Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Oldtimer question (valves/tubes)

On Tue, 14 May 2019 09:13:37 +1000, Clifford Heath wrote:

On 14/5/19 12:23 am, Cursitor Doom wrote:
On Mon, 13 May 2019 21:52:09 +1000, Lucifer wrote:
What's worth salvaging from old photocopiers? I vaguely recall there's
some exotic goodies in them somewhere.


Perhaps not exotic, but they tend to have a few nice 24V motors.


I was trying to remember what exactly it was last night. I *think*
there's a EHT generator in there to attract the 'soot' to the paper that
can be easily converted into a 60kV taser. But I might easily be
mistaken, so don't quote me on that.





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Default Oldtimer question (valves/tubes)

On Tue, 14 May 2019 17:26:55 +0100, Mike Coon wrote:

Too late; assuming they have not thrown it away, it has been at
Bletchley Park for several years, hopefully supporting their old
computer resusitation projects.

Mike.


I really must get around to visiting that place some time. I've heard
very good reports of it.



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Default Oldtimer question (valves/tubes)

On Monday, May 13, 2019 at 11:50:31 AM UTC-4, Cursitor Doom wrote:
On Mon, 13 May 2019 09:39:11 -0500, Fox's Mercantile wrote:

http://www.junkbox.com/electronics/lowvoltagetubes.shtml


Thanks!


It's a shame that mostly all the links in the project section point to sites that are gone....
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Default Oldtimer question (valves/tubes)

On Monday, May 13, 2019 at 7:13:40 PM UTC-4, Clifford Heath wrote:
On 14/5/19 12:23 am, Cursitor Doom wrote:
On Mon, 13 May 2019 21:52:09 +1000, Lucifer wrote:
What's worth salvaging from old photocopiers? I vaguely recall there's
some exotic goodies in them somewhere.


Perhaps not exotic, but they tend to have a few nice 24V motors.


yes, motors, drive pullies, belts, lead screws, stepper motors, microswitches,
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Default Oldtimer question (valves/tubes)

On 2019/05/14 1:46 p.m., three_jeeps wrote:
On Monday, May 13, 2019 at 11:50:31 AM UTC-4, Cursitor Doom wrote:
On Mon, 13 May 2019 09:39:11 -0500, Fox's Mercantile wrote:

http://www.junkbox.com/electronics/lowvoltagetubes.shtml


Thanks!


It's a shame that mostly all the links in the project section point to sites that are gone....


http://web.archive.org

John ;-#)#

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On Sunday, May 12, 2019 at 7:04:09 AM UTC-4, Cursitor Doom wrote:
Gentlemen,

I've got this RF sig gen I'm testing at the moment. It was made in 1955
and is all valve (I say "all valve" but there are only two tubes in it
and only one of those generates the RF - the other's 400Hz for the
modulation).
Anyway, it has 8 ranges in total covering 100KHz to 240Mhz. The
oscillator tube is a double triode, a 12AT7. One half handles range from
100Khz to 30Mhz and the other takes care of 30 - 240Mhz. Now, it all
works great EXCEPT for one range (the 3rd lowest) which has appreciable
distortion present on the output. It looks a bit like it's being over-
driven on my scope. My question is, does a valve like a 12AT7 require
different DC biasing points for every range of frequencies? Obviously the
range switch is switching in different combinations of coils and
capacitors, but is it likely to be also switching in different cathode-
grid DC biasing at the same time?

TIA


These simple generators were intentionally distorted. They were over driven for three reasons.

The first was to make sure that the output didn't drop out and kill the oscillation at the high end of each band.

The second was to produce harmonics on the higher bands.

The third was to allow the unit to continue to operate as the tube aged. As far as the coils failing, some adsorbed moisture, which lowered their 'Q'.

Often, the 400 or 1,000 Hz tone was distorted, as well due to the lack of AGC. It gave a distinct sound in the receiver being aligned. Look at what HP did in their 606 and 608 series generators to produce a clean signal. They certainly didn't attempt to do it with two tubes!

I remember the low voltage tubes in car radios. They weren't used for very long. It was an attempt to eliminate the Vibrator derived HV plate supply, without using the more expensive transistors of their day. I think that Philco/Ford went that route, while Delco and Motorola went straight to all transistor designs. For used Philco, Bendix and Motorola radios in the '60s and '70a. BTW, Galvin Manufacturing invented the car radio, then they changed their name to Motorola to reflect their main product line.
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Default Oldtimer question (valves/tubes)

On 2019/05/15 6:02 p.m., Michael Terrell wrote:
On Sunday, May 12, 2019 at 7:04:09 AM UTC-4, Cursitor Doom wrote:
Gentlemen,

I've got this RF sig gen I'm testing at the moment. It was made in 1955
and is all valve (I say "all valve" but there are only two tubes in it
and only one of those generates the RF - the other's 400Hz for the
modulation).
Anyway, it has 8 ranges in total covering 100KHz to 240Mhz. The
oscillator tube is a double triode, a 12AT7. One half handles range from
100Khz to 30Mhz and the other takes care of 30 - 240Mhz. Now, it all
works great EXCEPT for one range (the 3rd lowest) which has appreciable
distortion present on the output. It looks a bit like it's being over-
driven on my scope. My question is, does a valve like a 12AT7 require
different DC biasing points for every range of frequencies? Obviously the
range switch is switching in different combinations of coils and
capacitors, but is it likely to be also switching in different cathode-
grid DC biasing at the same time?

TIA


These simple generators were intentionally distorted. They were over driven for three reasons.

The first was to make sure that the output didn't drop out and kill the oscillation at the high end of each band.

The second was to produce harmonics on the higher bands.

The third was to allow the unit to continue to operate as the tube aged. As far as the coils failing, some adsorbed moisture, which lowered their 'Q'.

Often, the 400 or 1,000 Hz tone was distorted, as well due to the lack of AGC. It gave a distinct sound in the receiver being aligned. Look at what HP did in their 606 and 608 series generators to produce a clean signal. They certainly didn't attempt to do it with two tubes!

I remember the low voltage tubes in car radios. They weren't used for very long. It was an attempt to eliminate the Vibrator derived HV plate supply, without using the more expensive transistors of their day. I think that Philco/Ford went that route, while Delco and Motorola went straight to all transistor designs. For used Philco, Bendix and Motorola radios in the '60s and '70a. BTW, Galvin Manufacturing invented the car radio, then they changed their name to Motorola to reflect their main product line.


I thought the first car radio was back in the early 20s....seem to
recall seeing a picture in a magazine or old encyclopedia (I used to
read those for fun as a kid) in the 60s.

The Galvin/Motorola was the first commercially successful radio. Nice to
know where that famous name came from, thanks!

https://en.wikipedia.org/wiki/Vehicle_audio speaks of a car radio in
1924 in NSW, Australia.


John :-#)#
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Default Oldtimer question (valves/tubes)

On Wednesday, May 15, 2019 at 9:38:42 PM UTC-4, John Robertson wrote:
On 2019/05/15 6:02 p.m., Michael Terrell wrote:
On Sunday, May 12, 2019 at 7:04:09 AM UTC-4, Cursitor Doom wrote:
Gentlemen,

I've got this RF sig gen I'm testing at the moment. It was made in 1955
and is all valve (I say "all valve" but there are only two tubes in it
and only one of those generates the RF - the other's 400Hz for the
modulation).
Anyway, it has 8 ranges in total covering 100KHz to 240Mhz. The
oscillator tube is a double triode, a 12AT7. One half handles range from
100Khz to 30Mhz and the other takes care of 30 - 240Mhz. Now, it all
works great EXCEPT for one range (the 3rd lowest) which has appreciable
distortion present on the output. It looks a bit like it's being over-
driven on my scope. My question is, does a valve like a 12AT7 require
different DC biasing points for every range of frequencies? Obviously the
range switch is switching in different combinations of coils and
capacitors, but is it likely to be also switching in different cathode-
grid DC biasing at the same time?

TIA


These simple generators were intentionally distorted. They were over driven for three reasons.

The first was to make sure that the output didn't drop out and kill the oscillation at the high end of each band.

The second was to produce harmonics on the higher bands.

The third was to allow the unit to continue to operate as the tube aged.. As far as the coils failing, some adsorbed moisture, which lowered their 'Q'.

Often, the 400 or 1,000 Hz tone was distorted, as well due to the lack of AGC. It gave a distinct sound in the receiver being aligned. Look at what HP did in their 606 and 608 series generators to produce a clean signal. They certainly didn't attempt to do it with two tubes!

I remember the low voltage tubes in car radios. They weren't used for very long. It was an attempt to eliminate the Vibrator derived HV plate supply, without using the more expensive transistors of their day. I think that Philco/Ford went that route, while Delco and Motorola went straight to all transistor designs. For used Philco, Bendix and Motorola radios in the '60s and '70a. BTW, Galvin Manufacturing invented the car radio, then they changed their name to Motorola to reflect their main product line.


I thought the first car radio was back in the early 20s....seem to
recall seeing a picture in a magazine or old encyclopedia (I used to
read those for fun as a kid) in the 60s.

The Galvin/Motorola was the first commercially successful radio. Nice to
know where that famous name came from, thanks!

https://en.wikipedia.org/wiki/Vehicle_audio speaks of a car radio in
1924 in NSW, Australia.


I had never heard of the 1924 radio. Was it a real car radio, or a battery powered radio installed in a car? I also remember one of the old Roy Rogers TV show episodes with a battery powered radio on a horse that they used to catch the bad guys. I saw that over 50 years ago. ;-)

I remember when Bendix switched from TO-3 output transistors, to TO-220. Despite the warnings not to bend the leads at the case, they did. They had over a double digit failure rate within two months of the cars being sold. They used a tiny daughter board, and mounted it in one of the holes for the original package. They were very ****ty radios.
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On 2019/05/15 7:51 p.m., Michael Terrell wrote:
On Wednesday, May 15, 2019 at 9:38:42 PM UTC-4, John Robertson wrote:
On 2019/05/15 6:02 p.m., Michael Terrell wrote:
On Sunday, May 12, 2019 at 7:04:09 AM UTC-4, Cursitor Doom wrote:
Gentlemen,

I've got this RF sig gen I'm testing at the moment. It was made in 1955
and is all valve (I say "all valve" but there are only two tubes in it
and only one of those generates the RF - the other's 400Hz for the
modulation).
Anyway, it has 8 ranges in total covering 100KHz to 240Mhz. The
oscillator tube is a double triode, a 12AT7. One half handles range from
100Khz to 30Mhz and the other takes care of 30 - 240Mhz. Now, it all
works great EXCEPT for one range (the 3rd lowest) which has appreciable
distortion present on the output. It looks a bit like it's being over-
driven on my scope. My question is, does a valve like a 12AT7 require
different DC biasing points for every range of frequencies? Obviously the
range switch is switching in different combinations of coils and
capacitors, but is it likely to be also switching in different cathode-
grid DC biasing at the same time?

TIA

These simple generators were intentionally distorted. They were over driven for three reasons.

The first was to make sure that the output didn't drop out and kill the oscillation at the high end of each band.

The second was to produce harmonics on the higher bands.

The third was to allow the unit to continue to operate as the tube aged.. As far as the coils failing, some adsorbed moisture, which lowered their 'Q'.

Often, the 400 or 1,000 Hz tone was distorted, as well due to the lack of AGC. It gave a distinct sound in the receiver being aligned. Look at what HP did in their 606 and 608 series generators to produce a clean signal. They certainly didn't attempt to do it with two tubes!

I remember the low voltage tubes in car radios. They weren't used for very long. It was an attempt to eliminate the Vibrator derived HV plate supply, without using the more expensive transistors of their day. I think that Philco/Ford went that route, while Delco and Motorola went straight to all transistor designs. For used Philco, Bendix and Motorola radios in the '60s and '70a. BTW, Galvin Manufacturing invented the car radio, then they changed their name to Motorola to reflect their main product line.


I thought the first car radio was back in the early 20s....seem to
recall seeing a picture in a magazine or old encyclopedia (I used to
read those for fun as a kid) in the 60s.

The Galvin/Motorola was the first commercially successful radio. Nice to
know where that famous name came from, thanks!

https://en.wikipedia.org/wiki/Vehicle_audio speaks of a car radio in
1924 in NSW, Australia.


I had never heard of the 1924 radio. Was it a real car radio, or a battery powered radio installed in a car? I also remember one of the old Roy Rogers TV show episodes with a battery powered radio on a horse that they used to catch the bad guys. I saw that over 50 years ago. ;-)


I think it was more likely a battery radio that someone jammed into a
car. I have a RCA 24 in my collection of early 20's radios that was an
early luggable battery radio. Used a few WD-11s and had two spares in a
holder - I imagine the tubes did not like being bounced around so spares
were really needed!


I remember when Bendix switched from TO-3 output transistors, to TO-220. Despite the warnings not to bend the leads at the case, they did. They had over a double digit failure rate within two months of the cars being sold. They used a tiny daughter board, and mounted it in one of the holes for the original package. They were very ****ty radios.


I had little to do with car radios, mostly I played with home battery
radios as a teenager.

How that led to pinball and jukebox sales and service is a mystery...

(well, not really, I LIKE fixing things!)

John :-#)#
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MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
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www.flippers.com
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Default Oldtimer question (valves/tubes)

On Thursday, 16 May 2019 02:38:42 UTC+1, John Robertson wrote:
On 2019/05/15 6:02 p.m., Michael Terrell wrote:


I remember the low voltage tubes in car radios. They weren't used for very long. It was an attempt to eliminate the Vibrator derived HV plate supply, without using the more expensive transistors of their day. I think that Philco/Ford went that route, while Delco and Motorola went straight to all transistor designs. For used Philco, Bendix and Motorola radios in the '60s and '70a. BTW, Galvin Manufacturing invented the car radio, then they changed their name to Motorola to reflect their main product line.


I thought the first car radio was back in the early 20s....seem to
recall seeing a picture in a magazine or old encyclopedia (I used to
read those for fun as a kid) in the 60s.

The Galvin/Motorola was the first commercially successful radio. Nice to
know where that famous name came from, thanks!

https://en.wikipedia.org/wiki/Vehicle_audio speaks of a car radio in
1924 in NSW, Australia.


John :-#)#


The 1924 radio was experimental. Imagine trying to get stable reception with a mobile positive feedback circuit set to the brink of oscillation, powered by either HT dry batteries or a vibrator PSU. Plus the thing had a huge aerial rig over the car. It wasn't a practical commercial proposition.

Of course you can lose the PFB and have a row of valves, but then your HT battery drain is far worse.


NT


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On Wed, 15 May 2019 18:02:53 -0700, Michael Terrell wrote:

These simple generators were intentionally distorted. They were over
driven for three reasons.

The first was to make sure that the output didn't drop out and kill the
oscillation at the high end of each band.

The second was to produce harmonics on the higher bands.

The third was to allow the unit to continue to operate as the tube aged.
As far as the coils failing, some adsorbed moisture, which lowered their
'Q'.

Often, the 400 or 1,000 Hz tone was distorted, as well due to the lack
of AGC. It gave a distinct sound in the receiver being aligned. Look at
what HP did in their 606 and 608 series generators to produce a clean
signal. They certainly didn't attempt to do it with two tubes!


Very interesting, thanks!



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