I picked up a RCA Victor 66X2 Radio from 1946-47. It's a very unusual
radio. It is AM broadcast band and one Shortwave band. Amazingly this
radio worked right away, except for the broken dial string and a power
cord that needs to be replaced soon. All the tubes appear to be
original, and all capacitors appear to be original too. Even the filter
cap appears original, and there is no hum.

Other than replace the cord and dial string, I dont plan to do anything
with the components for now, except add a fuse.

The bakelite case is solid, but badly scratched. The bakelite under the
Ivory paint is black. This radio sold in black (unpainted - model 66X1),
Painted Ivory - Model 66X2, and two additional woodgrain models.

My plan is to remove the case from the chassis, remove or tape up the
grill cloth and trim. Then spray paint it with an Ivory colored spray
paint. (after sanding it with some very fine sandpaper to clean up all
scratches).

My question is whether I can use a common spray paint on bakelite, such
as Rustoleum? I may not get the exact color as original, but I dont see
any way to get the original paint.

Have any of you painted bakelite? Will common spray paint work on it?

One other thing, the dial bulbs are burned out. Bayonette base, wired in
series, two 3.2 volt bulbs. A schematic shows them as Mazda 1490. ( I
never heard of Mazda bulbs). Anyhow, where can I get such bulbs?
The bayonette base is the same as a #47 bulb.

BTW: The 6 volt feeding them comes from the filament center tap in the
35Z5 rectifier tube. How they get 6volts from that center tap evades me,
but that's how it is.....



Thanks

On 9/25/2017 11:46 PM, wrote:
One other thing, the dial bulbs are burned out. Bayonette base, wired in
series, two 3.2 volt bulbs. A schematic shows them as Mazda 1490. ( I
never heard of Mazda bulbs). Anyhow, where can I get such bulbs?
The bayonette base is the same as a #47 bulb.

Multiple sources online show them as in stock.

BTW: The 6 volt feeding them comes from the filament center tap in the
35Z5 rectifier tube. How they get 6volts from that center tap evades me,
but that's how it is.....

A lot of things evade you.
http://www.nostalgiaair.org/pagesbymodel/076/M0015076.pdf

From the 35Z5GT data sheet:
"Glass octal type used in power supply of ac/dc receivers. The heater
is provided with a tap for operation of a panel lamp. May be supplied
with pin 1 omitted. Requires octal socket."

Hint: It's not "center" tapped.



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

In article ,
wrote:

The bakelite case is solid, but badly scratched. The bakelite under the
Ivory paint is black. This radio sold in black (unpainted - model 66X1),
Painted Ivory - Model 66X2, and two additional woodgrain models.

My plan is to remove the case from the chassis, remove or tape up the
grill cloth and trim. Then spray paint it with an Ivory colored spray
paint. (after sanding it with some very fine sandpaper to clean up all
scratches).

My question is whether I can use a common spray paint on bakelite, such
as Rustoleum? I may not get the exact color as original, but I dont see
any way to get the original paint.

http://www.radiomuseum.org/forum/vin...abinets. html
has a good discussion of this.

He doesn't mention any specific sort of paint being required, but does
recommend spraying on a coat of primer after a thorough
cleaning... probably a good idea to help ensure good adhesion.

I recall that Rustoleum makes some paint varieties which are specified
as being suitable for use on plastics. This sort of multi-surface
paint might give you some additional defense against peeling, if you
decide to omit the primer step.

Dave Platt wrote on 9/26/2017 3:42 PM:
In article ,
wrote:

The bakelite case is solid, but badly scratched. The bakelite under the
Ivory paint is black. This radio sold in black (unpainted - model 66X1),
Painted Ivory - Model 66X2, and two additional woodgrain models.

My plan is to remove the case from the chassis, remove or tape up the
grill cloth and trim. Then spray paint it with an Ivory colored spray
paint. (after sanding it with some very fine sandpaper to clean up all
scratches).

My question is whether I can use a common spray paint on bakelite, such
as Rustoleum? I may not get the exact color as original, but I dont see
any way to get the original paint.

http://www.radiomuseum.org/forum/vin...abinets. html
has a good discussion of this.

He doesn't mention any specific sort of paint being required, but does
recommend spraying on a coat of primer after a thorough
cleaning... probably a good idea to help ensure good adhesion.

I recall that Rustoleum makes some paint varieties which are specified
as being suitable for use on plastics. This sort of multi-surface
paint might give you some additional defense against peeling, if you
decide to omit the primer step.

It all depends on the details. I used a paint for plastic to use on a
plastic container and it did not work well at all. I cleaned the surface
well, but did not rough it up and did not use a primer. It was not too long
before the paint started to peel. I don't know the type of plastic. It was
a food storage container with a seal ring commonly available in stores.
Just a data point for what it is worth.

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

On Tuesday, 26 September 2017 22:14:42 UTC+1, rickman wrote:

It all depends on the details. I used a paint for plastic to use on a
plastic container and it did not work well at all. I cleaned the surface
well, but did not rough it up and did not use a primer. It was not too long
before the paint started to peel. I don't know the type of plastic. It was
a food storage container with a seal ring commonly available in stores.
Just a data point for what it is worth.

Nothing sticks to polythene.


NT

wrote on 9/26/2017 6:31 PM:
On Tuesday, 26 September 2017 22:14:42 UTC+1, rickman wrote:

It all depends on the details. I used a paint for plastic to use on a
plastic container and it did not work well at all. I cleaned the surface
well, but did not rough it up and did not use a primer. It was not too long
before the paint started to peel. I don't know the type of plastic. It was
a food storage container with a seal ring commonly available in stores.
Just a data point for what it is worth.

Nothing sticks to polythene.

Are you in the UK? Is that what we call polyethylene? How does it happen
that we end up with different names for things like common plastic?

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

On Tuesday, 26 September 2017 23:43:46 UTC+1, rickman wrote:
tabbypurr wrote on 9/26/2017 6:31 PM:
On Tuesday, 26 September 2017 22:14:42 UTC+1, rickman wrote:

It all depends on the details. I used a paint for plastic to use on a
plastic container and it did not work well at all. I cleaned the surface
well, but did not rough it up and did not use a primer. It was not too long
before the paint started to peel. I don't know the type of plastic. It was
a food storage container with a seal ring commonly available in stores.
Just a data point for what it is worth.

Nothing sticks to polythene.

Are you in the UK? Is that what we call polyethylene? How does it happen
that we end up with different names for things like common plastic?

Yes, yes, it's easier to say. Polythene is the next best thing to ptfe when you want to keep friction low. Handy for moving heavy loads. Food storage containers are most commonly polythene.


NT

In article , rickman wrote:
wrote on 9/26/2017 6:31 PM:

Nothing sticks to polythene.

Are you in the UK? Is that what we call polyethylene? How does it happen
that we end up with different names for things like common plastic?

Tradition. It dates back at least as far as the day when we Americans
decided we couldn't afford to spell the new metal "aluminium" due to a
severe shortage of printers' slugs for the letter "i". :-)

On Tue, 26 Sep 2017 18:43:35 -0400, rickman wrote:

wrote on 9/26/2017 6:31 PM:
On Tuesday, 26 September 2017 22:14:42 UTC+1, rickman wrote:

It all depends on the details. I used a paint for plastic to use on a
plastic container and it did not work well at all. I cleaned the surface
well, but did not rough it up and did not use a primer. It was not too long
before the paint started to peel. I don't know the type of plastic. It was
a food storage container with a seal ring commonly available in stores.
Just a data point for what it is worth.

Nothing sticks to polythene.

That should be poly-mumble-ene.

Are you in the UK? Is that what we call polyethylene? How does it happen
that we end up with different names for things like common plastic?

There are naming standards for chemicals and compounds which I believe
includes plastics. Chemists are amazingly human (and childish) in
their naming of various compounds. There are enough examples to fill
a Wikipedia article:
https://en.wikipedia.org/wiki/List_of_chemical_compounds_with_unusual_names

Should you ever be in a position to assign a name, please resist the
temptation to be excessively clever. I didn't. Because I had one
foot in engineering and the other in marketing, I was honored with the
task of assigning a model number of a marine radio that I helped
design. Most of the other radios followed the pattern COM1, COM3,
COM21, etc (this was before the IBM PC serial ports used the same
designation). Without the slightest hesitation, I proclaimed that
COM1C will be the next model number. It was about a week before
anyone noticed the obvious. I soon became a candidate for immediate
execution by those who had to rewrite the product releases and hastily
retrieve those had been mailed.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

rickman wrote:

It all depends on the details. I used a paint for plastic to use on a
plastic container and it did not work well at all. I cleaned the
surface well, but did not rough it up and did not use a primer. It
was not too long before the paint started to peel. I don't know the
type of plastic. It was a food storage container with a seal ring
commonly available in stores. Just a data point for what it is worth.


If you are talking about 'Tupperware' type containers, that plastic
is the lowest grade available. It won't hold paint, and common adhesives
won't stick to it.

--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

On Thursday, 28 September 2017 11:55:48 UTC+1, Michael Terrell wrote:
rickman wrote:

It all depends on the details. I used a paint for plastic to use on a
plastic container and it did not work well at all. I cleaned the
surface well, but did not rough it up and did not use a primer. It
was not too long before the paint started to peel. I don't know the
type of plastic. It was a food storage container with a seal ring
commonly available in stores. Just a data point for what it is worth.


If you are talking about 'Tupperware' type containers, that plastic
is the lowest grade available. It won't hold paint, and common adhesives
won't stick to it.

They're food grade. Nothing sticks to polythene unless you torch it first or weld it.


NT

On Tuesday, 26 September 2017 20:42:20 UTC+1, Dave Platt wrote:
In article ,
wrote:

The bakelite case is solid, but badly scratched. The bakelite under the
Ivory paint is black. This radio sold in black (unpainted - model 66X1),
Painted Ivory - Model 66X2, and two additional woodgrain models.

My plan is to remove the case from the chassis, remove or tape up the
grill cloth and trim. Then spray paint it with an Ivory colored spray
paint. (after sanding it with some very fine sandpaper to clean up all
scratches).

My question is whether I can use a common spray paint on bakelite, such
as Rustoleum? I may not get the exact color as original, but I dont see
any way to get the original paint.

http://www.radiomuseum.org/forum/vin...abinets. html
has a good discussion of this.

He doesn't mention any specific sort of paint being required, but does
recommend spraying on a coat of primer after a thorough
cleaning... probably a good idea to help ensure good adhesion.

I recall that Rustoleum makes some paint varieties which are specified
as being suitable for use on plastics. This sort of multi-surface
paint might give you some additional defense against peeling, if you
decide to omit the primer step.

I've seen seasoned restorers use car spray paint, vauxhall brazil brown for bakelite.

When getting a colour match I always give the sample a good clean first, otherwise the wrong colour is inevitable.


NT

In article ,
wrote:

One other thing, the dial bulbs are burned out. Bayonette base, wired in
series, two 3.2 volt bulbs. A schematic shows them as Mazda 1490. ( I
never heard of Mazda bulbs). Anyhow, where can I get such bulbs?
The bayonette base is the same as a #47 bulb.

BTW: The 6 volt feeding them comes from the filament center tap in the
35Z5 rectifier tube. How they get 6volts from that center tap evades me,
but that's how it is.....

This looks to be the schematic for the set. It's an AA6, with an RF
amplifier ahead of the converter.
http://www.nostalgiaair.org/pagesbym...6/M0015076.pdf

We used to use schematics of sets like these back in the 1950's and
'60's as interview questions for EE and technician canditates. One very
good one was "talk to me about the rectifier circuit."

Understanding the circuit starts with understanding basic electricity,
particularly Kirchoff's current law and Thévenin's theorem. What you
are calling a "center tap" between pins 2-3 of a 35Z5 is at the 21.5%
point of the heater, not the center. According to the RCA data sheets,
with 35 volts between pins 2 and 7, you'll see 7.5 volts across pins
2-3. Now add a #47 (6.3v 150 ma.) bulb across pins 2 and 3, and feed
the plate from pin 3. RCA claims that the voltage across pins 2-3 (and
the bulb), with a 60 ma. draw on the cathode is now 5.5 volts and
between pins 2-7, 32 volts.

That, of course, doesn't "add up." Assuming RMS values, a 150 ma.
heater plus 60 ma. of DC is only 210 ma. RMS, which should explain the
lower voltage between pins 2-3. However, also consider that current
flow in the plate circuit, with a 40 mike cap connected to the cathode
is a pulse, not a full half sine wave, and that RCA measurements were
made with a VTVM, which isn't a "true RMS instrument." Those pulses,
and the low thermal inertia of the pilot lamp filament(s) explains why
the bulb is at full brilliance when the set is warmed up and playing.

Another "trick" to the series circuit is that during warmup, the series
filaments are a voltage divider that is essentially constant for any
current passing through the heater string. These heaters have a steep
positive temperature (heat/ohms) coefficient, so the startup current is
more like 1.5 amps. If you are going to fuse the radio, you need to
measure the resistance of the filament string cold, and work from there.

That's for starters.

Now, as to the rest of the set, take a look at the B+ circuit and
voltages. The tube data sheets give 100 volts on both plate and screen
as "typical operation" points for AA5 tubes. However, this set says 76
volts. Also note that "typical operation" specs an initial bias (-1
volt for 12SK7), while this set has the cathodes of the RF tubes
grounded.

Yes, that schematic is a very good interview subject.

Don't get foxed by "Mazda." That was a GE trademark from around 1910 to
denote "tungsten filament," and was licensed by other bulb
manufacturers. GE dropped using it in 1945. If you need bulbs, a 1490
is a 1490, readily available today.

If you are going to play the radio without recapping, the critical caps
are the coupling caps between stages, particularly the cap feeding the
audio power amp. Also, check the value of the grid leak resistor(s).
You should see zero volts DC at the grid of the 35L6.

The AA5 (and AA6) are, with the DC-3 airplane, and the GG-1 locomotive,
standout classics of American design. They look "simple" but there's a
lot of thinking that made them robust and reliable without being
complicated.

Hank

On Thu, 28 Sep 2017 06:27:49 -0000 (UTC),
(Hank) wrote:

In article ,
wrote:

One other thing, the dial bulbs are burned out. Bayonette base, wired in
series, two 3.2 volt bulbs. A schematic shows them as Mazda 1490. ( I
never heard of Mazda bulbs). Anyhow, where can I get such bulbs?
The bayonette base is the same as a #47 bulb.

BTW: The 6 volt feeding them comes from the filament center tap in the
35Z5 rectifier tube. How they get 6volts from that center tap evades me,
but that's how it is.....

This looks to be the schematic for the set. It's an AA6, with an RF
amplifier ahead of the converter.
http://www.nostalgiaair.org/pagesbym...6/M0015076.pdf

We used to use schematics of sets like these back in the 1950's and
'60's as interview questions for EE and technician canditates. One very
good one was "talk to me about the rectifier circuit."

Understanding the circuit starts with understanding basic electricity,
particularly Kirchoff's current law and Thévenin's theorem. What you
are calling a "center tap" between pins 2-3 of a 35Z5 is at the 21.5%
point of the heater, not the center. According to the RCA data sheets,
with 35 volts between pins 2 and 7, you'll see 7.5 volts across pins
2-3. Now add a #47 (6.3v 150 ma.) bulb across pins 2 and 3, and feed
the plate from pin 3. RCA claims that the voltage across pins 2-3 (and
the bulb), with a 60 ma. draw on the cathode is now 5.5 volts and
between pins 2-7, 32 volts.

That, of course, doesn't "add up." Assuming RMS values, a 150 ma.
heater plus 60 ma. of DC is only 210 ma. RMS, which should explain the
lower voltage between pins 2-3. However, also consider that current
flow in the plate circuit, with a 40 mike cap connected to the cathode
is a pulse, not a full half sine wave, and that RCA measurements were
made with a VTVM, which isn't a "true RMS instrument." Those pulses,
and the low thermal inertia of the pilot lamp filament(s) explains why
the bulb is at full brilliance when the set is warmed up and playing.

Another "trick" to the series circuit is that during warmup, the series
filaments are a voltage divider that is essentially constant for any
current passing through the heater string. These heaters have a steep
positive temperature (heat/ohms) coefficient, so the startup current is
more like 1.5 amps. If you are going to fuse the radio, you need to
measure the resistance of the filament string cold, and work from there.

That's for starters.

Now, as to the rest of the set, take a look at the B+ circuit and
voltages. The tube data sheets give 100 volts on both plate and screen
as "typical operation" points for AA5 tubes. However, this set says 76
volts. Also note that "typical operation" specs an initial bias (-1
volt for 12SK7), while this set has the cathodes of the RF tubes
grounded.

Yes, that schematic is a very good interview subject.

Don't get foxed by "Mazda." That was a GE trademark from around 1910 to
denote "tungsten filament," and was licensed by other bulb
manufacturers. GE dropped using it in 1945. If you need bulbs, a 1490
is a 1490, readily available today.

If you are going to play the radio without recapping, the critical caps
are the coupling caps between stages, particularly the cap feeding the
audio power amp. Also, check the value of the grid leak resistor(s).
You should see zero volts DC at the grid of the 35L6.

The AA5 (and AA6) are, with the DC-3 airplane, and the GG-1 locomotive,
standout classics of American design. They look "simple" but there's a
lot of thinking that made them robust and reliable without being
complicated.

Hank

Thanks for the detailed explanation. I had a suspicion that the "center
tap" of the rectifier tube was not actually CENTER. The more I work on
these old sets, the more I notice that they are all pretty much the
same, particularly if it's the same brand. One website I looked at, said
that the chassis is a number -xxxx-. (I forget the number, but it was a
4 digit number 10__). I guess that means this same chassis was used in
other RCA radios, not just these 66X_ (1 thru 4) models. But considering
the years they were made, that makes sense. They produced the chassis
and made numerous cabinets to fit around them.

I have to say that I am highly impressed that this 70 year old radio
still works, with it's old caps and all. I have considered recapping it,
or at least the critical caps and the power supply filter caps. But then
again, "if it works, dont fix it". Having it power up with no hum, was
what impressed me most, since the electrolytics are usually bad.

Thanks for explaining that "Mazda". That had me puzzled. In all the
years I have worked on this stuff, that is the first time I saw that
word used. I should have suspected it was a trademark....

That schematic is clearer and better than the one I had, so that will
help too.

On 9/28/2017 10:44 AM, wrote:
I have to say that I am highly impressed that this 70 year old radio
still works, with it's old caps and all. I have considered recapping it,
or at least the critical caps and the power supply filter caps. But then
again, "if it works, dont fix it". Having it power up with no hum, was
what impressed me most, since the electrolytics are usually bad.

Are you stupid, or do you just try to appear to be stupid?

"It works."
Yeah, right up until it doesn't and fries an IF transformer or something
else like one of the vacuum tubes.

A couple of examples:
1. A late '40s vintage Artone AM/FM/Phono console my parents bought new.
It was working when I left home in 1972. I pulled the chassis around
2001 and turned it on. I worked for about 10 minutes and paaaf! one of
the paper caps self-destructed. I replaced that one and tried it again.
This time it lasted 3 minutes and pafff! another paper cap went away.
After I changed the 4th one, I just replaced the remaining ones.'
After another 15 minutes the one of the filter caps self destructed.
I replaced all of them.
The radio sits in my living room and has been working fine for the past
16 years.
2. A Hallicrafters SX-110 general coverage receiver. It looked like new
and had the matching speaker. I set it on the work bench at the shop in
2007. Turned it on, and it worked perfectly. After 20 minutes the audio
slowly dropped to zero. I turned it off to checked what happened. The
filter can was hot enough to fry eggs.
I recapped the radio and gave it to a friend of mine. It's still working
perfectly and is one of his favorite radios.

But, by all means, do whatever you want.
Solid technical advice is wasted on you.



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

On Thu, 28 Sep 2017 16:10:58 -0500, Foxs Mercantile wrote:

On 9/28/2017 10:44 AM, wrote:
I have to say that I am highly impressed that this 70 year old radio
still works, with it's old caps and all. I have considered recapping
it,
or at least the critical caps and the power supply filter caps. But
then again, "if it works, dont fix it". Having it power up with no hum,
was what impressed me most, since the electrolytics are usually bad.

Are you stupid, or do you just try to appear to be stupid?

"It works."
Yeah, right up until it doesn't and fries an IF transformer or something
else like one of the vacuum tubes.

A couple of examples:
1. A late '40s vintage Artone AM/FM/Phono console my parents bought new.
It was working when I left home in 1972. I pulled the chassis around
2001 and turned it on. I worked for about 10 minutes and paaaf! one of
the paper caps self-destructed. I replaced that one and tried it again.
This time it lasted 3 minutes and pafff! another paper cap went away.
After I changed the 4th one, I just replaced the remaining ones.'
After another 15 minutes the one of the filter caps self destructed.
I replaced all of them.
The radio sits in my living room and has been working fine for the past
16 years.
2. A Hallicrafters SX-110 general coverage receiver. It looked like new
and had the matching speaker. I set it on the work bench at the shop in
2007. Turned it on, and it worked perfectly. After 20 minutes the audio
slowly dropped to zero. I turned it off to checked what happened. The
filter can was hot enough to fry eggs.
I recapped the radio and gave it to a friend of mine. It's still working
perfectly and is one of his favorite radios.

But, by all means, do whatever you want.
Solid technical advice is wasted on you.

Jeff was lucky, his capacitors failed quickly while he still had the
radio apart. My experience was different, each one lasted months, so I
ended up taking the set apart numerous times to replace one capacitor
each time. I learned from that, now I replace them all at one go. But
if you like taking things apart repeatedly, that's up to you.

--
Jim Mueller

To get my real email address, replace wrongname with eggmen.
Then replace nospam with expressmail. Lastly, replace com with dk.

On 9/28/2017 5:09 PM, Jim Mueller wrote:
Jeff was lucky, his capacitors failed quickly while he still had the
radio apart. My experience was different, each one lasted months, so I
ended up taking the set apart numerous times to replace one capacitor
each time. I learned from that, now I replace them all at one go.
The Artone was the third set I worked once I decide I was going to play
with old radios. The first was a Signatone code practice oscillator and
every cap and resistor was bad in it. The second was a Columbia phono,
AC/DC/Battery portable with a wind up clockwork mechanism.

After about ten years of playing with vintage tube gear, I opened a shop
to do this for profit. This means when you fix a radio, it has to stay
fixed once it goes out the door.

But if you like taking things apart repeatedly, that's up to you.

"You can't fix stupid."

--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

On 28 Sep 2017 22:09:50 GMT, Jim Mueller wrote:

Jeff was lucky, his capacitors failed quickly while he still had the
radio apart. My experience was different, each one lasted months, so I
ended up taking the set apart numerous times to replace one capacitor
each time. I learned from that, now I replace them all at one go. But
if you like taking things apart repeatedly, that's up to you.

Considering my age, it probably dont matter, but I bet all the modern
caps will fail in far less time than those old paper caps. Nothing these
days is made as well as in the old days. Caps that are still working
after 70 years were not poorly made. I think a lot of that was because
in those days, people had respect for their customers, anad wanted the
name of their company to stand out. That was before our "throw away
society". That is no longer the case.

Add to that, the fact that most caps are now made in China, and I know
they wont last. I try to get all NOS Orange Drop caps. They were made in
the USA and were top of the line. They cost more, but are the only ones
I consider worth buying.