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Old 27th Dec 2016, 3:50 pm   #101
indigo.girl
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Default Re: My first valve radio project - Philips 462A

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Sorry. I meant chassis to pin 2 or 8 of the rectifier.
No DC volts from chassis to pin2 or chassis to pin8. But I do get 2V AC across the filament (pin2 to pin8). (Or as expected from this voltage across the filament, I read chassis to pin2 ZERO VAC and chassis to pin8 2VAC)
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Old 27th Dec 2016, 3:52 pm   #102
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Default Re: My first valve radio project - Philips 462A

Your heater voltage is too low. Are you using one of the lower 2XX Volt mains settings?
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Old 27th Dec 2016, 4:15 pm   #103
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Default Re: My first valve radio project - Philips 462A

Using Trader Sheet 817 the mains primary tapping for 245 VAC is across h, m, not the full g, m, as might be expected because voltage selection makes use of phase and anti phase to get the combinations of voltages, i,j and k, l, are joined by the selector disc.

If the on/off switch has been bypassed then the mains input should be put on the radio side of the on/off switch and not across the outside connections to the mains transformer.
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Old 27th Dec 2016, 4:21 pm   #104
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Default Re: My first valve radio project - Philips 462A

Att. Nicola, re: my last PM...can't do the drawings via PM so I'll post them on here when I've done them for the world to scrutinize, whenever that may be.

Lawrence.
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Old 27th Dec 2016, 4:24 pm   #105
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Default Re: My first valve radio project - Philips 462A

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Using Trader Sheet 817 the mains primary tapping for 245 VAC is across h, m, not the full g, m, as might be expected because voltage selection makes use of phase and anti phase to get the combinations of voltages, i,j and k, l, are joined by the selector disc.

If the on/off switch has been bypassed then the mains input should be put on the radio side of the on/off switch and not across the outside connections to the mains transformer.
Well spotted. The OP is using the manufacturers sheet, but what you say still applies.
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Old 27th Dec 2016, 4:31 pm   #106
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Default Re: My first valve radio project - Philips 462A

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If still no HT, check that R2 and R3 (manufacturers sheet) aren't open circuit.
These two resistors check out ok

For reference:

R2 (manu) = R20 (traders) = 68 ohms service data = 63 ohms MEASURED

R3 (manu) = R19 (traders) = 33 ohms service data = 33 ohms MEASURED
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Old 27th Dec 2016, 4:33 pm   #107
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Default Re: My first valve radio project - Philips 462A

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Quote:
Originally Posted by Hetrodyne View Post
Using Trader Sheet 817 the mains primary tapping for 245 VAC is across h, m, not the full g, m, as might be expected because voltage selection makes use of phase and anti phase to get the combinations of voltages, i,j and k, l, are joined by the selector disc.

If the on/off switch has been bypassed then the mains input should be put on the radio side of the on/off switch and not across the outside connections to the mains transformer.
Well spotted. The OP is using the manufacturers sheet, but what you say still applies.
I've got both manu and traders in front of me
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Old 27th Dec 2016, 4:39 pm   #108
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Default Re: My first valve radio project - Philips 462A

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Using Trader Sheet 817 the mains primary tapping for 245 VAC is across h, m, not the full g, m, as might be expected because voltage selection makes use of phase and anti phase to get the combinations of voltages, i,j and k, l, are joined by the selector disc.

If the on/off switch has been bypassed then the mains input should be put on the radio side of the on/off switch and not across the outside connections to the mains transformer.
I think the mains is still across h and m despite bypassing the on/off switch. The double pole on/off switch had two input wires (L and N) and two output wires (L and N). I disconnected them all and simply connected L-L and N-N. I think I might have sloppily said that I connected the mains straight to the transformer but rather I joined up to the wires that I presume link to h and m.
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Old 27th Dec 2016, 4:41 pm   #109
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Default Re: My first valve radio project - Philips 462A

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Your heater voltage is too low. Are you using one of the lower 2XX Volt mains settings?
I'm set on 220V but I probably didnt give time for valves to warm up before I measured so I never got the 3V is saw before with 220V setting.
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Old 27th Dec 2016, 4:50 pm   #110
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Default Re: My first valve radio project - Philips 462A

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So no DC voltage from chassis to pin 7 of the rectifier?
Which pin on the rectifier?

I get measure 345V on DC settings on my mulitmeter between the anode pin 4 and chassis (same as anode pin 6 and chassis). I get 310V on AC setting on multimeter.
If there's 310V ac on the rectifier anodes, and nothing on the cathode, yet the heater is glowing, is it not likely that the rectifier valve is u/s?
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Old 27th Dec 2016, 4:52 pm   #111
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Default Re: My first valve radio project - Philips 462A

Yes. The rectifier's heater isn't at full volts though.
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Old 27th Dec 2016, 5:25 pm   #112
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Default Re: My first valve radio project - Philips 462A

I think the only thing to do is try the 220VAC and 200VAC mains settings to see whether the rectifier's heater voltage can be boosted to 4VAC.

If this can be done and there's still no HT voltage, then it's safe to assume that the rectifier is u/s.

Given the possible transformer problem, it might be advisable to replace the AZ31 with a couple of silicon diodes to allow testing of the rest of the radio.
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Old 27th Dec 2016, 5:43 pm   #113
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Default Re: My first valve radio project - Philips 462A

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If there's 310V ac on the rectifier anodes, and nothing on the cathode, yet the heater is glowing, is it not likely that the rectifier valve is u/s?
What does u/s mean?
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Old 27th Dec 2016, 5:45 pm   #114
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Default Re: My first valve radio project - Philips 462A

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I think the only thing to do is try the 220VAC and 200VAC mains settings to see whether the rectifier's heater voltage can be boosted to 4VAC.

If this can be done and there's still no HT voltage, then it's safe to assume that the rectifier is u/s.

Given the possible transformer problem, it might be advisable to replace the AZ31 with a couple of silicon diodes to allow testing of the rest of the radio.
At the 200V setting I get 3-4V AC across the rectifier filament - but still no HT voltage.
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Old 27th Dec 2016, 5:54 pm   #115
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Default Re: My first valve radio project - Philips 462A

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What does u/s mean?
Unserviceable. In other words, it's no good and needs replacing!
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Old 27th Dec 2016, 5:56 pm   #116
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Default Re: My first valve radio project - Philips 462A

There is something I find odd about those transformer secondary voltages...

The rectifier fillament should be 4V, but you measure 2V

The other valve heaters/dial lamp should be 6.3V and you measure 4V.

BUT the rectifier anode voltages (in the trader sheet) should be 285V and you measure 310V. OK, you're measuring off-load and they will drop a bit when you draw current, but given the ratios of the other voltages (measured and what they should be), if you got the fillament voltages up to what they should be, the rectifier anode voltages would presumably leap to 450V-500V. I don't believe that is right.

I am also puzzled as to how you managed to measure a DC voltage on the rectifier anodes (you mentioned this in a previous post).

'U/S' means 'unserviceable' i.e. defective.
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Old 27th Dec 2016, 5:57 pm   #117
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Default Re: My first valve radio project - Philips 462A

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I think the only thing to do is try the 220VAC and 200VAC mains settings to see whether the rectifier's heater voltage can be boosted to 4VAC.

If this can be done and there's still no HT voltage, then it's safe to assume that the rectifier is u/s.

Given the possible transformer problem, it might be advisable to replace the AZ31 with a couple of silicon diodes to allow testing of the rest of the radio.
At the 200V setting I get 3-4V AC across the rectifier filament - but still no HT voltage.
Assuming no wiring fault it's definitely u/s then.
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Old 27th Dec 2016, 6:31 pm   #118
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Default Re: My first valve radio project - Philips 462A

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There is something I find odd about those transformer secondary voltages...

The rectifier fillament should be 4V, but you measure 2V

The other valve heaters/dial lamp should be 6.3V and you measure 4V.

BUT the rectifier anode voltages (in the trader sheet) should be 285V and you measure 310V. OK, you're measuring off-load and they will drop a bit when you draw current, but given the ratios of the other voltages (measured and what they should be), if you got the fillament voltages up to what they should be, the rectifier anode voltages would presumably leap to 450V-500V. I don't believe that is right.

I am also puzzled as to how you managed to measure a DC voltage on the rectifier anodes (you mentioned this in a previous post).

'U/S' means 'unserviceable' i.e. defective.
Hi Tony - for clarity I've measured the voltages again using the dial setting at 245V, 220V and 200V


VAC across AZ31 filament = 2-3 (@245V) ; 3-4 (@220V) ; 4 (@200V)
VAC across pilot bulb and ECH21 heaters = 4 (@245V) ; 4-5 (@220V) ; 6 (@200V)
VAC across AZ31 chassis to anode = 290 (@245V) ; 319 (@220V) ; 355 (@200V)
DC voltage across AZ31 chassis to anode* = 320 (@245V) ; 352 (@220V) ; 388 (@200V)

* This is the reading on my multimeter when I switch to DC voltage mode - so I suspect this is just an anomaly and no really DC voltage
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Old 27th Dec 2016, 7:11 pm   #119
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Default Re: My first valve radio project - Philips 462A

This is going on a bit and getting confusing.
There is something amiss with the transformer's CONNECTIONS I think.
Mention has been made of "shorted turns"; If a transformer has a "shorted turn", it will get HOT! A shorted turn can be simply two adjacent turns touching. In a(n) (GOOD) open style transformer, you can simply put ONE loop of wire around with the ends joined and quickly spot the meaning of a "Shorted turn".
However, you established by a 1 hr test that it does NOT overheat, so forget all about shorted turns.
It sounds as if the transformer has multiple windings, some of which are connected "anti-phase" in some settings. It sounds to me as if there are some problems here. It could be time to disconnect ALL wires from transformer, then check every one against the circuit. Very simple but possibly very confusing at this stage of your knowledge.
I hope this does not add more confusion.
Les.
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Old 27th Dec 2016, 7:12 pm   #120
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Default Re: My first valve radio project - Philips 462A

Ref post#118, were those voltages measured with all the valves fitted or were they removed?

Lawrence.
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