Marantz IF Test Points

Discussion in 'Tuners' started by Todd D, Dec 16, 2017.

  1. Todd D

    Todd D AK Subscriber Subscriber

    Messages:
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    Location:
    Newport, Mn
    I've Googled this topic pretty thoroughly without any luck. Reading associated schematics and "The Theory and Servicing of AM, FM , and FM Stereo Receivers" has led me to believe I'm on the right track, but would like to confirm this with anyone else who has tried. Currently I'm checking out the alignment on a Marantz 4300 which is very similar to a 2325. I've narrowed it down to testing a point between R277, and diode H220, while lifting a leg on C242. As I'm relatively new to FM alignments, and using a newly acquired ST100A, I'm not entirely sure.

    The Marantz FM alignment instructions are pretty poor, and I'd like to do it visually with a scope if possible. I've had luck with my distortion analyzer and using the parts of their instructions that are passable, but I'd like to continue to improve at this stuff.

    Any help is appreciated! I'd like the answers for myself, but also to get it out there for anyone else trying to get into this stuff.
     
  2. I LIKE MUSIC

    I LIKE MUSIC Super Member

    Are you trying to improve on step 8 of the FM alignment procedure?

    In your other post you mentioned that you were looking for a good place to test the IF.
     
  3. Todd D

    Todd D AK Subscriber Subscriber

    Messages:
    19
    Location:
    Newport, Mn
    Depends on which instructions you look at. I believe it's step 5 in the 4300 manual (though I own 5+ Marantz tuners/receivers and they all have the same poor instructions). Tuning the IF coils and transformer. In reading the book mentioned in the first post, I was able to pick out the point listed above as an appropriate spot to test. However ST100A I acquired is new to me, and it takes some fiddling to get the right waveforms to show up on my scope. More than anything I'd like to find out what test points have worked for other people so I can use the same ones, and tweak my test equipment until it appears. At that point I can work on fine tuning alignments. Again, I've had some success using the Marantz instructions, but would like to do better.

    Thanks for any help!
     
  4. Todd D

    Todd D AK Subscriber Subscriber

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    Location:
    Newport, Mn
    To be clear, my intent is to do a sweep alignment.
     
  5. rcs16

    rcs16 Super Member

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    3,124
    Location:
    Baldwin, Ontario, Canada
    I realize Marantz instructions are probably the worst. You should read some of the ST documents on alignment procedure to familiarize yourself with the unit and techniques. Also read about other mfg tuners procedure that use the same sort of design techniques.
    A typical FM tuner requires.
    1) RF front end filter alignment, tracking, LP
    2) IF filter alignment
    3) discriminator alignment
    4) stereo decoder alignment

    the procedure depends on the design. sweeping is good for aligning tuned L/C or cavity filter stages. proper sweeping requires a sweeper/tracking gen(horizontal) and a detector for vertical to display the response of the filter. the typical bell curve. the St uses the line freq as the sweeper source.
    You can separately align the RF FE and the IF in some cases.
    usual fe alignment is to adjust for best quieting and/or detected IF response level. adj L's for the low end of the band and the c trimmers for the high end. make sure you use non-metal, plastic tuning tools
    If the IF is all ceramic filters, then you do not need to sweep the IF unless you want to select CF's for best response and matches. If IF is transformers, then you should sweep and tune the filter responses, could fine tune for best THD if you want to try that.
    Most discriminators require a DC balance that is done with no RF or a off station white noise source. You place the DMM across the disc where the center tuning meter will be driven from and adjust for 0DCV. It is usually one of the first things you do. the detector usually has a linearity control, (second slug on the detector coil/transformer). You adjust this for minimum THD with a 75KHz mod rate, 400/1K Hz mod source, full quieting signal level.
    i could write a lot more but this is more than what Marantz wrote for the techs :) hope this helps
     
  6. ConradH

    ConradH Addicted Member

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    Location:
    Canandaigua, NY
    Doesn't the 4300 use a boatload of ceramic filters, therefore almost nothing to adjust in the IF section? I've always found Marantz alignment instructions to be confusing because they talk about distortion when they really mean peaking at very low signal levels. Does the RF section still have a mystery neutralization capacitor with no instructions on how to adjust it? BTW, the IF is what it is in terms of frequency, so you use that, not an arbitrary 10.7 MHz, which may or may not be exact for that particular unit.
     
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  7. Todd D

    Todd D AK Subscriber Subscriber

    Messages:
    19
    Location:
    Newport, Mn
    The 4300 does use ceramic filter in the IF. Does this mean that there isn't a point for me to hook my oscilloscope probe to see the bell curve? The oscillator I follow the Marantz instructions. The FE i've been aligning per the Marantz instructions too (with my plastic tools). It is confusing that they ask for minimum distortion. The ST1000A manual instead suggests tuning for maximum amplitude on the scope. Using the scope isn't necessarily much help. I've used my distortion analyzer on it's voltmeter setting, with the scope on the output. That gives me decent results. The DC balance for the discriminator is called out as 0 volts in the manual, but if memory serves the value needed is actually .360 volts. Is this where I would see the S curve (if I could find the spot to probe)? The ST1000A uses a dual sweep to tune the discriminator. I haven't used it to tune yet, but have gotten the correct display on my scope.

    I haven't run across the mystery capacitor yet, but I look forward to it. I like a good mystery. You mentioned that the IF runs at some specific frequency that isn't necessarily 10.7 MHz? I might be making this up, but I feel like the 2325 I had on my bench a month or so ago allowed me to tune to 10.7 Mhz. I know for certain I had my counter on a test point specifically to tune a frequency. However, that was a month ago, and my brain does a hard reset once every few weeks. If I find it on the 4300, I'll make sure to post the spot.

    I do appreciate all the input on this subject. The people on here are a great resource. I hope that this info will be valuable to someone else down the road!
     
  8. rcs16

    rcs16 Super Member

    Messages:
    3,124
    Location:
    Baldwin, Ontario, Canada
    these marantz schematics are a bitch to follow, esp when the copy is crap.
    C107,111 are the neutralizing caps in the 1st jfet stage.
    J203 is the place you want to monitor for the s curve. you want dc coupling.
    the center meter is driven from J204 which is filtered.
    the place to tune the IF freq is the best center point in the IF filter response curve. you can not adjust this point as there are cf's. this is where your IF sweeper comes in, you tune the marker the best center point in the bell curve, read out marker F, which is usually equidistant as to the skirts. it could be at 10.705Mhz, but most people just tune to 10.7Mhz offset to make it easy, knowing that the cf's are selected for 10.7Mhz, red paint on them if murata's
     
  9. chazix

    chazix AK Subscriber Subscriber

    Messages:
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    Location:
    Groton MA
    There's a wrinkle here that's kept me from wading in so far (aside from not being intimate with Marantzes in particular). Where the OP says ST100A, I've been assuming that's a Sound Technology ST1000A. Unless there are options that mine doesn't have, there are no features in an ST1000A that are well-suited to doing an IF sweep alignment in the "usual" way. (Large grain of salt applies to "usual".) AFAIK, those generators don't output 10.7MHz at all - no sweep, no marker.

    So, I'm not sure to what extent the "usual" service manual's instructions and test points for IF alignment can be used. IMHO, if an ST1000A is the only FM generator on hand, one has to (selectively) ignore the service manual, and instead have faith in the dual-sweep and other techniques described in the Sound Tech manual.

    What am I missing? (Probably a lot. I don't actually rely very much on my ST1000A for IF sections.)

    Cheers,

    chazix
     
  10. rcs16

    rcs16 Super Member

    Messages:
    3,124
    Location:
    Baldwin, Ontario, Canada
    IF sections are usually peak tuned if they are tunable, there is usually one IF transformer in the path. you hardly ever swept an IF for alignment purposes. since this design is all CF's there is no need to sweep the IF as there is nothing to adjust unless you want to look at the filter responses and match filters in this case.
     
  11. Todd D

    Todd D AK Subscriber Subscriber

    Messages:
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    Location:
    Newport, Mn
    I just picked up the ST1000A (correct in the assumption is a Sound Technologies unit). I'm testing out it's capabilities with the 4300. In the past I have used my Leader LSG-216 to inject whatever frequency I'm looking for. However the LSG-216 doesn't have sweep capability. That's main reason I picked up the new equipment (plus it was cheap). The motivation behind the original post is to see if people have tips, test points, or general experience aligning Marantz units. My 4300 isn't out of alignment, which is why I am using it to learn where to see proper waveforms, and what they should look like. I have several other units that DO need alignment, but it's hard to know what waveforms should be present on a unit that isn't functioning properly. And the added bonus is I want to get more familiar with my test equipment at the same time.

    Thanks for everyone's input so far. Keep it coming!
     
  12. rcs16

    rcs16 Super Member

    Messages:
    3,124
    Location:
    Baldwin, Ontario, Canada
    okay so you need to learn to measure a tuner. try to test the 4300 for quieting sensitivity, mono/stereo thd, L/R separation s/n ratio etc. compare against the specs. you need a AC voltmeter and thd analyzer.
    like i said read the ST documentation on how to use the instrument to test a receiver
    I can not upload files since they are larger than permitted
    I got them from here, good info none the less
    http://www.stancurtis.com/soundtech.htm

    http://www.stancurtis.com/Soundtech/Fred/HowToAlignStereoReceivers.orig.PDF
    http://www.stancurtis.com/Soundtech/Fred/FMAlignmentGeneratorOverview.orig.PDF
     
  13. Todd D

    Todd D AK Subscriber Subscriber

    Messages:
    19
    Location:
    Newport, Mn
    I've got all of the ST documents, but thank you for posting them. I have read through them all, and it's great information. Some of the most straight forward I've come across. More than anything it's putting the rubber to the road on a Marantz unit. As I mentioned previously, I've done fine aligning per the Marantz instructions but am seeking out a better path. I have, and am familiar with the AC voltmeter and distortion analyzer. I guess my question comes down to this: Has anyone had better results aligning Marantz tuners following a different procedure than what's laid out in their manuals? Any tips, or tricks, or methods that make it more clear or offer better (easier) results? In reading various manuals for test equipment and receivers it's often the opinion that a visual alignment is superior to other methods used. Has anyone had luck doing this on Marantz equipment?
     
  14. txturbo

    txturbo AK Subscriber Subscriber

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    801
    Location:
    Austin, TX
    What are you using for your detector probe?
     
  15. rcs16

    rcs16 Super Member

    Messages:
    3,124
    Location:
    Baldwin, Ontario, Canada
    You have to realize that when they wrote these manuals they had an audience of techs with limited teat gear. They were lucky to have a THD analyzer, so they had to use what they had, a crt in x/y mode on the ratio detector o/p.
    You should do the experiment and prove to yourself what is the better method, adjust the discriminator with your eye and then use the THD analyzer to see how far you are off the best linearity.
     
  16. Todd D

    Todd D AK Subscriber Subscriber

    Messages:
    19
    Location:
    Newport, Mn
    I was using the Tektronix 10x probe in circuit, but the tape out jacks when following the ST manual alternative procedure. It's been too cold in the garage to much as of late, but I'll get out there again soon enough. I'm slowly developing a method that works well for Marantz. I have 4 different pieces in queue. Several will pull in stereo, and I try to use those as a reference. One piece is out of alignment. That's the guinea pig. Maybe once I am satisfied I will post some of the methods I've had luck with.
     

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