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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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21st Oct 2020, 7:29 pm | #41 | |
Dekatron
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Re: More BUSH DAC10 Woes!
Quote:
The DAC10 on LW covers 355 - 155 kHz (845 - 2070M). The DAC90A on LW covers 280 - 158 kHz (1070 - 1900M). That said, all anyone in the UK is likely to hear on LW are two French stations (but probably not on either a DAC10 or '90A which don't have external aerial provision), RTE on 252 Metres from Ireland and Radio 4 on 198 kHz. So really, if R4 appears on the dial where you'd expect t find it, and don't think it matters much what's the coverage is at each end of the band. Just my point of view. (Remember that whereas on MW, only the MW frame aerial is in circuit, whereas on LW, both the MW and LW coils are in circuit, connected in series).
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21st Oct 2020, 7:33 pm | #42 |
Octode
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Re: More BUSH DAC10 Woes!
In addition to the matters raised in my Post #40 above, the dial glass in this DAC10 is in a very poor condition:-
The Serial No. of the set is 62/85690 but I don't know if this is an earlier or later version as its different from the scan on the Vintage Radio website - Bush DAC10 Dial There have been many Threads detailing various attempts to recreate dial glasses e.g. using water transfer decal paper, but I get the impression that this procedure hasn't been entirely successful? Forum member David G4EBT has advised "The reason is that originally, the dials were screen printed - not transfers." Anyone found a better solution?
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21st Oct 2020, 7:41 pm | #43 |
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Re: More BUSH DAC10 Woes!
Hi Donald.
Don't be put off by doing alignment. Just make sure you have everything to hand and follow the instructions to the letter. Radios are actually easy to realign. One thing you really need is an isolating transformer though. Having earthed test equipment and an AC/DC set is unsafe even when you remove the earths on test equipment you are really taking a chance. If we were not on restrictions here in Central Scotland you could have done the realignment here in Kilmarnock.
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21st Oct 2020, 7:57 pm | #44 | |
Heptode
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Re: More BUSH DAC10 Woes!
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22nd Oct 2020, 10:35 am | #45 |
Octode
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Re: More BUSH DAC10 Woes!
Thanks David - as you state the DAC90A inductance and resistance will be different from the DAC10 but would, at least, give indicative figures to show that my LW winding measurements are at least in the same ball park?
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22nd Oct 2020, 4:39 pm | #46 |
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Re: More BUSH DAC10 Woes!
If it's any help the MW coil on my DAC90a is 0.18mH and the LW coil is 1.17mH
Arthur |
22nd Oct 2020, 4:45 pm | #47 |
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Re: More BUSH DAC10 Woes!
Also don't forget that the inductance as presented to the tuning capacitance will include any mutual inductance.
Lawrence. |
22nd Oct 2020, 5:22 pm | #48 | |
Octode
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Re: More BUSH DAC10 Woes!
Quote:
I know that these will be different in the DAC90A and the DAC10 but 1.17mH vs 1.69mH seems a bit of a big difference to me, even if we take into account mutual inductance as Lawrence suggests? Would be good to get an actual DAC10 measurement, if only to satisfy my curiosity, so apologies for labouring the point!
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29th Oct 2020, 10:02 pm | #49 |
Octode
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Re: More BUSH DAC10 Woes!
I've managed to measure both the MW and LW windings on another DAC10 and they are broadly in keeping with those on my own Frame Aerial. Didn't think this was the source of the problem but just useful to rule it out.
Next areas of investigation will be currently inaccessible components, possible dry solder joints, problematic switch contacts and dodgy coil windings associated with the pre-set switches! In order to achieve this it looks as if I will need to 'bite the bullet' and remove the Tuning Unit, something I've been trying to avoid! Remember that this set had been got at by the 'Phantom' so any advice or guidance on what and where to check next would be welcomed.
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30th Oct 2020, 12:53 pm | #50 |
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Re: More BUSH DAC10 Woes!
Hello Donald, it’s good to see your gentle but solid progress with this project. Good luck with the next stages and keep us posted !
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30th Oct 2020, 1:48 pm | #51 | |
Octode
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Re: More BUSH DAC10 Woes!
Quote:
I've already replaced a couple of dodgy wires that were crumbling and now have access to the rear of the switches to enable me to give the contacts a good clean. Measuring the coils and tuning caps is next to impossible as everything is wired up in tandem - don't want to start messing about disconnecting these with my soldering iron!! The 'Phantom' had replaced all the waxy caps under the chassis but based on previous experience here some of the solder joints appear 'interesting' to say the least! And all of this just to get better reception for Radio 4 LW on this set.
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1st Nov 2020, 4:15 pm | #52 |
Octode
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Re: More BUSH DAC10 Woes!
Due to crumbling and split wiring I ended up replacing all nine connections from the Tuning Unit - a really difficult job to reconnect all these wires to their respective homes!
While the Tuning Unit was out of the chassis I redid about half a dozen of the most 'interesting' solder joints as well as cleaning the sliding contact switches. The most difficult job was re-soldering the connection to the tuning capacitor as it acts as a heat sink - a bit concerned about some of the vanes becoming detached. Tuning Unit reunited with the chassis and all connections checked - switched on set and MW is still good while LW has much improved, at least in terms of volume. So something I've done has improved the situation? I still have a distinctive but annoying background crackling, but only on LW, that increases as I turn up the volume which strongly suggests it's a fault prior to the audio stage? I adjusted the RF by ear to ensure maximum output (don't have my audio output level meter or single loop coil built yet) but haven't touched the IF as I don't have an isolating transformer. Any information on the source of the background crackling would be welcomed along with advice on whether or not this would be improved by doing IF adjustments?
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BVWS Member Last edited by DonaldStott; 1st Nov 2020 at 4:22 pm. |
1st Nov 2020, 9:33 pm | #53 |
Hexode
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Re: More BUSH DAC10 Woes!
I find Long wave to be very noisy compared to Medium wave. at least here in North Wales
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1st Nov 2020, 10:13 pm | #54 | |
Octode
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Re: More BUSH DAC10 Woes!
Quote:
The crackling is specific to Long Wave and is not an issue with any others sets I have so there must be something 'unique' to this DAC10? I've checked the anode and oscillator grid resistors and they are both within tolerance but I've read elsewhere that these could be the source of the problem?
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2nd Nov 2020, 4:24 pm | #55 |
Octode
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Re: More BUSH DAC10 Woes!
Moving on quickly, I have now replaced all resistors and capacitors associated with V1 (UCH 42), Frequency Changer, buy this has had minimal effect on the crackle and general background noise on LW. It's probably just expectation bias but it may sound slightly better?
Tuning Radio 4 LW on Manual Tuning and on the Pre-set switch now delivers the same volume, so I'm putting this down to work done to the Tuning Unit e.g. cleaning the rear of the sliding switches? MW continues to sound good on both Manual tuning and on the two Pre-sets. Anything else I can do or is it just time to move on :- https://www.vintage-radio.net/forum/...4&postcount=13
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2nd Nov 2020, 4:42 pm | #56 | |
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Re: More BUSH DAC10 Woes!
Quote:
Will you be uniquely listening to Radio 4 in the long-wave setting? Is it listenable?
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Al Last edited by Al (astral highway); 2nd Nov 2020 at 4:49 pm. |
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2nd Nov 2020, 5:17 pm | #57 |
Nonode
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Re: More BUSH DAC10 Woes!
What is the AGC voltage when tuned to a strong LW station compared to a strong MW station?
If the radio is struggling to process long-wave signals due to a fault or misalignment issues, it will have the mixer and IF gain at maximum and will pick up noise that it would normally ignore. Have you replaced the mains filter capacitor C27? |
2nd Nov 2020, 7:29 pm | #58 | ||
Octode
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Re: More BUSH DAC10 Woes!
Quote:
I note what you write and have taken measures to eliminate EM hash wherever possible but this set is much worse than any other set in the same room e.g. Bush DAC90A. Radio 4 on Long Wave is listenable and you do tend to 'tune out' the background noise. For me, every restoration is both a technical challenge and an educational journey so that is why I often tend to persevere with certain matters that others may see as not worthwhile! Quote:
I do, however, still need to ask a few questions:- 1. Where do I measure the AGC voltage? 2. Would IF realignment help with the background noise/hash? 3. The set did not have a mains filter cap and it hasn't been replaced? Opinion seemed to suggest that this cap was optional but not a problem to fit one - Class X of course.
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2nd Nov 2020, 11:07 pm | #59 | |
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Re: More BUSH DAC10 Woes!
Good evening, Donald!
If you haven't already found this, there's an excellent write-up on relevant theory-meets-practice here...https://www.vintage-radio.com/repair...rf-stages.html Can I invite you to take a look and you'll be able to find the AGC line on your set pretty easily. Sounds like a bit of sleuthing is right up your street! Quote:
I don't think LW can be cleaned up very easily thesedays. For me, even on my most selective and sensitive AM set (Hacker Herald), there are no listenable stations on LW whatever, whereas I have some good clean and strong choices on MW. Of course, I know that this experience is partly dependent on topology, TX location and many other factors, but just to illustrate and for comparison. Happy exploring and I hope you find a satisfactory outcome and more enjoyment along the way!
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Al Last edited by Al (astral highway); 2nd Nov 2020 at 11:17 pm. |
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3rd Nov 2020, 9:27 am | #60 |
Dekatron
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Re: More BUSH DAC10 Woes!
The issue with long wave is how susceptible it is to noise from SMPS and other interference that is all around us these days. Ofcom isn't interested in medium and long wave interference complaints. Drive out of the towns and cities and reception can be very good. There is one line of defence we have and that is the magnetic loop antenna, they massively help reduce interference. Also remember an AC/DC set will always be worse as its directly wired to the mains. Things are better with an AC set with an isolated internal mains transformer so long as there is no cap fitted between one leg of the mains and chassis. Filter caps rarely help to remove mains bourne interference on AC/DC sets as they are directly connected to the mains. Better would be a proper LC filter or even each leg of the mains wound round a ferrite ring in antiphase.
My long wave reception is good here with the loop and a proper mains filter prior to the radio I'm listening to. Bring any AC/DC set indoors and forget it, it's totally useless.
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