November 27, 2015

Bad light...

Q: Where does bad light end up?
A: In a prism.

November 20, 2015

November 13, 2015

The ocean is made of waves...

An ocean traveller has even more vividly the impression that the ocean is made of waves than that it is made of water. — Sir Arthur Stanley Eddington

November 8, 2015

Vintage Fender Champ Amplifier Restoration

We have been using a weathered looking vintage Fender Champ "silverface" guitar tube amplifier ever since it was given to us by a friend a few years ago.  It had acquired innumerable cosmetic warts and battle scars over the decades as well as a set of extremely dirty/noisy potentiometers and input jacks.  The issues all seemed manageable and we decided this great little amp was worthy of restoration.

Beat up Fender Champ Silverface amplifier
Fender Champ Silverface Front View (before restoration)
Top view of the beat up Fender Champ
Fender Champ Silverface Top View (before restoration)
Beach up Fender Champ amp side view
Fender Champ Silverface Side View (before restoration)

Beat up Fender Champ amp side view
Fender Champ Silverface Side View (before restoration)

Planning the Restoration

Our objective for the restoration was to return the amplifier to its original function and beauty. We made a list of the restoration work that we intended to perform:

  • Replace electrical power plug - connector pulled away from the outer insulation
  • Replace speaker grill - original color had faded, dirty, punctures
  • Clean the Fender logo - minor corrosion, dirty
  • Clean the knobs and panel face - dirty
  • Replace the black Tolex - dirty, several large damaged areas
  • Clean all hardware - corrosion and dirty
  • Clean inside of cabinet - dust bunnies and layers of dirt
  • Replace all three potentiometers - super noisy and intermittent
  • Clean both input jacks - noisy and intermittent
  • Replace carrying handle - original handle was missing

Sourcing Parts

We ordered the parts we needed from Antique Electronic Supply including:

  • Black Tolex - we ordered extra in case we made a mistake cutting a piece
  • Original Fender amp carrying handle
  • 250K Ohm audio potentiometer (qty 2)
  • 1M Ohm audio potentiometer

We purchased a 207g spray can of 3M Super 77 Multipurpose Adhesive at our local ACE Hardware.  We used nearly the entire can for the project.  The spray on application worked perfectly for adhering the Tolex to the cabinet.  We had replacement grill cloth on-hand so we didn't need to order it.  We also had a good supply of staples, tacks, and an replacement electrical plug in the workshop.  The total cost of all the parts and materials was about $80.00 USD.

Preparation

  1. Photograph all sides of the amplifier.  Photographs are excellent reference resource during any restoration.  Photographs can answer questions that your memory cannot, such as, "So where did this do-hicky go?"
  2. Unplug the amplifier from the wall and let it discharge the capacitors which carry potentially dangerous voltages.
  3. Cut the power plug off and discard.
  4. Unscrew the back panels.  Save the screws and panels for reuse.
  5. Remove the grill by prying it off.  It is held in place by heavy Velcro.
  6. Unscrew the Fender logo from the grill.  Save the logo and screws for reuse.
  7. Unplug the speaker.
  8. Remove the speaker.  Store with care to protect the delicate cone.
  9. Remove the metal feet.  Using a flat head screw driver and tack hammer, carefully pry up the feet.  Save these for reuse.  Straighten any points that are bent during removal.
  10. Unscrew the hardware holding the amplifier module in place.  Hold onto the amplifier module case to prevent it from falling to protect the delicate vacuum tubes.
  11. Seek qualified help to remove the amplifier module.  Beware of the capacitors that are potentially storing deadly voltages.  Don't touch anything inside.  Photograph the wiring so you have a reference for how the potentiometers are wired. Store the amplifier carefully out of reach of anyone.
  12. Carefully remove the staples holding an aluminum shield to the inside top of the cabinet.  Retain the shield for reuse.  Discard the old staples.
  13. Remove the knobs and store for reuse.
  14. Vacuum the dust bunnies from inside the cabinet.
  15. Carefully peel the old Tolex off the cabinet.  Try to pull each section off whole if possible since these can help you by providing a template for cutting and reapplying new Tolex.  Save for later reference.
  16. Sand the wood surfaces smooth and clean.  Remove the old adhesive and Tolex residue.  This step also helps remove small nicks and dings in the wood.
  17. Fill any major damage (divots, deep abrasions, missing slivers ...) to the wood and sand smooth.
  18. Vacuum and wipe all surfaces with tack cloth to remove dust and dirt.
  19. Remove and discard all the old staples that were used on the grill cloth and Tolex.

Restoration

You will need a box cutter with a new blade and scissors for cutting the Tolex and grill cloth.   An electric stapler is very handy.  You will also need flat head and Phillips head screw drivers, a hammer, a roller, and a square.
  1. Gently clean all the hardware and logo using alcohol and cotton swabs.  Use Never-Dull to remove any light corrosion.
  2. Using cotton swabs and alcohol gently clean the input jacks contacts.
  3. Cut a piece of grill cloth about the same size as the original.  Install in the frame using an electric stapler.  Four hands are helpful with this step.  Two hands for stretching the fabric while the other person staples.
  4. Install the Fender logo.
  5. Using the old Tolex panels, cut new pieces.
  6. Apply the new Tolex panels in the following order: left side, right side, top, bottom
  7. To apply each piece, you must spray the surface with adhesive where the Tolex piece will be applied as well as the Tolex itself.  We found a liberal coating of adhesive on both worked best.  Avoid spraying areas that you are not working on since it only makes the job messier than needed.  Take care not cover up the Velcro strips.
  8. Use the roller to smooth out the fit and remove air bubbles.
  9. Using the box cutter and scissors, cut and fit each piece following the old Tolex as a template / guide.  We found it more effective and precise to make the cuts with the piece in place for the purpose of optimizing the fit.  Use your hands to make sure that each corner it good and tight.
  10. Once all the Tolex is in place, let it dry and harden for awhile before proceeding.
  11. Using a small sharp screw driver, poke holes through the Tolex where each screw is supposed to go.
  12. Install the aluminum shield.  Carefully align the shield holes with the cabinet holes.  We used brass flat head tacks instead of staples using the holes left by the old staples.
  13. Install the feet by tapping in gently with a hammer.
  14. Install the handle.
  15. Replace the potentiometers one at a time.  Take care to wire exactly as original.  Inspect visually when complete to make sure there are no cold solder joins or shorts between leads.
  16. Gently clean the amplifier face and knobs with cotton swabs and alcohol.
  17. Install the speaker
  18. Reinstall the amplifier module into the cabinet.
  19. Reconnect the speaker.
  20. Install the speaker grill.
  21. Install the back panels.
  22. Install a replacement power plug.
  23. Test the amplifier.

Results

We were very pleased with the outcome of our restoration work.  The restored amplifier looked just beautiful.  It was a wonderful experience to be able to adjust the potentiometers silently.  All the intermittent issues went away as well.  The amp was quiet and sounded warm and wonderful.  Plugging and unplugging the amplifier from the wall was no longer a scary task.  We were also delighted to find that all the materials we had purchased were perfect for the job.

Beautifully restored Fender Champ amp front view
Fender Champ Silverface Amplifier - front view (after restoration)

Beautifully restored Fender Champ amp side view
Fender Champ Silverface Amplifier - side view (after restoration)

Rear view of the restored Fender Champ amp
Fender Champ Silverface Amplifier - back view (after restoration)

Restoring the amplifier helped us see just how well Fender designed and built the Champ.  With a little tender loving care the amplifier still sounds great after a having endured decades of considerable apparent hard use.

We would like to extend a special thank you to our friend who gave us this little gem-in-the-rough of a vacuum tube amplifier and the opportunity for a wonderful father-and-son restoration project.

Good DX and 73,

NJ2X & KC2VSR


© Michael W. Maher and NJ2X.COM, 2015. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Michael W. Maher and NJ2X.COM with appropriate and specific direction to the original content.

November 6, 2015

Notably to electrons...

After long reflection in solitude and meditation, I suddenly had the idea, during the year 1923, that the discovery made by Einstein in 1905 should be generalised by extending it to all material particles and notably to electrons. — Prince Louis-Victor de Broglie