Old Power Tubes

[TIMBO]

Hi guys, Got some old power tubes that may have come from a 1950 Stromberg Carlson Organ Amp.
There is no tube type marking that I can find and from photos googled they could be a 6L6 or 6F6.
The OT that was used also hard to tell its type, had a marking that could be OPM 14, if this is whats mark, it could a local Ferguson OT with a primary impedance 6k.

[kde]

I'm sure that i've seen other branded 6V6's that look like that, I have a Brimar 6V6 same shape dark glass etc ?

[kagliostro]

If the OT comes from the same amp of the tubes, I would like to investigate around it

determining the primary impedance and weight (and so power) may be of some help on identifying the tubes

Franco

[PRR]

An octal Cunningham without the RCA meatball is odd.

Measure the heater current. 6L6 will be 0.9A, 6V6 will be 0.45A, 6F6 is 0.7A. 6K6 is 0.4A, but I don't see any clue that 6K6 was made coke-bottle.

[TIMBO]

Thanks guys, The local guys say this amp was part of a KIT published in a magazine (Radio,Tv and Hobbies in 1962) build your own electric organ. So the power tubes may have been a "on hand" as it looks like there has been some modding of the layout.
Most of the Ferguson OT were fairly standard with 6k/8k primary and 15,7.5,3.5 and 2 ohm secondary, but this one has a couple of extra taps 
I did a trace of the PI and power amp and there wasn't anything out of the ordinary circuit wise. Thanks

[PRR]

Wait-- this is Australia? Then Cunningham/no-RCA may be "normal".

RCA had a fair tube-business in the east (US). Cunningham built a killer unlicensed tube business in the west. When they ran into each other's turf and licenses, the result is RCA bought Cunningham's operation, gave him a Vice-President's job, and sold tubes under both names, usually both-in-one. This was 1920s, well before the Octal.

But licenses and brand-names would be different in Australia. Maybe Radio Corp of America was not a popular brand outside America, whereas "Cunningham" could be an Australian senator or footballer.

[mresistor]

Those look like my 1957 6L6G's so I am pretty sure that is what they are. Look like rebranded RCAs.

http://www.ebay.com/itm/Cunningham-6L6G-Grey-Glass-Date-Code-739-Tube-TV7-Tested-/381125508980?nma=true&si=ZoQXv6lfo%252FSzGptc60k%252Fd8qz59E%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

[TIMBO]

Thanks PRR, I was able to get a better pic of the type, OPM14 and the specs are  http://www.retrovox.com.au/ferguson.pdf which explains the extra taps.

[darryl]

"Cunningham" could be an Australian senator or footballer.

Unlikely. Any Australian product named after a politician ( or footballer ) would have a credibility problem. Although we do have "Menzies" Hotels, named after a former Prime Minister.   

RCA had a number of licensing arrangements with Amalgamated Wireless Australasia ( AWA ), so many RCA products had Australian made equivalents. This included valves, which were branded AWV - Amalgamated Wireless Valve. AWV also had the rights to the "Radiotron" brand in Australia. Timbo's Cunningham valves are very likely an import, unless AWV also had the rights to use the Cunningham brand.

An aside. The Radiotron Designers Handbook was originally published by AWV, and subsequently republished by RCA in the US.

[mresistor]

"Cunningham" could be an Australian senator or footballer.

An aside. The Radiotron Designers Handbook was originally published by AWV, and subsequently republished by RCA in the US.

Darryl - that's an interesting tidbit...   

[HotBluePlates]

I'm sure that i've seen other branded 6V6's that look like that ...

... I don't see any clue that 6K6 was made coke-bottle.

Those look like my 1957 6L6G's so I am pretty sure that is what they are.

The "6- ___" codes are date codes; could be 1946 or 1956 or 1966. In the 40's the tubes would have likely been metal-envelope for 6L6 and 6V6 (though I suppose glass 6L6 probably existed). In 1966 the tubes would have been straight-sided glass bottles of the "GT" variety. So we can guess 1956 as the year for these (which coincides with the smoked glass).

I have coke-bottle 6K6's among my unreasonably-large batch of 6K6 tubes, so it could be 6K6G or 6V6G or 6L6G. So measure the height and width of the tube. The 6K6G's I have are shorter and narrower than 6V6G, and both smaller than 6L6G. I'm pretty sure I can look up the proper "outline" in an RCA manual for each type, and see which dimension matches your tube. We can probably tell you with a good measure of confidence which tube it is.

[TIMBO]

Hi HBP,From top of glass to bottom of base(not pins)4.5" and at the widest 2".Thanks

[HotBluePlates]

Looking through RCA manuals, I see where PRR figured the 6K6 never came in the ST envelope... All the way back to a 1948 manual, it shows the straight GT bottle (but I don't think my coke bottle 6K6's are older than late-40's).

Anywho, the ST16 bottle is 4-9/16" tall, not counting pins. Close enough to your 4.5" and that makes your tubes 6L6G's.

[mresistor]

Actually my RCA 6L6Gs are both from 5-22 so that would be 1955. They are out of a Baldwin organ that is from late 56 or 57.

[TIMBO]

Thanks guys,The tubes had a cathode bypass of 240/25u so I will set up the biasing around these values as the OT is rated 35w. Just a nice size output.Thanks

[PRR]

> the OT is rated 35w

If you are "sure" these bottles go with that OT, this is a strong clue they are not 6K6 or 6V6 or any other small tube that can hardly muster a dozen Watts a pair.  A 35W OT would be much more money and likely special order; whereas 10W-15W OTs were common and cheaper. Of the likely suspects in an RCA-dominated land, 35W is sure 6L6 territory.

[TIMBO]

There is very little info on any vintage stuff here in oz and the biggest problem I see is "anything goes" and because of this there is a high mortality rate of PT and OT.

[kde]

TIMBO....does this look like what you have ?

[TIMBO]

THATS AWSOME,I look every where for info, WELL done.

[sluckey]

I don't think those coke bottle tubes will fit that SC chassis?

[TIMBO]

This is how it looked http://www.ebay.com.au/itm/VALVE-POWER-AMPLIFIER-FROM-VINTAGE-ORGAN-1950s-/281558470468?nma=true&si=meYIhzQByJf3g%252BljZJu%252BOjoqs%252Bg%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

[sluckey]

I guess they will fit. 

[TIMBO]

Hey Sluckey, I bought it mainly for parts.
As you can see the transformers are different.
The PT only has 2xHT and 2xhearters.
Now that I know the PT specs should be able to build something nice, IF..............

There is quite a lot of taps on the secondary side.
RED,BLACK,BROWN,ORANGE, these are connected as there is continuity between them.
GREEN,YELLOW,BLUE, ORANGE(thin) again these have continuity.
The BLACK and RED were connected to the speaker jack and the rest were taped off, Although the two ORANGE were twisted together but not soldered.
I would have thought that if the BLACK was - and RED was + there would be a DC resistance, but I'm not getting a reading.

[HotBluePlates]

... RED,BLACK,BROWN,ORANGE, these are connected as there is continuity between them.
...
I would have thought that if the BLACK was - and RED was + there would be a DC resistance, but I'm not getting a reading.

Dunno what you mean. Infinity ohms or zero ohms?

[TIMBO]

Hi HBP, With a working transformer, if I measure between black- and green(8ohm tap)I get .9ohms and black and yellow(16ohm) I get 1.2ohms.
I don't know if this is a way to check the health of a OT.

[HotBluePlates]

I meant you said red & black showed continuity, then said "no reading" between them. What did you mean by "no reading"?

[darryl]

I look every where for info

You should acquire a copy of "Radio Television & Hobbies on DVD-ROM" It contains scans of every issue of RTV&H from April 1939 to March 1965.

http://www.siliconchip.com.au/Shop/3

[TIMBO]

HBP, By NO reading I mean no DC resistance. I get a continuity 'BEEP"thats it

[HotBluePlates]

What resistance do you read between one of those leads and every other lead with continuity? The idea is to figure if it's just a very small resistance between those 2, with some sensible relationship to the other taps.

[TIMBO]

There is on resistance reading unless its under 1ohm as my MM first setting is 0-200ohm in either group.

[HotBluePlates]

Ok, now I get it. Given your result, the answer I was looking for was "0Ω" because "no resistance" is ambiguous (some say that and mean "0Ω" while others say it and mean "∞Ω"). Sorry for being difficult.

There are 2 ways to proceed: either find a Ferguson catalog which might show the winding arrangement, or apply an a.c. voltage to the primary and measure voltages present among the various secondary wires.

For the 2nd method, a voltage increase of √2 between successive taps indicates a 2x increase of impedance. Your results so far suggest 2 secondary windings intended for either series or parallel connection, possibly to allow for different primary:secondary impedance ratios, but other than connecting the 2 orange wires (for a possible series-secondary arrangement) we have no info on how to hook up the OT.

Since the impedance taps claimed in your price list are 2Ω, 3.7Ω, 8Ω, 15Ω you should expect a little less than a 1.4-times increase in voltage between successive taps. You might wind up identifying the red-black portion of the secondary winding as shorted; a voltage test would tell you for sure.

[TIMBO]

Thanks HBP, With approx. 6.1v AC connected to the two YELLOW primary leads and using the BLACK as COMMON, the following.....
RED - .127v
ORANGE - .140v
BROWN - .105v

YELLOW - .210v
BLUE - .165v
GREEN - .580v
ORANGE(thin) - .271v

[HotBluePlates]

One more test, mostly due to curiosity: Use the green lead as common, and measure resistance to all other leads (no connection between any leads). What do you get?

[TIMBO]

Sorry HBP. That green should have been .085v 

[TIMBO]

Hi guys, I am able to confirm the tubes are 6L6G. There was no visible markings on the glass and other similar looking tubes had the marking above the "C" of Cunningham.
I was told the trick was to put the tube in the freezer for a bit then BREATH on the area and this will reveal the marking.
It did kinda work and I was able to confirm that there was an original marking.
After a few goes I was able to see the marking but the "G" could be a "C" but I could not find a "6L6C" so i'll take it as a "G". Thanks

[HotBluePlates]

This is a puzzle with too many variables. 

Can you do the resistance measurements? I want to figure out for certain if we're dealing with 2 separate coils, or multiple taps on a single coil.

Why? I found a Ferguson catalog which has an OPM14 on page 4, which offers 6 different secondary impedances. If you do have 2 different coils, the voltage measurements using a single lead are invalid for the 2nd coil (you'd need a lead from that coil to get voltage ratios among the taps).

The argument against the 6-impedance taps is that you have 8 leads, implying 7 impedances if they're all on 1 coil. If there are 2 coils, and 2 wires to connect to place coils in series, then 6 impedance taps would make sense.

So far, I find several sets of taps have voltage ratios which fit the load impedance ratios: In a nutshell, the sequence 2 - 3.1 - 3.7 has the same jumps in impedance (ratio of higher to lower) as the sequence 8 - 12.5 - 15. So there is one pair of leads which have voltage ratios between them which could represent a 3.1Ω-to-3.7Ω jump or a 12.5Ω-to-15Ω jump. There are 2 pairs of leads with voltage ratios which could represent a 2Ω-to-3.1Ω jump or an 8Ω-to-12.5Ω jump.

If there are 2 separate coils, and the voltages are known for each tap with respect to the common lead for that coil, then I could probably figure out if there is a non-obvious connection between the coils, as in Hammond's 1600 series OT's.

[TIMBO]

HBP,Trying to find a answer in the transformer itself.
The black - 2 conductors - 0v common
      brown - 4 conductors - .105v 2 pair continuous loop (this  means that 1 pair is a single wire that is returned on itself)
      red - 4 conductors - .129v 2 pair continuous loop
      orange - 2 conductors - .143v

     blue - 1 conductor - 0v common
     green - 2 conductors - .027 1 pair continuous loop
     yellow - 2 conductors - .077 I pair continuous loop
     orange - 1 conductor - .143 
These are the TWO groups that ARE NOT connected to each other.
It appears that the top winding may be two strands that are wound together and the brown and red taps (4 conductors in a plastic sleeve) are twisted together
The black and orange are two single wires (in a sleeve) that are not loop
The blue is a single wire (in a sleeve)
Green and yellow are single strand in a continuous loop each in a sleeve
Orange is a single strand but NOT in a sleeve, is insulated wire
When I got this the only two wires used were black and red.
And the two orange were twisted together and taped.
SO, connecting the two orange together I now get
Yellow - .209v
Green - .260v
Blue - .286v
Hope this helps Thanks

[TIMBO]

Hi guys, I was having a think about this again and I had a Hammond universal OT that has multiple tap arrangements.http://www.hammondmfg.com/125.htm
Looking at the chart at the speaker ohms, say 8 there is a number of different tap arrangements for the primary load.
Looking at the particular part of the secondary winding at certain plate loads there is some loads that only use a small section of the winding, so I am starting the think that using the RED and BLACK as it was when I got it is the winding section that is probably the winding I need to use??????

[Greenmachine]

For what it's worth, I had a stormberg Carlson pa with those tubes that were 6l6s

[TIMBO]

Hi Greemachine, I have solved the valve mystery. The OT has me stumped, do you have any info on how the secondary wiring is configured. Thanks

[TIMBO]

Hi guys, Thanks To K for this http://el34world.com/Forum/index.php?topic=18637.0

I have followed this procedure and hopefully I can determine the secondary to this OT.

The OT has two primary's Orange and Yellow, With MM I get
RED (CT) - ORANGE 76.8ohm and 71.4ohm
ORANGE - ORANGE 148.4ohm
RED (CT) - YELLOW 78.0ohm and 84.7ohm
YELLOW - YELLOW 162.8ohm
The SECONDRY has 8 taps BLACK,BROWN,RED,ORANGE, ORANGE(single strand) YELLOW,GREEN and BLUE. The first four seem to be one winding and the second a separate.
When taking the first readings the first four they looked to be with reason of the amount of turns there should be, but the second winding were all over the place. When I got this amplifier the two yellows were connected(twisted not soldered)
When I got this OT the only clues to the PRIMARY and SECONDRY connections was the Yellow primary's were connected to the power tubes and the BLACK and RED secondary's.
Both the PT and OT are NOT as per the original amplifier and this one had 6L6s and the original had 6CA7s
I was able to find the OTs specs but NOT the wiring colour code.

I made a 9v ac PSU for testing this procedure and I hoping I have got if right, I took the readings with the TWO windings in SERIES.
Using this to calculate :-
9.7vac to yellow (orange)primary's
9.7/volts=TURNS,TURNS SQUARD=Z, ZxSPEAKER LOAD= plate RESISTANCE, match this to PRIMARY IMPEDENCE 
So could any confirm my findings :-
YELLOW-YELLOW :-8000ohms
ORANGE - ORANGE :-6600ohms
BLACK - 0 (common)
Brown - 2
RED    - 3.1
ORANGEx2 - 3.7
YELLOW - 8
GREEN - 12.5
BLUE - 15