Help troubleshooting old camcorder AC adapter/charger

[Jeffrey J. Kosowsky]

I have an old Sony VC-35A power supply that both charges camcorder
batteries and serves an AC adapter for my (old) Sony V701 Hi8
camcorder.

The adapter suddenly started to blow fuses (1.25A). The fuses blow as
soon as the adapter is plugged into the 115V wall outlet. Nothing else
seems to smoke or get hot, perhaps because the fuse blows almost immediately.

This happens even when there is no load attached to the supply and
even when the charge-off-vtr slide switch is in the off position (note
this switch is not really a power switch since it sits on the low
voltage side of the circuit).

There doesn't seem to be a direct short since the dc resistance across
the AC terminals is near infinite. Also there is no obvious external
damage to the circuit board or any of the components.

Interestingly, the charger was charging camcorder batteries just until
it blew. However, I had noticed some flakey behavior a couple of weeks
before. Specifically, a couple of times, I noted that the ac adapter
seemed to fail to supply enough current to the camcorder so that it would
start to power up and then immediately shut down. However, the voltage
was ok when not under load and it still seemed to be able to
charge batteries (which presumably draws less current). By the time I
got some 10W 10ohm resistors to measure the voltage properly under load, it all
seemed to be working again with the adapter powering the camcorder ok,
charging batteries, and giving the correct DC out under load.

Then all of sudden while in the middle of charging the 2nd of two
camcorder batteries, it started to blow fuses...

Any thoughts on what might be going wrong here and how I might
troubleshoot/fix it?

-----------------
Specs for the AC-V35A are:
AC in: 110-240V, 50-60Hz, 20W (note circuit senses 110 vs 240
automatically)

DC Out: 7.5V @1.6A (VTR)
10V @1.3A (battery charger)

------------------

Thanks,
Jeff

[Jerry G.]

These are considered to be non serviceable by Sony. You can order a new
adaptor from any Sony rep that handles Sony replacement options. If the
unit is more than about 7 years old, the unit may be hard to find.

Repairing these is considered non feasible. Most of the time, it is bad
caps and the driver transistors. Sometimes other support components are
also defective. In this case there are probably a number of components
that are shorted.

Your ohmmeter will read infinite on the AC input, because the load is
isolated by the bridge rectifier. Your ohmmeter probe output does not
have a high enough voltage to overcome the bridge diodes.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
==============================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
Instruments http://www.zoom-one.com/glgtech.htm
==============================================
"Jeffrey J. Kosowsky" <koso...@consult.pretender> wrote in message
news:m2k7hwe...@consult.pretender...

[Gene E. Bloch]

If you can't find a replacement Sony charger, you might be able to get by
with an after-market charger. Ray-O-Vac is one brand that comes to mind -
oh, yes, maybe Sima too. There are others, IIRC. They usually cost around
$50.

Try Sears, Best Buy, etc, or on-line.

They won't operate the camera, but they will charge batteries off-camera.

Just make sure you pick one that supports your battery type (NiMH, LiIon, or
NiCad) and has terminals or an adapter plate for your specific battery
model.

BTW, some of them come with a 12V car cord as well for an added bonus.

HTH,
Gino

--
--
Gene E. Bloch 650.966.8481
gino37 at earthlink.net
--