sony tan 15 power amp faulty

Discussion in 'Technical Repair' started by simon500, Dec 16, 2017.

  1. simon500

    Thread Starter New Member

    Dec 16, 2017
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    Hi guys
    Im newby here so be gentle with me. I have a 1980 sony falcon power amp (tan 15 f ) , both channels work with very good sound quality to my ears , after around 5-10 minuits there are clicks/low volume popping to right channel. i have cct. layout etc and it is available on web, I did think let me replace all elect.acps on boards first then look at what i think on drawings are fusable resistors , which i am not familiar with .
    Any help would be great .
    simon
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    If you have a link to the circuit post it,

    Does the popping sound disappear at zero volume, ?
     
  3. simon500

    Thread Starter New Member

    Dec 16, 2017
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  4. simon500

    Thread Starter New Member

    Dec 16, 2017
    8
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    I i
    HI Dave, thanks for reply, I have attached service manual below, (pdf)
    Cant wait to get this baby fixed as its so nice, whatever is connected to it just sounds......I was running it into a pair of monitor audio GS20 floorstanders and ive tried a few amps on these speakers and this Sony power amp is out in front every time. 1979 class A rules (when its works that is)
     
  5. simon500

    Thread Starter New Member

    Dec 16, 2017
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    Hello Again Dave,
    ansner to your question about popping , clicks and popping still present at zero volume , but popping does not get louder with volume you can just hear it same level, which to me ruled out interference rfi etc. I may be wrong , it is ok for around first ten minuits of use then when heatsinks on rear start to warm It starts to pop , if I drive it harder the pops get more , I disconected M audio speakers and have been testing it with old pair of bookshelf speakers just in case , but at no time has speaker protection relay tripped and ive checked output for DC and nothing , AC showing around 1.1volt with nothing playing thru input. I checked bias adjustment ( after 10 mins) as to service manual, left channel was spot on at 33mV , right channel was 16mV so adjusted to 33mV run it for further 10 min and it had gone high 49mV so pulled it back again and turned off sprayed contact cleaner on min pot. repeated process again and bias stayed at 33 -39 mV on both channels . I checked PSU voltages AC in /out all about right, checked rectifier 80volts DC accross about -42/+40 to 0 v
    Thanks Simon
     
  6. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    Sounds like thats the fault, the DC bias is changing on the Right channel. I would start by replacing the capacitors D204,205 and maybe the small transistors Q212,213 or Q214,215

    D201 is the Temperature feedback regulator, which is bolted to Q216 output transistor
     
    Last edited: Dec 30, 2017
  7. simon500

    Thread Starter New Member

    Dec 16, 2017
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    1
    Hello Dave , I had to shelve the repair due to house move, unpacked all now and back on with the sony tan 15 f, I have ordered parts and will let you the results , I have run the amp for upto 4-5 hours cont. I noticed right channel heatsink is hotter (to touch ) than left. I attached a dual temp monitor to fins of both and within 30 mins of switch on right channel goes 3 - 4 deg. C . hotter than left and cracking noises start to happen more often the longer its on , do you think power output transistors are faulty too? or is it voltage reg transistors / caps giving up? (Q 212,213. 214 and 215 . which are on order .
    Regards Simon
     
  8. simon500

    Thread Starter New Member

    Dec 16, 2017
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    Hi again Dave,
    Update ... I have replaced C204 , C205 , Q212,213,214,215. Still cracking and popping when warm (after around 1hour in ) does not matter whether source is played at volume and it still cracks pops with open input . I have noticed since replacing the above components both rear heatsinks are about same heat. Before I replaced the above the right heat sink was 4-5 C hotter after about an hour again regardless of cd player connected or not . The next thing ive noticed is that the right after ten Minuit warm manual says to set bias to 33mV . left channel sets and stays put at 33mV , right Channel climbs steadily to around 60mV and then the noises begin, Any Ideas where I should be looking next?
    Many Thanks in advance to anyone who can help please.
     
  9. simon500

    Thread Starter New Member

    Dec 16, 2017
    8
    1
    Hello Again , just a note to say all problem sorted , I forgot to check the bias adjustment setting after I replaced the 2 x caps and 4 x transistors, got it down to 33-35 mV and checked again after two hour burn in and was reading 31 mV , no more clicking and popping , I now have it connected to a pair of monitor audio floorstanders (GS 20 ) and sound is...... I can only say its making me go through my entire music collection as the detail coming from this 1980 amplifier is like no other I have owned or demoed. Its letting me hear just the music . I've tried on budget bookshelf speakers too and it still gives me goosebumps when I listen .
    I must say a huge THANK YOU to Dodgydave as your diagnosis was also amazing. Thank you once more. Kindest Regards Simon
     
    Dodgydave likes this.
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