|
Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
|
Thread Tools |
17th Oct 2007, 7:04 pm | #1 |
Heptode
Join Date: Apr 2003
Location: Newton Abbot, Devon, UK.
Posts: 759
|
Bush VHF 70 with new relay
Hello everyone;
After a break from repairs, I am working on a Bush VHF 70. The wavechange switch in this is OK, having removed the HT from it (tracking and smoking). What I want to do is to use the contact to switch a relay. Where in this set could I get the 6 or 12 volts that the relay would need - ideally without having to install a transformer just for this....? Any suggestions? Thanks in advance Colin |
17th Oct 2007, 7:19 pm | #2 |
Dekatron
Join Date: Sep 2003
Location: Bolton, Greater Manchester, UK.
Posts: 6,644
|
Re: Bush VHF 70 with new relay
The problem here is how to drive the relay (i.e. get 6v) without affecting the performance of the set.
Can the VHF90 mod be used? http://www.vintage-radio.com/recent-...h-vhf90-1.html Or, take the volts from the Dial Lights via a small diode.... Trader Sheet 1419 refers. Cheers, Steve P
__________________
If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...? |
17th Oct 2007, 7:47 pm | #3 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,783
|
Re: Bush VHF 70 with new relay
You can leave the HT connected to the VHF front end permanently, even when the radio is switched to AM. The only downside is that the valve life will be reduced if the radio is mostly used on AM.
This is the normal workaround for these wavechange switch problems - fitting a relay is a sledgehammer to crack a nut Paul |
17th Oct 2007, 8:11 pm | #4 |
Octode
Join Date: Nov 2005
Location: Surrey, UK.
Posts: 1,869
|
Re: Bush VHF 70 with new relay
The last time I repaired one of these, I used a miniature microswitch which was tripped by the end of the switch slider. These are rated to take mains voltage and work well.
Leon. |
17th Oct 2007, 8:15 pm | #5 |
Heptode
Join Date: Apr 2003
Location: Newton Abbot, Devon, UK.
Posts: 759
|
Re: Bush VHF 70 with new relay
Yes, that was what I did in the end, remove the switch and join the HT feed to the AM and FM sides. However, I wasn't sure this wouldn't give worse performance on FM - they must have put in the switch in for some reason.
Probably as you say though it's more in the way of powering the FM front-end down when not needed. Cheers for the advice folks, I think it will stay as it is (hotwired!) Regards Colin |
17th Oct 2007, 8:22 pm | #6 | |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,783
|
Re: Bush VHF 70 with new relay
Quote:
Paul |
|
17th Oct 2007, 9:26 pm | #7 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,171
|
Re: Bush VHF 70 with new relay
Try a small capacitive dropper (say 10 to 100nF) and a bridge rectifier to give the DC for the relay coil.
Ed |
18th Oct 2007, 8:31 am | #8 |
Octode
Join Date: Apr 2007
Location: Hampshire, UK.
Posts: 1,574
|
Re: Bush VHF 70 with new relay
How about the cathode of the output valve? This is the traditional place to "borrow" a small DC voltage from. If you choose a relay with a high resistance 12V coil (with resistors in series to make up the voltage) then the change in bias would be minimal.
|
18th Oct 2007, 2:48 pm | #9 |
Dekatron
Join Date: Jan 2003
Location: Bradford on Avon, Wiltshire, UK.
Posts: 3,301
|
Re: Bush VHF 70 with new relay
Nice elegant solution Leon, nearly tried once or twice!!
Nice to hear from you again.
__________________
"Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly." |