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Thread: Loud hum coming from Hammond Aurora

  1. #1

    Loud hum coming from Hammond Aurora



    I came across an "Aurora" at an estate sale last week. The people didn't really know what it was, they just reffered to it</p>

    as "A nice piece of furniture." So they sold it to be for a buck (I guess they just wanted it hauled off the property.) After</p>

    I got it home and powered it up all I could here was a loud, distinct, 60 Hz hum emenating from the speaker. So, I started flipping some </p>

    of the 1200 switches this thing has on it hoping to isolate the cause, and that did nothing. When I tried the manuals, no sounds other </p>

    than hum could be heard. I took the back cover off, tapped the spring reverb and I could hear a crash. I talked to a repair tech friend </p>

    and he said it could be a faulty filter cap allowing that AC to pass. The people here seem pretty knowledgable, so I'm hoping </p>

    somebody has some suggestions. I'd hate to have to part out this organ, it doesn't have a scratch on it.
    </p>


    </p>

  2. #2
    Junior Member BOZ's Avatar
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    Re: Loud hum coming from Hammond Aurora

    I saw this response by jimmywilliams on the topic just above this one. He gives a warning to get it looked at since further damage may result. To quote:<DIV><BR class="khtml-block-placeholder"></DIV><DIV class="ForumPostTitleArea"><H4 class="ForumPostTitle"><SPAN class="Apple-style-span" style="font-family: Tahoma; "><SPAN class="Apple-style-span" style="color: rgb(51, 51, 51); font-size: 16.128px;">"Re: What model could this Wurlitzer be?<SPAN class="Apple-style-span" style="color: rgb(0, 0, 0); font-family: Arial; font-size: 12.096px; font-weight: normal;"></SPAN></SPAN></SPAN></H4><H4 class="ForumPostTitle"><SPAN class="Apple-style-span" style="font-family: Tahoma; "><SPAN class="Apple-style-span" style="color: rgb(51, 51, 51); font-size: 16.128px;"><SPAN class="Apple-style-span" style="color: rgb(0, 0, 0); font-family: Arial; font-size: 12.096px; font-weight: normal;">When you say "major humming" , do you mean there is a loud hum coming out of the speaker even when you are not playing any notes?* If so the large filter capacitors in the organ's power supply are suspect.* Having bad filter caps in the power supply can eventually fry the power transformer.* If the organ is that old, and hasn't been played in a while, you will probably have to have the power supply serviced.* If the hum is very very loud I would recommend that you get it taken care of right away.*</SPAN></SPAN></SPAN></H4></DIV><TABLE cellpadding="0" cellspacing="0" border="0" width="100%" height="100%" style="table-layout: fixed; "><TBODY style=""><TR style=""><TD style=""><DIV class="ForumPostBodyArea"><DIV id="ctl00_ctl01_bcr_ctl00___PostRepeater_ctl09_Pos tViewWrapper" class="ForumPostContentText" style="text-align: left;"><P style="text-align: left;"><SPAN class="Apple-style-span" style="font-size: 12.096px;">- Jim</SPAN></P><DIV id="ctl00_ctl01_bcr_ctl00___PostRepeater_ctl09_Pos tViewWrapper" class="ForumPostContentText"><SPAN class="Apple-style-span" style="font-size: 12.096px;">Jimmy Williams<BR style="">Gulbransen Model D, hobby organist/technician</SPAN></DIV></DIV></DIV></TD></TR></TBODY></TABLE>"

  3. #3
    Junior Member OrganicBud's Avatar
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    Re: Loud hum coming from Hammond Aurora

    The Aurora is an LSI organ, so they are prone to doing strange things. The hum is likely to be caused by a bad filter cap, so you should check them first. If it continues after that, pop the hinges in the back and lift the top up. You should find 2 hinges inside the back that are locked, and once you unlock them, pull up on the front next to the tabs. The top should lift up completely, giving you access to the circuitry. Check for loose wires and dirty connections. Auroras are prone to that problem. When I was working on mine, I lifted up one of the manuals and found a bunch of aluminum oxide interrupting some of the connections.<DIV><BR class="khtml-block-placeholder"></DIV><DIV>Theyre prone to problems, but still worth fixing.</DIV>

  4. #4

    Re: Loud hum coming from Hammond Aurora



    Yeah, the humming is exactly that. It's present even when I'm not playing a single note. Also, I can control it's
    amplitude using the expression pedal. I figure from that, the cause has to be in a stage prior to the
    volume control or in the power supply. I'm leaning towards the power-sup. Thanks for the info.
    </p>

  5. #5

    Re: Loud hum coming from Hammond Aurora



    I can understand why these things are prone to failure, their so damn complicated. It looks like Hammond loaded these things with every option imaginable. Your right about the dirty connections though, as many boards as there are in that top section, some of those connectors have to be loose or corroded by now. I'm going start with those caps first and see if that resolves the problem. Also, I was wondering if you knew where I could find an owners manual for this model. </p>

    Anyway, thanks for the response,</p>

    Kurtis</p>

    </p>

    </p>

  6. #6
    Senior Member Orgrinder010's Avatar
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    Re: Loud hum coming from Hammond Aurora



    I have this organ, and I've had this issue. For me, it had nothing at all to do with capacitors. Instead, the organ was picking up loud hum from the nearby*fluorescent*lighting. At one point, I was picking up talk-radio*through*the spring-reverb tank.</p>

    The*corrosion*on the molex connections is easily fixed, but you must be <span class="Apple-style-span" style="font-style: italic; font-weight: bold;">very</span>*careful when removing them. Hammond did a very poor job crimping the wiring to the actual connection. I've had to track down about 10 different open circuits because the wire lost contact. You'll know when this happens, because you'll put the organ back together and turn it on only to find that your pedals don't function and your reverb slider works in reverse. []</p>

    Hope all goes well.</p>

    *</p>
    ~1936 Hammond AV - Leslie 122 & PR40~~1954 Wurlitzer ElectroStatic 4602 - Leslie 125~

  7. #7
    Junior Member OrganicBud's Avatar
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    Re: Loud hum coming from Hammond Aurora

    You can get a manual from these guys:<DIV><BR class="khtml-block-placeholder"></DIV><DIV>http://www.mitatechs.com/organcom.html#manuals</DIV><DIV><BR class="khtml-block-placeholder"></DIV><DIV><BR class="khtml-block-placeholder"></DIV>

  8. #8
    Member lparsons21's Avatar
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    Re: Loud hum coming from Hammond Aurora



    I tried opening my new Aurora. *Removed the two dark brass colored screws holding the hinges down. *But when pulling up on the front as you describe, it doesn't budge. *I noticed that there are two holes underneath the cowling, are there screws in there?</p>

    Help, please!</p>

    *</p>
    Lloyd
    Lowrey SU-630 Palladium, Lowrey GX-1, Hammond Aurora

  9. #9
    Junior Member Simon Dolan's Avatar
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    Hi,
    I work on the aurora That have the same hum problem. I was thinking about the capacitor in the power section. But I'm skeptical about that because I've worked on older machine that doesn't hum like this.

    I already cleaned the connectors on the card, but didn't did the molex connector. So a ground maybe open circuit into on those molex connector?

    To be continued...

  10. #10
    Senior Member geoelectro's Avatar
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    Have you cleaned the connectors on the amplifier boards? That is the usual Hum culprit.

    Geo

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