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From: Bob F <bobnospam@gmail.com>
Newsgroups: sci.electronics.repair
Subject: Re: Altec Lansing ATP3 Speaker system transformer failed.
Date: Sun, 28 Apr 2024 20:49:16 -0700
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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.
> 
> 
>