Pye v4

[PJL]

You could try swapping out the V1-V5 too. Do you still have the problem with sound and video tuning? I guess we may have to conclude it is a frequency response problem and RF/IF re-alignment is needed. Sorry, that's it from me.

[oldticktock]

Thanks Peter for those last bits, no probs with sound or tuning, other than those litlle smears in the centre blocks the TV is fine.

This thread has run its course and I shall just say thanks to all for the advice, it's all added to the learning curve and has been a great experience.

Standing back and looking at the exercise it's gone from a dead necked set, to displaying a 95% quality picture which is a result in my book. For now I shall do the last bits necessary (need to figure out fitting some resistors or finding a new dropper as I have to run on 220V) close up and maybe come back to it when my experience is greater.

Friday I get my TV22 so it's back to the Bush's for me....

Chris

[oldticktock]

Sorry to ask another question on this already tiresome thread, I have been working on the set with chasiss on it's side for the last week. Decided to put the chassis flat and replace V8 as suggested. This was the result, put the original back in and it's still the same.

What!!!!!! the....... how could the move cause this?

[Tazman1966]

That's the line timebase running at half speed. You should notice that the line whistle sounds odd. Check the setting of the line hold control.

[oldticktock]

that's the only way I could get the testcard on screen to have it that low. If I wind it up it just won't resolve.

[oldticktock]

Taz thanks for jogging my memory, I remembered this same situation happening a few days ago.It was around the line sync discriminators, I up ended the chassis and was expecting maybe the diodes were the problem area, nope they tested ok, I then noticed that one leg of C39 look odd poked it and it was loose, clipped it in and all is well.

Bummer, that answers my question can up ending as chassis cause issues Yes! if one of your solder joints is bad,all adds to the experience book.

I think that was the final raspberry from the V4, i'm sure this TV has got it in for me

[oldticktock]

Could someone advise regarding replacing a O/C dropper.

I do not have any spare droppers and I'm unlikely to find one (wanted ad has not turned up anything) but i do have a lot of high wattage wirewounds and was wondering If there is anyway I can use these to rig the correct power so the set is wired at 240V.

The dropper is a 10R/20R/20R

Not having ever done this before as usual i'm unsure. I have mapped out the setup as it is currently and to get the set on 240 I would have put A(red) in 1, B(black) in 2, C (yellow) in 5.

I would like to totally remove the old dropper and put in place replacements that would either replicate the current setup or just fix it a 240.

Any advice would be fantastic

Chris

[oldticktock]

I think this is how the new circuit should be to fix it at 240V not sure on the wattage though, or where to get them I thought I had low values but no such luck.

anyone?

[ppppenguin]

They're not going to be dissipating much power if they are just dropping the supply to the HT rectifiers. Even if they are passing 300mA (very unlikely) it's still under 4W. Just make up 40R using whatever you have to hand, in series or parallel. For example 4x 10R 1W in series would be OK. Likewise a pair of 82R 2W in parallel.

EDIT: I'm talking rubbish here. Just noticed that feed off to what looks like the heater chain. This means anything up to 15W to be dissipated. If you've got some wirewounds you can do the same series or parallel methods. WW resistors are readily available from RS etc. A common solution in the old days would have been Radiospares dropper sections. Wonderful things but no longer made.

[DangerMan]

In the attached diagram, the dropper R135/136 does carry the heater current as well as AC to the rectifiers. The size of the original component can be used as a guide to what size wirewound resistor is necessary. If you replace each part with a w/w resistor of similar surface area you probably won't go far wrong.
Without reading all 549 posts I'm not sure how much of the dropper is actually faulty... it may be possible, for example, to use the 10 ohm section to partially substitute for one of the 20 ohm ones if only one is kaput. That way you would be able to get away with a smaller (10 ohm) resistor as a repair, and this might be easier to fit in.
Pete

[oldticktock]

Thanks for the idea Pete, R135 is the only working section, hence having to run on 220V, as this is the cement type dropper i wonder how this section will fair and only want to do this repair once.

[Techman]

It's very unlikely that you will be able to find an exact replacement dropper for that set. So, as said above, you'll have to make up the missing dropper sections with various series & parallel 'watty' wire wound resistors that you can find around...(yes, those RS round white sections that you used to be able to get were wonderful for bodging droppers - I've still got several new ones).

The normal 'bodge' (& it is really a bodge, but it works) is to leave the old dropper in place & use it to 'piggy-back' the replacement sections on. To do this you must first cut into the old dropper section with a small blade & try to wind off a few (or all) of the turns of wire from it - it's not unheard of for a faulty dropper section to suddenly repair itself after it's been bridged with a replacement section, thus halving the resistance value...not good!

You should really use special high melting point solder & a very hot, high wattage soldering iron to do the job of soldering the replacement dropper sections (droppers WILL run hot enough in normal use to melt their own solder in some cases & 'drop off', which can be a bit dangerous to say the least). You can get round this by wiring the dropper connections securely in place with bare, tinned copper wire before soldering. By doing this you may be able to get away with using standard solder & soldering iron - there is a risk that the solder will eventually melt with the heat from the dropper, but at least the component will still stay connected & won't fall off inside the cabinet.

[oldticktock]

Hi Techman,

Interesting info and very much welcome.

The top wire wound for R134, has un-spooled itself like a clock spring, likewise the bottom section R136. The middle section (the one i'm running) is fine.

Getting the wire out from those duff sections will be easy due to the above, following your advice I think I will install the new resistor for R134 by wrapping its legs around the arms of that section which protrude out see pic in post #137 , likewise for R136 and then solder that way should the solder melt they at least wont fall and cause issue.

Just need to find some low value high wattage now all mine are high 200R upwards

Cheers for the tip


Chris

[oldticktock]

Had a hunt through boxes of old resistors and found these, not all have wattage and none are exact but could these be used or are they a no go.

I only need a 10R and a 20R as one 20R section works. These values are near so I would imagine a 22R or 25R would be near enough.

Chris

[ppppenguin]

Well there's any number of ways of bodging up your needs fom those. +/-10% is quite adequate.

[oldticktock]

I thought so but my main concern is the wattage if you reckon 15W then these would all be no go.

[ppppenguin]

Please do the sums! It's only Ohm's law and knowing that power is voltage times current. I made a worst case assumption that the current would be no more than 600mA and that figure of 15W was for the whole 40R.

An example: A 10R resistor carrying 600mA will drop 6V so the power dissipated will be 0.6A x 6V = 3.6W.

Hence a pair of 10R in series carrying 600mA, each will disspate 3.6W. A pair of 20R in parallel makes 10R. If the total current is 600mA each will only dissipate 1.8W.

PS: We often say Power = I^2 x R. This is simply combining Power = I x V; V = I x R (ohm's law) so substituting for V we get Power = I x I x R = I^2 x R.

[oldticktock]

I suspect most are sick to death of this V4 thread, for those who are sort of perversley interested then this is the stage i'm at.

I have removed the dropper from circuit and have created my most mammoth clip-in so far. This is allowing me to test combinations of resistors. I may recreate the dropper using a mounted tag strip with the resistors wired on or just hard wire as 240V not sure yet.

My main issues are the resistors I have, some are unknown wattage, some are quite high, they get bloomin hot too, had them on my mat and it started to melt

p.s the V4 continued to stick it's fingers up at me, after cutting out the dropper and clipping in, I had a raster but no testcard or tone. I thought here we go, but I was 100% sure I had not recreated the clip in wrong, it had to be something else. I noticed one EF80 looked odd, bright white at the bottom, changed it out and all was well, it was a knackered old one I had as a spare knocking about that will teach me.

Chris

[Red to black]

Posted by OTT:

I suspect most are sick to death of this V4 thread, for those who are sort of perversley interested then this is the stage i'm at.

Not so!,
Following with interest!
Thanks for the pics
Cheers,
Baz

[audiomagpie]

We've seen you get this far Chris, we don't want you to be beaten!

It takes as long as it takes, you've a lot of loyal followers here!

Greg