Re: Altec Lansing ATP3 Speaker system transformer failed.

On 4/28/2024 7:57 PM, Jeff Liebermann wrote:

On Sun, 28 Apr 2024 16:08:57 -0700, Bob F <bobnospam@gmail.com> wrote:
 

This speaker system I used on my main computer died yesterday - no power
at all.
>
I traced the problem to the transformer, a 12.5V 2.5 A TP57U25F from Ten
Pad Industrial.

 Check your typing.  The company is Ten Pao.
<https://www.google.com/search?q=ten+pao+transformer>
There is usually a part number on their transformers.  Find the number
and

A2061

 

Testing the transformer coils, neither the 117V input or
the 12.5 V secondary show conductivity - they are both open circuit. The
fuse for the primary circuit was not blown.

 Conductivity?  Plug it in and measure the AC voltage produced at the
output of the transformer.

No output. Ohmmeter resistance shows infinite on primary and secondary. 2 leads on primary, 2 on secondary, going to 4 diodes on the circuit board.

 

My question here is, if both coils are open circuit, does this suggest
that a major short on the PC board got the transformer too hot so it
tripped temp circuit cutoffs in both coils, so it is unlikely that
replacing or fixing the transformer will fix the speaker? Or, is this
kind of failure common for such transformers?

 I've seen opens on commodity power transformers are when there is
mechanical or chemical damage to the wires.  More common are the
thermal fuses hidden under the tape covering the transformer windings.
 

If I wanted to try a different transformer to test the board, what
should I want the transformers open circuit voltage to read on my
Greenlee DM-20 DVM.  Should that be 12.5V? I do have a variable voltage
variac I could use to adjust a slightly higher voltage transformer down
to 12.5 or whatever should be needed.

 I can't answer that without knowning something about the type of power
supply.  Is the bridge full wave, full wave center tapped, or
something else?  Is the 12.5 V before or after the voltage regulator?
Digging with Google:

12.5 is the voltage written on the transformer.

<https://www.badcaps.net/forum/troubleshooting-hardware-devices-and-electronics-theory/troubleshooting-audio-equipment/58859-system-dead-atp3-altec-lansing-computer-speak-system-with-subwoofer>
Looks like you're not the only one with a transformer problem in the
ATP3.  At least we now have the part number, but for the 230 VAC
version:
   TEN PAO Model no.:TG51219F0
   Input: AC 230V/50Hz
   Output: AC 12.5V/2.5A
I can't figure out the 117VAC version part number.
     "Hacking an Altec-Lansing ATP3 Subwoofer for Stand-Alone Operation"
<http://www.kk4ice.com/?p=570>
This doesn't answer your question, but might be useful reading. Please
note the external on-off switch wiring.  One a different model speaker
system, I had a similar "no power" failure that was caused by me
kicking the sub-woofer enclosure and eventually breaking the on-off
switch.