It's been a longtime since I repaired classic stereos like this one , since been focusing on marketing Laptops . That one is for a dear friend so I couldn't escape his insistence . Symptoms , nothing showing life but a continuous flashing on the power button . upon opening , first remarks i took , were , this unit was exposed to a heavy drying air conditioning process throughout long periods , rendering each and every soldier point rusty , and secondly , soldiering initially is truly pathetic , i never expect such low level from Sony , at least when comparing with boards taken from a similar unit made by JVC . Anyway , At that point , I knew i brought big trouble to myself and this isn't an easy job ..
Starting to disassemble each part on this unit and re-soldering hundreds of weak points was a priority , at least to understand the circuits and check components on a visual basis .
Taking easy like drawing a paint took me a whole day , but I was confident through the process that I was eliminating tens of possible error protection initialisers . A look at the pathetic display pins status , for one example , was truly abiding .And yet , I wasn't surprised at first tests that the error remained unchanged .
Checking the standby transformer revealed that the 10 ever voltage was present while the big transformer was zero voltaged anywhere . Checking the first relay , a Massuse ME-7C showed a fully burnt contacts due to excessive attempts , but i knew then there's ahead some big dying capacitor , basically keeping away the possibility of burnt regulators or power transistors . That assumption was backed up by 5 intact proper fuses , and the fact that this unit has not run 10% of its life while the Airconditioning process done the initial damage .
Dealing with the relay , I found out its coil is at 144 ohms , meaning it's set for 6 or 9 volts , a difficult one , so i had here to invent . From a similar good relay in my arsenal , I cut enough winding from 270 Ohms coil to nearly 145 Ohms , yep , a difficult job , but better than ordering for a month delay , lol . Checking the born relay , it makes now clicks , but very powerful ones , indicating my original assumption .
Next , a quick check up on Silicons in general revealed healthy components and no any shorts .
Next step was also a quick check on capacitors , starting the 4 big ones on the Amplification board , and the main culprit showed . It was a Nova , 3300mf , 80 volts openly shorted . One similar kenwood from the JVC board was ready . And the unit is up and running for a long testing .
All this work was done without referring to the schematics , lol , which relief me from avoidable headaches , So only using experience and logic .
I thought it's good for sharing with dear friends ..
I took many pictures , i'll post em later ..
Starting to disassemble each part on this unit and re-soldering hundreds of weak points was a priority , at least to understand the circuits and check components on a visual basis .
Taking easy like drawing a paint took me a whole day , but I was confident through the process that I was eliminating tens of possible error protection initialisers . A look at the pathetic display pins status , for one example , was truly abiding .And yet , I wasn't surprised at first tests that the error remained unchanged .
Checking the standby transformer revealed that the 10 ever voltage was present while the big transformer was zero voltaged anywhere . Checking the first relay , a Massuse ME-7C showed a fully burnt contacts due to excessive attempts , but i knew then there's ahead some big dying capacitor , basically keeping away the possibility of burnt regulators or power transistors . That assumption was backed up by 5 intact proper fuses , and the fact that this unit has not run 10% of its life while the Airconditioning process done the initial damage .
Dealing with the relay , I found out its coil is at 144 ohms , meaning it's set for 6 or 9 volts , a difficult one , so i had here to invent . From a similar good relay in my arsenal , I cut enough winding from 270 Ohms coil to nearly 145 Ohms , yep , a difficult job , but better than ordering for a month delay , lol . Checking the born relay , it makes now clicks , but very powerful ones , indicating my original assumption .
Next , a quick check up on Silicons in general revealed healthy components and no any shorts .
Next step was also a quick check on capacitors , starting the 4 big ones on the Amplification board , and the main culprit showed . It was a Nova , 3300mf , 80 volts openly shorted . One similar kenwood from the JVC board was ready . And the unit is up and running for a long testing .
All this work was done without referring to the schematics , lol , which relief me from avoidable headaches , So only using experience and logic .
I thought it's good for sharing with dear friends ..
I took many pictures , i'll post em later ..
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