Welcome to Australia's only Vintage Radio and Television discussion forums. You are not logged in. Please log in below, apply for an account or retrieve your password.
Australian Vintage Radio Forums
  Home  ·  About Us  ·  Discussion Forums  ·  Glossary  ·  Outside Links  ·  Policies  ·  Services Directory  ·  Safety Warnings  ·  Tutorials

Tech Talk

Forum home - Go back to Tech talk

 Circuit Diagram for Dick Smith Q-1312 RF signal generator
« Back · 1 · 2 · Next »
 Return to top of page · Post #: 16 · Written at 10:17:45 AM on 5 August 2019.
Keith Walters's avatar
 Keith Walters
 Location: Sydney, NSW
 Member since 16 January 2008
 Member #: 219
 Postcount: 66

FINALLY cracked it!
After being driven completely up the wall trying to find where the voltages were going on the oscillator PCB, I discovered that the plates of the 2-gang air-spaced tuning capacitor were touching.
On closer examination I found that the tuning capacitor frame is simply soldered together, and one of the joints had given way!
The reason this wasn't so obvious was because the oscillator ground PCB foil also had a high-resistance contact to the tuning gang frame, because the screws were loose! So instead of getting 0V I was getting something like 1V.....
No doubt my other Q-1312 has the same fault, and the "inexplicable" is now explained.
The 2SK55 FET is a real weirdo; no US-types (2N5485 etc) will work.
 
« Back · 1 · 2 · Next »
 You need to be a member to post comments on this forum.

Sign In

Username:
Password:
 Keep me logged in.
Do not tick box on a computer with public access.

Vintage Radio and Television is proudly brought to you by an era where things were built with pride and made to last.

DISCLAIMER: Valve radios and televisions contain voltages that can deliver lethal shocks. You should not attempt to work on a valve radio or other electrical appliances unless you know exactly what you are doing and have gained some experience with electronics and working around high voltages. The owner, administrators and staff of Vintage Radio & Television will accept no liability for any damage, injury or loss of life that comes as a result of your use or mis-use of information on this website. Please read our Safety Warning before using this website.

WARNING: Under no circumstances should you ever apply power to a vintage radio, television or other electrical appliance you have acquired without first having it checked and serviced by an experienced person. Also, at no time should any appliance be connected to an electricity supply if the power cord is damaged. If in doubt, do not apply power.

Shintara - Keepin' It Real · VileSilencer - Maintain The Rage