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Old 4th Sep 2018, 2:15 pm   #1
Singlofty
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Default 1S105 diode information.

Looking to start my next guitar amp build and came across the attached circuit for a Selmer amp. It contains a 1s105 diode and I've been unable to unearth much information on it although I believe it is a tunnel diode. Can anyone explain the reason for its use and the significance of the 17v note beneath it.?

Cheers
Dave.

Mods, the schematic is in the public domain on the Selmer users site.
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Old 4th Sep 2018, 2:21 pm   #2
TonyDuell
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Default Re: 1S105 diode information.

From the position in the circuit, I would think it's just a normal rectifier diode. It half-wave rectifies half of the HT secondary winding on the mains transformer to give a -ve supply rail.

I wonder if the '-17V' is actually '-170'. That would make more sense to me, it's the sort of voltage I could believe getting by half-wave rectifying that winding.
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Old 4th Sep 2018, 2:24 pm   #3
Ambientnoise
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Default Re: 1S105 diode information.

Looks like it is just a rectifier producing a negative rail. Googling suggests a 1A, 600v rating.

HTH

Ken
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Old 4th Sep 2018, 2:28 pm   #4
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Default Re: 1S105 diode information.

I think 1S could be Texas Instruments
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Old 4th Sep 2018, 2:45 pm   #5
Singlofty
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Default Re: 1S105 diode information.

Thanks for the replies, googling it returned nothing for me. I managed to find a Toshiba nos one on ebay.
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Old 4th Sep 2018, 3:02 pm   #6
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Default Re: 1S105 diode information.

That looks like a nothing-special rectifier diode. A 1N4007 probably would do the business.
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Old 4th Sep 2018, 6:22 pm   #7
buggies
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Default Re: 1S105 diode information.

600V PIV 750mA 1Vf Silicon according to 1969 Diode & SCR D.A.T.A.Book
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Old 5th Sep 2018, 10:12 am   #8
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Default Re: 1S105 diode information.

R37 and R39 form a voltage divider. The -17V could well be correct. R39 will have a large effect since it is passing pulses.
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Old 21st Sep 2018, 9:24 pm   #9
Philips210
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Default Re: 1S105 diode information.

Hi.

In my ECA data books, the 1S105 is listed as a 600V 0.75A general purpose rectifier. Suggested equivalents, BY126, BY127, BY133, BY134, 1N4005, 1N4006 and 1N4007.

Regards
Symon.
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Old 21st Sep 2018, 10:00 pm   #10
Maarten
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Default Re: 1S105 diode information.

Quote:
Originally Posted by AC/HL View Post
I think 1S could be Texas Instruments
1S is the JEDEC prefix for single junction semiconductors such as diodes, just as 2S is used for transistors. In the US 1N and 2N were used, though I'm sure TI may have used in house codes which may be similar.
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Old 22nd Sep 2018, 5:50 pm   #11
Trevor
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Default Re: 1S105 diode information.

very simple -17 volts is about correct grid bias for an El84 1n4007 will work well
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Old 22nd Sep 2018, 8:59 pm   #12
Singlofty
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Default Re: 1S105 diode information.

Once again thank you for the replies and observations, I've started to build this now and will post again as it progresses.
Cheers
Dave
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Old 22nd Sep 2018, 10:56 pm   #13
'LIVEWIRE?'
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Default Re: 1S105 diode information.

If it's any help, the Marshall JTM45 uses a similar circuit to provide the grid bias for it's output valves (2 x 5881 or equivalent in that case), and that amp uses a 1N4007 as the rectifier.
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Old 23rd Sep 2018, 7:52 am   #14
Singlofty
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Default Re: 1S105 diode information.

Yes, I've seen the same sort of circuit in other amp schematics, but being unable to find any data on that diode and the -17v reference being the only voltage marked on the drawing I thought I'd better clarify it.
I'm building this for my niece who's a music student and would like to optimise one of the input channels for bass. The original unit had twin 12" speakers but I'll be fitting a pair of 10" . Are there any pro's, con's for series or parallel wiring, I have a multi tap output transformer so can match either output impedances.
Dave
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Old 23rd Sep 2018, 11:16 am   #15
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Default Re: 1S105 diode information.

Dave

A bit late to the party, but I've found the full 1S105 data in Texas Instruments Data Book 5. I've taken photos of the pages as the binding of the book is a bit too fragile to go in my scannner.

Ron
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Old 23rd Sep 2018, 4:25 pm   #16
Singlofty
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Default Re: 1S105 diode information.

Thank you for that Ron

Dave
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