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Old 9th Sep 2011, 12:11 pm   #61
HamishBoxer
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Default Re: Restorers dream part 2 the chassis.

The PY32 could be duff or overloaded,worth trying another and slow run up.
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Old 9th Sep 2011, 12:42 pm   #62
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Default Re: Restorers dream part 2 the chassis.

It's possible the PY32 was faulty or there was a short on the HT rail.

As I've suggested before, get the heater chain working first. Disconnect the HT voltage selector, the one that goes via the pair of 35R surge limiter Rs to the PY32 anodes. Then you can get all the heaters glowing nicely. Except of course the U25 which will only light up when the LOP is working.

Once the heaters are happy you can connect the HT selector to mains via a variac and/or lamp limiter. No problem using a 1N4007 etc temporarily in place of the PY32 if that's u/s. Just leave the PY32 in place as part of the heater chain. Unless it's gone h/k short in which case the cathode will have to be disconnected.
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Old 9th Sep 2011, 1:02 pm   #63
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Default Re: Restorers dream part 2 the chassis.

It sounds like you might have duff electrolytic smoothers.

I can't remember what equipment you've got col but a test might be to lift the D11 connection from the radio/telly switch and apply a high DC voltage (say 250V) via a resistor (say 100k to start) between D11 and chassis and see what happens. You should get slowly rising voltage as the capacitor rights itself then you can change over to a lower value resistor as it improves to speed up the process. I'm saying all this but I bet you've got a capacitor reformer anyway among all your kit!

It sounds like what has happened is the PY32 has started to work (with the low heater volts before it was probably just trickling) and dumped full power into an un-reformed capacitor.

It might not be that but not a bad place to start...I'm sure the real experts will be along with better advice shortly!

D
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Old 9th Sep 2011, 4:08 pm   #64
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Default Re: Restorers dream part 2 the chassis.

Hi,

Thanks for the information David; please see the following.

I checked before first power up for the mains cap but could not find one so assume it has already been removed; I'll not bother adding a replacement.

I've just had a workshop session and added an earthing lead between the CRT coating (Aquadag; thanks for the name David) and the chassis as you kindly suggested Dom.

Reading the information from both Dom and Jeffrey I wondered if it would be possible to re-form the electrolytics and also run the heater chain after first removing the connecting lead to the pair of 35R resistors? With this in mind I went into the workshop.

I do have a lot of gear Dom but unfortunately not a cap re-former but I do have a good Hunts component tester and one of David's (Yorkie) excellent ESR meters so thought the first job would be to test the electrolytics. I de-soldered all the leads from the two positive tags on the can leaving the chassis connection in place; both electrolytics tested OK on the Hunts and for good measure whilst I was at it and having never used the ESR meter before hooked it up and again both tested OK; the ESR meter can be seen testing in the picture below; the "led" is just a power on reminder. I then re-soldered the leads and located the connecting wire to the pair of 35R's and de-soldered it at the chassis post.

Next I pulled a lot of the valves one at a time to give them a wipe with a meths wetted rag as they were dirty and I wanted to be able to see the heaters.

I put the PY32 back in its holder and switched on only to blow another 3A fuse? I didn't expect this but out of curiosity I pulled the PY32 and blew yet another 3A fuse so I am still unable to apply power even to run the heater chain.

Yesterday the chassis wasn't complaining when connected to the test lamp and Variac with the Variac at 240V so this fuse blowing appears to be something regarding applying full 240V and the obvious answer would be a short as the test lamp was doing its job yesterday (limiting).

In a way this has cheered me up because it is now possible that the PY32 might be OK once this fuse blowing has been resolved. I don't know if it would make any difference but with the pair of 35R's isolated the PY32 still flashed blowing the fuse?

I'm trying to learn as I go along; am I on the right track in thinking the problem to be associated with the heater chain as I believe the HT is now isolated? Please keep the advice and information coming and I'm certainly trying to follow it.

Kind regards, Col.
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Old 9th Sep 2011, 4:22 pm   #65
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Default Re: Restorers dream part 2 the chassis.

Disconnect the tube heaters (pull the base off the tube) and see if it still does it.

It could be the switch of course. Short it out and see.

It could be a capacitor on the heater chain that's gone short circuit, Are the valves in the right places?

It may be a fault in a valve.

Cheers,

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Old 9th Sep 2011, 4:22 pm   #66
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Default Re: Restorers dream part 2 the chassis.

I think your PY32 may have an internal short which is blowing the fuses. If you disconenct its anode and cathode then you should be able to get the heater chain to work regardless. Unless a heater is open circuit or one of the heater chain decouplers is shorted. There's an additional complication of the radio/TV switch but let's hope that's OK for now. If necessary it can always be disconnected and the heaters wired in TV mode.

PS: Crossposted with Steve
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Old 9th Sep 2011, 5:01 pm   #67
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Default Re: Restorers dream part 2 the chassis.

Sounds like the PY32 does have a heater-cathode short, as Jeffrey suggests.
If you disconnect both anode and cathode, you can run the heater chain to check all is ok, and then use a silicon diode to get the set running until you get hold of a new valve.
But before you do that, if you put a temporary resistor.. something like a 1k wirewound... in series with the diode, and unplug the PY32 to disconnect the heater chain, you could use your variac to very slowly bring up the HT in perfect safety and thus reform the electrolytics.

Pete
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Old 9th Sep 2011, 5:24 pm   #68
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Default Re: Restorers dream part 2 the chassis.

Hello Colin,
Take a very close look at the 'trombone' radio/television change over switch mounted on the side of the chassis. You may find this has broken down on one contact causing the heater of the PY32/33 to blow. It was a very common fault at the time. Just needs to be linked for television only operation if this is the case. I have a few spare rectifiers and can send you a working one FOC if this will help. It's unlikely you have an H.T. short. It can happen but I have plugged in terrible examples of this series of Ekco receivers and never had a short but there is always a first time! You can't do much damage whatever the cause. Regards, John.
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Old 9th Sep 2011, 9:20 pm   #69
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Default Re: Restorers dream part 2 the chassis.

Hi
Colin has said in post 64 that the fuse blows even with the PY32 removed! I would be inclined to check that the switch hasn't an internal short (unless Col has bridged it out and removed the cables)
The other thing is to have anther look for the mains filter cap as it could well be short circuit!
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Old 9th Sep 2011, 10:06 pm   #70
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Default Re: Restorers dream part 2 the chassis.

Hi,

Thanks everyone for your input and I'm taking a lot of notice of all the suggestions.

Well spotted Trevor; yes the fuse still blows even with the PY32 sitting on the bench; I don't know much about working on a TV but I quickly sussed out that if I removed it I could get it out of the equation.

A couple of days ago I printed off a lot of your excellent suggestions and in particular those from post #6 which I've just finally got around to studying in detail; thanks for these John and item no 1 is indeed the "trombone" switch; I haven't a clue what this switch looks like as my T311 service sheets don't appear to show it but I've a feeling it will become apparent when I have a look at the chassis tomorrow; I know I'm sad because whilst Bron has been watching Doris Day on TV I've been reading all this printed information and looking through the service sheets.

Tomorrow's first job will be to locate the Trombone switch and take my time checking it; hopefully this will then allow non fuse blowing power to be applied to the valve heaters; if not then the simple suggestion by Steve to remove the end connector from the CRT and check and if the fault remains I'll attack all the waxies which I suspect anyway and I also note a number of the small Hunts caps kicking around. I have plenty to play around with but I'm learning quickly with all your generous help.

Everything felt so strange to me a few days ago; it is the first time I've had the bench loaded with a big chassis and equally as big CRT; today I was more settled with it and even found it easy to tip the chassis on it's back by gently lifting with both knobs making everything very accessible.

Keith (KeithsTV) whilst paying us a most welcome visit a few months ago kindly marked a copy of the circuit diagram with valve numbers but as it is only a diagram I will struggle to identify which valve is which on the chassis as I don't have a proper schematic of either the deck or under chassis and there are a lot of valves on this chassis compared to the radios I've previously worked on.

I've only been working on the chassis a few days but progress is being made and I now feel more comfortable with it under my nose with mains applied; I'm not over confident but then I'm certainly not scared of it either. I feel like a kid learning to walk again but I'm enjoying it.

Thank you so much for your generous offer of a PY32/33 valve John I really do appreciate it and will only accept if I do establish that my valve is truly dead.

I doubt this chassis will take long to restore into working order given the excellent instructions pointing me in the right direction.

Kind regards, Col.
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Old 9th Sep 2011, 10:20 pm   #71
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Default Re: Restorers dream part 2 the chassis.

Bussman must love you!

I got some components today including a supply of DMM fuses as I'm very good at blowing them; that's why I like my AVO.

Thanks for the updates.

- Joe
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Old 9th Sep 2011, 10:42 pm   #72
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Default Re: Restorers dream part 2 the chassis.

Fuses!!? What happened to a rusty nail or the silver paper from a fag packet??

Cheers,

Steve P.
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Old 10th Sep 2011, 10:13 am   #73
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Default Re: Restorers dream part 2 the chassis.

Hi,

Thanks Joe and Steve.

I had considered using a six inch nail Steve but I didn't want to encourage novices with even less experience than me into such practices although it might come to it when my stock (large) of 3A fuses runs out. Tin foil from cigarette packets isn't as widely available these days because cigarettes can damage your health and I've never smoked anyway.

Years ago I bought some 1A fuses that automatically reset once the overload was removed; I've forgotten what they were called and have just checked Maplin website as I think I bought them there but can't now find them. I decided against using them thinking they could possibly be unsafe.

I've not checked and as I still have a lot to learn I wondered if there was an MCB rated at 3A that I could wire into my test circuit; this would at least save blowing fuses. I've just had a quick look at Farnell website and found this which looks promising as it is a push button re-set;

http://uk.farnell.com/eaton/kd1-3/ci...-3a/dp/1338864

Being from a mechanical engineering background I'm finding all this electrical work fascinating; my older brother is a self employed electrical contractor but it is something I never considered as I'm colour blind hence I went into mechanical engineering where all the hammers are mostly the same colour!!

Any comments regarding building in a circuit breaker into a test circuit for this type of work would be most welcome; it might even be covered elsewhere.

Kind regards, Col.
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Old 10th Sep 2011, 11:07 am   #74
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Default Re: Restorers dream part 2 the chassis.

It may well be that a 6A MCB will trip as fast as a 3A fuse would blow.

My old DMM had a 2A fuse which I used to mend with a strand from extra-flex and that always blew OK - I'd had the micrometer on it and it was the correct diameter. The meter was eventually scrapped as the LCD display gave out with age.

As you say these things are not to be encouraged but what consenting adults do in their own workshop is up to them.

- Joe
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Old 10th Sep 2011, 5:29 pm   #75
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Default Re: Restorers dream part 2 the chassis.

Hi,

What a hectic day Iíve had. After tiring myself out trimming hedges with a large petrol hedge trimmer I finally got into the workshop this afternoon with my clothes sticking to me.

What a knowledgeable bunch of guys you all are; I took all the printed suggestions and information into the workshop and made a start. So thatís what a Trombone switch looks like John? I spent a while trying to find it not really knowing what I was looking for; I looked on the outside of each chassis side but could only find the three knobs in a cluster then had a look inside the chassis; then I noticed what looked like a tag strip bristling with contacts and as I operated the channel switch the Trombone description fell into place I had found it. All the contacts appeared to be in excellent order but to be sure I switched on the hand held spotlight and had a really close look; the action was good so I gave it a heavy spraying with switch cleaner followed by a spray of WD40; I wondered what difference if any this would make so blew another 3A fuse finding out.

Next I popped another fuse with the end cap removed from the CRT. At this point I suddenly remembered I had obtained a pair of breakers a lot of years ago at the same time as I bought the automatic fuses and sure enough they were staring at me; one was rated at 3A the other at 1.6A so I added the 3A breaker into the mains circuit and tested through the 100W lamp just to ensure all was well.

I put the end cap back onto the CRT and switched on only for the breaker to do its job. This time it also took down a 5A fuse as I had upgraded thinking the breaker would now stop the fuse blowing; well it didnít but I think perhaps one of the modern breakers would work much better. Thanks for the suggestion Joe it is possible a 6A breaker would possibly trip before a 3A fuse would blow; perhaps the experts have knowledge of this?

Anyway I was getting nowhere fast and not wanting this chassis restoration to last longer than the four month cabinet restoration I had a think about what was happening; it was obvious there was a direct short and as Trevor suggested I had another look around for a mains cap but without luck although by now I had a feeling one was present but where the heck was it; I donít have a component layout at all and there are a lot of caps; even trying to trace the wires was difficult so I thought Iíd get the chassis to talk to me and tell me where it was hurting?

I fitted a 13A fuse and watched very carefully as I switched on; there was a loud bang and a flash; both John and Steve would have been very impressed. The cap had been completely buried but the bang shook a lot of the dirt off and at last I knew I had found the short even before removing the cap.

What an obscure fault this turned out to be; the flash I had seen in the bottom of the PY32 envelope was actually not inside the valve at all; I was standing just in the right position to see the cap flash directly behind the valve which lit the bottom of the valve up.

Iím learning fast and found all the information so far kindly supplied to be of great help; had I found the cap up front I would have missed so much; I even know what a Trombone switch looks like and am pleased I decided not to mess around with it but had there been signs of distress I would have gladly followed Johnís excellent advice.

At the moment Iíve reached the point that Iím following Jeffreyís suggestion and the chassis is sitting on the bench looking like a well lit Christmas tree with every heater I can see glowing merrily away even the end of the CRT is lit up nicely; the only valves which still appear dead are the two inside the LOPT enclosure but I think this is normal at this stage. Yes it is also working from a 3A fuse so what a result; with your help I can see first light wonít be far away.

Whilst looking around under the chassis I noticed a small Hunts black cap has self destructed and this connects pin 2 from the tall valve next to the LOPT to chassis this valve has lost its markings but it is next to the U191. Without a component layout Iím going to find it very slow going as I want to change the caps but at this point Iíll follow your advice as you take me by the hand until the set is working. I havenít removed the screening covers but think I should just to ensure the valves are lit up? I also noticed a dual 16uF electrolytic with a lot of corrosion around one of the terminals so this too is suspicious it is rated at 275V.

I feel too tired at the moment to do more in the workshop after the heavy session in the garden but rest assured Iíll be on the job again tomorrow. Itís taken me ages to sort out what you experts would have done in a few minutes but for me Iíve got a result and Iím delighted. Thanks everyone. Tomorrow Jeffrey do I re-connect the two 35R resistors to have a go at obtaining HT?

Kind regards, Col.
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Old 10th Sep 2011, 5:40 pm   #76
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Default Re: Restorers dream part 2 the chassis.

Bit surprised that TWO valves aren't glowing. The U25 shouldn't be lit but the 30P4 (line output pentode) and U191 (boost diode) in the LOP can should be.

The failed cap sounds like a heater chain decoupler. My schematic shows 3, each of 1nF, around the LOP valves. Since octal valves have their heaters on pins 2 and 7 this is probably one of them. Can be safely left out for now. Have to say that I don't think I've replaced them on my set so I'm probably storing up trouble for later. A failure in one of these caps could blow a valve heater.

Suggest you download the TCG316 data from http://www.thevalvepage.com/tvmanu/ekco/ekco.htm This iwll give a chassis layout. While it's not 100% correct for a T311 much of it is relevant.
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Old 10th Sep 2011, 8:24 pm   #77
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Default Re: Restorers dream part 2 the chassis.

Hi,

Many thanks for the information Jeffrey; I'm pleased to say that every valve was lit up when I went to switch off; I even removed the screening cans to check the ones inside; it was nice to see them all glowing with the lights off.

I'll download and print the data off as suggested; I'm sure it will be a huge help to me.

I'll snip the blown Hunts cap at the chassis end and try to get some HT tomorrow; I'm looking forward to the next session as things are now progressing well.

Kind regards, Col.
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Old 11th Sep 2011, 11:51 am   #78
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Default Re: Restorers dream part 2 the chassis.

Hi,

First job; sorry Jeffrey the blown Hunts cap was attached to pin4 not pin2 as stated earlier; I've been having a good look around with the spotlight.

I've had a good morning; I snipped the blown cap and re-soldered the connection to the pair of 35R resistors then applied power directly from the mains.

At first I thought everything was dead apart from the glowing valves but turning the volume control brought some very healthy crackles as it did whilst I prodded around under the chassis. I thought I could just detect a very; very light whistle?

Readings at the electrolytics are 170V and 187V.

Readings on PY32; pins 3 & 5 -20V; Pin 4 99V; pin 8 186V.

I had to walk outside to view the CRT through the workshop window but it was blank and I noticed U25 was not lit up either I assume U25 should light up.

I'm wary of taking voltage readings near the LOPT but both 30P4 and U191 were lit up is it OK to take voltage readings on both these valves with my DMM?

Also thanks Jeffrey; I've printed off the full set of TCG316 sheets.

Once again as I don't want to do anything silly I'm in your hands for guidance so please guide away and I'll follow.

Kind regards, Col.
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Old 11th Sep 2011, 12:40 pm   #79
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Default Re: Restorers dream part 2 the chassis.

Looking good!

First thing Col, you really need to be able to see the screen while you are making adjustments so eitheryou need to extend the wires and turn the tube round (error prone and a lot of hassle) or get a nice big mirror.

Next I'd seeif you can draw a spark from around U25 using a prodder of some kind - a big fat 10M resistor soldered onto a well insulated screwdriver with the screwdriver shaft earthed.

Have you checked that extra 500mA fuse in the LOPT area? I'd measure the voltage around the lop valve except at the top cap first. You should be safe with an AVO8 just remember to attache the black lead to chassis first!

Dom

PS: I love this - it's nearly as much fun as restoring a set myself without the hassle of getting it past the missus!
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Old 11th Sep 2011, 1:12 pm   #80
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Default Re: Restorers dream part 2 the chassis.

Bless em
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