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Problem - Tuner amp AKAI AA 1175

Discussion in 'General Electronics Discussion' started by mike1856, Dec 9, 2017.

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  1. mike1856

    mike1856

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    Dec 9, 2017
    Bought above tuner amp and it has just worked for 40 years but just stopped working mid way through playing a record last week. I am highly under qualified to attempt to fix it myself but wonder if there is anything I should look at before deciding its fate. Having done a bit of googling I understand these units have a good reputation so probably worth repairing. The lights are on as usual but no sound coming from the speakers. Have tried it with a CD and the tuner so have determined it is not the record deck. Wondering if there is a fused output to the speakers?. Any advice much appreciated. Mike
     
  2. 73's de Edd

    73's de Edd

    2,922
    1,235
    Aug 21, 2015
    Sir mike1856 . . . . .

    The lights are on as usual but no sound coming from the speakers.
    That means that the MAIN 2.5 A AC line fuse at the top rear just under the dust cover is good.

    Wondering if there is a fused output to the speakers?

    NONE SEEN

    Have tried it with a CD and the tuner so have determined it is not the record deck.
    I think that I think that I read that as no sound coming from the unit in ANY function.

    FOR SURE GIVEN . . . .That unit has CERTAINLY kept its support unit firmly upon the floor for 40 years.

    If you want to explore farther, use of a DVM for measurements and close up pic exchange would be necessary.

    73's de Edd
     
  3. dorke

    dorke

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    Jun 20, 2015
    Welcome to EP.

    This is a very good vintage receiver ,absolutely worth repairing!!!

    Here are some things to for starters :

    1. Are the LEDs operational?
    2. Are the meters moving when the dial is moved ?(in FM with an antenna connected).
    3. this unit has 2 main transformers,each with it's own fuse,you need to remove the cover after you have disconnected from mains to check them (For 240V units they should be 3.15A each).
     
  4. mike1856

    mike1856

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    Dec 9, 2017
    Thanks for replies, Will have a look at LED's and meters as soon as I have the opportunity.

    I will also check the fuses and report back. Might be a day or two.

    Mike
     
  5. mike1856

    mike1856

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    Dec 9, 2017
    Thanks, Yes no sound in any function. Will let you know how I get on. Mike
     
  6. mike1856

    mike1856

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    Dec 9, 2017
    Sorry have not replied until now. Life is complicated!. Just replying now to let you know I am still alive!. Can confirm the LED,s are operational. All red from left to right FM stereo/AM/FM/Phono/Aux.

    Also both the meters move as normal when the dial is moved.

    Will extract the unit from its home (built into a cupboard) next day or so and check the fuses and get back to you.

    Thanks

    Mike
     
  7. mike1856

    mike1856

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    Dec 9, 2017
    Just thought I should mention I do have the original owners manual as well as a schematic diagram for this unit although as I made clear in my original post I am highly under qualified to be attempting to fix this myself so I am not sure what good they are to me.

    Mike
     
  8. dorke

    dorke

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    Jun 20, 2015
    Well,
    Do you have a DMM and know how to use it?
    Do you know how to solder and did that before?

    If the answer to the 2 above is a definite yes,we can help you with the repair,otherwise you need someone else to do it for you.

    In #1 you said "The lights are on as usual",if you refer to the dial bulbs then I think both fuses are fine,
    but do check them.

    It may be helpful to post the schematics you have of the unit.
     
  9. mike1856

    mike1856

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    Dec 9, 2017
    Have the unit upside down on kitchen table with top casing and bottom removed. Wife away so no panic!. Having the unit upside down gives good access to the fuses. There are 2 inline and 8 in a bank. The inline are 5 amp and are unusual. They seem to be regular glass fuses with metal end caps but the fuse wire has a tiny bulb half way along. Do not appear to be blown but I have never seen a fuse like it before, both exactly the same. The bank of 8 consist of 4 x 4amp, 2 x 2amp and 2 x 1 amp. All look OK.

    I have owned boats for 30 years and have always soldered any electrical connections although any soldering required here may be more delicate than I have attempted before. Also I have recently bought a new (well 20 year old) boat which has on board a multi metre complete with instruction manual which I intend to learn to use.

    Just to reiterate.....The tuning indicators (2) are working, the back lighting for these needles is working as well as the red LED lights (5).

    Had a good look inside the unit and nothing obvious.

    Mike
     
  10. mike1856

    mike1856

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    Dec 9, 2017
    Googled slow blow fuse 250v 5amp images and found photos of fuses which have the same bubble in the fuse wire to which I refer so I am now pretty sure my problem is not just a simple fuse replacement.

    If anyone could suggest what the next stage should be I will judge whether I am capable. Alternatively there is a TV repairer in Whitby (UK) and I am considering calling to see if he has any ideas. OR does anyone know of a vintage hi fi repairer in Yorkshire?

    Thanks

    Mike
     
  11. dorke

    dorke

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    Jun 20, 2015
    Mike,
    The schematics show only 2 fuses on the inputs of the receiver.
    In the UK, for 240V,(according to the schematics) they should be 3.15A each.
    Can you please post some photos of the fuse locations?

    A TV repair shop isn't the place to go for that job,
    you need someone who repairs vintage audio gear,and that can be costly.

    What do you mean by :" boat which has on board a multi metre" ?
     
  12. 73's de Edd

    73's de Edd

    2,922
    1,235
    Aug 21, 2015
    Sir mike1856 . . . . .

    Looks like both Sir Dorkes and my manuals are different from yours.( With that high of a fuse count that would be about one fuse per each 4 kilos of amplifier weight.)
    The two 5 amps should be for both of the AF output to speaker feeds.
    BUT I don't see them on my schematic
    That's a slow blow type such that it wont blow on heavy audio peaks but blow on a definite sustained overload.
    I believe that a Buss fuse brand will look like this:


    [​IMG]

    In looking at the AKAI AA-1200 schematic which purportedly assimilates with its little brother AA-1175.
    In looking at the schematic page which has the two power transformers being located at bottom right corner, as T901 and T902 designations, each transformer has 3 fuse holders, of which you use ONLY the fuse in the holder relevant to your line voltage supply.
    With you being a You-are-a-peein', that would be the 230VAC or 240VAC holder, with You-a-knowin' . . . and the correct fuse being a 3.15 A in either case.
    NEVER saw any 4 amps fuses in the speaker lines on the schema..

    Your units problem will VERY likely be a problem with its overload circuitry which is associated with the units two audio output stages that connect into your speakers.
    Look at the 10 o clock position from those transformers on the schema towards the center of the page.
    There is RL1 overload relay that has the right and left outputs from the power amps coming in on its left side and exiting from the right side and they pair with shared ground connections at the speakers other terminals.
    If all is WELL, to then feed amplifier audio to the right and power your speakers, the relay closes and there is sound..

    ( There is a possibility that 2 speaker line fuses might be in the cryptic rectangle to the left of the relay.)
    They are being in the speaker audio output flow path.

    In normal turn on of the system there is some delay for all conditions to settle and THEN the RL1 closes to engage your speakers.
    What I think that is happening on your unit, is that there is some imbalanced DC voltage being on one of the power amp output lines and is detected by the overload circuitry and it in turn either never engages the RL1 relay, or it powers down and opens the connection to the speakers, potentially saving them from being fried if that voltage is excessive.
    • TEST 1 . . . .
    Find that RL1 and hold your finger to its case to detect its action during a power up of the amp.
    No clickee ? 1 Clickee? 2 Clickee?

    which has on board a multi metre complete with instruction manual which I intend to learn to use
    RELEVANCE . . .

    I read that as just being INHERITED BOOTY, in amongst the adjunct equipment that the last owner decided to leave for the new owner. Unless it was an Estate sale and you might have scored all kinds and sorts of desirable goodies.



    73's de Edd
     
    Last edited: Dec 18, 2017
  13. mike1856

    mike1856

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    Dec 9, 2017
    Hello dorke, Thanks. Definitely 10 fuses. Sorry I have no way of posting any photos of locations, hope following description helps. None of the fuses are accessible with the top cover removed but all perfectly obvious with unit upside down with bottom cover removed and can be seen through the slots in the bottom cover with it in place. LOCATIONS...the 2 x 5amp fuses are located just behind the power switch just above the front foot, the other 8 fuses are about 8 inches farther back more or less above the rear foot on the same side as the power switch. The 2 fuses inline, by this I mean in some spring loaded plastic holders are definitely 5 amp. The unit was bought new about 30 plus years ago and has never had the cover removed until yesterday when I had a look at it. Ref the boat reference.........I was just trying to point out that although I did not have a multi meter there just happens to be one among the goodies I have found on board a boat I have recently bought. Just need to read instructions and learn to use it. Mike
     
  14. mike1856

    mike1856

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    Dec 9, 2017
    Thanks Edd, Yes fuses are exactly as your picture. Will read your post a few times to absorb and have a look at the unit tomorrow. Mike
     
  15. mike1856

    mike1856

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    Dec 9, 2017
    Hello, me again, Might have made some progress but first a confession. You will be aware I confidently stated I had a schematics diagram for this unit. Well I was studying your post along with the schematic when I noticed the words on the schematic "light for stylus". The schematic is in fact for the record deck which I doubt will not be much use!. Nor will the schematic for for the Aiwa cassette deck that I do have. However I do have the unit on the kitchen table in front of me and have studied the wires between the 4 way speaker switch OFF/A/B/A+B and the 4 speaker outlets. They are connected by 4 wires green/brown/orange/grey. There are also 2 other wires connected to this switch yellow and blue which in fact irrespective of the position of the switch are always live. These 2 wires are connected to a circuit board and in turn to a clear plastic box which seems to have a removable cover about 1 inch cube. Clearly visible on the clear plastic are the letters OMRON type MY4 (in the moulding) and printed on 02 US 40L DC 24. Visible inside the box are 4 red wires connected to terminals, a white barrel shaped thing in the middle with OMRON written on, 4 brass strips and a spring. I am assuming this is an electronic switch that has the power to decide whether to allow a feed to the speakers depending on its mood????????????. As the visibility into this box is excellent I decided to power the unit up and listen & observe and can confirm complete silence and no movement. Look forward to reply. Thanks Mike
     
  16. dorke

    dorke

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    Jun 20, 2015
    Mike ,
    That electronic switch is actually elctromechanic ,it is called a relay in our lingo.
    It should switch on (and make a "click sound").
    If it doesn't,it means the unit recognizes a fault condition or there is a general fault at it's power supply.

    What you can do is put the speakers switch to "off" (that is equivalent to disconnecting the speakers),
    and listen to the relay click again,if it does at least one of your speakers is shorting.

    The coloring of wires is of no relevance,only the way they are connected is.
    Please post photos,they are worth 1000 words... ;)
     
  17. mike1856

    mike1856

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    Dec 9, 2017
    Hello Dorke, Thanks. Will have to see if I can get someone to help me with the photo, I have no phone or camera. In fact I do not have any speakers connected at the moment I have just been listening for the click and observing any movement and can confirm any sound and movement is conspicuous by its absence. Mike
     
  18. dorke

    dorke

    2,342
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    Jun 20, 2015
    Well,
    With some photos (of tour Multi-meter too) we can try to guide you further.
    Otherwise it is a job for the repair shop.

    addendum : What is the model and make of that Multi-meter?
     
  19. mike1856

    mike1856

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    Dec 9, 2017
    Thanks again, I really do appreciate your help. In my earlier post I said the yellow and blue wires leaving the speaker switch which are connected to the relay are always LIVE. I now realise I should have said always in the ON position, whether they are live depends on whether the relay is supplying power. I have fished out the multi meter and have it to hand. It is a RAPITEST Electrical Multimeter. Cannot find a model number. Mike
     
  20. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    Is your meter like this generic one?
    If not, google "RAPITEST Multimeter" and look for it in the images search ,then link to it.

    You can learn how to use a basic DMM here ,
    concentrate on voltage measurements and ohm/diode/continuity.

    For more in-depth look here
     
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