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Old 13th August 2011, 05:16 AM   #1
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Default Traced an old valve with no specs - thoughts please

Hi people,

I've got hold of a decent sized bunch of MHLD6, an old duo-diode/triode valve from the 30's. Specs are pretty hard to find for them so I thought why not trace them out myself, I've never done this before but it seems to have worked, see attached.

I'm trying to ascertain the utility of these things, as I can probably get a lot more. They are all ex-government stock, I suspect ex PMG or Victorian Railways.

mu is about 23
rp is about 7.3k
gm is about 3000 umhos

No idea of max plate dissipation but the structure is a bit under twice the size of a 6SN7.

The curves don't look bad to me, but I'm not an expert and I haven't run any loadlines as I don't have a printer at the moment.

What do other people reckon?

EDIT: I've only bothered about the triode section, obviously.
Attached Files
File Type: pdf MHLD6.pdf (95.5 KB, 78 views)
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Old 13th August 2011, 10:52 AM   #2
bigwill is offline bigwill  United Kingdom
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Looks very 6SN7-ish!
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Old 13th August 2011, 03:12 PM   #3
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Join Date: May 2005
Location: near Duesseldorf
MHLD6 @ The National Valve Museum

MHLD 6, Tube MHLD6; Röhre MHLD 6 (MHLD6)

VR101 @ The National Valve Museum

Regards Andreas
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Old 14th August 2011, 05:13 AM   #4
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Quote:
Originally Posted by bigwill View Post
Looks very 6SN7-ish!
That was my thought also, I was hoping it wasn't just wishful thinking on my part. It was introduced at around the same time as the 6J5 so that makes some sense I suppose.

Cheers Andreas, those pages are where I got the pinout etc. It seems to be impossible to get any more info than that though. Hence tracing it out myself.
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Old 14th August 2011, 05:06 PM   #5
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This valve seems to have dropped out of sight very early. Neither the 1949 nor 1966 versions of the Wireless World / Iliffe Radio Valve Data manuals list it and the Mullard manual (1955 ish) gives no suggested alternative which is most unusual. Still, your measurements and the similarity to a DL63 should enable you to get some use out of them.

Barry
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