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Old 25th Dec 2016, 6:25 pm   #41
ms660
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Default Re: My first valve radio project - Philips 462A

Referring to the Trader sheet most folk's convention would be to connect the mains live to switch S18 and the mains neutral to switch S19.

This post might cross.

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Old 25th Dec 2016, 6:49 pm   #42
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Default Re: My first valve radio project - Philips 462A

Ref. post#41: Near the bottom of the third page of the Trader sheets is the mains voltage selector table, in each case the "m" connection is common to all voltage tapings, that would normally suggest by convention that "m" is the neutral (via the switch)

Connections for 245 volts AC mains input are given as "h" & "m"

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Old 25th Dec 2016, 6:55 pm   #43
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Default Re: My first valve radio project - Philips 462A

What Tony and the others have said is correct Nicola. The only concern is that you apparently mistook the two pins at the mains input for the aerial and earth sockets, which are [sometimes] needed to improve the signal. This could have been disastrous/dangerous and suggests you might need to familiarise yourself with the various stages of the circuitry more-especially as you are new to valve radios. You're otherwise methodical, unhurried approach is to be applauded. A recent poster was confused between mains and radio earth and that situation was quite alarming Perhaps this was just a case of "Christmas Confusion?"

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Old 25th Dec 2016, 8:09 pm   #44
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Default Re: My first valve radio project - Philips 462A

Can someone verify my eyesight, it might have got distorted due to the contents of my Xmas puddin'? Magnifying the 2nd pic in post#12 seems to me to show that the mains input pins might be marked + & -

If so then following the one marked + to the voltage selector panel via the switch, it looks as though it's connected to the center tag which I think is the pole of the selector which might suggest that the pin marked + is the live pin?

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Old 25th Dec 2016, 8:24 pm   #45
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Default Re: My first valve radio project - Philips 462A

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Originally Posted by dave walsh View Post
What Tony and the others have said is correct Nicola. The only concern is that you apparently mistook the two pins at the mains input for the aerial and earth sockets, which are [sometimes] needed to improve the signal.
Oh dear - I rather embarrassingly got my left and rights mixed up as I looked at the circuit diagram, hence thinking the 2 mains pins were labelled A and E At no point however was I going to connect up the mains to the aerial & earth sockets

Based on the info in the comments I can now see that BOTH live and neutral wires go into the on/off switch (therefore a double pole) incorporated into the volume pot and from there they go straight to the transformer via the connections on the tapping plate. So from this it doesn't matter which way the plug is connected

Its nice to see how many of us are still here on Xmas day
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Old 25th Dec 2016, 8:29 pm   #46
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Default Re: My first valve radio project - Philips 462A

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Can someone verify my eyesight, it might have got distorted due to the contents of my Xmas puddin'? Magnifying the 2nd pic in post#12 seems to me to show that the mains input pins might be marked + & -
I can't see a + and - at the pins Lawrence?
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Old 25th Dec 2016, 8:43 pm   #47
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Default Re: My first valve radio project - Philips 462A

Ah..that pic is a bit clearer from the one I was looking at which I had saved on my PC...must be the Xmas pud

That said, the top pin does appear to connect via the mains switch to the selector pole on the selector board (the unnumbered tag) so far as I can make out, If that's the case then normal convention would be to make that pin the mains live in and if you want to, mark it as such.

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Old 25th Dec 2016, 9:31 pm   #48
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Default Re: My first valve radio project - Philips 462A

The big moment arrived....lamp limiter in place and switched on.... Nothing happened :-(
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Old 25th Dec 2016, 9:44 pm   #49
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Default Re: My first valve radio project - Philips 462A

Oh.

Unplug the mains lead from the wall and the set. Switch your multimeter to continuity. Start with one probe on the live pin of the mains plug, and the other at the "set" end connector. If that proves through, plug the mains lead back into the radio and follow the circuit all the way through until you lose continuity.

The most likely culprit is the mains switch. They have been known to fix themselves with repeated operations .....
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Old 25th Dec 2016, 9:44 pm   #50
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Default Re: My first valve radio project - Philips 462A

Power off at the wall and remove the mains connector, switch receiver on and check the resistance between the two mains input pins on the back of the chassis, should be low resistance, report the reading in ohms if poss. Did the bulb glow at all?

EDIT: Post crossed with Julie's

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Old 25th Dec 2016, 10:47 pm   #51
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Default Re: My first valve radio project - Philips 462A

I started to trouble-shoot before your posts Julie and Lawrence....this is what I found...

To start with the lamp limiter bulb didn't glow at all suggesting no current was getting through to the radio at all. So I checked the on/off switch that's part of the volume pot. I could measure 85V AC across the L and N going into the switch but zero volts coming out no matter how I turned the dial. So I presume that switch is broken.

I decided then to bypass the switch and so I connected the switch outputs to the mains input. Still nothing but the lamp limiter bulb does faintly glow now. There are lots of wires connected into the transformer that I can't identify but there are two output wires than connect directly to a small bulb that illuminates the wavelength selector screen. I measured across here and there is zero voltage across these outputs which at first suggested to me that there was something wrong with the transformer since I was not getting an output. However, I can now see that all three valves are beginning to glow. (AZ31 the rectifier is not) so something must be getting through.

EDIT: Upon further testing I can now measure 4V AC across the screen bulbs - no glow but I'm wondering if thats because 4V AC is too low and perhaps the bulbs may work when I remove the lamp limiter (Not going to do that yet until I'm sure its OK to do so).

Last edited by indigo.girl; 25th Dec 2016 at 11:00 pm.
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Old 25th Dec 2016, 11:14 pm   #52
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Default Re: My first valve radio project - Philips 462A

Are the rectifier (AZ31) heaters glowing yet? Switch your meter to measure DC 250 volts or the nearest range to that, connect the -ve meter lead/probe to chassis and the +ve lead/probe to the HT output from the rectifier which is the +ve connection of C26, 47uF (Trader sheet) and see what (if any voltage) is measured. Still with the lamp limiter in circuit.

This post might cross.

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Old 26th Dec 2016, 12:46 am   #53
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Default Re: My first valve radio project - Philips 462A

The rectifer heaters are not glowing. At pins 2 and 8 (filament pins) I can measure no voltage relative to chassis. However at pins 4 and 6 (anode pins a' and a") there is 240V AC relative to chassis. So based on my understanding of this type of valve there's no electron exchange from the filament cathode to the anodes and so no current output. I presume this means a replacement AZ31 is required :-(
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Old 26th Dec 2016, 2:13 am   #54
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Default Re: My first valve radio project - Philips 462A

I expect you should be measuring for AC between pins 2 and 8 of the rectifier, rather than measuring either pin to chassis.

I noticed in post 51 you said you measured 85v AC between the L and N wires going into the mains switch? That can't be right, you should have full mains here. Then again you've measured 240v AC on the rectifier valve, so I think you've made an error with one measurement, probably at the input to the mains switch. That could simply be a poor contact between the meter probe and the terminal giving you the odd reading. It's a bit hairy measuring at the switch since you're dealing with 2 probes on 2 terminals fairly close together.

Before you condemn the AZ31, with the power disconnected check resistance between the 2 filament pins. If you get high resistance or infinity, remove the valve and do the test at the valve pins themselves to rule out the socket.

You should have AC supplying the filament, or it will not heat up and therefore no current will flow.
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Old 26th Dec 2016, 5:13 am   #55
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Default Re: My first valve radio project - Philips 462A

Quote:
Originally Posted by indigo.girl View Post
I started to trouble-shoot before your posts Julie and Lawrence....this is what I found...
Excellent stuff! Just don't be afraid to stop and ask, if you get out of your depth.
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Originally Posted by indigo.girl View Post
To start with the lamp limiter bulb didn't glow at all suggesting no current was getting through to the radio at all. So I checked the on/off switch that's part of the volume pot. I could measure 85V AC across the L and N going into the switch but zero volts coming out no matter how I turned the dial. So I presume that switch is broken.
A reasonable assumption so far ..... Sometimes they come to life with a bit of exercise; but for now, bypassing it is fine. 85V sounds a little bit low, though; it would leave 145V for the bulb, which would light it quite brightly though obviously not full-on. Never mind; perhaps that's an error.
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I decided then to bypass the switch and so I connected the switch outputs to the mains input. Still nothing but the lamp limiter bulb does faintly glow now.
That's a good sign. It means some power is going into the set. What wattage bulb are you using?
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There are lots of wires connected into the transformer that I can't identify but there are two output wires than connect directly to a small bulb that illuminates the wavelength selector screen.
There will be various connections to the primary windings, which can be rearranged so as to give different turns ratios to suit different supply voltages. The Manufacturers' data shows the connections for each voltage setting, but you need only go there if you suspect a transformer fault.
Quote:
Originally Posted by indigo.girl View Post
I measured across here and there is zero voltage across these outputs which at first suggested to me that there was something wrong with the transformer since I was not getting an output. However, I can now see that all three valves are beginning to glow. (AZ31 the rectifier is not) so something must be getting through.
Probably just a bad connection of one of the meter probes, or something. It happens sometimes. All you can do is keep trying.
Quote:
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EDIT: Upon further testing I can now measure 4V AC across the screen bulbs - no glow but I'm wondering if thats because 4V AC is too low and perhaps the bulbs may work when I remove the lamp limiter (Not going to do that yet until I'm sure its OK to do so).
Or it's quite possible the bulbs are just dead, or not making good contact ..... They should light, even if a bit dimly, at 4V.

The AZ31 (rectifier) valve has its own separate winding on the transformer for its filament, which will be at HT potential when the rectifier has warmed up. Carefully remove this valve and measure the resistance between pins 2 and 8. (Should be very low, 1 Ω or even dead short.) With the rectifier still out, switch your to AC 20V range, put your probes on pins 2 and 8 of the rectifier's socket and power up the set. Nothing much will happen (since it's not going to get any HT) but you should measure 4V AC there.

If the rectifier filament is open-circuit, don't worry too much; there is a "cheat" we can do in the meantime while waiting for a new one to arrive, which will allow you to continue testing the set.
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Old 26th Dec 2016, 8:44 am   #56
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Default Re: My first valve radio project - Philips 462A

Damn - just as we are getting to the fun bit Christmas gets in the way! I'm off to my brothers today so no more testing for a day.... however I have quickly sneaked in a couple of tests before I go...

Input mains is 210V AC (not 85 V)

Resistance between pins 2 and 8 is 2 ohms.

There is 2V AC across pins 2 and 8 (AZ31 removed and set switched on) and also 2V AC across pins 2 and 8 when AZ31 replaced.

My lamp limiter bulb is only 42W - all that I had to hand.
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Old 26th Dec 2016, 10:15 am   #57
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Default Re: My first valve radio project - Philips 462A

Try to get a 60w bulb while you are out, it may be enough to bring the heater volts up to 3v and after a few couple of minutes the set may even start to work, and get crackles in the speaker when the wave change is operated and maybe even the odd station or 2.
Have a long wire aerial plugged in, and make sure the speaker is connected up correctly.
I always measure the voltages as the HT rises at various points in the circuit around the smoothing capacitor as the rectifier starts to do its job.
Keep a check on the smoothing capacitor, if it is the original, if it starts to warm up switch off.
I would also suggest cutting out C28 for now (Trader sheet). If it is a paper type it is likely to be faulty it could put a heavy load on one HT winding of the mains transformer.

Good luck
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Old 26th Dec 2016, 11:46 am   #58
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Default Re: My first valve radio project - Philips 462A

Please forgive me if I'm wrong, but what sort of light bulb are you using to get 42W ? The incandescent bulbs that you need are usually rated in round numbers eg 40W. You don't want a modern energy saver bulb.

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Old 26th Dec 2016, 11:49 am   #59
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Default Re: My first valve radio project - Philips 462A

Good question, well spotted John.

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Old 26th Dec 2016, 12:12 pm   #60
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Default Re: My first valve radio project - Philips 462A

Some halogens are rated at 42 watts.

Lawrence.
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