7th Feb 2016, 6:36 pm | #1 |
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Vidor CN430 My Lady Anne
Hi all,
I have a Vidor CN430 My Lady Anne which is in very good condition. It looks completely untouched and some of the capacitors date it to March 1957. The correct valves are fitted and the heaters are fine, as are the two transformers. A touch on the speaker contacts with my Avo produces a sound, so I think the speaker is good too. Everything else looks to be original according to the circuit diagram, and the metal rectifier is still present. As this is a battery mains set, I would like to try it on the lamp limiter. However, as I haven't tackled one of these battery/mains portables before I am wondering if there are any other items to check replace before doing so. I know the valves are or can be a little more sensitive in these sets, I don't want to do any damage. Any help and advice would be greatly appreciated please. Regards, Gary |
7th Feb 2016, 7:38 pm | #2 |
Nonode
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Re: Vidor CN430 My Lady Anne
I have two of these sets and they needed the minimum of work to get them up and running. You won't have to worry about "that" cap as it's a 470pf ceramic. Be aware that on mains extra resistors are switched into the filament chain so the top of the chain is, from memory, about 9V instead of the 7V you would expect. The preset resistor adjusts the filament current and shouldn't need adjusting. If it does the setting procedure is in the service manual.
One feature of these sets is that if the lid is closed while the set is on the output stage is turned into an oscillator as a warning that it is still on. My grandmother had one of these and that was one feature my brother and I loved to try out, much to her annoyance. There are several wax paper caps that should be changed. To access them the chassis has to be separated from the from panel after removing the knobs. The volume and wavechange/power knobs are push fit and can be gently prised off but the tuning knob is secured with a clamp which is undone by turning the tuning to one extreme and accessing the bolt through the gap in the chassis. It's all explained in the service manual (available top right if you haven't already got it). The rectifier seems to be reliable but it's worth checking the HT supply is within spec. The DK96 is prone to losing its emission causing loss of signals. I reformed the electrolytics on mine in situ but it's advisable to remove the valves if you do this. Once checked over and the waxies replaced they are good performers. I've never tried mine on batteries. My grandmother tried running hers on batteries until she discovered the cost of them back in the late 50s. It spent the rest of its life mains powered. Keith |
7th Feb 2016, 9:55 pm | #3 |
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Re: Vidor CN430 My Lady Anne
It's the heaters that are very fragile, in a series heater chain if you slip with a test prod and short a heater pin to chassis there is a chance of blowing the heaters further up the chain.
Use well insulated prods/tools with just the tip exposed to try and prevent damage. Frank |
7th Feb 2016, 10:26 pm | #4 |
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Re: Vidor CN430 My Lady Anne
Hi Frank,
Thanks for the advice, I'll be very careful. Regards, Gary |
7th Feb 2016, 10:29 pm | #5 | |
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Re: Vidor CN430 My Lady Anne
Quote:
Many thanks for the information, very interesting. I have the trader sheet, do you happen to know if Vidor produced any information themselves? I will let you know how I get on with the set. Regards, Gary |
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8th Feb 2016, 10:42 pm | #6 |
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Re: Vidor CN430 My Lady Anne
Hi all,
I've been investigating this little battery mains further. Before applying any power I tested the output transformer again. With my Avo 7 I can get a resistance reading across the secondary and a few scratches from the speaker. However, I was not able to measure anything at all across the primary. Nevertheless I decided to give the set a go on the lamp limiter. The on/off switch worked and when powered there wasn't even a glimmer from the lamp. The only noise that I managed to get from the set was a faint hum from the speaker, which did not change at all when I operated the volume control. I wasn't able to receive any stations on either waveband. An application of Servisol made no difference either. I also have an Ultra R825 which uses the same valve set and which works very well. Hence I swapped the valves one by one, but again it made no difference. The one thing I didn't try was swapping the entire valve set in one go. I did recheck the heaters for continuity afterwards, they were are fine. Can anyone suggest what the fault maybe please? I am inclined to suspect the output transformer, but I could be wrong of course. Thanks in advance. Best regards, Gary |
9th Feb 2016, 12:43 am | #7 |
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Re: Vidor CN430 My Lady Anne
Power it up briefly and check the voltages on the O/P TX primary. One end should be HT, t'other should be slightly lower. Much lower and it's toast.
Can you see the screen grid in the O/P valve glowing?
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9th Feb 2016, 8:54 am | #8 |
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Re: Vidor CN430 My Lady Anne
If you can obviously see the heaters glowing SWITCH IT OFF.
It is very hard to see them if they are working at the correct voltage. If it is the speaker humming, you must have a working output transformer and there must be some anode & cathode current through the output valve. Check output valve grid coupling and the screen decoupling capacitors. Is there volts on the screen grid? |
9th Feb 2016, 9:39 am | #9 |
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Re: Vidor CN430 My Lady Anne
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9th Feb 2016, 9:54 am | #10 |
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Re: Vidor CN430 My Lady Anne
Hi Sam,
Thanks for the help. I did have a quick look at the valves, even with the lights off I don't recall seeing any glowing. I don't think I can see anything with my Ultra R825 either. I think the output valve grid coupling capacitor (C20?) is a silver mica, but I will check it. Do you know the reference number for the screen decoupling capacitor please? I'll need to check the screen grid, is that g2? Regards, Gary |
9th Feb 2016, 10:49 am | #11 |
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Re: Vidor CN430 My Lady Anne
Gary, if you haven't done so already I would advise cleaning the valveholder contacts and the valve pins very thoroughly. I use a pipe cleaner soaked in Servisol for the valveholders, and a rotary wire brush for the valve pins. In my experience, B7G valveholders are responsible for a lot of faults in battery valve sets. I had one once with a cracked screen grid pin which took me a good while to trace, as the voltage was pretty well correct but the valve was completely non-conducting.
By the way, I will have a nice Avo 8 Mk III ready for you in a couple of weeks - I will PM in due course.
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Phil Optimist [n]: One who is not in possession of the full facts Last edited by Phil G4SPZ; 9th Feb 2016 at 10:50 am. Reason: Clarity |
9th Feb 2016, 11:42 am | #12 |
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Re: Vidor CN430 My Lady Anne
Hi Phil,
With regards to the valve holders and the valve pins, I haven't cleaned them as yet. I did try the known working valves from my Ultra in the Vidor, so I think it would make sense to start with the valve holders. Thanks again for the advice, let me know when the Avo 8 is ready. Regards, Gary |
9th Feb 2016, 4:22 pm | #13 |
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Re: Vidor CN430 My Lady Anne
Hi all,
I found this related thread: https://www.vintage-radio.net/forum/...ad.php?t=48103 The issue described at the outset seems very close, if not identical to the one that I have. However, I am not sure about the capacitor numbers quoted by the original poster. I am using trader sheet 1215. The poster above refers to wax capacitors C13 and C17. the latter I can see on the chassis diagram, but not C13. The schematic shows C13 as being part of the IF tuning circuit, is this in one of the IF cans and therefore is C13 the correct capacitor? Or does he have another service sheet? Regards, Gary |
9th Feb 2016, 7:00 pm | #14 |
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Re: Vidor CN430 My Lady Anne
There isn't another service sheet on Paul's CDROM other than the Trader Sheet.
As to making progress, much depends on whether you simply want to diagnose the fault and get the set working, or to restore it. It's sixty years old, and has several paper caps as well as four electrolytics - two in one can, and two in separate cans. Given that the set is mains/battery, clearly it's more useful than a battery only set, so may be worth spending some time on, but before you start a wholesale cap replacement exercise for example, it would be wiser to first diagnose what's stopping the set from working, then when you've traced and rectified the fault(s), change the caps, testing as you go, rather than swapping the lot and risking an error. As a first step, you need to check if you're getting HT to the valves. If either S7(M), S11(M) and/or S12(M) are open circuit, that would silence the set (on mains power) as no HT would get to the valves. Another culprit which could cause low of no HT is the metal rectifier, so check that you have HT (say 90 - 100V DC) between the output of the rectifier and chassis. If yes, do you have HT at the anodes and screens of the valves, in line with the table of Voltages on the Trader Sheet chart? If not, investigate why. You've eliminated the valves as culprits as you've tested them by substitution, and if the Voltages look within reason, personally, for quick diagnosis I always use the signal tracer/injector method. Firstly, if you inject an audio signal into the slider of the volume control, you should get a loud tone out of the speaker. If you don't have any form of audio signal, then simply scratching the volume control slider with a screwdriver should be very audible in the speaker. If not, there's a fault in the audio stage. The weak areas to look at I'd suggest would be S6, the output transformer and the speaker. The output transformer primary should be approx. 570 Ohms and the secondary, 0.38 Ohms. If the audio stage is faulty, if you have a small amplifier of any sort - a powered computer speaker amp for example, if you apply that to the slider of the volume control, if the RF/IF stages are working, you should hear tunable signals coming through the amplifier. If not, something is adrift in those earlier stages. As to the paper cap which the other thread refers to as being ' C13, close to the volume control' if you look at the diagram you'll see that there are three caps very close to the V.C. - C18, V3 Screen Grid Coupling, which is 0.01uF paper; C19, which is 0.005uF, and is the Alarm Oscillator coupling; and C20, 470pF AF Coupling cap, which will doubtless be ceramic, and unlikely to be duff. As you say, C13 is in IFT2, and probably a silver mica cap, almost certainly not faulty. On the balance of probabilities, I think the cap that the earlier thread referred to as 'C13' was most likely C18. Looking at the under chassis layout and the component list, there are several paper caps, which I think most restorers would consider changing, namely: C3,10,11,18 & 23 - all 0.01uF C24 & 25 both 0.1uF The elctrolytics are: C22 & C28 (twin can 32uF reservoir/smoothing) in one can C26 & C27: 100uF & 50 uF, filament smoothing in separate cans Hope that helps a bit Gary. Good luck with the set!
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9th Feb 2016, 10:43 pm | #15 |
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Re: Vidor CN430 My Lady Anne
Hi David and all,
Many thanks for some comprehensive advice, theres a lot to work through there and it does rather more than help a bit! I have made a start though, but maybe not in the order you suggested. Firstly as suggested in a post above I attempted to measure the voltages at each tag on the output transformer to the chassis. I found HT on one end of the primary, but nothing on the other. Likewise I measured nothing on either of the tags on the secondary, so I suspect that isn't good news for the output transformer. I tried scratching the volume control slider, nothing. However, given the voltages (or lack of) I'm now pretty sure the faint hum I thought I was hearing was not coming from the speaker, maybe it's my slowly ageing ears! So next I decided to check whether I had HT along the line. I started with the rectifier and got about 97v on the output tag. So then I started to look at the valve voltages. First I rechecked the valve heaters, all were okay. I checked that I have LT, although I haven't as yet measured the voltage accurately at each valve. As I had LT on all valves I checked the valve voltages, this is what I got: V1: Anode 97V, Screen 39V. V2: Anode 97V, Screen 50V. V3: Anode 5V, Screen Nil. V4: Anode 0V, Screen 97V. All readings on an Avo 7 Mk1, on the 100V scale. The screen voltages on valves 1 and 2 seemed a little low, however, there was clearly an issue with the output valve. To repeat what I said in an earlier post, I have an Ultra with the same valve set, so a couple of days ago I tried the valves from that set one by one in the Vidor and it made no difference. I didn't try the Vidor valves in the Ultra, so this time I tried the output valve from the Vidor in the Ultra. I got sound (a buzzing) from the speaker but couldn't receive any stations. So I guess the output valve is no good. It seems to me that at a minimum I need an output transformer, an output valve and to change the wax capacitors. Any advice on exactly how to proceed from here would be greatly appreciated. Phil: I have some pipe cleaners so I will give the valve holders a clean whilst I'm at it. Regards, Gary |
9th Feb 2016, 11:13 pm | #16 |
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Re: Vidor CN430 My Lady Anne
The output valve may be ok but the transformer looks to be faulty, unless you can see a break in the winding connection to the tag on the transformer.
Not sure what V3 is but if it is a DAF96 I would be checking the voltages and circuit for faults, those voltages seem very low.If the feed resistors are very high value the AVO 7 would give lower readings though, those seem a bit too low. |
10th Feb 2016, 12:03 am | #17 |
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Re: Vidor CN430 My Lady Anne
I agree, you almost certainly have an open circuit output transformer primary. This is quite a common fault. Your circuit voltage measurements won't make much sense with this fault present as the output valve won't be drawing any current. You need to resolve this fault before doing anything else, by either repairing or replacing the transformer.
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10th Feb 2016, 12:36 am | #18 |
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Re: Vidor CN430 My Lady Anne
I'd just change the output transformer before changing the DL96. Almost any output transformer from a battery valve set would do to test it. If the replacement physically fits that's even better.
Keith |
10th Feb 2016, 9:34 am | #19 |
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Re: Vidor CN430 My Lady Anne
Hi all,
First of all thanks again for the advice. I did try the output valve in my Ultra but it didn't seem to be working. I agree, it does look as though the output transformer is o/c. I knew that the Avo 7 reads a little low, but I agree the other voltages don't luck right. At this stage though, as Paul says, I'm not hugely concerned as I have identified other issues which need addressing first. I put a note in the "wanted" section for a valve and transformer. Once again, thanks for some first class assistance. Best regards, Gary |
10th Feb 2016, 10:10 am | #20 |
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Re: Vidor CN430 My Lady Anne
The fact that you have 97V at the screen (and hence the HT at the input to the primary of the Output transformer) proves that the HT is fine. Hover, zero Volts at the anode of V4 shows conclusively that the OPT primary is open circuit. Hopefully someone will have a scrap chassis which will yield a suitable small OPT - it doesn't have to be from a Lady Anne, and looking at the pic of the chassis on page 2 of Trader Sheet 1215, there seems to be space for a slightly larger OPT if need be.
Good luck with the restoration Gary.
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