Most amplifiers built in the 70's has no output capacitor, I built a few
power amplifiers around 1974, they are all OCL (Output Capacitor-Less). You
can measure the output voltage without load, it should be less than
100mV.
C.H.Ling
----- Original Message -----
From: "Tim Hughes" <timhughes@xxxxxxxx>
Charles,
good idea to check that the DC voltage across the speaker terminals, is well
less than 1V.
But,with nothing connected to speaker terminals you might still get a
voltage, while the output capacitors charges, even though nothing is wrong.
I would connect a dc voltmeter and check that the speaker volatages are less
than 1V with nothing connected. If there is a significant voltage I would
leave voltmeter conected and *very briefly* connect a speaker to charge any
coupling capacitors. If the voltages do not drop then you have a problem. If
the voltage is low then connect up speakers properly and play your favourite
music , preferably piano or something with single notes whre you can here if
there is distortion.
I recently tried to sell a 200W Sony Amplifier in perfect condition on
Craigslist. Although a consumer product, this unit has a huge industrial
size power supply transformer and heatsinks and must weigh 30+ lbs.
I had no takers even at $30.
Tim Hughes
--- On Wed, 6/2/10, James King <jking@xxxxxxxxxxxxxx> wrote:
From: James King <jking@xxxxxxxxxxxxxx>
Subject: Re: [OM] [OT] Amplifier Question
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Date: Wednesday, June 2, 2010, 4:34 PM
once you have a dummy load you prabably want to measure both DC and AC
voltage - ac for noise and DC because its bad news. A large DC offset
positive or negative is going to supply current to the voice coils of
the speaker and the speaker cone will not move because only an ac
current generates a moving magnetic field and a moving magnetic field
moves the cone. A large DC offset can fry the voice coils in the speaker
without you hearing anything... :-(
On 02/06/2010 21:13, Charles Geilfuss wrote:
> Given the vast experience of this group, I'm hoping one of you can answer
> a question for me. Sunday evening I was bike riding in my neighborhood.
> Since Monday is trash day people start putting things to the road for pick
> up. I noticed a pile of stereo gear at the curb and went to investigate.
> Picked up a Technics CD player and tape deck that work fine. There was
> also
> a Technics SE-A50 Amplifier in mint condition. It weighs as much as a Yugo
> but I managed to get it home. Alas, someone else had already taken the
> Preamp. This brings me to the question: when I power up the unit there is
> a
> brief pause then a click (seems normal so far). There are two small lights
> on the front; one for each channel. The left channel light glows but the
> right does not. If only the bulb is burned out then all is well and good.
> How could I simply test the unit to see if the right channel is working?
> Is
> it safe to put a multimeter across the speaker terminals on the back?
>
> Thanks,
> Charlie
>
--
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