SX-1010 Tuner Question

Discussion in 'Tuners' started by ZeroJunk, Dec 15, 2016.

  1. ZeroJunk

    ZeroJunk AK Subscriber Subscriber

    Messages:
    1,123
    Location:
    Browns Summit N.C.
    Unfortunately I don't have the other SX-1010. I just cleaned the controls and set the bias and offset for a friend so he could sell it.

    Q3, 13 measures .7 millivolts DC and 2.3 millivolts AC on the strongest station I can find if that means anything. The meter is a Fluke 87 III and it is not an RF voltmeter by any stretch.
     
    Last edited: Mar 17, 2017
  2. rcs16

    rcs16 Super Member

    Messages:
    2,674
    Location:
    Baldwin, Ontario, Canada
    Well that is very low and this is for a antenna signal level that lights up the stereo lamp?
    Q3-13 is supposed to be a DCV, there is no RF at this point. So with that DC level, the meter would not deflect very much at all. max DC should be around 3-4VDC at Q3-13 with a strong signal.
    Suggest you get a better antenna than a piece of wire to act as an FM antenna. get at least a folded dipole, similar to the one that would have come with the unit when it was new. If you have some old TV tower 300 ohm twin lead, you can make up your own folded dipole.
    http://cyberpoet.net/writes/web/infwiz/spant.html
    Not that this going to solve your problem, but something that is better than a piece of wire to get some more sig into the unit.
    So we are going to compare the signal level as shown on the sig meter of the sx-1010 and tx-9100 with the same antenna.
    try the mtf finger trick, place your finger in areas around the ceramic filters and IF amps HA1201(back/foil side of the pcb) ( or use the 10nF capacitor coupling trick as I mentioned earlier), to see if the capacitance of your finger couples the signal across these elements and gets a larger signal into the HA1137 and deflects the sig meter somemore.
     
  3. ZeroJunk

    ZeroJunk AK Subscriber Subscriber

    Messages:
    1,123
    Location:
    Browns Summit N.C.
    I can pull the feedline for a FM beam antenna back in here which I was using when the signal fell off the cliff to begin with. I'm thinking it was maybe 1.2 on the S meter with the beam when it had been being pretty much full scale and now it is maybe .7, not even S 1 on the pieces of wire.

    The thing is, I get Stereo indicator and Stereo signal on stations even weaker than that. Pretty much full quieting.

    I'll try Mark's trick first. I thought I knew what a ceramic filter looked like, but I am having trouble figuring out what they are on this.


    OK. On the outside beam antenna the voltage goes up to .9 millivolts.

    Are the ceramic filters the wire wound component that looks like a choke ?
     
    Last edited: Mar 17, 2017
  4. ZeroJunk

    ZeroJunk AK Subscriber Subscriber

    Messages:
    1,123
    Location:
    Browns Summit N.C.
    Well, now after getting the board moved where I can get my fingers under it the tuner seems to be back working properly.

    I know I am not crazy because the tuner tech told me it was not an alignment issue because the signal was non existent from one end of the band to the other.

    Probably work until I get it all back together. Out of curiosity I tried Mark's trick and finger contact decreases the signal strength.

    Don't know what to do now. Nothing I guess.

    RCS16, I appreciate the education more than you know.
     
  5. rcs16

    rcs16 Super Member

    Messages:
    2,674
    Location:
    Baldwin, Ontario, Canada
    Well actually that is good, see easy fix :), just mess around with it a bit. swear,curse at it :) it probably is a connection issue somewhere. Could investigate where it is to figure it out for good. Hard to say exactly, could be a flaky component as well. Start checking/inspecting, pushing on the pcb slightly might uncover an intermittent connection or a cracked trace. Giggle some of the wires, it could be one of those wire wrap connections.
    At least with it working you can do measurements to figure out what a working unit should measure. A reference point.
    Certainly would not hurt to touch up solder joints, inspect for cold solder joints etc.
    The ceramic filters are usually thin 3 legged, tan colored, and have a strip of paint on the top usually red to indicate the pass band freq, usually red for 10.7MHz. Usually Murata SFExxx. They maybe also blue too but usually tan. They sit between the Hitachi HA1201 IF amps, in 8 lead black plastic dip package.
    Look at the foil picture in the S/M p34, they are just beside the IF i/p from the FE, terminals 8,9 on AWE-040.
    If it is working properly, depending where your finger is placed, the capacitance would be shorting the signal out.

    Cheers
    Rick
     
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