Anyone recognise this ancient CRO?

[Bob Parker]

A bloke's contacted me in the hope that I might know something about a
simple oscilloscope his late father built many years ago. It's got a 2"
RCA CRT and only four (octal) valves.

I've uploaded the photo he sent me, to
http://members.ozemail.com.au/~bobpar/CRO.JPG

One of the visible valves looks like it could be a 5Y3G and another a
6J7G. A lot of the visible capacitors look like those yellow Philips
polyester(?) ones from the 1960s but his father quite likely replaced
original waxed papers caps with them.

Does anyone recognise it?



Cheers,
Bob

 

[Rodwell]

On 5/07/2013 11:11 AM, Bob Parker wrote:

A bloke's contacted me in the hope that I might know something about a
simple oscilloscope his late father built many years ago. It's got a 2"
RCA CRT and only four (octal) valves.

I've uploaded the photo he sent me, to
http://members.ozemail.com.au/~bobpar/CRO.JPG

One of the visible valves looks like it could be a 5Y3G and another a
6J7G. A lot of the visible capacitors look like those yellow Philips
polyester(?) ones from the 1960s but his father quite likely replaced
original waxed papers caps with them.

Does anyone recognise it?



Cheers,
Bob

Perhaps it is one of the designs that were in the ARRL Handbook 30 - 35
years ago.

 

[Don McKenzie]

On 05-Jul-13 4:28 PM, Rodwell wrote:

On 5/07/2013 11:11 AM, Bob Parker wrote:
A bloke's contacted me in the hope that I might know something about a
simple oscilloscope his late father built many years ago. It's got a 2"
RCA CRT and only four (octal) valves.

I've uploaded the photo he sent me, to
http://members.ozemail.com.au/~bobpar/CRO.JPG

One of the visible valves looks like it could be a 5Y3G and another a
6J7G. A lot of the visible capacitors look like those yellow Philips
polyester(?) ones from the 1960s but his father quite likely replaced
original waxed papers caps with them.

Does anyone recognise it?



Cheers,
Bob


Perhaps it is one of the designs that were in the ARRL Handbook 30 - 35 years ago.

I believe it dates back a lot further than that

have a look at examples from the 30s through to the 50s.
http://www.myvintagetv.com/vintage_test_equipment.htm

some brand names, some home brew diy.

Cheers Don...


--
Don McKenzie

$30 for an Olinuxino Linux PC:
http://www.dontronics-shop.com/olinuxino.html

The World's Cheapest Computer:
DuinoMite the PIC32 $25 Basic Computer-MicroController
http://www.dontronics-shop.com/the-maximite-computer.html
Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
Arduino Shield, Programmed in Basic, or C.

 

[Phil Allison]

"Bob Parker"

A bloke's contacted me in the hope that I might know something about a
simple oscilloscope his late father built many years ago. It's got a 2" RCA
CRT and only four (octal) valves.

I've uploaded the photo he sent me, to
http://members.ozemail.com.au/~bobpar/CRO.JPG

** Bloody heck !!

The chassis looks like something Radio & Hobbies mag could have published
circa 1940 - then, in the early 70s, it was refurbished with new hardware
& film caps.

The AC tranny must be remote, to keep 50Hz mag fields away from the CRT.

Many details remind me of my own Electronics Australia, 3 inch CRO from May
1966 - but that has 5 x 9 pin valves, all of them twin section, plus
silicon diodes. It has the same knobs as that black one down the bottom.

One of the visible valves looks like it could be a 5Y3G and another a
6J7G. A lot of the visible capacitors look like those yellow Philips
polyester(?) ones from the 1960s but his father quite likely replaced
original waxed papers caps with them.

** How can you even make a CRO with just four single valves ?

Is the CRT a 2AP1 ??

Does anyone recognise it?

** I doubt anyone alive still does.



..... Phil

 

[keithr]

On 5/07/2013 5:51 PM, Phil Allison wrote:

"Bob Parker"

A bloke's contacted me in the hope that I might know something about a
simple oscilloscope his late father built many years ago. It's got a 2" RCA
CRT and only four (octal) valves.

I've uploaded the photo he sent me, to
http://members.ozemail.com.au/~bobpar/CRO.JPG


** Bloody heck !!

The chassis looks like something Radio & Hobbies mag could have published
circa 1940 - then, in the early 70s, it was refurbished with new hardware
& film caps.

The AC tranny must be remote, to keep 50Hz mag fields away from the CRT.

Many details remind me of my own Electronics Australia, 3 inch CRO from May
1966 - but that has 5 x 9 pin valves, all of them twin section, plus
silicon diodes. It has the same knobs as that black one down the bottom.


One of the visible valves looks like it could be a 5Y3G and another a
6J7G. A lot of the visible capacitors look like those yellow Philips
polyester(?) ones from the 1960s but his father quite likely replaced
original waxed papers caps with them.

** How can you even make a CRO with just four single valves ?

Yep less actually, we had to make one as an exercise in our apprentice
scheme. It had a DG7 tube; two EF91s , and a rectifier, possibly a 6X7.
The EHT rectifier was a selenium one. It wasn't exactly a Tektronix.

We would have definitely got a failing mark though if it looked like that.

http://www.thevalvepage.com/testeq/homebrew/no1/no1.htm

Is the CRT a 2AP1 ??

Does anyone recognise it?


** I doubt anyone alive still does.



.... Phil

 

[Bob Milutinovic]

"Don McKenzie" <5V@2.5A> wrote in message
news:b3n8v5Fnnd5U1@mid.individual.net...

On 05-Jul-13 4:28 PM, Rodwell wrote:
On 5/07/2013 11:11 AM, Bob Parker wrote:
A bloke's contacted me in the hope that I might know something about a
simple oscilloscope his late father built many years ago. It's got a 2"
RCA CRT and only four (octal) valves.

I've uploaded the photo he sent me, to
http://members.ozemail.com.au/~bobpar/CRO.JPG

One of the visible valves looks like it could be a 5Y3G and another a
6J7G. A lot of the visible capacitors look like those yellow Philips
polyester(?) ones from the 1960s but his father quite likely replaced
original waxed papers caps with them.

Does anyone recognise it?



Cheers,
Bob


Perhaps it is one of the designs that were in the ARRL Handbook 30 - 35
years ago.

I believe it dates back a lot further than that

Indeed. I got a start in electronics about 35 years ago and by then valves
had well and truly disappeared from the hobbyist scene (yes, there were a
very few devices still being made using valves, but easily 99% of all kits
and published schematics were solid-state).

I'd say it'd easily date back to the 50s, possibly earlier - though
hobbyists were still building their own oscilloscopes in the '60s, by then
there were far better CRTs available, for likely an equal or lower price
than the older models. This page shows three RCA CRTs which are similar in
appearance to the one used, and all were released during the '40s;
http://aade.com/tubepedia/1collection/tubepedia2.htm

have a look at examples from the 30s through to the 50s.
http://www.myvintagetv.com/vintage_test_equipment.htm

some brand names, some home brew diy.

Cheers Don...

--
Bob Milutinovic
Cognicom

 

[Don McKenzie]

On 5/07/2013 5:51 PM, Phil Allison wrote:

We would have definitely got a failing mark though if it looked like that.

It starting to look like a chassis that had holes drilled-punched for yet another project, and with the above chassis
components, I would doubt that it was a kit of any description.

Possibly home brew from just a schematic.
I remember buying my first transistor in 1959? so I figure a valve CRO could be anywhere from about 1935 to 1965.

CRO tube could have been war surplus, maybe even an ex radar part.

Don...


--
Don McKenzie

$30 for an Olinuxino Linux PC:
http://www.dontronics-shop.com/olinuxino.html

The World's Cheapest Computer:
DuinoMite the PIC32 $25 Basic Computer-MicroController
http://www.dontronics-shop.com/the-maximite-computer.html
Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
Arduino Shield, Programmed in Basic, or C.

 

[Andy Wood]

Don McKenzie <5V@2.5A> wrote:

On 5/07/2013 5:51 PM, Phil Allison wrote:

We would have definitely got a failing mark though if it looked like that.

It starting to look like a chassis that had holes drilled-punched for yet another project, and with the above chassis
components, I would doubt that it was a kit of any description.

Possibly home brew from just a schematic.
I remember buying my first transistor in 1959? so I figure a valve CRO could be anywhere from about 1935 to 1965.

CRO tube could have been war surplus, maybe even an ex radar part.

I remember seeing several DIY 'scope designs base on WWII surplus
tubes, particularly the VCR139A . By the mid 1960's when I could
afford to build something like that, VCR139As were getting scarce, but
I did manage to find one somewhere, to use in a design from one of the
UK mags. I think is was from PE, the original mag is probably still
buried in a box here, if only I knew which box...

I used the DIY scope for a few years, but when I got some money for my
21st birthday, I blew the lot on a 10MHz Philips PM3200. I gave the
still working DIY scope to somebody else in 1979.

The PM3200? It is now over 40 years old and I still use it
occasionally. Besides the CRT it has one tube, ECC83, which has only
been replaced once. I also had to replace the bridge rectifier in the
power supply, and the BNC socket on the front panel which simply wore
out.


Andy Wood
woodag@trap.ozemail.com.au

 

[Phil Allison]

On 5/07/2013 5:51 PM, Phil Allison wrote:

We would have definitely got a failing mark though if it looked like that.

** No I didn't.


..... Phil

 

[Bob Parker]

On 5/07/2013 16:55 Don McKenzie wrote:

On 05-Jul-13 4:28 PM, Rodwell wrote:
On 5/07/2013 11:11 AM, Bob Parker wrote:
A bloke's contacted me in the hope that I might know something about a
simple oscilloscope his late father built many years ago. It's got a 2"
RCA CRT and only four (octal) valves.

I've uploaded the photo he sent me, to
http://members.ozemail.com.au/~bobpar/CRO.JPG

One of the visible valves looks like it could be a 5Y3G and another a
6J7G. A lot of the visible capacitors look like those yellow Philips
polyester(?) ones from the 1960s but his father quite likely replaced
original waxed papers caps with them.

Does anyone recognise it?



Cheers,
Bob


Perhaps it is one of the designs that were in the ARRL Handbook 30 -
35 years ago.

I believe it dates back a lot further than that

have a look at examples from the 30s through to the 50s.
http://www.myvintagetv.com/vintage_test_equipment.htm

some brand names, some home brew diy.

Cheers Don...

Thanks for the link Don.

The RCA model 151 from 1936 onwards is pretty well described in its
advertisement at
http://www.myvintagetv.com/oscilloscopes/rca_151_adv.jpg It too has
four valves in it, namely a pair of 6C6 + an 80 + an 885 thyratron for
the timebase. The RCA 151-2 CRO is the same except it's got a 2AP1 CRT.

The one in the picture I was sent looks like it's got a 6J7G which has
similar characteristics to the 6C6 + either an 80 or its octal
equivalent 5Y3G, and what looks like a thyratron on the other side.
Quite likely the valve we can't see is another 6J7G.

Maybe this bloke's late father cloned the RCA 151-2 design onto a
chassis he originally made for something else? I wonder where he got the
power transformer from.

Thanks everyone for all your helpful replies. Did you see the specs for
the RCA 151 in the ad?


1.75V RMS for 'full scale deflection'

Flat response from 30Hz - 10kHz

Timebase 30Hz - 10KHz


Things have changed a bit since then.


Cheers,
Bob

 

[Bob Parker]

On 5/07/2013 17:51 Phil Allison wrote:

"Bob Parker"

A bloke's contacted me in the hope that I might know something about a
simple oscilloscope his late father built many years ago. It's got a 2" RCA
CRT and only four (octal) valves.

I've uploaded the photo he sent me, to
http://members.ozemail.com.au/~bobpar/CRO.JPG


** Bloody heck !!

The chassis looks like something Radio & Hobbies mag could have published
circa 1940 - then, in the early 70s, it was refurbished with new hardware
& film caps.

The AC tranny must be remote, to keep 50Hz mag fields away from the CRT.

Many details remind me of my own Electronics Australia, 3 inch CRO from May
1966 - but that has 5 x 9 pin valves, all of them twin section, plus
silicon diodes. It has the same knobs as that black one down the bottom.


One of the visible valves looks like it could be a 5Y3G and another a
6J7G. A lot of the visible capacitors look like those yellow Philips
polyester(?) ones from the 1960s but his father quite likely replaced
original waxed papers caps with them.

** How can you even make a CRO with just four single valves ?

Is the CRT a 2AP1 ??

Does anyone recognise it?


** I doubt anyone alive still does.



.... Phil

I wouldn't have thought so either, but it is possible to make a CRO with
only four valves.

Have a look at the schematic of the RCA 151 which looks a lot like the
one I've been asked about, at
http://www.hgsitebuilder.com/files/writeable/uploads/hostgator629582/image/rca151-2schematic.jpg


Bob

 

[keithr]

On 6/07/2013 6:41 AM, Don McKenzie wrote:

On 5/07/2013 5:51 PM, Phil Allison wrote:

We would have definitely got a failing mark though if it looked like
that.

It starting to look like a chassis that had holes drilled-punched for
yet another project, and with the above chassis components, I would
doubt that it was a kit of any description.

Possibly home brew from just a schematic.
I remember buying my first transistor in 1959? so I figure a valve CRO
could be anywhere from about 1935 to 1965.

CRO tube could have been war surplus, maybe even an ex radar part.

When I was a kid and TVs were rare luxury items, the guy from up the
road who was a radar tech built his own. He used a CRT from a radar
display, interesting picture, bright green and the persistence turned
any moving object into a smear across the screen.

 

[Phil Allison]

"Bob Parker"

Have a look at the schematic of the RCA 151 which looks a lot like the one
I've been asked about, at
http://www.hgsitebuilder.com/files/writeable/uploads/hostgator629582/image/rca151-2schematic.jpg

** Positive ground system with the 6.3V heater run left floating = OK.

CRT plates near ground or grounded with the cathode linked to the floating
6.3V supply ?

Most CROs have high, negative voltages applied to the cathode, but this is
whacky.



..... Phil

 

[Bob Parker]

On 7/07/2013 01:14 Phil Allison wrote:

"Bob Parker"

Have a look at the schematic of the RCA 151 which looks a lot like the one
I've been asked about, at
http://www.hgsitebuilder.com/files/writeable/uploads/hostgator629582/image/rca151-2schematic.jpg


** Positive ground system with the 6.3V heater run left floating = OK.

CRT plates near ground or grounded with the cathode linked to the floating
6.3V supply ?

Most CROs have high, negative voltages applied to the cathode, but this is
whacky.



.... Phil

It looks like the CRT cathode + one side of the 6.3V heater supply (CRT
pin 2) connects back to the bottom end of the Intensity pot. I was
starting to wonder how it could work...

 

[Don McKenzie]

On 06-Jul-13 8:03 PM, keithr wrote:

On 6/07/2013 6:41 AM, Don McKenzie wrote:
On 5/07/2013 5:51 PM, Phil Allison wrote:

We would have definitely got a failing mark though if it looked like
that.

It starting to look like a chassis that had holes drilled-punched for
yet another project, and with the above chassis components, I would
doubt that it was a kit of any description.

Possibly home brew from just a schematic.
I remember buying my first transistor in 1959? so I figure a valve CRO
could be anywhere from about 1935 to 1965.

CRO tube could have been war surplus, maybe even an ex radar part.

When I was a kid and TVs were rare luxury items, the guy from up the road who was a radar tech built his own. He used a
CRT from a radar display, interesting picture, bright green and the persistence turned any moving object into a smear
across the screen.

I saw part of the 56 Olympic games in a techs shop window in Williams road Windsor (Vic) on a 5" green ex radar tube.

Don...

--
Don McKenzie

$30 for an Olinuxino Linux PC:
http://www.dontronics-shop.com/olinuxino.html

The World's Cheapest Computer:
DuinoMite the PIC32 $25 Basic Computer-MicroController
http://www.dontronics-shop.com/the-maximite-computer.html
Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
Arduino Shield, Programmed in Basic, or C.

 

[Don McKenzie]

On 05-Jul-13 1:11 PM, Bob Parker wrote:

A bloke's contacted me in the hope that I might know something about a simple oscilloscope his late father built many
years ago. It's got a 2" RCA CRT and only four (octal) valves.

I've uploaded the photo he sent me, to http://members.ozemail.com.au/~bobpar/CRO.JPG

One of the visible valves looks like it could be a 5Y3G and another a 6J7G. A lot of the visible capacitors look like
those yellow Philips polyester(?) ones from the 1960s but his father quite likely replaced original waxed papers caps
with them.

Does anyone recognise it?



Cheers,
Bob

Bob,
Sean Clarke from the back shed forum, provided this link:
http://members.melbpc.org.au/~sean/Famparc/RTnH_1963_-_Fully_Calibrated_Oscilloscope.pdf

A pdf of the CRO project Jim Rowe did in 1963 in R, TV & H

Cheers Don...


--
Don McKenzie

$30 for an Olinuxino Linux PC:
http://www.dontronics-shop.com/olinuxino.html

The World's Cheapest Computer:
DuinoMite the PIC32 $25 Basic Computer-MicroController
http://www.dontronics-shop.com/the-maximite-computer.html
Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
Arduino Shield, Programmed in Basic, or C.

 

[Phil Allison]

"Bob Parker"

Phil Allison wrote:
"Bob Parker"

Have a look at the schematic of the RCA 151 which looks a lot like the
one
I've been asked about, at
http://www.hgsitebuilder.com/files/writeable/uploads/hostgator629582/image/rca151-2schematic.jpg


** Positive ground system with the 6.3V heater run left floating = OK.

CRT plates near ground or grounded with the cathode linked to the
floating
6.3V supply ?

Most CROs have high, negative voltages applied to the cathode, but this
is
whacky.


It looks like the CRT cathode + one side of the 6.3V heater supply (CRT
pin 2) connects back to the bottom end of the Intensity pot. I was
starting to wonder how it could work...

** Despite being a 1.5MB jpeg, that scan has low resolution so the existence
of dots is ambiguous.

BTW:

I once paid $25 for a service manual ( a B&W booklet ) with multiple
schematics that lacked ANY dots - when the manual was prepared somehow
they all failed to print.

The manual was for the EV " 2.0kW" power amplifier featuring dual SMPSs and
an unusually high component count.

It was real fun trying to work out where the dots should be and put them
in....


..... Phil

 

[Bob Parker]

On 7/07/2013 12:03 Phil Allison wrote:

"Bob Parker"
Phil Allison wrote:
"Bob Parker"

Have a look at the schematic of the RCA 151 which looks a lot like the
one
I've been asked about, at
http://www.hgsitebuilder.com/files/writeable/uploads/hostgator629582/image/rca151-2schematic.jpg


** Positive ground system with the 6.3V heater run left floating = OK.

CRT plates near ground or grounded with the cathode linked to the
floating
6.3V supply ?

Most CROs have high, negative voltages applied to the cathode, but this
is
whacky.


It looks like the CRT cathode + one side of the 6.3V heater supply (CRT
pin 2) connects back to the bottom end of the Intensity pot. I was
starting to wonder how it could work...


** Despite being a 1.5MB jpeg, that scan has low resolution so the existence
of dots is ambiguous.

BTW:

I once paid $25 for a service manual ( a B&W booklet ) with multiple
schematics that lacked ANY dots - when the manual was prepared somehow
they all failed to print.

The manual was for the EV " 2.0kW" power amplifier featuring dual SMPSs and
an unusually high component count.

It was real fun trying to work out where the dots should be and put them
in....


.... Phil

The mid-1970s Yamaha service manual circuit diagrams had random dots and
errors galore in them. Whoever drew them didn't have the slightest
knowledge of electronics. I'd often waste more time trying to work out
what was really connected to what, than finding the cause of the fault.

 

[Bob Parker]

On 7/07/2013 11:52 Don McKenzie wrote:

I saw part of the 56 Olympic games in a techs shop window in Williams
road Windsor (Vic) on a 5" green ex radar tube.

Don...

I remember a bloke in the early 1960s who built a TV using a 5BP1 CRT,
complete with a beautiful black and green picture. Who said we didn't
have colour TV until 1975?


Bob

 

[Bob Parker]

On 7/07/2013 11:56 Don McKenzie wrote:

Bob,
Sean Clarke from the back shed forum, provided this link:
http://members.melbpc.org.au/~sean/Famparc/RTnH_1963_-_Fully_Calibrated_Oscilloscope.pdf


A pdf of the CRO project Jim Rowe did in 1963 in R, TV & H

Cheers Don...

Thanks, Don. I hadn't looked at that site for a while. The CRO looks
like the 1963 unit Phil built.

I've gotta say that Jim Rowe is one incredibly knowledgeable bloke and
he's still going >50 years later.


Bob