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From: Mark Carver on 14 Dec 2009 10:38
A friend of mine has just bought himself, and imported here to the UK an
American RV. It is fitted with a Concertone ZX75 car audio system.

There's one problem with the FM radio tuner, it only tunes in 200kHz
steps, 88.1, 88.3, 88.5 etc.

In the UK we have stations every 100 kHz, for instance one station in
our local area is on 98.2 MHz.

Is there any modification (grounding a pin on one of the chips for
instance) that will make the tuner tune in 100 kHz steps ?

He has contacted Concertone's service dept, but they refuse to help,
saying that it is for the US market only.

TIA
From: N_Cook on 14 Dec 2009 12:27
Mark Carver <mark.carver(a)invalid.invalid> wrote in message
news:7on4jrF3p7h7oU1(a)mid.individual.net...
> A friend of mine has just bought himself, and imported here to the UK an
> American RV. It is fitted with a Concertone ZX75 car audio system.
>
> There's one problem with the FM radio tuner, it only tunes in 200kHz
> steps, 88.1, 88.3, 88.5 etc.
>
> In the UK we have stations every 100 kHz, for instance one station in
> our local area is on 98.2 MHz.
>
> Is there any modification (grounding a pin on one of the chips for
> instance) that will make the tuner tune in 100 kHz steps ?
>
> He has contacted Concertone's service dept, but they refuse to help,
> saying that it is for the US market only.
>
> TIA

Without inside knowledge this is the only fudge I'm aware of, from my repair
briefs

Sony MDX C150 car CD+tuner conversion from Japan to UK (+New Zealand)
Made for Japan use and FM band set to 76MHz to 90MHz, UK is
about 88 to 108 MHz
Monitoring the VT line to the tuner varies from 1.52V to 4.2V from end to
end of this band. 2 banks of 6 channels programmable in this 76 to 90 M
range plus 3 more that come up annunciated as 1ch with a VT of 5.66V, 2ch
of 6.83V and 3ch of 8.04 V which coincides with a local station on 107.8MHz,
B+(for FM ) on the tuner is 8.3V.
I changed the 7.2M crystal associated with the LC7216 PLL to a double PAL
frequency crystal of 8.867238M
and this brought the range up to almost ideal, a slightly lower frequency
would be better.
LCD reading of 80.0 gives a tuned in station on 96.1M and 89.5 on LCD gives
a station at 107.8MHz.
7.2M is used on LC7218 FM circuits so probably fairly generally applicable.
For anyone wanting to put an analogue tuning knob on a pot
using regulated voltage of 8.3V at pin 8 of absent IC02
then VT of 8.04V gives 107.8MHz
and 4.21V gives 89M
Tuning voltage from LC7216 is pin 18 via FET ? Q2 marked G19



--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



From: Adrian C on 14 Dec 2009 14:00
Mark Carver wrote:
> A friend of mine has just bought himself, and imported here to the UK an
> American RV. It is fitted with a Concertone ZX75 car audio system.
>
> There's one problem with the FM radio tuner, it only tunes in 200kHz
> steps, 88.1, 88.3, 88.5 etc.
>
> In the UK we have stations every 100 kHz, for instance one station in
> our local area is on 98.2 MHz.

Any chance of popping off the lid and giving us a few chip numbers?
internal photographs?

The large do everything chip is bound to have been used in other radio
designs, and step options for those may be more forthcoming. Maybe even
the PCB is used elsewhere.

--
Adrian C
From: RV Guy on 14 Dec 2009 15:35
On Dec 14, 7:00 pm, Adrian C <em...(a)here.invalid> wrote:
>
> Any chance of popping off the lid and giving us a few chip numbers?
> internal photographs?
>
> Adrian C

Here you go

http://picasaweb.google.co.uk/ian.westwood/ZX75?authkey=Gv1sRgCKar9YSSwYaviQE&feat=directlink
From: RV Guy on 14 Dec 2009 15:36
On Dec 14, 7:00 pm, Adrian C <em...(a)here.invalid> wrote:
> Mark Carver wrote:
> > A friend of mine has just bought himself, and imported here to the UK an
> > American RV. It is fitted with a Concertone ZX75 car audio system.
>
> > There's one problem with the FM radio tuner, it only tunes in 200kHz
> > steps, 88.1, 88.3, 88.5 etc.
>
> > In the UK we have stations every 100 kHz, for instance one station in
> > our local area is on 98.2 MHz.
>
> Any chance of popping off the lid and giving us a few chip numbers?
> internal photographs?
>
> The large do everything chip is bound to have been used in other radio
> designs, and step options for those may be more forthcoming. Maybe even
> the PCB is used elsewhere.
>
> --
> Adrian C

Here you go ..

http://picasaweb.google.co.uk/ian.westwood/ZX75?authkey=Gv1sRgCKar9YSSwYaviQE&feat=directlink
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