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Thread: Help calibrating a Sony TC-399

  1. #11
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    Quote Originally Posted by Dan LB View Post
    They show a signal when I monitor the source and they show the signal of what is on the tape, but as there is nothing getting to tape in record mode they show no signal when recording and monitoring the playback head.




    I don't have any probes for the scope but the guy I borrowed it from has. I'll get them from him on Monday.



    I'll have to wait til I get the probes.



    Yes it was recording before I changed the transistors.


    Dan
    Transistors!! You mentioned changing some caps not 'king transistors! Small signal TO92 types can have any of 3 pinouts!

    Cannot recall Dan are you UK? If so I have some scope bits you can have including a probel I am sure. No longer have a scope.

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    Transistors!! You mentioned changing some caps not 'king transistors!
    Ah but I did mention it
    Bias traps eh? I've replaced some of the electrolytic caps (the previous owner replaced the rest of them) and most of the transistors...... Might need a tweak.
    Small signal TO92 types can have any of 3 pinouts!
    The ones I replaced were put in correctly observing the pinout

    Cannot recall Dan are you UK? If so I have some scope bits you can have including a probel I am sure. No longer have a scope.
    Very kind of you Dave (as always) but I'm in Ireland.

  3. #13
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    Quote Originally Posted by Dan LB View Post
    Ah but I did mention it



    The ones I replaced were put in correctly observing the pinout



    Very kind of you Dave (as always) but I'm in Ireland.
    Ok so I missed that! (old, one eyed and poorly y'know) Ireland? No worse than my lad in France and I post him stuf all the time. If you want the bits Dan, post me a PM with an addy.

    Time for some serious voltage checks methinks?

    Dave.

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    If you want the bits Dan, post me a PM with an addy.
    Dave, thank you so much for the offer, I appreciate it, I really do, but I don't have my own scope (I borrowed this one) so it would only be a waste of your time and effort.


    Time for some serious voltage checks methinks?
    I'll crack on with that so!

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    OK, here's what I've found...... The image below show's the voltages for each leg of the transistors that I've swapped out, according to the schematic, the measurement of the original transistor and the measurement of the replacement transistor

    tc-399-transistor-voltages-png

    There are 4 that I don't have measurements for the original transistors that got replaced. Do you think the voltages measure within tolerance? I imagine they didn't need replacing in the first place!
    The reason I changed them was because of reading about transistors failing in these models (TC 366, 377 and 399).

    Also I do still physically have the original transistors.


    What I found strange is that I have a few conflicting things going on - the schematic says that certain transistors are of a certain type (eg. it says Q104 is a 2SC458 but the electrical parts list in the service manual says Q104 is a 2SC1345 - which it physically was). The electrical parts list also has all the ones that I changed listed as 2SC1345 but some of them physically were C945. Unfortunately I didn't take note of where the C945s were removed from as I presumed the electrical parts list to be correct and proceeded to replace all of those listed as 2SC1345s with KSC1845s.

    Also on the schematic it says the voltage at the collector of Q101 and Q201 should be 11V but on the actual PCB there is a print with an arrow showing it should be 8V (which it measures) so perhaps the schematic I have is from an earlier version? Maybe there was a revision? I really don't know. I'm taking what's written on the PCB to be accurate in that case.

    Anyway, what do you reckon about the measurements that I've shown above......


    Dan
    Last edited by Dan LB; 08-24-2019 at 11:14.

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    Quote Originally Posted by whome View Post
    What DMM also measures frequency not just voltage current and resistance?
    I have an Amprobe AM-510 but lots of other DMMs will measure frequency.
    Last edited by Dan LB; 08-24-2019 at 16:25.

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    OK! I'm back up and running! The machine is now recording again. There was a broken trace on the OSC board. Soldered in a jumper cable and all is well - nearly!

    Recordings are lacking in treble somewhat - bias?

    Going to clean the heads again now and use a different tape to confirm.

    I'll post results of that shortly.

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    Just cleaned the heads and tried recording on a different tape. MUCH BETTER!!!

    I'll start my calibration process over again tomorrow.

    Bias probably still needs a tweak I'd imagine....?
    Should that be done before anything else?


    Sleep now

  10. #19
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    Quote Originally Posted by Dan LB View Post
    Just cleaned the heads and tried recording on a different tape. MUCH BETTER!!!

    I'll start my calibration process over again tomorrow.

    Bias probably still needs a tweak I'd imagine....?
    Should that be done before anything else?


    Sleep now
    Hi Dan, Sorry I did not get back to you after that marathon voltge table! I had to go for my monthly eye check and the drops leave me blurry after. Better now.

    I WAS going to say, all those values look ok except Q113/203 where you have a 2.5ish b/e voltage differential. Cannot be, Silicon transistors have Vbe of 0.6.to 0.7V. But, you are up and running so no matter.

    Treble loss: Run the test tape and yes, set the azimuth. If that does not deliver on spec treble you might have a worn head.

    Dave.

  11. #20
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    Quote Originally Posted by ecc83 View Post
    .....values look ok except Q113/203 where you have a 2.5ish b/e voltage differential. Cannot be, Silicon transistors have Vbe of 0.6.to 0.7V.
    Thanks Dave, care to explain to me as I'm a complete newbie to this?

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