Can a PAL-fluent person help me understand sound carriers?

[AlanInSitges]

Hello PAL people!

I've come across something that's got me stumped while working on several PAL sets: the sound is always "off" - smeary and distorted - like it's mistuned or something. I can generally bring it in clearly with fine tuning, but lose the picture in the process.

This has happened to me with two different Philips generators (one analog and one digital) as well as a cheap Chinese modulator. It's identical behavior across all the working sets I have; an early-60s Philco, a mid-60s Zenith, and an early-80s Telefunken solid-state color set.

I have the generator/modulators set to PAL B/G, which is the same region (Spain) as where these sets were built and sold, and presumably worked for many years.

I understand that sound carrier spacing is different across the different PAL flavors, but I'm not sure what I'm coming up against here. If it were one set I could believe maybe it was brought from the UK or something and tuned for a different sound carrier, but three Spanish-made sets that's not going to be the case.

So, the questions:

1. What would the symptom be if I were set to the wrong PAL version in my modulators/generators? That is to say, does the mistuned audio sound like the culprit?

2. Am I crazy to think I should try to do an alignment or even get in there and diddle on the quadrature coil? I'm leery of touching any of those since I don't really know what I'm doing yet, and worse still risking de-tuning any of those circuits when the problem lies somewhere else.

Thanks (as always) for the help and insight.

-alan

[dieseljeep]

Originally Posted by AlanInSitges

Hello PAL people!

I've come across something that's got me stumped while working on several PAL sets: the sound is always "off" - smeary and distorted - like it's mistuned or something. I can generally bring it in clearly with fine tuning, but lose the picture in the process.

This has happened to me with two different Philips generators (one analog and one digital) as well as a cheap Chinese modulator. It's identical behavior across all the working sets I have; an early-60s Philco, a mid-60s Zenith, and an early-80s Telefunken solid-state color set.

I have the generator/modulators set to PAL B/G, which is the same region (Spain) as where these sets were built and sold, and presumably worked for many years.

I understand that sound carrier spacing is different across the different PAL flavors, but I'm not sure what I'm coming up against here. If it were one set I could believe maybe it was brought from the UK or something and tuned for a different sound carrier, but three Spanish-made sets that's not going to be the case.

So, the questions:

1. What would the symptom be if I were set to the wrong PAL version in my modulators/generators? That is to say, does the mistuned audio sound like the culprit?

2. Am I crazy to think I should try to do an alignment or even get in there and diddle on the quadrature coil? I'm leery of touching any of those since I don't really know what I'm doing yet, and worse still risking de-tuning any of those circuits when the problem lies somewhere else.

Thanks (as always) for the help and insight.

-alan

Go to the website, UK Vintage Radio and Restoration.
It's an excellent website and the members are naturally very knowledgeable in the PAL and CCIR systems.
It's the same format as this website.

[Mr Hoover]

Hi,
Try changing the RF channel on your
modulator,is it then any different.
If you've got say UK system I 6MHz
sound vision spacing set being fed by
a B/G 5.5MHz modulator the video will be there but almost no audio.
Don't forget most modulators
are double sideband whereas the
original TV transmissions weren't.
You'll get smeary video and some audio
if tuned to the lower sideband,just fine tune
up as far as it will go for best pic and sound.
Another possibility is you're tuned to a
modulator harmonic.If set say to band3/high band Channel E5 video carrier
175.25 MHz(same as US Channel 7) the
third harmonic will be at the low end of UHF and not give a good picture if the set is tuned there by accident.
Hope that's of some help.Make sure you've set them to a definite channel
and then try and find on the TV,some modulators can have vague instructions.
Does the modulator have switchable audio to go from
5.5 to 6..or even 6.5 system D,E.Europe?
Don't twiddle anything in the TVs yet..
We're at the opposite ends of the Iberian peninsula,
I'm near Faro in Portugal.
Hugh

[Mr Hoover]

This may be like your modulator?
https://www.ebay.co.uk/itm/Pro-Digit...item2ac69df94b
Reading the specifications the RF output
can be set rather high which might be overloading your TV,make sure RF out is
turned almost to minimum.

[AlanInSitges]

Thanks again to those who responded. I solved this, and it turns out I was way off. The audio output level from my DVB tuner was way too high for the inputs on my modulators. Reducing it to almost zero cleared up the problem and I have clean audio now.