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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 2nd Jun 2010, 2:54 pm   #1
PWH
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Default Osram Four New Music Magnet

Hi could someone please advise the voltages for the supply

LT 2V

SG?

HT+

GB-

I can't find the circuit on disks 1-3 (as supplied by Paul.)

Thanks
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Old 2nd Jun 2010, 3:50 pm   #2
wireful3
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Default Re: Osram Four New Music Magnet

I can't remember the specific voltages quoted for this set but The HT is almost certainly 120v. The SG is about 90v but 60v might also be OK. The GB will depend on the valve used but will probably be round about -3v or -1.5 volts. The original grid bias batteries had taps at 1.5 volt steps and I think the intention was to use trial and error. It would be less than 9v as this was the usual max voltage of the batteries.

The 9v batteries might even be later than the Music magnet, because it was normally used with a variable Mu valve as a volume control (RF gain)
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Old 2nd Jun 2010, 4:42 pm   #3
Boom
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Default Re: Osram Four New Music Magnet

On the (3 valve) set I am playing with it has two grid bias battery connectors and from what I can see two is normal, one for the output stage and one for the earlier stage(s)

The bias volts are giving on the valve museum site if you are not sure.

Dave
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Old 2nd Jun 2010, 6:14 pm   #4
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Default Re: Osram Four New Music Magnet

MM4 installation Instructions part 1
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Old 2nd Jun 2010, 6:21 pm   #5
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Default Re: Osram Four New Music Magnet

MM4 installation Instructions part 2

For some reason, they are uploading as thumbnails, not attachments. On my PC they can be read quite easily. If you PM your Email address, I'll send them direct.
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Old 2nd Jun 2010, 8:04 pm   #6
Ed_Dinning
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Default Re: Osram Four New Music Magnet

Hi PWH, just a note of caution. Do not adjust the GB tappings with the LT supply ON as this can damage the valves.

Ed
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Old 3rd Jun 2010, 8:20 am   #7
PWH
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Default Re: Osram Four New Music Magnet

Thank you all, I now have the information I need

For the reference of others HT is 120V, SG is 72-60V depending on volume (lower voltage = greater battery economy) GB is -9 to -3V as the LT battery dies away...
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Old 30th Aug 2010, 6:38 pm   #8
g3zilgwyn
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Default Re: Osram Four New Music Magnet

Quote:
Originally Posted by AC/HL View Post
MM4 installation Instructions part 2

For some reason, they are uploading as thumbnails, not attachments. On my PC they can be read quite easily. If you PM your Email address, I'll send them direct.
Dear Bill
I've just come across your very helpful post. Having just written a short article for the BVWS Bulletin on the restoration of my Osram Four New Music Magnet, without the benefit of the pages you've scanned, I must recall my article and make some changes, even from what I can see in the thumbnails. Would it be possible for you to email me higher resolution scans?

In particular have you any comment on the "Super Power" P2 valve suggested as an alternative audio amplifier?

many thanks

Gwyn G3ZIL BVWS member
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Old 31st Aug 2010, 6:24 pm   #9
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Default Re: Osram Four New Music Magnet

Hello Gwyn,
Send me your Email address by PM and I'll send by return.
Regards, Bill

PS as regards the super power valve it's just a more powerful triode as far as I know, hence the higher HT consumption. It was also popular to replace the last valve with a pentode at this time, necessitating replacing the four pin holder with a five.
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Old 1st Sep 2010, 4:54 pm   #10
g3zilgwyn
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Default Re: Osram Four New Music Magnet

Bill
Many thanks. Will PM you my email address in a moment.

Thanks for the comment re the P2 super power valve. I had got confused, in that I remembered that a P2 was a bright emitter valve, but on delving deeper, this was a Cossor valve, and Marconi used P2 for their equivalent of the Mullard PM202.
The set was very confusing as I received it, for there was a KT2 in the output valve position, in a 5 pin socket, with the screen unconnected, and a 220OT in the detector position! But, all sorted now.

Would it be OK with you if I quoted from the material you've scanned in the article I've written for The Bulletin, I will of course credit you as the source.

regards
Gwyn
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