems like the hum in the power stage is acceptable. Am I right?

      BTW
      When you are "all done", if you haven't already done so, you should look at adding the power supply choke option. I think Ella really benefits from the choke and more capacitance on the B+.

      Have you checked and then double checked your feedback connections? What happens if you disconnect the feedback? A lot of people like Ella in triode mode with no feedback. (I happen to like it for what it is. A nice push-pull UL amp.) It's an easy test to disconnect the feedback and play some music. Then, without changing anything else (volume control levels, source, music), reconnect the feedback. Did the volume of the music go down? If so, then the feed back is correct and you can move on from there. If not, you need to find out why not.

      Have fun.

      Pete.

      
      
      

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    • Re: One step at a time. - Victor_A 16:05:19 04/07/06 (9)
      In Reply to: Re: One step at a time. posted by tokyofist on April 2, 2006 at 18:23:14:

      You have to short inputs to the ground.
      
      

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      • Re: One step at a time. - PeterP 17:21:33 04/08/06 (8)
        In Reply to: Re: One step at a time. posted by Victor_A on April 7, 2006 at 16:05:19:

        .....and when you do short them to ground you should:
        1. Remove the wires from the volume control (at the PWB)
        2. Solder in a jumper to short the inputs right at the PWB
        3. Do you still have hum?

        And now for just a couple of general questions.

        Have you tried with the feedback disconnected?
        Do you have the optional power supply choke installed?
        In the ones that I've played with, I feel that Ella needs the choke and could use more capacitance. But it should still be quite acceptable stock.

        Have fun.

        Pete.
        
        
        

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        • Re: One step at a time. - tokyofist 18:26:49 04/10/06 (7)
          In Reply to: Re: One step at a time. posted by PeterP on April 8, 2006 at 17:21:33:

          Thanks for all the help, Peter. I shorted the inputs and the hum was still present, if not a bit louder. When I disconnected the coupling caps, I do still have hum, but it's barely audible and only in one channel. I noticed that it follows one of the output tubes if i switch in from left to right. Possibly a bad tube? Not a huge concern as far as hum, but if it could have other repurcussions WRT the functioning of the amp, I'll of course replace it.

          Now on to look closely at the amp stage. Any pointers at this step?

          Also, is it normal for B+ to drop from about 430V to ~390 or so once tubes heat up? I also notice that the B+ drops really quick when power is cut, down to ~10V within a few minutes. I seem to remember it holding a steady high voltage for much, much longer than that previously. Victor got me thinking that a tube might be shorting out internally when hot.
          
          

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          • Re: One step at a time. - PeterP 05:11:35 04/11/06 (6)
            In Reply to: Re: One step at a time. posted by tokyofist on April 10, 2006 at 18:26:49:

            Seems to me that your power tubes are fine and I don't remember what the B+ dropped down to (seems a little low but not too much it's less than 10%). As long as the current through the power tubes remains stable after things warm-up you should be just fine. What is the voltage at the test points after 30 minutes or so? Is it the same after an hour? Have you disconnected the feedback yet? You need to keep the inputs shorted and disconnect the feedback. You should have more hum than just the power section alone, but let's see if it is less than with the feedback connected.

            The other area to look at is the heater voltage. Have you checked, double, and triple checked your heater center-tap connection? As well as the connection to chassis? Did you remove the paint at that connection? Is there any DC or AC voltage the the heater center-tap? Verify that there is a dead short between the power safety ground and the circuit ground. Do a visual inspection of the heater wiring on the PWB and make sure that the heater wires (bare wire) and solder connections are not in contact with anything else.

            Lots of things to look at. And...who knows, it may turn out to be a tube after all.

            Keep at it. You'll find it.

            Pete.
            
            
            

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            • Re: One step at a time. - Victor_A 19:12:58 04/14/06 (5)
              In Reply to: Re: One step at a time. posted by PeterP on April 11, 2006 at 05:11:35:

              Maybe one of the recifier diodes is dead (shortcut). That may explain the constant hum and fast hight voltage drop.
              
              
              

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              • Re: One step at a time. - tokyofist 16:44:29 04/15/06 (4)
                In Reply to: Re: One step at a time. posted by Victor_A on April 14, 2006 at 19:12:58:

                I desoldered the 5 diodes on the PS board. they all tested fine.

                I spent several hours going over every connection in the amp section, rewiring the filament wires, tube connections, ground connections, etc. the amp still hums - left channel is 2.3mV, right is 1.8mV.

                Peter - bear with me :) - i'm familiar with what feedback does, but i'm can't figure out which connections are part of the feedback loop just by tracing the circuit. could you be specificy which wires need to be disconnected? also, what is the heater center-tap?

                I had previously removed paint at the circuit ground and safety ground. There is continuity between the ground bus and chassis. Resistance between ground bus and safety ground pin of the IEC socket floats between 0-0.3 ohm.

                also, i'm confused by your reference to heater wiring on the PWB. are you referring to the filament wires?

                btw - in response to your questions from a while back: this is the P-P ella and with choke.
                
                

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                • Re: One step at a time. - PeterP 10:00:11 04/17/06 (1)
                  In Reply to: Re: One step at a time. posted by tokyofist on April 15, 2006 at 16:44:29:

                  I haven't abandoned you. My home computer has a virus so I'm using a laptop on a different network.

                  The feedback that I'm referring to is the small gauge wires connected to the output transformer or output terminals. IIRC there is an RC across the output terminals and feedback is the wire that goes from the output to the input stage. (Since I haven't seen one, in the P-P Ella, it could be either from the output transformer or the output terminals.)

                  As for biasing up the heater voltage, don't worry about that for now. Let's get it working stock first.

                  I'll be back. ;^)

                  Take care.

                  Pete.
                  
                  
                  

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                  • Re: One step at a time. - tokyofist 18:50:38 04/18/06 (0)
                    In Reply to: Re: One step at a time. posted by PeterP on April 17, 2006 at 10:00:11:

                    With inputs shorted and feedback disconnected, the hum is audibly louder. In fact, with just the inputs shorted, hum is also louder than with inputs connected.
                    
                    

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                • Re: One step at a time. - Victor_A 02:55:00 04/16/06 (1)
                  In Reply to: Re: One step at a time. posted by tokyofist on April 15, 2006 at 16:44:29:

                  Are the Power Supply filter capacitors OK ? I am almost sure, that the problem is in the power supply. (B+)
                  
                  

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                  • Re: One step at a time. - tokyofist 06:32:08 04/16/06 (0)
                    In Reply to: Re: One step at a time. posted by Victor_A on April 16, 2006 at 02:55:00:

                    Unfortunately, I don't have equipment to properly test them. Upon visual inspection, none are bulging and I don't see any signs of leakage. On the PS PCB, the smallest caps (on the far righthand side) measure ~12Kohm across the leads. The larger two pairs of caps measure in the megaohms.
                    
                    

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• Re: help with ella hum - Graham 19:51:41 03/25/06 (0)
  In Reply to: help with ella hum posted by tokyofist on March 15, 2006 at 18:42:23:

  You could try going about it in the opposite direction. The ground is supposed to come in from the RCAs through the vol control, at the tubes it goes to the ground bus and then via the PCB/chassis mounting to the case and then out via the IEC. If you are getting a ground hum you probably have an extra grounding somewhere.

  You could test this by disconnecting one of these. For example, undo the power supply PCB from the chassis. There should now be no ground between the RCA in and the IEC out. If so then make sure that only one of the PCB mounting screws is actually grounding - there should be a plastic washer on the other to isolate it.

  If you still had RCA-IEC ground then try disconnecting the yellow wire at "S" to the ground bus. Still have RCA-IEC? Then the ground must be in the RCA-vol control section, otherwise it was somewhere around the tubes. And so on.

  Good luck. Take heart too - it will be worth it in the end!
  
  

  • My Ella site   (Open in New Window)

  
  

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• Re: help with ella hum - tokyofist 19:05:55 03/23/06 (2)
  In Reply to: help with ella hum posted by tokyofist on March 15, 2006 at 18:42:23:

  well, i'm really running out of ideas here, guys.

  new RCA jacks did not fix the problem.
  I noticed that barrels on two of the bias jacks were shorting out to the chassis, so I isolated them. still the same noise. right channel is deifinitely worse.

  I notice now that both positive speaker posts show continuity with ground. the 24ohm resistors across the + and - post reads fine. could both posts be shorting to ground through the OPTs? could this cause the problem that I describe? any help is appreciated.

  dave
  
  

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  • Re: help with ella hum - RHone 21:00:36 03/23/06 (1)
    In Reply to: Re: help with ella hum posted by tokyofist on March 23, 2006 at 19:05:55:

    Dave,
    The OPT are just one long, long wire between the speaker + and - terminals hence the continuity you observed. I would go back and double, triple and quadruple check all the changes you made. I know sometimes I just have to stare at the circuit for ages until I recognise a problem. Also you might try verifying all the ground connections around the circuit ie. one probe of the multimeter on a known good ground eg PS PCB and then rove around the audio PCB and o/p tubes checking all the ground connections. If you've real buzz-saw hum your probably looking for a disconnection, not just fractions of ohms.
    Good luck!
    Rod
    
    

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    • Re: help with ella hum - tokyofist 04:40:52 03/24/06 (0)
      In Reply to: Re: help with ella hum posted by RHone on March 23, 2006 at 21:00:36:

      thanks rod. sometimes all you need is a little encouragement.
      
      

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• Re: help with ella hum - tokyofist 17:45:31 03/21/06 (0)
  In Reply to: help with ella hum posted by tokyofist on March 15, 2006 at 18:42:23:

  well i just installed new RCA jacks. the verdict: no dice! still same as before. i guess i'll see if i can isolate the barrel of the bias jack for tube socket 'A' from ground. any thoughts?
  
  

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• Re: help with ella hum - dave19 06:58:39 03/16/06 (0)
  In Reply to: help with ella hum posted by tokyofist on March 15, 2006 at 18:42:23:

  For your "tiny bit of hum" you might also want to consider a 14g silver wire for the center ground wire - I used it and my amp is dead silent. A good source for .9999 silver wire is
  http://www.ccsilver.com/silver/fines.html#four

  
  
  
  

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• Re: help with ella hum - BillEpstein 03:05:29 03/16/06 (6)
  In Reply to: help with ella hum posted by tokyofist on March 15, 2006 at 18:42:23:

  Get a 3 to 5X magnifier and look for solder bridge from hot to neutral of the RCA jacks. Also wiggle and twist the hot pins; if they can rotate in the barrel, they're toast. Excessive heat will do that.
  Check that the speaker output leads are tight to the terminals.
  The original "tiny bit of hum" may also be from the grounds on the power supply board.
  
  

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  • Re: help with ella hum - tokyofist 13:55:48 03/16/06 (5)
    In Reply to: Re: help with ella hum posted by BillEpstein on March 16, 2006 at 03:05:29:

    thanks bill. yeah, i think i overheated some of the rca jacks when wiring the grounds. i'll order some new ones with grounding tabs, as i think they're much easier to solder.

    as far as checking the PS grounds, what is an acceptable resistance between a grounding point and the chassis? my meter fluctuates b/w 0-0.1 ohm for the ones i've checked thus far.

    thanks again.

    dave
    
    

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    • Re: help with ella hum - BillEpstein 03:51:43 03/17/06 (4)
      In Reply to: Re: help with ella hum posted by tokyofist on March 16, 2006 at 13:55:48:

      The variation is just your meters drift.
      When my Ella was dead quiet I could get a reliable bias reading wih the neg probe anywhere on the chassis. When it was, briefly, humming, I had to use the neg speaker out. Try scraping hte powder coat away from the chassis ground point.
      
      

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      • Re: help with ella hum - tokyofist 14:46:47 03/21/06 (3)
        In Reply to: Re: help with ella hum posted by BillEpstein on March 17, 2006 at 03:51:43:

        thanks again bill. both grounding points (PS PCB and IEC socket) are bare metal, powder coat and primer have been scraped away. new rca jacks should arrive any minute now with the rest of my PE order.

        I just discovered something else, though. The center pin of the bias jack for tube socket 'A' has a resistance of 10 ohms (to ground), as it should. The grounding tab, however, shows continuity to ground, which it shouldn't. Nothing that I can see is shorting it out. My only thought is that some paint has been scraped away accidentally and it's grounding directly to the chassis. Is this a problem?

        
        As an aside, I get an open loop when probing the from a ground wire to chassis through the powder coat - maybe the paint is just thicker on my amp?
        
        

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        • Re: help with ella hum - Victor_A 19:16:58 03/25/06 (2)
          In Reply to: Re: help with ella hum posted by tokyofist on March 21, 2006 at 14:46:47:

          You may have shortcut between heater and cathode inside one of output tubes.
          
          

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          • Re: help with ella hum - tokyofist 20:11:29 03/25/06 (1)
            In Reply to: Re: help with ella hum posted by Victor_A on March 25, 2006 at 19:16:58:

            can i measure this with a conventional dmm?
            
            

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            • Re: help with ella hum - Victor_A 15:55:42 03/26/06 (0)
              In Reply to: Re: help with ella hum posted by tokyofist on March 25, 2006 at 20:11:29:

              "...As an aside, I get an open loop when probing the from a ground wire to chassis through the powder coat - maybe the paint is just thicker on my amp? ... "

              "...The grounding tab, however, shows continuity to ground..." -- it have to be, because ground is connected with chassis at one point. (Remember paint "scratching" when installing the power supply board?)

              Ground have to be connected with chassis at one point -- near the power supply -- as it described in the manual. When Power Supply board installed, Dmm have to show continuety between PS ground and the chassis (through the powder coat). Please check it.

              Re: shortcut (heater, cathode) inside the tube--

              It often can not be checked with Dmm. The shortcut may occure only when the tube is hot...

              First of all, try to change tubes between channels -- one tube at time.
              Of course, amp have to be turned off when changing the tube (Just to remind...).

              Change one tube, turn amp on, listen, then the next, etc.
              If the tube is defect, you will find (hear) it.

              If you still have the humm from the same channel -- it looks like construction problem, or defect part in power supply chain, Bias. Try to look at bias filter condenser -- may be it is defect or have "cold soldered".
              Check the bias grounds, etc (I think you have double checked them already...)
              Check the filament soldering -- maybe "thin" shortcut on the tube socket.

              
              
              

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