|
Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
|
Thread Tools |
14th Aug 2017, 3:12 pm | #1 |
Triode
Join Date: Aug 2017
Location: Strood, Kent, UK.
Posts: 14
|
Wobbulator.
Help, can anyone assist?
I am building a simple wobbulator from Practical Wireless June 1972, so as to become involved in radio alignment procedures. I have bought the specified Denco coil, so I thought' but as you can see there are only two windings. What is wrong? Has anyone out there built this circuit? If so how do I proceed. |
14th Aug 2017, 3:29 pm | #2 |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,642
|
Re: Wobbulator.
Two separate coils could be wound one on top of the other. Are there 6 pins in use, or just 4?
|
14th Aug 2017, 3:43 pm | #3 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
|
Re: Wobbulator.
This webpage may help:-
http://www.vintageradio.me.uk/info/M...CO/dtb4_p3.jpg You can use a meter on ohms range to check for continuity of each winding.
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
14th Aug 2017, 4:00 pm | #4 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
|
Re: Wobbulator.
2DP is two windings for valve oscillator (Armstrong)
2T is three windings for transistor oscillator (Reinartz) The PW article to be precise, should have specified Range 2T instead of Range 2 to avoid any confusion. So it's a Red Range 2T you need. Lawrence. |
14th Aug 2017, 4:07 pm | #5 |
Octode
Join Date: Jan 2004
Location: Southport, Merseyside, UK.
Posts: 1,156
|
Re: Wobbulator.
I've got a Denco 3t Blue coil and from a cursory glance it appears to have only 2 windings but as AC/HL suggested there are in fact 3 windings with 6 wires going to the pins.
John Just seen ms660's post, so you have the wrong coil. |
14th Aug 2017, 4:14 pm | #6 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,289
|
Re: Wobbulator.
__________________
Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
14th Aug 2017, 4:31 pm | #7 |
Dekatron
Join Date: Nov 2010
Location: Oxford, UK.
Posts: 4,991
|
Re: Wobbulator.
https://mullard.org/ seems to have red range 2T Maxi-Q for £15
|
14th Aug 2017, 4:31 pm | #8 |
Pentode
Join Date: Jul 2015
Location: Newbury, Berkshire, UK.
Posts: 243
|
Re: Wobbulator.
Hi Allyblack, one question, why did you choose it?
|
14th Aug 2017, 4:38 pm | #9 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
|
Re: Wobbulator.
You could use an osc coil from an old transistor radio.
Lawrence. |
14th Aug 2017, 6:37 pm | #10 |
Rest in Peace
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,234
|
Re: Wobbulator.
I would agree, you seem to have a 2DP instead of a 2T. The DP range were really aimed at valve projects and have only two windings instead of the three required for low impedance transistor applications. You may be able to wind your own coil if you can find a suitable former.
Alan. |
14th Aug 2017, 8:51 pm | #11 |
Dekatron
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,997
|
Re: Wobbulator.
I did exactly that and wired in a few varicap diodes and attached it to the scope sawtooth output. It was a bit experimental but was good enough to align a crystal filter and IF of a comms receiver. It's probably in my box of abandoned Vero projects.
|
14th Aug 2017, 9:43 pm | #12 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,899
|
Re: Wobbulator.
This can be a bit non-linear in the frequency direction, so you may need to mix in a bit of RF from a stationary sig gen to act as a marker pip.
Keep your eyes open for an old HP 8601A sweeper, sometimes they go for junk money because they look too old and clunky to some people. Can do gentle wobbulation all the way up to 0 to 110MHz sweeps, and has a proper attenuator on the output.
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
17th Aug 2017, 2:15 pm | #13 |
Triode
Join Date: Aug 2017
Location: Strood, Kent, UK.
Posts: 14
|
Re: Wobbulator.
thank you all so much for your answers. firstly i liked the look of this project, and have constructed everything per the artical in question. my understanding of electronics is somewhat limited compared to the forums but im leaning. i will endevour to obtain a 2t or modify what i have. Ive` always liked grundig radios and will use the instrument on various 70`s models i have.there table radios sounding especially good.
|