To Align, or not to align - that is the question
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- Опубліковано 12 вер 2024
- I attempt to reach some conclusions about how often a radio should be aligned. I have a Bush DAC10 which I know hasn't been aligned for at least 50 years, and probably never aligned from new. I take some measurements before and after alignment. I look at how the AGC circuit works and how to keep it constant whilst taking the measurement.
Downloads:
Bush DAC10 service manual: 1drv.ms/b/s!As...
Alignment spreadsheet : 1drv.ms/x/s!As...
8BA spanner : 1drv.ms/u/s!As...
Adjuster converter : 1drv.ms/u/s!As...
Please make more videos! Anything valve radio related is fascinating to me - and no doubt to many others who were born later on in the transistor era.
I'm sure I will at some point, but right now I have too much going on I'm afraid
Very good video. Now just need to work out how to get from my knowledge, down here, to yours, up there!
Good to hear from you John
Nice overview of the yes or no need to do a radio alignment. I usually align after any repair, especially if I've replaced a lot of parts, as I feel that matches the new parts with the remaining old parts and helps them "get along" with each other better. It also teaches me more about how radios work and why the engineers designed them the way they did. As you know, radios often reflect not just the period technologies used in their manufacture but also the methodologies that were employed in their country of origin. For example, I picked up a Japanese radio two days ago at a flea market for 3,000 Yen (about 23 Euros). Not sure of the date of manufacture but I know it's from the Occupation just after the war. It's about the size of yours but the case is veneered wood, and the chassis and parts came from a standardized kit sold to radio shops by parts dealers who assembled them as no-name sets in order to sell them at prices much lower than the name-brand sets. The name-brand sets at the time came with a high tax and many people couldn't afford to spend one or two month's salary on them. The cheaper sets thus made the new heterodyne radios very popular with the public and helped spark the comeback of Japan's electronics industry (I find radio history fascinating). However, finding a schematic for these old sets, and then aligning them with no or scant Japanese instructions is often the hardest part of restoring them.
Thanks for your comments. There is certainly something to be said about understanding how these things work by alignment. That's a very good point. Fortunately, I haven't yet found a radio where I couldn't obtain the schematic, but I can imagine it being frustrating if you can't obtain one. I agree, radio history is fascinating
Sixty-three? You're just a kid! Love to watch your videos! Thanks!
Hi Tony, I’ve just found your channel and have really enjoyed watching your videos.
Looking forward to seeing more in the future.
Thanks for that. So glad you liked it
Nice video. Waiting for the next one.
Like your explaining and such
Excellent. Thanks for that
I think the decision about twiddling is driven by circumstance. If the radio in question is your property, and you know for a fact that it hasn’t been diddled, then I think it’s reasonable not to mess with it. However, if you have found it necessary to do major maintenance on it, then perhaps at least a check of the IF and the oscillator would be in order.
However, if the radio is not yours, or the history is not known, then a check of the alignment, as a final step in the process might be a good idea.
Prior to the second world war, IF strips were capacitively tuned here in North America. Those IF cans were remarkably stable, and trouble free. Then some cost-cutter got the brilliant idea of tuning the IF transformers inductively. This lead to the development of silver-on-mica capacitors in the IF cans. This was fine for the first 40 years, or so. Then the silver degrades, and “silver-mica disease” sets in. This can be cured only by removal of the mica wafers from the IF cans, and replacing them with discrete capacitors. This is not as simple a process as it sounds. The value of the original capacitors is almost never marked on the schematics. If you can accurately measure the inductance of the coils, you can calculate a value, but it’s often easier to just install variable capacitors temporarily, and twiddle until it works, then measure the value of the variable, and install the closest standard value you can find. This isn’t an operation for the faint of heart, and even experienced techs can destroy the IF can in the attempt.
I agree that circumstances have a lot to do with it. I think though (as I found out) that it's easy to get wrong . The trouble is that the only real way of finding out if you have done it right is to do a full frequency response check which is tedious. Its interesting what you say about the silver mica caps in the IF cans
Tony,
great video but wondered if you found the same problem as me with your DDS ( mine is the 6800) as follows,
if you input a low signal level to your RX at 14mhz -say below 40dbm 2mv rms (the DDS outputs at 50ohm) there is always a remnant warbling tone like modulation which becomes more evident as you go towards the receiver noise floor.
regards
mike g4wam
Hello Mike. I've not had a problem, but then I haven't really tried very low amplitude signals. I wouldn't be surprised though if there was such a problem. You get what you pay for I think, and the unit was cheap. I think for what it does though it's good value
I have just bought a Windsor signal generator. I think when you rewound those output transformers I was out of my depth . I have only just figured out how to work my pre war AVO valve tester.
Transformer winding is not difficult. Just tedious and shouldn't be rushed. Glad you have a valve tester. Hold on to it. They are very sought after now
Hello. Avo valve data came from Crowthorne Electronics from where I bought a Hedgehog and Aurora
Ah yes. I know of Crowthorne tubes
Hi Tony, tuned into your "how to repair radio" videos, but as a (now retired) Joiner, found out immediately I am wholly unequipped educationally to even consider repairs to my Radio. I have had It for nearly 30 years, and have only briefly heard it working (less than a minute) in all that time. Is this something you would undertake to repair for me?
It is a rather pretty HMV Model No 1104, from the 1930s I think. Atb Martin.
I had considered doing repairs, but the main problem is the public liability insurance. If the radio goes bang 2 weeks after I have repaired it, and burns you house down, I have a major problem on my hands.. However, having said that, I am quite happy to give you advice by answering questions. I am sure the questions you ask will help other people as well.
@@tonydurrant Thanks for reply Tony. I wouldn't know the right questions to ask as such, re repairing. I would ask though is there anyone you would recommend that could repair?
I wonder about the chap on the repair shop. I believe he is called Mike stuck I think
Thanks Tony, a question, are you a licensed radio amateur? If not you should be , you could show us some older ham gear then. Best regards, carl .👍🇬🇧
I never got into amateur radio. Perhaps I will one day !!
I think that the European and Australian radios, which rely on inductors much more than capacitors as with their American counterparts are much less susceptible to drifting. I don't know that European radios are susceptible to silver mica disease either which is becoming a big problem in the states. Also most radios of that era from the states do not have lock nuts and some i.f. cans just have a big screw sticking out the top which anyone can go twisting, and I find frequently has been. All in all, European radios of this era were definitely a mark higher than the American in my opinion.
we in the UK do not have the trouble with SMD due to a diffent design of IF transformers.
ok - well that's very interesting. I have no experience with American radios, Thanks for the info
Every day Ihave 30 radios I prefer the uk radios especially the old radios my greeting yas shaheen from Iraq
30 radios !!. That must keep you busy
Hey, get IN-FRAME !