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. 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.

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?

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.

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

>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.

>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:
<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.

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

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.
>
>
>

Bob F <bobnospam@gmail.com> wrote:

[...]
> 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.

Does it look badly burnt or is there no physical sign of stress?

It would be very unlikely that both windings would go O/C simultaneously
unless it had failed catastrophically and that would be rather obvious
from the outside.

Simple question: Did you measure the resistance between the two ends of
the same winding or are the terminals laid out in a confusing way, so
you measured resistance between two different windings?

--
~ Liz Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

On 4/29/2024 1:28 AM, Liz Tuddenham wrote:
> Bob F <bobnospam@gmail.com> wrote:
>
> [...]
>> 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.
>
> Does it look badly burnt or is there no physical sign of stress?

No sign of either. I just pulled out the circuit board, and no visual
sign of damage. The diodes and cap on the power input to the board test OK.

>
> It would be very unlikely that both windings would go O/C simultaneously
> unless it had failed catastrophically and that would be rather obvious
> from the outside.

Kind of weird. It worked one day, but not at all the following morning.

>
> Simple question: Did you measure the resistance between the two ends of
> the same winding or are the terminals laid out in a confusing way, so
> you measured resistance between two different windings?

I measured across the wires going toward the power cord for the primary,
and the wires going to the circuit board for the secondary. 2 pairs of
wires completely different wires, one pair from each side.

I moved a system that used to be used in my exercise room up, and it fit
in my space, so no crisis. Maybe I will try unwinding the transformer
coil some time I'm feeling bored.