No sound from any source in SONY JJ-700B

[Old Sparky]

This 'tabletop' music centre has been stored for a considerable time, and now, as stated, produces no sound from it's tuner, Cassette, or record deck. The o/p stages are working correctly, and there are DC supplies at various points indicated on the PCB. I don't have a circuit diagram for this late 70s/early 80s product, so tracing the signal paths is difficult. The only other things I've checked so far are the conventional push-button switches which select L,M, or VHF manual/VHF Pre-set tuning, and they are all working. The Functions (Tuner, Phono, Aux, & Tape) are selected electronically There is a 16 pin DIL IC, typeIR2E18. Could this be an electronic switching device? Never come across one before! Any help and advice welcome.

[AlanBeckett]

http://www.ebay.com/itm/Sony-JJ-700-700B...tronics_R2&hash=item2ea4418ec4
Depends how keen you are.

Alan

[Nick]

There is a 16 pin DIL IC, typeIR2E18. Could this be an electronic switching device? Never come across one before! Any help and advice welcome.

The IR2Exx series were Sharp LED drivers but without a manual, who knows...

[Refugee]

Does the tape run mechanically in play?
How did you test the output stages?
Most tape decks were pretty well self contained and playing a tape might help tracing signals to where they disappear.
It will then be time to Google chip part numbers.

[Old Sparky]

I might get that service manual, Alan, but at about £16 it's a trifle expensive. Nick, thanks for the info re. the IR2E I.C. At least I can rule that out. As to testing, I injected 1Khz from my AF Generator at the Volume control, which produced full volume from both channels (about 8 wpc into 8 ohms). I haven't yet tried to monitor the o/p from the cassette deck, so maybe that's the next step. The deck is a front loading, solenoid operated type, and, apart from being a little sluggish starting, runs O.K. Whether the fact that the stereo has been stored in a cellar for several months, and was working before then has any bearing on the cause of the fault I know not.

[Skywave]

The deck is . . . a little sluggish starting, [but] runs O.K. Whether the fact that the stereo has been stored in a cellar for several months, and was working before then has any bearing on the cause of the fault, I know not.

Here I have extracted that quote (slightly edited) since I believe that that is where you should start to think about fixing this. The one significant bit that motivates me to say that is "it was working, prior to being stored: now it doesn't work". So I need to dig a bit deeper and ask two Qs. . . . . .

Was that cellar particularly cold and damp? (Cellars often are).
When you say "it was working", does that mean that all the functions were working - i.e. all those functions which are now not working?

However, in anticipation of your response, if your answers are an unqualified "yes" to each of those, then I reckon you should start thinking along the lines of poor switch contacts, dry solder joints and similar mechanical-type faults. I note you state "the deck is a little sluggish starting": that's a lead worth investigating for a start.

Al. / Oct. 25, '13 //

[Old Sparky]

I had a further delve into the JJ-700 this afternoon, and found that a -13v line was missing. The culprit turned out to be an o/c 330 ohm resistor (R907) on the audio o/p & PSU board. This is supplied from the main 'HT' - 28v line. A new 330 ohm 2Watt resistor has restored sound, at least on the Cassette Deck and Record Player. Haven't yet tried the radio,
but hopefully that should be O.K., too. The resistor didn't appear burnt or otherwise damaged so I'll put the set on long term 'soak' test in case the replacement fails. The cassette mechanism is still mechanically sluggish to start, probably due to it's having been stored for quite a long while in the Cellar, which, yes, does get damp.

[Refugee]

I have seen resistors go open circuit without showing any tell tail signs and the set usually works again with a replacement.

[Skywave]

Open cct. 330 Ω resistor in the PSU: obviously it's good that you've found a fault that fits the symptoms, but it does make me wonder how that failure came about - considering that the unit was working O.K. before storage. Just a thought: is the failed resistor a wire-wound? And if so, could it be that the damp had corroded the resistance wire where it joins the resistor body lead-out wires? A visual inspection - possibly with a magnifying glass - might reveal.

Al. / Oct. 25, '13 //

[Old Sparky]

Al, It is/was a metal film resistor, which I've replaced with a similar type. I guess it was one of those inexplicable failures which occur from time to time!