Aiwa P30 Power Amplifier Fault

M.Joshi

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Sep 27, 2011, 4:41:36 PM9/27/11

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Hello,

I am trying to diagnose a fault with an Aiwa P30 DC Stereo Power Amp.
It is part of a mini separates system consisting of a separate tuner and
pre-amp.

The power amplifier does not output any audio to the speakers from
either channels. I have checked that the startup relay engages and both
the positive and negative power rails seem to be OK?

Any other pointers would be useful.

Thank you.

--
M.Joshi

Mark Zacharias

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Sep 28, 2011, 8:08:35 AM9/28/11

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"M.Joshi" <M.Joshi...@diybanter.com> wrote in message
news:M.Joshi...@diybanter.com...

If the amp is functioning to this level, maybe the audio input is missing?
Have you checked the audio level going in? Flat wire connectors make this
difficult, and I'm almost betting this unit uses them... grrr.

Mark Z.

Arfa Daily

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Sep 28, 2011, 8:12:08 PM9/28/11

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"Mark Zacharias" <mark_za...@labolgcbs.net> wrote in message
news:4e830e43$0$31312$a826...@newsreader.readnews.com...

When he says "startup relay", is he referring to a relay that turns on the
main power transformer from a standby supply ? I'm not familiar with this
model of Aiwa, but it occurs to me that it may also have an output relay
that's not coming in ?

Arfa

Wild_Bill

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Sep 29, 2011, 8:03:05 AM9/29/11

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Or.. maybe he means a protection circuit relay. I have no experience with
this unit either, but it would be good/fantastic if people would take an
extra freakin minute to type more details regarding their electronic
problems.

These unclear questions generally take a few days of asking the OP for more
info, to even get an idea of what might be taking place.

And, because the OP is posting from one of those gypo/clone DIY sites, he
may miss seeing some replies.

--
Cheers,
WB
.............

"Arfa Daily" <arfa....@ntlworld.com> wrote in message
news:WIOgq.5$6v...@newsfe16.ams2...

raypsi

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Sep 30, 2011, 7:38:13 PM9/30/11

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On Sep 28, 8:08 am, "Mark Zacharias"

Hey OM:

I seen where peeps have left out the jumpers that go in the RCA jacks
on the back the jumpers re feed the signal back into the amp for say
you don't have an EQ that needs to be attached.
To find out take a small screwdriver that will fit into the RCA jacks
and with the volume cranked up all the way, poke the screwdriver in
each jack to find out which one is inputting direct to the amp.

Once you hopefully find that jack the use a RCA cable to find the
output just keep plugging the RCA cable into every jack until you find
it don't forget the turn the volume back down though.

Been there done that that's my story and ima sticking to it.

M.Joshi

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Oct 5, 2011, 3:32:16 PM10/5/11

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I have investigated further - the gain sections appear to be working
fine. If I inject a 1KHz signal at the input on the RCA jacks, an
amplified version is present on one side of the protection relay. The
other side feeds the speaker output terminals. The relay is just not
switching for some reason? I have tested the relay out of circuit and
it does work.

The protection circuitry is built around a TA7137P IC.

I also found a zener diode which is measuring short circuit. The part
number is D162 - I cannot seem to find any data on this?

Thanks.

--
M.Joshi

Arfa Daily

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Oct 5, 2011, 8:58:11 PM10/5/11

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"M.Joshi" <M.Joshi...@diybanter.com> wrote in message
news:M.Joshi...@diybanter.com...
>

In what part of the circuit is this zener ? Are you sure it's a zener and
not just an ordinary diode ? Have you checked it out of circuit to make sure
that you are not reading across some parallel device ?

The relay might not be closing for one of two reasons. First, that it's
doing its job, and protecting your speakers from a DC offset at the midpoint
of one of the amplifier channels. The first thing that you must do is to
determine if this is the case, by measuring with a multimeter set to a DC
range, at the input side of the relay switching contacts, for each channel.
You should do this with no signal present, and not expect to see more than a
few mV - probably 15 mV maximum.

If there is no offset, then the chances are that the problem is around the
7317 (that's 7317, not 7137 as you stated) protection IC. In my experience,
it is seldom the IC itself which is faulty. Most often, it is one of the
components that defines the delay time before activation of the relay -
about four to six seconds for most amplifiers. The two components involved
are a small electrolytic, and a high-ish value resistor feeding it with
charge current. Either of these components, when faulty, can cause the IC to
malfunction in the way you are experiencing.

see

http://pdf1.alldatasheet.com/datasheet-pdf/view/86921/TOSHIBA/TA7317P.html

and take a look at the test / application circuit. Look at the components at
pin 8 for instance.

Arfa

M.Joshi

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Oct 6, 2011, 5:23:10 PM10/6/11

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Thanks for your reply Arfa - I have downloaded the schematic of the
protection IC and will take a look at the test circuit.

The shorted component is definately a zener as the PCB symbol indicates
(a diode symbol with two opposite diagonal tails). The zener measures
short in circuit and out of circuit too. I cannot seem to find any data
on it (W162). Do Japanese manufacturers use W to denote something?

Arfa Daily;2720819 Wrote:
> "M.Joshi" M.Joshi...@diybanter.com wrote in message

> news:M.Joshi...@diybanter.com...-
>
> M.Joshi;2716810 Wrote:-

> Hello,
>
> I am trying to diagnose a fault with an Aiwa P30 DC Stereo Power Amp.
> It is part of a mini separates system consisting of a separate tuner
> and
> pre-amp.
>
> The power amplifier does not output any audio to the speakers from
> either channels. I have checked that the startup relay engages and
> both
> the positive and negative power rails seem to be OK?
>
> Any other pointers would be useful.
>

> Thank you.-

>
> I have investigated further - the gain sections appear to be working
> fine. If I inject a 1KHz signal at the input on the RCA jacks, an
> amplified version is present on one side of the protection relay. The
> other side feeds the speaker output terminals. The relay is just not
> switching for some reason? I have tested the relay out of circuit and
> it does work.
>
> The protection circuitry is built around a TA7137P IC.
>
> I also found a zener diode which is measuring short circuit. The part
> number is D162 - I cannot seem to find any data on this?
>
> Thanks.
>
>
>
>
> --

> M.Joshi-

> 'TA7317P pdf, TA7317P description, TA7317P datasheets, TA7317P view :::
> ALLDATASHEET :::' (http://tinyurl.com/3w8jszb)

>
> and take a look at the test / application circuit. Look at the
> components at
> pin 8 for instance.
>
> Arfa

--
M.Joshi

N_Cook

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Oct 7, 2011, 3:40:55 AM10/7/11

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Assuming the shorted zener has not caused collateral damage then matter of
suck it and see to find a range of values that let the unit work and then
pick the middle value to solder in

spamtrap1888

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Oct 7, 2011, 3:38:22 AM10/7/11

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On Oct 6, 2:23 pm, M.Joshi <M.Joshi.8d41...@diybanter.com> wrote:
> Thanks for your reply Arfa - I have downloaded the schematic of the
> protection IC and will take a look at the test circuit.
>
> The shorted component is definately a zener as the PCB symbol indicates
> (a diode symbol with two opposite diagonal tails). The zener measures
> short in circuit and out of circuit too. I cannot seem to find any data
> on it (W162). Do Japanese manufacturers use W to denote something?
>

Yes, if W162 is silkscreened on a circuit board, it is likely to refer
to a wire jumper. This would be consistent with a zero ohm reading.

Franc Zabkar

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Oct 7, 2011, 3:47:42 AM10/7/11

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On Thu, 6 Oct 2011 21:23:10 +0000, M.Joshi
<M.Joshi...@diybanter.com> put finger to keyboard and composed:

>The shorted component is definately a zener as the PCB symbol indicates
>(a diode symbol with two opposite diagonal tails). The zener measures
>short in circuit and out of circuit too. I cannot seem to find any data
>on it (W162). Do Japanese manufacturers use W to denote something?

Is there an electrolyic capacitor in parallel with the diode? If so,
then its voltage rating will put an upper limit to the rating of the
diode.

Are there any similarly marked zeners elsewhere on the PCB? If so,
then measure their voltages in-circuit and compare them against their
marking codes.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

Mark Zacharias

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Oct 7, 2011, 7:50:36 AM10/7/11

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As I recall, the notation is short for WZ162 and would indicate a 16 volt
zener.
So...
I looked up a WZ162 using NTE cross refence software, and yes, it's a 16
volt zener, equivalent to an NTE 5025A.

Mark Z.

Winston

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Oct 7, 2011, 6:43:41 PM10/7/11

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M.Joshi wrote:
> M.Joshi;2716810 Wrote:
>> Hello,
>>
>> I am trying to diagnose a fault with an Aiwa P30 DC Stereo Power Amp.
>> It is part of a mini separates system consisting of a separate tuner and
>> pre-amp.

The 'speaker' switches on the front panel are
turned 'on', yes?

--Winston

M.Joshi

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Oct 10, 2011, 6:30:32 PM10/10/11

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Winston;2723966 Wrote:
> M.Joshi wrote:-
> M.Joshi;2716810 Wrote:-

> Hello,
>
> I am trying to diagnose a fault with an Aiwa P30 DC Stereo Power Amp.
> It is part of a mini separates system consisting of a separate tuner
> and

> pre-amp.--

>
> The 'speaker' switches on the front panel are
> turned 'on', yes?
>
> --Winston

Winston: Yes, I have tried different combinations of the A/B speaker
selector switches!

Mark: I suspected that it was either a 16.2V zener or something similar.
Thanks for checking the data book, I'll try a 16V zener.

--
M.Joshi