How to Restore Your
Tube Radio
A Paul Pinyot, Solder Smoke and Burnt Finger
presentation at,
W3KWH
Steel City Amateur Radio Club
August 8th 7:30pm
Let’s get Cookin’
2
Schedule

March 7, 2012 Open to all!
Kick off. This presentation
and preparation discussion.

March 8 through 27.

March 28 pick parts and test tubes.
documentation (see presentation).
Acquire your radio and service
tube tester, parts bins (capacitors, resistors, lamps)
replacement parts at my cost to you.
I will bring a
for you to purchase
April 4 and 25, and May 2. Continue restoration at
NHARC.
 May 17-20 Dayton Hamvention.
 May 23 electronic alignment. (see presentation).
 End of project.

3
What you need to COMPLETE your
project





An understanding of electrical safety and
hazards.
A radio and new replacement components
Service documentation (schematic, alignment data).
A moderate to high soldering skill level
Hand tools including:




Soldering iron >=25w, rosin core solder, small wire cutters,
Needle nose pliers, screw drivers
Extension cord for activities at NHARC meetings.
Optional “lead wire twister” (see presentation).
An assortment of other non specified hand tools are helpful.
4
What you need cont’.
Contact cleaner and light lube oil.
 A copy of the steps in this presentation.
 About 8 to 16 hours for a five tube radio.
 About 10 to 40 hours for > five tube
multi-band consumer radio chassis.
 Work at home commitment. There will

NOT be enough time at NHARC meetings to
complete a restoration.
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Beyond this project’s scope
Cabinet Restoration
 Communications gear including but not
exclusive to:

 Receivers
like Hammarlund, Collins,
Hallicrafters (except the S-38 line and similar).
 Transceivers.
 Transmitters.
 Hybrid gear (transistors, IC).
6
Steps to restoration
7
Steps to restoration
Locate your radio.
 Find documentation before purchasing.
 Inspect and photograph (before
restoration).
 Test for operation
 Disassemble and save all parts
 Cold test all Transformers and coils.
 Test all tubes.

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Order replacement tubes and other long
lead items.
 Shine up chassis if so desired.
 Inspect wire insulation. Replace power
cord.
 Acquire capacitors, resistors and lamps.
 Lay out copy of schematic including red
and green pencils
 Replace capacitors
 Replace resistors
 Open IF cans and replace resistors.

9
Replace power cord
 Clean controls and switches
 Dim bulb test your work then direct to
line.
 Alignment
 Burn-in for => 8hours
 Check alignment
 Clean cabinet
 Return to cabinet and enjoy.

10
Locate your radio.
eBay is popular.
 Ham fests.
 Flea markets.
 Garage/Estate sales.
 Family.

11
Find documentation

http://www.nostalgiaair.org/Resources/
Domestic US consumer radios.

http://www.radiomuseum.org/
For European and some domestic

http://bama.edebris.com/manuals/
 Boat

anchors/test gear
http://www.ppinyot.com/HomePage.htm
 For
more links and resources.
12
Inspect and document
13
Inspect and document
One picture is much better than your (my)
memory. Take lots of pictures. This is how
most of my web site pictures are captured.
Simply as a record of what went where.
 The cheapest digital camera is better than no
camera at all.
 Macro capability is great. Or hold a surplus
macro lens in front of a digital camera with out
macro capability. It works. Believe me.

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Test for operation
This step saves a lot of time. If you can hear
the faintest of transmitters then most if not all of
your tubes, oscillator coils, chokes, IF
transformers, Audio Output Transformer,
speaker, band switch, volume pots and many
more things are working.
 Use a Variac set-up or a Dim Bulb Tester (DBT)
to protect the parts made from Unobtainium.

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Dim Bulb Tester
Current limiting
device.
 A “Must Use” on all
restored chassis.
 To make and use one
see:

http://www.ppinyot.com/
dimbulb/dim_bulb_tester.
htm
Alternative:
Variac plus an
amp meter
plus a volt
meter.
16
HOT Chassis!
17
Hot switched
18
Neutral switched
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Disassemble



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
Take the chassis out. Pulling off the knobs can
be a challenge. They are often held on with set
screws and rust.
Have Zip Lock bags available and a sturdy
cardboard box.
The box will help protect your glass tubes.
Wrap and tape the speaker with cardboard. I
have put too many screwdrivers through paper
cones. It will make you sick.
Take pictures too.
20
Cold test all Transformers and coils
If you had a successful DBT test you can
skip this step.
 Use an ohm meter to DC test the coils,
transformers, speaker for continuity.
 Mark off (highlight) these items in green
on your schematic.
 Schematics often have a DC resistance on
the coil schematic.

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Test all tubes
It helps to have all tubes tested. A weak
tube can throw you for a loop.
 Most tubes will be fine
 Guitar amp tubes take a beating.
 AA5 audio (50C5) and rectifier tubes
(35w4) take a beating too. Look for hot
shorts in the rectifier tubes.
 Put the tubes back into the chassis or use
duds in place. More on this later.

22
Order long lead items
23
Order long lead items.
This is rather self explanatory.





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
Order needed tubes.
Grill cloth
Rebuild crystal cartridges/idler wheels
Re-cone speakers
Special caps and high watt resistors
Send off cabinet to refinisher.
etc
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Shine up chassis if so desired.

PROTECT or remove the variable air
condenser (Tuning gang capacitor) !!!
Lots of manual labor and elbow grease.
 See: http://www.ppinyot.com/P/shiny_chassis.htm for
ideas.

25
Inspect wire insulation
kB3URN
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Inspect wire insulation
Many radios manufactured during WWII
has rubber insulation that does not last.
It is hard as sugar candy or soft and
gooey as chewed bubble gum.
 It needs to be replaced or covered with
“spaghetti” or heat shrink insulation.
 Replacement is the desirable solution.
 Heat shrink over transformer leads is
second best.

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Inspect wire insulation
continued.
Spaghetti is third.
 Avoid paint on insulation. Thickness is not
controllable.
 Keep a tube in all the sockets. This is
where socket breakage is high!
 Use 600 volt UL rated insulation.
 Use stranded for any connection off of the
chassis (i.e., speaker, dial lamps, antenna,
etc).

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A Tube Socket story
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A Tube Socket story
A broken tube socket degrades the performance
of a radio. Dust and dirt accumulate and cause
a short. Once an arc has occurred a carbon
track is laid down. It is very hard to remove all
the carbon and replace with a high insulation
material.
 Put a tube into any socket before soldering or
de-soldering any pin connector!


Practice this preventative measure and all will
live happily ever after.
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Acquire capacitors, resistors and
lamps
Most schematics have a list of parts. Electrolytic
and paper containing capacitors are a priority for
replacement. Mica and ceramic caps are good
to keep.
 Use 630 volt polypropylene (<1 uf) capacitors in
all positions (unless a higher voltage is needed).
 Use 450 volt Electrolytic capacitor in the power
supply (160 volts for AA5)
 I will bring my parts bins to pick your parts. (Your

$ cost will be my $ cost. No mark-ups.)
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Tubular Axial Capacitors
Orange Dips
Metalized Polypropylene Film
Good replacement for Wax/paper caps.
Metalized Polyester Film
Self-healing property
Metal-Foil Polypropylene Film
500 Volt Dipped Silver Mica Capacitors
•Orange epoxy coated for superior
heat, solvent and moisture resistance.
•Excellent stability for High Current /
High Frequency / Temp.
Compensation Applications.
1 pF to 5000 pF,
Metalized Polyester Film
•Highly reliable with "self-healing"
performance
Electrolytic Capacitors
Y2 Safety and
Interference Suppression
Capacitors
Line to Line (X) and
Line to Chassis.
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Micamold & “Black Beauties”



Mica Mold is a company
that made nano and pico
farad capacitors that look
like mica or ceramic
“domino” capacitors. But
they used paper.
These capacitors must be
replaced!
“Black Beauties” or
“Bumble Bee” capacitors
also have paper inside
and MUST be replaced.
33
Acquire capacitors, resistors and lamps
continued.

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
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Most carbon composition resistors are bad. If
not now they will be later after getting hot.
They have been sitting absorbing moisture and
thermal cycling for decades of non use.
Just replace them now and avoid the failures
later.
Use ½ watt 5% Carbon Film resistors.
Use new Carbon Composition for circuits
operating over say 18 MHz (HF).
Do NOT use New Old Stock (NOS) carbon
composition resistors. They go bad on the shelf.
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Carbon Film 1/2 w 5% about $0.07
Carbon composition ½ w about $0.20
•Use above 18 MHz
•5 % tolerance
•Low inductance
•Low capacitance
•Watch for inductance.
•High quality performance at
economical prices
•1/2 & 1 Watt
•General shotgun replacement.
Metal Oxide 1 and 2 watt 12/17 cents
• 5 % tolerance
•Power Supply section.
•Cathode Bypass
•Candohm replacements
Metal Film ½ w about 11 cents
POWER Resistors Wire Wound very inductive.
1 % tolerance
•Epoxy coated precision resistors
5 watt $0.37
Power Supplies
Candohm replacements
10 watt $0.50
AKA Sand, cement,
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Ceramic, wire wounds
Lay out copy of schematic with red and
green pencils


Mark off or Highlight
components in Red when
replaced.
Trace the connections in
green to verify the circuit
is original factory design.

Undocumented,
unapproved, mods were
made to gear when parts
were not available (war
time) or the shop was too
cheap to properly repair
the fault.
36
Replace capacitors



Replacing the capacitors
first will give you more
room to replace other parts.
Use hook and crimp
method. This makes for a
fast and strong
replacement. It also more
importantly keep the part in
the same relative place as
the original.
The performance of plenty
of radios is affected by parts
placement and wire dress.
37
Replace resistors
Use the hook, crimp and solder method.
 A Lead Twister tool is really helpful with
resistor replacement.

38
39
Lead Twister





A lead twister adds little coils
to the lead wires of the new
parts.
Cut out the original part near
the body.
Slip the new part’s coils over
the old lead wires and solder.
This maintains the original
component position and makes
for a quick secure solder joint.
See:
http://www.ppinyot.com/lead_
twister.htm to make one.
40
Open IF cans and replace resistors
Replace Resistors
Sliver Mica disease (AA5)
See:
http://www.ppinyot.com/if_t
ransformers.htm
41
Hot test restored chassis
Please use a dim bulb tester…….
42
Hot test restored chassis
Use a Variac, volt and amp meter OR DBT.
Once passed then plug directly into the
line (mains).
 Tune in a strong station on Broadcast.
 More than likely you will hear a station or
more.
 If you are lucky the dial frequency may be
close.

43
Alignment
Get alignment data.
 Warm up RF generator and frequency
counter.
 Connect voltmeter to AGC or AC meter to
speaker terminals.
 Perform Alignment

44
Trouble?
If the DBT passes trouble shoot after your
first alignment. The IF transformers could
be so far off the radio will not receive.
 If still dead use appropriate trouble
shooting techniques to repair.

45
Alignment
I will bring alignment gear.
 Follow the alignment procedures.
 An RF generator with AM modulation is
commonly required.
 A Frequency meter (or general coverage
receiver) is needed to set the RF gen.
 Burn in the radio 4 to 8 hours.
 Perform the alignment again.

46
Put it all back together.
Clean your cabinet.
 Make cosmetic improvements.
 Check for electrical safety again.
 String up an antenna and enjoy your new
old radio.

47
Hotel Radio 6A
Detrola 576
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Thank You
54
Objective and Goals

Make an old tube radio chassis work good
again. There will be minimal cabinet restoration techniques
covered or suggested.
To get hands on practical experience with
old radio technology
 Enjoy listening to the product of your
Hands-On efforts.
 Have fun!

55