Electronics Forum / Repair / February 2008

I've bought some rather cheap Sony headphones (MDR-V150), say 2 months
ago. Suddenly the sound level on the right channel was weaker and there
were almost no low frequencies when compared to the left channel. I
first thought it was a loose soldering point because every time when ...

I'm having current regulating problems figuring how to build an
electrical muscle stimulator and perhaps some of you may be able to
help.
A couple years ago I decided to have a sex-change operation due to my

    My Compaq Presario 1200XL laptop/notebook won't power up (dead).
    Note: I service TVs, etc. but not computers except my own.
    I checked the power micro switch (AOK).  I removed the
battery, then tried to power it up again the next day without

No sound,nothing.I have my BLU-RAY plugged in to it with a HDMI and
HDMI cable to the T.V. the picture is beautful just no audio.There is
no audio on anything else, AM, FM, CD. Tried everything i know can't
anything. HELP. Thanks, Ed

What is the prognosis for such a battery , run down to 0 volts.
Recovered perfectly happily taking normal charge and holding, but will it be
reliable, have much reduced capacity etc.
--

I carelessly attached a battery with reverse polarity to my Electro
Industries 3002A PSU. I didn't realise until I saw a wisp of smoke
after maybe 10 seconds. Needless to say it now does not work
correctly. Looking inside the circuit board is populated with easily

I have NEC multisync FP912SB monitor that exhibits strange behavior. I
wanted to get feedback  if it is worth repairing/fixing it.I already
have a new monitor and I was planning on giving this old one to
charity if it can be fixed easily. Thanks

I have a Kenwood KT815 tuner - pretty decent 5 gang tuner...  At the
bottom end of the tuning dial it is very difficult to tune -
inconsistant tuning, does not smoothly transition through the tuning
range, but rather jumps around, then does not necessarily stay tuned

Was working fine but had a vague, slight burning-resistor smell. All of a
sudden gave up the ghost tonight after a month of the smell. Is the smell
any kind of clue? I plan to open it but from the slightness of the scent,
I don't expect to find anything more than slightly browned.

I have a Tek 475A whose CH1 bandwidth falls off as the input frequency
increases. At 200MHz, the vertical amplitude is about half of what it
should be. CH2 is working fine. The fault seems to exist no matter what
the vertical sensitivity is so I don't think that it's the extenuator, ...

not exactly reapir related but, I think, interesting.
I've been studying SMPSs for a while out of personal interest, and I stumbled
upon an old schematic for a discrete component-based SMPS:
http://bitman3.altervista.org/SMPS.png

Help! Trying to open a Sony CFD8 portable boombox. The case has deep
recessed rivets (thanks a lot Sony). Other than a sledge hammer (or long
drill bits), does anyone have any experience with this?
Thanks!

Hello, I am hoping someone may have an answer for me. I have a toshiba
portable tv and all of a sudden when you turn the set on manually, it
will continue to change channels over and over as if it where stuck in
auto program mode. Not always but when you try to lower or raise the

Some years ago, I built the flyback tester that was described in
Sams FAQs - the one with the simple two-transistor oscillator,
connected by winding your own 10 turns onto the flyback core. The
flyback is of course tested out-of-circuit. Over the years it has been

I got a HP YIG Oscillator type HP 5086-7337, made in USA f=2.3-7.0 GHz  
without technical documentation. On the device is a PCB, connectors well  
marked, and an 16 pin DIL for a configuration socket without any marks.  
Thats the problem. I didn't found on the HP-site any ...