[Jukebox-list] Seeburg DS160 tube?

[Jay Hennigan]

Jim Algar wrote:
> I have a Seeburg DS160 with the "scans twice but won't select" problem. 
> I've gone through the troubleshooting guide tests, with the result 
> (according to the guide) that it's either the pulse amplifier tube 
> (12AX7) or the pulse amplifier itself. Thought I'd start easily (and 
> less expensive) with the tube. I see all kinds of 12AX7 tubes on eBay.
> 
> My questions:
> 
> 1.) are any and all 12AX7 tubes the same? I notice that some of them 
> carry additional numbers/letters after the 12AX7 as sort of 
> "suffixes"...do they mean anything or can they be ignored, as long as 
> the tube is listed as a 12AX7?
> 
> 2.) Any brands and/or countries of origin to be sought out or, 
> conversely, avoided?

For this application, it makes little difference.  In the pulse 
amplifier, the tube amplifies a magnetic pulse to trigger a thyratron or 
SCR.

The differences between various brands, countries, etc. can make a 
difference in the sound quality when the tube is used in the audio 
signal chain.  Noise, microphonics, and subtle differences in gain, 
frequency response, etc. can affect the sound quality of tube 
amplifiers.  Some of this is a matter of preference, "religion", or 
mystique with various brands, etc.  Some high-end audio aficionados and 
electric guitar players will do quite a bit of "tube rolling" in pursuit 
of the best sound.

In this case, any tube that meets specs will amplify the signal from the 
Tormat sufficiently to trip the mechanism, and won't affect the sound. 
The tube isn't in the audio signal chain.   There is no need to pay 
extra for premium audiophile tubes.

The suffix letters can denote small differences such as warm-up 
characteristics, ruggedization for military use, etc.  This isn't going 
to be a factor in this application.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
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