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 Post subject: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 3:46 pm 
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I have a rogers majestic 6m531 radio with a tube line up of 80 6f6m 75m 6k7m and 6a7m according to schematic. In the spot of 75m is a tube with no markings and has a 8 pin socket base so what tube would it be? Thanks from a0e 1k0 nl Canada.


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 6:13 pm 
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Location: Bothell, WA
Looking at the Rogers tube conversion document I found I see this.
75M -6Q7G or 6B6G

Hope this helps. If you would like a copy of the word doc send me an email and I'll get it to you.

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Chris

Looking for mid to late 1930s Canadian Rogers, Majestic, and DeForest Crosley radios


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 6:57 pm 
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My problem is the 75m socket has a 8 pin base instead of a 6 pin base for a 75 tube.


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 7:02 pm 
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If you look up the tubes Chris cited, you'll see they are both octal.

Does the set look modified? If not, it is totally plausible that this was a factory change. EDIT--since several other tubes are octal, it is plausible that they started the run with 75s--until their inventory was used up, and then switched to an octal.

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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 7:20 pm 
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It looks like a original octal base so what tube would replace a 75.


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 7:25 pm 
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Chris already told you that!!

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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 7:31 pm 
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So how would I tell if it is a 6q7 or 6b6 to test it thanks.


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 7:36 pm 
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First, compare to a known tube to see if it looks like either one. If so, then test it using the specified settings for that tube.

The easier way is to find or buy the right tube.......

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"It's always something". --Gilda Radner (1946 - 1989)


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 7:54 pm 
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The Rogers Majestic radio company developed their own set of tubes, and some of them are almost impossible to find now. Many were sprayed with a metal coating and that coating was connected to pin 1 which gave them an integral tube shield. They used their own numbering scheme, so you can't say that a 75M is the same as a 75. That's what the conversion chart is for. Many people over the years were able to come up with equivalents to the Rogers tubes, and so the 6Q7 or 6B6 should work fine.

Here is a basic conversion chart from JustRadios
http://www.justradios.com/typeM.html

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Chris

Looking for mid to late 1930s Canadian Rogers, Majestic, and DeForest Crosley radios


Last edited by cwysong on Mar Tue 06, 2018 9:19 pm, edited 1 time in total.

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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 8:38 pm 
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Thanks I will try one of them.


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 9:26 pm 
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cwysong wrote:
The Rogers Majestic radio company developed their own set of tubes, and some of them are almost impossible to find now. Many were sprayed with a metal coating and that coating was connected to pin 1 which gave them an integral tube shield. They used their own numbering scheme, so you can't say that a 75M is the same as a 75. That's what the conversion chart is for. Many people over the years were able to come up with equivalents to the Rogers tubes, and so the 6Q7 or 6B6 should work fine.

Here is a basic conversion chart from JustRadios
http://www.justradios.com/typeM.html

How is your logic affected by the OP's statement that the set appears to have an octal socket from the factory?

sp;
Once you find a good tube, check the wiring to be sure it is appropriate.

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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Tue 06, 2018 10:17 pm 
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Mark, these were octal tubes right out of the factory. The 6M531 as discussed here was a 1936 model, 5 tube radio. I have 3 1936 Rogers/Majestic/DeForest Crosley radios. Two of them have the 75M tube and are octal. I substituted a 6Q7G for a missing 75M and it works fine.
The 6M531 is a Majestic. The 6R531 is a Rogers. Chassis is the same, the letter denotes what model it is.
Here is the 6R531 schematic. Page 2 shows a nice chassis layout.
http://pacifictv.ca/schematics/rogers11-52data.pdf

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Chris

Looking for mid to late 1930s Canadian Rogers, Majestic, and DeForest Crosley radios


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Wed 07, 2018 12:25 am 
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So you are saying you have two radios with a 75m tube with a octal base instead of a 6 pin base .


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Wed 07, 2018 1:36 am 
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That is correct. The 75M is a Canadian Rogers tube, and has nothing to do with the US 75 tube. They just happen to have the same number. When dealing with the Canadian radios like the Rogers line, you have to forget your US tube numbers.

My radios all have Rogers 6F7M tubes and these are octal as well. They have nothing to do with the US 6F7 tubes. The closest electrically speaking to the 6F7M is the 6P7G. Both are octal, but the pinouts are different.

Take a look at the schematic I linked to. You'll see them on page 2.

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Chris

Looking for mid to late 1930s Canadian Rogers, Majestic, and DeForest Crosley radios


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Wed 07, 2018 1:50 am 
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Ok I see that now but how do I find the correct info to try and test it on a tube tester or are they both the same characteristics but different base.


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Wed 07, 2018 3:07 am 
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Location: Bothell, WA
Buy a 6Q7G.

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Chris

Looking for mid to late 1930s Canadian Rogers, Majestic, and DeForest Crosley radios


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Wed 07, 2018 10:36 am 
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I know buying the 6q7 will work but how do one find out how to test the 75m octal verses the 75 6 pin.


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Wed 07, 2018 12:34 pm 
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Chris stated earlier that he successfully subbed a 6Q7 for a 75M. That implies that you can test a 75M using the settings for a 6Q7.

Assuming you have recapped the set, why not just see if it works?

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"It's always something". --Gilda Radner (1946 - 1989)


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Wed 07, 2018 8:57 pm 
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more on the 75M---follow the links for 6B6M and 6Q7:
https://www.radiomuseum.org/tubes/tube_75m.html

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-Mark http://pixellany.com

"It's always something". --Gilda Radner (1946 - 1989)


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 Post subject: Re: Rogers Majestic 6m531
PostPosted: Mar Wed 07, 2018 10:38 pm 
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I used a 6q7 and have the radio recapped and it works fine. It is one of the better sounding radios I have. But the middle band has no reception but lots of static at all but the last band I can receive about 20 stations in the evening.


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