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Old 23rd Jul 2020, 8:34 am   #1
Nipkowdisc
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Default Thorn TX9 Audio Question

Hello again fellow enthusiasts

I have come across another old Thorn TX9 which has the third version of the chassis (PC1044) and this one is rather more "got at" than the last.

I wonder if anyone can tell me what the value of the Treble Control Potentiometer is supposed to be as it appears to be missing from this Set.
Also when Treble and Bass Controls were included in these Sets (selected models only) did you always get both of them?

All the best
Mike.
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Old 27th Jul 2020, 8:53 am   #2
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Default Re: Thorn TX9 Audio Question

Hello again folks

The value of the Treble Control Potentiometer is on the Schematic.
A nice chap did provide me with a Scan of the one for this Set a while back but sadly this part is not legible due to the way the paper being scanned was folded.

All the best
Mike.
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Old 27th Jul 2020, 10:21 am   #3
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Default Re: Thorn TX9 Audio Question

As a guess, the treble control's value will be similar to the Bass control, assuming that's legible oin your diagram.
Never knew the TX9 had these controls - is it for the 20" stereo Supersound version?
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Old 27th Jul 2020, 8:16 pm   #4
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Default Re: Thorn TX9 Audio Question

I too have never seen a TX9 fitted with both bass and treble, usually on the mono sets behind the flap there was just volume and tone i.e. the treble pot. There may have been some models as there is an option for bass on the circuit diagram, what model set are we talking about here? The pot which is missing is RV145 and it’s value is 10k on the circuit kindly donated by Glyn

The stereo versions of the TX9 and TX10 did not have physical pots for bass and treble, control was via the T9001N IC on the remote control extension/display board.

John.
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Old 28th Jul 2020, 6:57 am   #5
Nipkowdisc
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Default Re: Thorn TX9 Audio Question

Hello again

My sincere thanks to both Glyn and John.
It is just a basic Mono sound model with a 20 inch Picture Tube and a version 3 Chassis.
The Supersound Models which pretended to give Stereo results with the old Analogue Broadcasts came later (I think) and had far more "guts" inside.
The missing Potentiometer (which can now be replaced) for Treble did go behind the Flap and was marked for the customer with what looks like a Treble Clef Symbol to me.

All the best
Mike.
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Old 28th Jul 2020, 7:49 am   #6
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Default Re: Thorn TX9 Audio Question

The Ferguson 37090 has both treble and bass controls and in this case is a stereo sound ctv. However in the PC1044 service sheet it says to look at the specific model number additional service sheet. The treble control is given as RV145 and the bass control is RV149. Often the panel with the controls was referenced as a single part number for the whole assy. Having said that most of the customer controls for the TX9 are 10K ohm linear track, this is the case for the 37090 and most likely your model.
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Old 28th Jul 2020, 8:02 am   #7
Nipkowdisc
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Default Re: Thorn TX9 Audio Question

Thanks Dave.
They did seem to look after the sound reproduction quality a bit more in this part of history (1980's) with some Set Makers giving you a Woofer and a Tweeter I seem to remember.
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Old 28th Jul 2020, 11:15 am   #8
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Default Re: Thorn TX9 Audio Question

I used to work with TV in the early 1980s.
Stereo chips started to appear in Ferguson sets well before AV became standard.
A lot of TX10 sets came in with half of a stereo chip used on mono sets.
I was working in a place that provided the sets for small presentations and had the backs off hundreds of new sets to fit optional AV kits.
New thread if we want more...
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Old 29th Jul 2020, 9:08 am   #9
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Default Re: Thorn TX9 Audio Question

Thanks Refugee.

It seems wasteful to me to use a Stereo Power-Amp Chip for Mono unless it's for a Bridge-Tied Load arrangement.
I guess the A.V. Plugs and Sockets were B.N.C. for Composite Video and DIN for audio (pre S.C.A.R.T. or Euroconnector as they called it).
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Old 29th Jul 2020, 12:11 pm   #10
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Default Re: Thorn TX9 Audio Question

They certainly were BNC/DIN.
The first ones we fitted them to had a mono chip.
Then the later boards used half a stereo chip.
Sets with stereo speakers began to appear within a year.
There was a place for the board on the chassis behind a "knock out".
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Old 29th Jul 2020, 12:17 pm   #11
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Default Re: Thorn TX9 Audio Question

Back in the day I did think it was odd using half a chip, but of course it would save on tooling and spares stocks plus they could buy in bigger quantities. The IC didn't mind and the difference in cost was probably negligible.
Think now of the ICs that are used to a fraction of their capabilities and it does make sense - they were a bit ahead of their time!
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Old 29th Jul 2020, 12:22 pm   #12
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Default Re: Thorn TX9 Audio Question

Everything was becoming stereo at the time so mono chips were being made in smaller more expensive quantities.
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Old 30th Jul 2020, 9:01 am   #13
Nipkowdisc
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Default Re: Thorn TX9 Audio Question

Thanks Refugee and Glyn.
That explains it perfectly.
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