Pye LV20 Help?

[stevehertz]

When I say change waxies 'en masse', just to be clear, I mean change them one at a time, consecutively, until they're all done. Otherwise cutting them all out and potentially having problems remembering where they're all terminated is not to be recommended and not what I meant.

[itainthard]

Hello All,
I take the point that it is better to just replace the caps as they will only fail in the end anyway and if this was a radio or amplifier i would probably have gone down that route however i am keen to understand what i am doing (as much as i ever do) and so have taken to replacing caps as i go. That said i have now replaced all the wax caps except C26 and the little ones in the RF stage as i am awaiting parts.
This is the first vintage television i have ever played with and so any input is greatly appreciated.

Today i have replaced the last of the caps Freya suggested and checked through R40, R41, R35, R34 and R42 and was still getting nothing then I noticed I had broken a wire off one of the sliders on the back, this reconnected I now have a picture of sorts.
It is rolling and can't seem to be stopped currently but i have a picture! and was feeling so chuffed i plugged the speaker output back in and have sound too!
Its all progress

[mark pirate]

Looking good, you need to set the picture width by lifting the rod on the top of the line output transformer cover.
Once you have replaced the caps in the frame stage, you should be able to lock the frame hold.

Mark

[itainthard]

Hello,

I have recapped nearly the whole set now and things are coming along nicely, i have a fairly stable picture except for a slight giggle to the top few lines and i now have very low sound volume.
I have gone through the manual checking as suggested but now ive run out of ideas.
Can anyone point me in a direction please?

Thanks Joe

[Freya]

When you say you have re capped it all, have you done C35 To C50.
If so, try adjusting the output level on the Aurora. It may be already at maximum.

[Heatercathodeshort]

If you had good sound before you recapped the chassis I would suggest checking for an incorrect connection in the sound RF section.

First check that the audio amplifier stage is working OK of course.

This is a TRF receiver and the decoupling components [if you replaced them] particularly the ones connected to the RF amplifiers need to be in exactly the same position as the originals. They also need to be ceramic or silver mica types.

If these have indeed been replaced, it's worth a probe around with a plastic rod to see if moving them slightly improves the sound.

The originals may be silver mica types and rarely need replacement and should be left alone.
Remove each EF50. Clean all the pins separately including the center spigot and the base of the valve can. [skirt] Smear a TINY amount of MS4 silicon grease on each pin and spigot and again a TINY trace of good quality switch cleaner to every valve pin socket in the valve holders. A drip on the end of a needle to each socket is sufficient. This will guarantee a good connection and will eliminate future intermittent problems.

If all else fails you may need to realign the RF coils. The picture displayed shows a bit of 'ringing' suggesting incorrect alignment that may have been caused by movement of components on the crowded RF section.

It's a simple job if you know the 'knack' but you really need a basic signal generator to make life easier. Looks good so far. John.

[itainthard]

I have replaced every cap exept c60 and c26, c26 i have tested and it is within tolerance while i await the replacement and c60 I replaced with a 400v 56uf cap but this messed things up so i have put it back for now.
I replaced all the caps in the rf stage with ceramic types and tried to put them back as near to how i found them even measuring the overall length to try and keep things the same.
The funny thing is the sound wasn't perfect before and it seems that if i turn the volume down i get a nasty hmm on the audio which goes when at full volume but full volume doesn't seem that loud.
Another thing i have noticed it the contrast control doesn't seem right, when moved it can seem to cause frame collapse or massive over brightness.
Joe

[Heatercathodeshort]

Yes itishard!
The replacement of ALL of the capacitors is astonishing. Completely unnecessary and I feel you may have introduced man made faults in doing so. The faults you describe are odd for a B18T/LV20. I don't think I can help much with this thread but will continue to follow it with interest. Good luck with it. You have a picture and some sound so there is hope yet. Regards, John.

[itainthard]

I replaced one or two caps at a time and then checked to see the outcome as i went through i tested every cap upon removal and found most of them miles out of value and as i recapped the faults i had became less and less leaving me with what i have now so I could have caused a problem but Im fairly confident in saying that I didn't.
I have tried to move around the caps and any nearby components with a pair of plastic tweezers this morning to see if that effected either sound or vision but to no avail, think I'll look into how to tune it next.

Joe

[stevehertz]

Many caps, especially mica ones and the likes are associated with tuning and should not, and don't need to be changed as the chances are they're absolutely fine. My suggestion - that I strongly recommended and with good reason stand by - was to change all WAXIES, not all caps. For optimum performance the set will almost certainly need to be re-aligned as both the physical position and the finite value of tuning circuit caps will have changed, rendering the set out of alignment. Oops.

[itainthard]

Oops indeed, seems I have dropped a right one here!

[peter_scott]

Not really! Half the fun of these old sets is the struggle to get them right. It looks as if you will need to re-align the set but that can be very satisfying if you get it right. If the IFs have dust iron cores you do need to be very careful that you don't crack them by forcing them. If they are already cracked and stuck in position you will probably need to find a source of replacements.

If the cores have slots that pass right through them it is best to use a trimming tool that also passes through so that the stresses are better distributed.

HTH

Peter

[itainthard]

Is it wise to have a little gentle play with the pots and see what difference each makes or should i get my head around aligning it as per the manual only?

[stevehertz]

Originally Posted by itainthard

Is it wise to have a little gentle play with the pots and see what difference each makes or should i get my head around aligning it as per the manual only?

They're not "pots" they're tuning coil slubs. If you play around with them you may be able to effect a perceived 'improvement', but it could go disastrously wrong. Secondly, a proper instrument based re-alignment is best due to the need for setting bandwidth, not just 'peaks' that may, on the TV screen give the impression of improving things but in actual fact, are not.

[itainthard]

Ok, Ill have to make some time to really read and understand this then.

[beery]

Don't just adjust the cores without knowing what you are doing.

Do follow the procedure in the manual. However you will need an RF signal generator to do this.

It is possible to align just the sound using the output of the Aurora, but it is far from ideal. L24/L25 and L26/L27 can be adjusted for maximum sound, but adjustment of L23 on its own may have some effect on the vision response, so be careful with this one. Don't adjust anything else.

One of the ways in which a TRF set can become out of alignment is if the valves have been mixed. By which I mean if you removed an EF50 to clean it then it should be put back in the same socket that it came from. This is because there is a slight variation in the capacitance of each valve which can have a significant effect when working in the VHF band. Superhet sets, particularly later valves (e.g. the EF80) are not so bothered by valves being swapped around.

Cheers
Andy