[TechAssist] Re: Toshiba CF32C50, very low audio, FIX
- From: gulftech@xxxxxxxx
- To: techassist@xxxxxxxxxxxxx
- Date: Tue, 21 Jun 2005 11:01:38 -0500
Friends,
Thanks to all who sent suggestions and to those who only thought about
it.
This would have been simple with a schematic, but that was not to be. I
found that when I floated the base of QN61 & QN62, the sound returned.
These may be muting transistors. Tracing the base ckt back came to QN14,
2SC2878, NTE85. It tested good, but replacing that transistor fixed the
problem.
Regards,
Ken Smith
Gulf Technical Services
3034 Gulf Breeze Parkway
Gulf Breeze, FL 32563
850-934-8324 (Voice) 850-932-0819 (Fax)
On Tue, 21 Jun 2005 07:41:04 -0700 (PDT) Randy Evans
<tvsvc2000@xxxxxxxxx> writes:
> Hi Ken:
>
> I had the same model, and the same problem a few months ago.
> The customer was in a hurry so I never was able to resolve the
> problem.
> I installed the SKUP9102......with no change in the symptom.
> It makes me wonder if the SK version of the SBX1637 is any good
> any more? The next time that I need one I'm going with the Sony
> Original ! If I were you I'd try another chip before going any
> further.
>
> Below is a post from this list for a CF30C50
>
> Randy Evans
> VCR SERVICE
> Delta, Ohio 43515
>
>
> CF30C50 TAC9301 Low Audio Problem
>
> Thanks Andrew, but replacing the MPX Decoder "again" solved the low
> volume problem.
> Paul Worthen
> C&W Electronics
> 117 W Main St
> Azle Texas
> c_w_electronics@xxxxxxxxxxx
> ----- Original Message -----
> From: Andrew Rose<mailto:badandy2@xxxxxxxxxxxxx>
> To: repair@xxxxxxxxxxxxxxx<mailto:repair@xxxxxxxxxxxxxxx>
> Sent: Wednesday, January 12, 2005 8:54 AM
> Subject: [TechAssist-B] Re: CF30C50; TAC9301 low audio problem -
>
> I think I have that schematic let me know and I will look for it
> and
> send it
> out snail mail
> Andrew Rose Action TV. Holbrook ny.
> ----- Original Message -----
> From: "Paul Worthen"
> <c_w_electronics@xxxxxxxxxxx<mailto:c_w_electronics@xxxxxxxxxxx>>
> To: <repair@xxxxxxxxxxxxxxx<mailto:repair@xxxxxxxxxxxxxxx>>
> Sent: Tuesday, January 11, 2005 10:31 PM
> Subject: [TechAssist-B] CF30C50; TAC9301 low audio problem -
>
>
> > No sound, found/changed corroded SBX1637 in MVUS32S module,
> which
> brought
> audio back, but low. At max volume, sound is only at normal
> listening
> level.
> > No diagram - any similar sams number for audio circuit or audio
> tips would
> be appreciated.
> >
> > Paul W
> > C&W Electronics
> > 117 W Main St
> > Azle Texas
> > 817-444-4520
> >
>
> gulftech@xxxxxxxx wrote:I am missing something here that is driving
> me crazy.
>
> I originally thought it was the typical Sony sound module (SBX1637)
> bad.
> I replaced that a little over three years ago, but put a new one in.
> No
> change. It uses a TA8200AH audio output. I have audio in and out
> both
> channels and at the speakers, but only the slightest sound FROM the
> speakers. I subbed the speakers with no improvement. The 470 ufd
> coupling caps are good. Tried a new TA8200. No change. Checked the
> internal/external speakers switch. There is audio present at the
> audio
> out jacks.
>
> The output stage seems to be working, because the signal is greater
> on
> the output than the input. The darn thing SHOULD work, but it
> doesn't!
> I have 27v B+, 5V on the mute, and about 11V on each output pin. No
> print, but I think that is about normal.
>
> If you have a scan of the output stage or the voltages on IC610
> (LA7800AH), it would sure help. Winstips lists QN14 and QA60 as
> possible
> causes for no audio, but they check good and besides I do have audio
> present at both inputs and outputs.
>
> Had enough fun for today.
>
> TIA,
>
>
> Ken Smith
> Gulf Technical Services
> 3034 Gulf Breeze Parkway
> Gulf Breeze, FL 32563
> 850-934-8324 (Voice) 850-932-0819 (Fax)
>
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