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Need help with Toshiba receiver, no FM stereo

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Anonymous
September 17, 2005 6:16:08 PM

Archived from groups: rec.audio.tech (More info?)

New moving sale purchase. Toshiba SA-620 1978 ish AM/FM stereo
receiver, analog tuner. Everything works fine except the FM stereo
reception. It picks up stations fine, but has no stereo separation and
no stereo light. Light checks out ok, no voltage on the leads when
properly tuned. It obviously sounds mono. What might be wrong?
Anonymous
September 18, 2005 5:37:23 AM

Archived from groups: rec.audio.tech (More info?)

<menwagoh@msn.com> wrote in message
news:1126991768.858523.48710@g44g2000cwa.googlegroups.com...
> New moving sale purchase. Toshiba SA-620 1978 ish AM/FM stereo
> receiver, analog tuner. Everything works fine except the FM stereo
> reception. It picks up stations fine, but has no stereo separation and
> no stereo light. Light checks out ok, no voltage on the leads when
> properly tuned. It obviously sounds mono. What might be wrong?
>
Look for a button or switch that says something like stereo or mono and set
it for stereo : )

Okay, seriously, if it has this switch, check that it is functioning with an
ohm meter. If that is not it, the circuit that detects the stereo pilot
signal could have a failed component.
John
Anonymous
September 18, 2005 7:11:57 AM

Archived from groups: rec.audio.tech (More info?)

<menwagoh@msn.com> wrote in message
news:1126991768.858523.48710@g44g2000cwa.googlegroups.com...
> New moving sale purchase. Toshiba SA-620 1978 ish AM/FM stereo
> receiver, analog tuner. Everything works fine except the FM stereo
> reception. It picks up stations fine, but has no stereo separation and
> no stereo light. Light checks out ok, no voltage on the leads when
> properly tuned. It obviously sounds mono. What might be wrong?
>

Most likely the VCO needs adjustment. It's a small potentimeter near the
stereo decoder IC. A small tweak is usually all that's required. When the
stereo comes on reliably, you're done.

Mark Z.
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Anonymous
September 18, 2005 12:01:23 PM

Archived from groups: rec.audio.tech (More info?)

I found the stereo decoder IC (Sanyo A3350) and the VCO. Tweaking the
VCO doesn't change anything. Pin 1 on the IC has 11 VDC (ref to grnd).
The stereo light leads have 15 VDC both sides (ref to grnd). I have
already cleaned all the switch contacts with Deoxit. I have a Sylvania
ECG ref book (says ECG1217 PLL FM stereo decoder), so I can use the IC
schematic to check for VCC and such, right?
Anonymous
September 18, 2005 8:31:24 PM

Archived from groups: rec.audio.tech (More info?)

menwagoh@msn.com wrote:
> It picks up stations fine, but has no stereo separation and
> no stereo light. Light checks out ok, no voltage on the leads when
> properly tuned.

Insufficient signal stength for it to switch into stereo mode? (Most
tuners degrade to mono before giving up entirely.)
Anonymous
September 18, 2005 10:01:33 PM

Archived from groups: rec.audio.tech (More info?)

<menwagoh@msn.com> wrote in message
news:1127055683.049938.282650@z14g2000cwz.googlegroups.com...
>I found the stereo decoder IC (Sanyo A3350) and the VCO. Tweaking the
> VCO doesn't change anything. Pin 1 on the IC has 11 VDC (ref to grnd).
> The stereo light leads have 15 VDC both sides (ref to grnd). I have
> already cleaned all the switch contacts with Deoxit. I have a Sylvania
> ECG ref book (says ECG1217 PLL FM stereo decoder), so I can use the IC
> schematic to check for VCC and such, right?
>

Yes, the IC pinout is a useful "mini-schematic". If it's a digital tuner,
the discriminator may also need adjustment - you'll need a DC voltmeter and
some information on what are the test points and the discriminator (primary)
adjustment. Too bad that VCO didn't get it, that's pretty common.

Mark Z.
Anonymous
September 19, 2005 12:37:59 AM

Archived from groups: rec.audio.tech (More info?)

This is an analog tuner. There are plenty of strong stations here in
Denver and the signal strength meter shows good signals.
September 19, 2005 9:03:07 PM

Archived from groups: rec.audio.tech (More info?)

On 18 Sep 2005 20:37:59 -0700, menwagoh@msn.com wrote:

>This is an analog tuner. There are plenty of strong stations here in
>Denver and the signal strength meter shows good signals.


I believe there is a 470pf or 1000pf clear polystyrene capacitor by
the vco potentiometer. Replace this with a polystyrene or silver mica
capacitor (other types don't work) then try adjusting the vco again.
Chuck
October 7, 2009 5:54:40 AM

hello; My experience with Toshiba SA-520 and 620 receivers has been when the Stereo indicator lamp is out..so will be the stereo reception.. i have found that replacing the stereo indicator lamp will restore your stereo reception.it did for me....
hope this is helpful... m.r.
!