UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Television and Video

Notices

Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

Reply
 
Thread Tools
Old 25th Feb 2024, 2:36 pm   #1
Max Ripple
Pentode
 
Join Date: Oct 2016
Location: Near Coventry, West Midlands, UK.
Posts: 191
Default Toshiba 14N31B-no sound!

I was drawn to this little telly by it's smart design and build quality.
It appears to be a rebadged Orion,and still produces a good picture,so I thought it would be worth proceeding with.
However,I'm bemused by the lack of sound from the unit.
All that happens is a full volume loud hiss,unless mute or zero volume is activated.Ie,the volume control changes between silence or "brain damage",in one step!
Any pointer's appreciated.
Thanks,
Nick
Max Ripple is offline   Reply With Quote
Old 25th Feb 2024, 4:07 pm   #2
Welsh Anorak
Dekatron
 
Welsh Anorak's Avatar
 
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 7,047
Default Re: Toshiba 14N31B-no sound!

What are you feeding it with? Always worth a check first to make sure the fault is actually with the TV.
__________________
Glyn
www.gdelectronics.wales
Welsh Anorak is offline   Reply With Quote
Old 25th Feb 2024, 4:18 pm   #3
Max Ripple
Pentode
 
Join Date: Oct 2016
Location: Near Coventry, West Midlands, UK.
Posts: 191
Default Re: Toshiba 14N31B-no sound!

Thanks Glyn.
I've tried with no external equipment connected via either the Scart or RCA av ports,and also by using the internal tuner.
The same effect occur's even when a vcr is connected to the Scart port.
The effect is'nt present when in the tuner mode,but then I assume that "no signal muting",kicks in there anyway?
The vcr does'nt have an rf output,but I'll try and find something else that does.
Nick
Max Ripple is offline   Reply With Quote
Old 25th Feb 2024, 4:58 pm   #4
Welsh Anorak
Dekatron
 
Welsh Anorak's Avatar
 
Join Date: Apr 2005
Location: North Wales, UK.
Posts: 7,047
Default Re: Toshiba 14N31B-no sound!

A very distant bell is ringing suggesting a software problem that ISTR was easily fixed. Maybe a hotel mode? Otherwise no idea!
__________________
Glyn
www.gdelectronics.wales
Welsh Anorak is offline   Reply With Quote
Old 26th Feb 2024, 11:37 am   #5
Max Ripple
Pentode
 
Join Date: Oct 2016
Location: Near Coventry, West Midlands, UK.
Posts: 191
Default Re: Toshiba 14N31B-no sound!

Thanks again.
Yes indeed,there is mention of software issues in the rather informative service manual.As a result,I've carried out a "to factory setting's" reset,to no avail,alas.
It's quite a neat design,with microcontroller and a "jungle" ic to process the signals,including it seems sound.
The sound output stage is a Panasonic AN7511,which is simply a power amp,with integral (dc controlled)attenuator.
It's still available,so I'll drop another in before admitting defeat.
Nick
Max Ripple is offline   Reply With Quote
Old 26th Feb 2024, 12:44 pm   #6
ben
Dekatron
 
ben's Avatar
 
Join Date: Aug 2006
Location: Madrid, Spain / Wirral, UK
Posts: 7,557
Default Re: Toshiba 14N31B-no sound!

As a last ditch effort, I wonder if it would be possible to link the audio input from the SCART (presumably you wouldn't need the UHF tuner these days) to the output stage directly, thus bypassing the control and signal processing circuitry? if the attenuator still works, it might just be usable. If not then you'd have to add a pot across the input.
__________________
Regards,
Ben.
ben is offline   Reply With Quote
Old 26th Feb 2024, 5:09 pm   #7
G6ONEDave
Octode
 
G6ONEDave's Avatar
 
Join Date: Dec 2019
Location: Owston Ferry, North Lincolnshire, UK.
Posts: 1,748
Default Re: Toshiba 14N31B-no sound!

Might not apply to this model but does the settings control menu have the correct audio mode selected, as in 6Mhz carrier or UK sound etc.

Dave
__________________
Quote "All is hyperthetical, until it isn't!" (President Laura Roslin, Battlestar Galactica)
G6ONEDave is offline   Reply With Quote
Old 27th Feb 2024, 11:13 am   #8
Max Ripple
Pentode
 
Join Date: Oct 2016
Location: Near Coventry, West Midlands, UK.
Posts: 191
Default Re: Toshiba 14N31B-no sound!

Thanks for pointer's.
I have'nt been able to test the set via it's rf input yet,but I'm sure that I have an old sat box inc modulator somewhere to try.
We had hoped to use the set together with an old Atari game console,which only has rf output,but I don't have it here to try.
Yes indeed Ben,some sort of audio bypass to the output stage,if all else fails
The curious thing is that the mute control line to the output chip does'nt seem to alter (pin continually high)with mute or volume commands,which suggests that the output chip is'nt responding,or the "jungle" chip is'nt sending?
More new's when the new output chip arrives.
Thanks for your interest.
Nick
Max Ripple is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 5:24 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2024, Paul Stenning.