"Jazzer" wrote in message
ups.com...
Arfa Daily wrote:
"Jazzer" wrote in message
ups.com...
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.

Arfa
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
47uF at 50v. Good Luck !

Arfa