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Old 1st Mar 2016, 3:15 pm   #41
gary_crutchley
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Default Re: Vidor CN430 My Lady Anne

Apart from the yellowed plastic. Any tips on cleaning that?
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Old 1st Mar 2016, 3:51 pm   #42
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Default Re: Vidor CN430 My Lady Anne

Can someone also tell me where switch S6 is located please?
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Old 1st Mar 2016, 4:12 pm   #43
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Default Re: Vidor CN430 My Lady Anne

Operated by the lid stay I would guess. Instead of the battery switch on battery only sets. It could be missing without affecting normal operation.
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Old 1st Mar 2016, 4:16 pm   #44
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Default Re: Vidor CN430 My Lady Anne

Yup, left hand side I would say:

http://www.vintageradio.me.uk/valve/...30_chassis.jpg

Lawrence.
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Old 1st Mar 2016, 5:14 pm   #45
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Default Re: Vidor CN430 My Lady Anne

That's the one. It doesn't, or shouldn't, affect normal operation.

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Old 1st Mar 2016, 5:30 pm   #46
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Default Re: Vidor CN430 My Lady Anne

That's brilliant, I thought that was it but they don't show it in the trader sheet. They must have assumed it was obvious!
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Old 1st Mar 2016, 5:43 pm   #47
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Default Re: Vidor CN430 My Lady Anne

Quote:
Originally Posted by pwdrive View Post
Thanks for the image Lawrence, much appreciated.

Gary
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Old 1st Mar 2016, 7:39 pm   #48
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Default Re: Vidor CN430 My Lady Anne

Quote:
Originally Posted by gary_crutchley View Post
They don't show it in the trader sheet. They must have assumed it was obvious!

In 195whatever it would have been 'cos it was a typical way of doing it.

Nowadays it's like telling a youngster to pull the choke out before starting from cold...
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Old 1st Mar 2016, 8:10 pm   #49
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Default Re: Vidor CN430 My Lady Anne

Good point!
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Old 1st Mar 2016, 8:13 pm   #50
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Default Re: Vidor CN430 My Lady Anne

I measured the resistance of R10 and got 1.3MegOhms, the trader sheet says 1.0MegOhms. R11 should be 2.7MegOhms and my meters only go to 2.0. On the DMM the resistance did climb steadily to 2, then of course went off scale. Both measurements were with the resistors in circuit.

If R11 is critical I will have to borrow another meter. Advice please!

Last edited by gary_crutchley; 1st Mar 2016 at 8:19 pm.
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Old 1st Mar 2016, 10:23 pm   #51
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Default Re: Vidor CN430 My Lady Anne

High value resistors are best measured out of circuit, for the cost involved I would replace them.

Even though your meter only measures resistance up to 2 megohms you can measure the 2.7megohm by connecting a resistor of high value in parallel with it and do a quick sum, not saying you should but it is a trick that can be employed, a known correct value ie: a new one such as 1.8, 2.2, 2.7 or 3.3megohm in parallel should put you in the ball park.

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Old 1st Mar 2016, 10:27 pm   #52
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Default Re: Vidor CN430 My Lady Anne

Thanks Lawrence, that sounds like a good idea. What about the one that measured 1.3 megohms? Is that okay?
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Old 1st Mar 2016, 10:32 pm   #53
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Default Re: Vidor CN430 My Lady Anne

It's out of 20% tolerance, the receiver will probably work ok with it as it is but for reliability I personally would replace it.

Lawrence.
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Old 1st Mar 2016, 10:33 pm   #54
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Default Re: Vidor CN430 My Lady Anne

Quote:
Originally Posted by gary_crutchley View Post
If R11 is critical I will have to borrow another meter.
Be patient, Gary, all you need is that Avo Model 8! It will measure resistance up to 20 Megohms.
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Old 1st Mar 2016, 10:35 pm   #55
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Default Re: Vidor CN430 My Lady Anne

I know, I'm just waiting on my supplier! I do like having the right tools!

Thanks Phil!
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Old 1st Mar 2016, 10:47 pm   #56
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Default Re: Vidor CN430 My Lady Anne

You can improvise with a 9-volt battery in series with your DMM on a volts range and with the resistor. You need to know your meter's input resistance for the calculation.
For example, with a 1M meter, a 2M resistor would give a reading of 3V.
For a 10M meter instead, about 8.2V.

Last edited by G8UWM-MildMartin; 1st Mar 2016 at 11:03 pm. Reason: missed "with"
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Old 1st Mar 2016, 10:48 pm   #57
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Default Re: Vidor CN430 My Lady Anne

You have to remember that the tolerance of the typical resistors used in these sets was 20% meaning the value of R11 can be anywhere between 2.16Meg and 3.24Meg. The value of these resistors tends to increase over time however valve circuits are generally tolerant of these changes, unless they are excessive. The value of R10, although out of tolerance, will not cause the DAF96 amplifier to fail. You'll probably find R11 is also outside it's tolerance range but, unless it's open circuit or way above the maximum 3.24Meg, the circuit will function. The current drawn by the screen grid on these valves is very small, the current drawn by the meter is probably much higher! which is hat cause the low voltage reading What can affect the operation is any additional leakage current through the resistor. This is usually due to a leaky decoupling capacitor. The wax paper caps used for these purposes up to the 60s were OK when new but over time have absorbed moisture from the air and have become leaky. We have to remember most of these sets were probably only intended to have a life of a few years, not 50 or more years so we should expect a few out of spec components. However we now know these components will almost certainly need replacing so many people, myself included, will replace wax paper caps on sight and check the resistor values and only replace those which are significantly out of tolerance

Keith.
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Old 1st Mar 2016, 10:57 pm   #58
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Default Re: Vidor CN430 My Lady Anne

Thanks again Keith. I am planning to replace the capacitor that is associated with the screen grid of V3. I am getting an Avo 8 shortly so I will check these two resistors properly and go from there.

I really appreciate all of the advice.
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Old 1st Mar 2016, 11:13 pm   #59
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Default Re: Vidor CN430 My Lady Anne

I don't know if you've seen this thread but it has the notes for the talk I gave last year at the Golborne meet on Measurements and an Introduction to fault finding.

https://www.vintage-radio.net/forum/...=120552&page=2

Keith
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Old 2nd Mar 2016, 10:12 am   #60
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Default Re: Vidor CN430 My Lady Anne

Hi Keith,

I hadn't seen that thread, so thanks very much indeed. That is a very informative document that you have created, I will enjoy reading it.

Regards,

Gary
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