Sony TC RX70ES.

[John M1JWR]

hi
the problem with this chap is strange, basically if i plug it into the wall outlet and when i switch it the wall outlet on a loud crack/ bang goes through the speakers, the amp a kenwood 3020se is on at the time though has a different source selected, however if the tape deck is plugged into a extension and i do the same thing it dosent happen, i have looked at the line mute section but the service manual isent very helpful in that regard as the voltages needed on the two transistors are not clear and believe it or not d718 is nowhere to be found,
enlighteners would be most welcome

[John M1JWR]

[DMcMahon]

It does sound strange indeed. Have you tried more than 1 extension cable ? maybe there is a wiring difference like neutral/live swap over or earth not connected ?

Not familiar with the line mute circuitry.

David

[DMcMahon]

Can see where diode D718 is supposed to be, shown in attached drawing section towards the top edge 2/3 to the right on the Main Board.

[John M1JWR]

thats the catch, it isent and d715 is inbetween two block connections close to q710, which when looking at the real thing so to speak is nowhere near where shown on the diagram, i did measure d715 with player on and it was 8.15v at one side and 7.45v at the other, dont think a lot of these diagrams corrispond too well with this deck, they could be for the standard 70 model and this is the es one, though i wouldent know for sure.

[ben]

Basically switch noise at powerup it seems.
Some kind of suppression problem? If the deck's on-off switch is on the mains side of the tfmr, I suppose you could try adding a 0.1uF/450v suppressor MKP cap across its contacts.

Needless to say, check the plug wiring.

[John M1JWR]

Hi
the plug wiring is fine
did find out that the mainboard in this player is different to the one in the sm, well its basically the same but parts are in different places or missing in relation to line mute circuit.
there are about 6 wires from the tfmf to a block connector on main board, will look at putting a cap there somewhere though dont have one of that spec in stock, will have to get hold of one

[John M1JWR]

two pics the one titled rx70 is from a possibly later deck of the same model, the other dsc 53 is mine, looks like sony updated the main circuit board on this deck, and on mine it can be seen where c715/d715/d718 are missing from the other pic, d715 and c715 are eleswhere and d718 is not on the board at all, anywhere.

[DMcMahon]

Yes looks like a different revision of the board. Confusing especially if a schematic and board layout cannot be found to match your version of the board.

David

[John M1JWR]

yes cant find a shematic for this version anywhere if it existed in the first place, the revision obviously happened because of the bang through speakers at switch on, nowadays this would have resulted in a recall, not sure that would have happened in 1990, and if it did then this one must've fell through the net