Can anyone tell me of a URL where I could download a Service Manual for Aiwa NSX-999 compact disc stereo system.I have downloaded circuit diagrams only to find they do not match the unit although listed as NSX-999. My model has two FL displays on the front, shown as FL500 & FL501.( one being a separate Graphic Equalizer display) The circuit I have shows only a FL200 yet page is headed NSX-999.
Identification No. on mainboard is 83-NF6-622-199 with HEHR, and on front board 83-NF6-611-219. Help appreciated. Jazzer.
Presumably, you are still having trouble getting the displays to work ? Did you determine if the -30v was present ? You can measure it up at the front panel by checking between chassis and any of the VFD heater pins, as the low AC which energises the heaters, is 'floated' on the negative supply to reduce the voltage differentials within the display. If the -30v is missing, it will be one of the multiplier caps open, and these are easy to locate without a schematic, if you have access to a scope, or even at a pinch an AC meter.
Your presumption is correct Arfa, I have not found the open capacitor and there is no AC component on the heater pins other than a small reading of 2.7v AC. I shunted a number of electros in turn in the area of the main board that seemed to me to be the most likely area with a
4.7uf 50v electro but no display resulted. Do not have a scope (my own homebrew 5meg scope went some years ago) only good analogue and digital multimeters.Still floundering and regret my lack of electronic knowledge which is unfortunately compounded with my advanced years.I was an enthustiastic experimenter and licenced amateur years ago and have even built and used my own homebrew radio gear, from the "big bottle" days, then to making my own digital readout modular solid state multi band HF Transceiver. Seem to have lost my memory of the technicalities of all this. Thanks Arfa for your continued interest and patient advice. Jazzer.
OK. 2.7v AC across the heater is correct. This should also be floating at -30v with respect to chassis, and this would seem to be where your problem lies. On most Aiwas, the connector between the front panel, and main board, is labelled as to connector pin functions. You will normally find a couple of pins called something like " FLAC " and another " -VFL ". That is the one you are looking for. You could try following the print trace back across the board. It will lead you ultimately to the voltage multiplier for the supply, but it's usually right over the other side of the board, so a long way to follow fine traces ...
The voltage multiplier is usually at the left side of the main board, looking from the print side, about half way up. You are looking for a cluster of two or three electrolytics, with a couple of diodes nearby. Even if the schematics that you have don't exactly match what you have got, the same basic circuit will be present to power the VFD, and should give you an idea of exactly what you are looking for.
With a 'scope, it's very easy. You just look in that area for likely candidates ( and there are DOZENS of variations of chassis fitted to Aiwas, all with slight differences of functionality but broadly similar layout ) and then start scoping them until you find one that's got massive line frequency AC on it. Chances are that the other side of it, or one of the others nearby, has got nothing on. You could do the same with an AC voltmeter, but you will need to put a cap of say 10uF 50v in line with one of the probes. This will make sure that the meter *only* reads AC, and doesn't produce a reading if you touch on somewhere with DC on it. Touch the outboard end of the cap to chassis between each check, to ensure that the cap isn't charged from the previous measurement, when you take the next. IIRC, the sort of value cap you are looking for as the faulty one, is around
Alas I did manage to find a open cap and on replacing the ac appeared across it but still never got to the fills. Checked for more open caps in the multipler chain but all seemed ok. But Arfa did you say Good Luck! In my clumsiness managed to drop a tool on the main board and blew the secondary fuses in PS board. On replacing DC ok but power switch not switching unit on. Only lights show in CD selector and tape arrows. Bad luck and I will shelve this one for a while and take another look when I feel a little better. Thanks for your help and patience and hope to contact you again in the future. Cheers, Jazzer.
That's a shame. You may now have landed yourself with more trouble than you would care to contemplate ... The power supply circuitry on most models is pretty complex, employing a dual level rail system to the output stages. Under low load, low volume conditions, the output stages run from low (ish) rails, but when the vol is ramped up, and the demands of the output stages increase, the supply rails are jacked up ' on the fly ' as it were, using a pair of FETs. These FETs fail and cause all sorts of problems. You only have to look at them wrongly for them to fail all on their own. Not all models use this sytem, however, and as I said at the start, the model that you quote is not one that I remember having specific dealings with. However, on most models, there is a complex fault monitoring circuit. It checks such things as presence of AC to the power supply ( via two little surface mount dual diode packs that look like s.m. transistors ), output DC offset, heatsink temperature, output stage current, and funnels the whole lot finally down to a line called " /PROTECT ". This line goes right on back to the system control micro on the front panel, and if it's low, will cause the micro to just halt in the non-reactive state that you describe.
The usual way to tackle this problem is to locate one of the jumpers that is labeled " /PROTECT " ( there are a couple dotted about the main board usually, one around the middle towards the left, and sometimes another up by the connector which joins the front board to the main board ) and lift one end. This should allow the micro side to come back up to +5v via a pull-up resistor that's on the front panel. Making sure that you have no speakers connected (!!), you can now power up, and with luck, the unit will come on and stay on. You can then use normal fault finding to determine which branch of the fault detector circuit is being activated, and then work out why. For what it's worth, you might find some additional pico fuses on the main board near the outputs. Make sure that these have not failed. Check also that all of the pico fuses on the transformer board are actually ok. I won't say " good luck " this time ...
I am away for a couple of weeks from Monday. Feel free to post or mail me direct, but don't expect a reply for a while after Sunday.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.