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Old 31st Mar 2010, 9:44 pm   #101
Top Cap
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Default Re: Tv62

Very intrigued about the hum myself, especially with the HT fuse pulled.
Could there be a problem with C31 or C38?
Perhaps it is possible to isolate the main smoothers and check them (reform?) in isolation on a DC supply. A fantastic project for you Chris.
Make sure that any soldering you do in the EHT section that you do not leave any sharp spiky bits of solder which can encourage corona discharge. With any soldering, like on the EY86 lead, you should try to leave a smooth finish to the metal cup. These are the things we old engineers were taught by our mentors or we discovered the hard way.
Hands up anyone who went to change an EY51 with a Henley Solon iron, big bang and a soldering iron that now rattles with dozens of porcelain beads inside! Then the hair drier treatment from the Boss - you only make those mistakes once
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Old 1st Apr 2010, 2:17 pm   #102
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Default Re: Tv62

Hi,

Visually investigated the state of the Smoothing can and its has a pronounced bulge where the tags protrude. Will need replacing, John (HCS) is kindly sending me a replacement, so I will have to wait until then.

Incidently my gut feeling on the hum was smoothers right back when i started last Saturday, but Jeffrey and others what I fail to understand is why the hum was present when the F2 (fuse) was removed does anyone have a clue on that.

Re TopCap advice, thanks for that I was not aware regarding the EY86 lead and making sure its solder head is smooth. I have resoldered and it has a nice smooth top now.
Chris

Last edited by oldticktock; 1st Apr 2010 at 2:42 pm.
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Old 2nd Apr 2010, 9:04 pm   #103
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Default Re: Tv62

Seeing as how the main smoothing can C33/C34/C35 will need replacing I decided that in preparation I would removed the Main Deck. Glad I did as I think I found something relevant.

I Followed the Bush dismantling procedure for the Main Deck and took my own notes and took photos. It boiled down to six steps with 9 disconnections.

Now I can see the full extent of the Smoother bulge quite pronounced, now to the interesting bit. I also discovered the cause of the dripping wax, It was coming from C31 a .05 Huge BIG waxy!

It would seem from reading the circuit description that C31 along with a resistor (R43?) are connected between the mains input circuit and the H.T. line to neutralise residual H.T. mains hum. I think I just found the source of my HUM...................

I find using the Bush manual and the Trader sheet actually works best for me as the Trader offers me the benefit of circuit description, Even though the component labels differ.

Some photos attached

Chris
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Old 2nd Apr 2010, 9:08 pm   #104
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Default Re: Tv62

Hi OTT, a popular Bush trick this one, its even on the TV22 set. It is possible to "tune " it to fully minimise hum by adjusting the resistor.
Also look at chassis connections on smoothers etc as these often go higher resistance with time.

Ed
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Old 2nd Apr 2010, 9:38 pm   #105
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Default Re: Tv62

Hi
That big waxy went splat on my TV62 as well!! made a right mess all over my chair.. I didn't actually know what it was for as I don't have the service info for mine. my set seemed to work with it just snipped out. is it ok to replace it with yellow poly caps or should it be an x or y rated thing?

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Old 2nd Apr 2010, 9:43 pm   #106
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Default Re: Tv62

Hi Lloyd,

It's a 0.05 250VAC I was just going to replace it with a big fat 0.47 500VAC poly I have in spares. I don't think it irequires X or y class but will wait until the guru's comment before doing anything.

Chris
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Old 2nd Apr 2010, 10:45 pm   #107
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Default Re: Tv62

I might have to go shopping and get a few new caps! mine is actually a 0.5 @ 250vac. went off like a smoke bomb, but the set was still working while it did it!
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Old 2nd Apr 2010, 10:49 pm   #108
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Default Re: Tv62

Lloyd yeah your right 0.5 is the value, think I'm calling quits for tonight i'm obviously tired and getting my .'s in the wrong place.

The replacement I have is a .47 500VAC which should suffice. I ordered a whole load of replacements from justradios for this set.

Interesting that you say your set worked without the cap in circuit, so it can't be providing much neutralisation of residual H.T. mains hum, so maybe not what I thought. When the can arrives from HCS I will put a new C31 and then try firing up again. I read Sean Williams TV62 restoration hope this is all I have wrong and it turn out like his, looking forward to getting the Aurora and seeing a testcard.

Chris

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Old 2nd Apr 2010, 11:37 pm   #109
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Default Re: Tv62

Quote:
Originally Posted by Top Cap View Post
Could there be a problem with C31 or C38?
Looks like I was partly right with my diagnosis. Fascinating thread, must be many years since I last saw one of these.
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Old 2nd Apr 2010, 11:41 pm   #110
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Default Re: Tv62

Also noted that a cap connected to pin 4 of the PL81 (this was the broken valve) value 0.05uF is in an awful state too.
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Old 3rd Apr 2010, 11:50 am   #111
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Default Re: Tv62

The TCC 100+100+200 removed ready for replacement and my noddy diagram to remind me of the wiring.
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Old 3rd Apr 2010, 8:32 pm   #112
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Default Re: Tv62

It certainly looks like that capacitor was ready to go bang! The .05 connected to the PL81 is probably the boost capacitor. You'll need a good quality 1000 volt replacement for reliable operation.



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Old 3rd Apr 2010, 9:31 pm   #113
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Default Re: Tv62

Hi Rich

Its C38 on the Bush schematic and is connected to pin 4 of PL81

Is that 1000VDC? I have 630VDC

The big fat white one is a Dubilier 1000VDC the yellow poly is 630VDC.

I will have trouble fixing the white one in place is its about 4 times larger than the current TCC waxy.

Chris

P.S. Just in case Heatercathodeshort/ppppenguin are reading all this, I will not change anything other than the smoother and follow your advice as given. But one question, do you not think i should replace C38 or is it likely to be ok with the awful current condition cap, I just don't want to blow or stress my new PL81.

Chris
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Old 4th Apr 2010, 8:06 am   #114
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Default Re: Tv62

630V should be OK for the boost capacitor. Mainly because modern parts are quite a bit more reliable. Those big mixed dielectric parts were pretty good for their time and widely used as replacements (Radiospares was a big supplier, theirs had a grey case) but I'm not sure I'd like to trust them now.
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Old 4th Apr 2010, 12:28 pm   #115
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Default Re: Tv62

Hello Chris,
No problem replacing capacitors that are in an obvious state of collapse, such as C31. You can leave it out of circuit for the time being in you wish. It has little or no effect in practise. The problem is that if you do this in quantity you may introduce faults that believe me are very difficult to trace. Suggest you take digital pictures first so that if the phone rings or you are taken off the job for some reason you can check the connections. I have spent more time tracing faults that I have put on sets than the original fault! It's very easy to miss place a component or connection. As British Rail used to say WE'RE GETTING THERE...John.
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Old 4th Apr 2010, 12:30 pm   #116
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Default Re: Tv62

Quote:
Originally Posted by ppppenguin View Post
630V should be OK for the boost capacitor. Mainly because modern parts are quite a bit more reliable. Those big mixed dielectric parts were pretty good for their time and widely used as replacements (Radiospares was a big supplier, theirs had a grey case) but I'm not sure I'd like to trust them now.
I remember changing lots of 0.47uf mixed dielectric caps on CVC5 -8 series sets. Those boost caps were rated at 1000 volts, and still managed to go short circuit!

As Jeffry suggests, be a little wary of their reliability now.



Good luck, Chris, you are doing well so far.

Cheers. SimonT.
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Old 4th Apr 2010, 1:25 pm   #117
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Default Re: Tv62

Hi John, Yep photo's notes etc all good, believe me I have stripped down many a clock movement with many parts and experience has taught me to be methodical.

Whilst the main deck was out I could also see that the heat reflectant paper was in poor condition througout. I assume this is to stop the Bakelite from over heating and cracking from the high temp generated, this would need replacing so I thought at some point this has got to be taken down further so, removed the RF Deck, this was even more simple and out it popped and put to one side (I will refrain from touching John)

The screen also had lots of crud behind the glass so I thought oh well in for a penny in for a pound, lets have the CRT out. I did this ever so carefully mindful of not upsetting anything.

Once out, the heat paper what was left of it, was removed and replaced. The Rubber around the CRT removed and crud removed from between the glass plate & screen, cleaned and replaced. All put back together again.

I know some of you will think get it working before doing any of this, but I thought whilst it's partly disassembled I would make the most of the spare time before the caps turn up and the serious business end starts, at this point theres not a lot else I can do, itchy fingers and all that.

I have been extra extra cautious, mindful of all previous advice.

Chris
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Old 4th Apr 2010, 5:26 pm   #118
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Default Re: Tv62

Its not actually heat paper Chris but a very clever thought. [Bakelite can withstand quite considerable heat.] Its metal backed paper, cabinet screening in a partial attempt to stop the radiation of the line timebase. 10.000 kc/s would divide very nicely by 200kc/s the frequency of the old Light Programme on Long Wave. A radio placed on the opposite wall to the television receiver in a 30's semi would be completely drowned out by the whistle! The capacitor connected across the set side of the on/off switch [that explodes to everyone's shock] also short circuits line frequency that has sat itself on the mains supply. Its not a problem today because very few people listen to A.M. radio. In this area, W.Sussex I don't know anyone who has A.M. tuned on their car radio's. When doing service calls in the 60's you would hear the line timebase radiation rise and fall on your car radio as you drove down a suburban road. Just like being a television detector van! Regards, John.
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Old 5th Apr 2010, 1:59 pm   #119
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Default Re: Tv62

Ran the 5 EF80's through the valve tester, according to the AVO data gm should be 6 and my valve data book states 7.4

they all have poor gm readings of 0.2, 0.1, 0.6, 0.2 and the best was 2.6 and they show up as replace.

Two questions:

1. Do these lead a hard life?
2. Do they recover with use.

I have 12 others in stock and will test those to see if they are ok or give same poor readings

Chris

P.S.

Tested the other 12 and they all test as either indiff or good with gm's of
3.4, 3.2, 3.4, 3.6, 3.2, 3.6, 4.2, 4.6, 4.4, 2.2, 3.8

One was a Brimar 6BW7 and although a Brimar answer to a EF80 is not a direct replacement even though pin compatable.

Anyway looks like the ones out of the TV62 maybe duff, we will see.

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Old 5th Apr 2010, 2:42 pm   #120
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Default Re: Tv62

What you will probably find Chris, and it will get on your nerves is that after cleaning the rubber surround and putting it all back together there is always just one small piece of fluff/dust you have missed or that flakes off the surround and sticks to the tube after you have assembled it all. I took my TV32 tube out four times before I gave up.

An idea that I got from Gerry at Crowthorne and used on a TV22 was to dip the rubber surround in paint stripper (yep really, it won't affect rubber) to remove all traces of old paint before repainting it.

EF80s? I thought they were pretty reliable beasties.

Dave
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