Rare tube question

famous beagle

famous beagle

Well-known member
So I had some extra money that was burning a hole in my pocket, and I'd always wanted a low-wattage vintage tube amp to use for recording. I ended up buying a 1966 Kay model 752, which I think should fit the bill well.

However, I didn't realize it when I bought it, but the power tube it uses, a 50c3, seems to be incredibly rare. In fact, I can't find any information about it online except in links that reference amps that use it. And actually it seems to be only two amps that come up: the one I bought, and a vintage Victoria amp.

But I can't find any information on where to find more of these tubes; eBay comes up blank.

Does anyone have any info on these at all?

Thanks
 
35c5 is about all I got over here. Yours could last another 50-years, though. Mine are outputs on a dinky Stereo amp, along with a 12ax7 and 35w4
 
I looked up your tube in an extensive database where you can find info and subs....but it comes up as not found...I even tried the "0" with an "O"...still nothing.

Are you sure that's the tube designation?
This database is pretty comprehensive, with thousands of tube types. Even if there were only two amps that used that tube, I'm sure it wouldn't have been manufactured just for the two amps...IOW, it should have other, non-amp uses, and it should be in the database (though it's possible it was just never included).

I figured if it was in the database, they would also list substitutions...something more available.


Is it maybe an 03C type...?...which is an octal tube often used for voltage regulation.
 
It's a 50C5 power output tube. My old Hickok tube tester didn't list a 50C3, so I got suspicious. the 50 is the filament voltage and usually the last number signifies the number of elements in the tube, 3 or 4 is usually a rectifier and 5 or 6 is a pentode which the power out tube would generally be. The filaments of the tubes are likely run in series (50+35=85 volts) with an additional resistor (250 ohms in schematic) to drop another 40 volts. The 50C5 and 35W4 were common tubes in old radios and should be found fairly easily online, but not at a music shop. If the amp has a two wire cord, which I'm guessing it does, get it converted promptly to a proper 3 wire grounded one (unless you enjoy getting shocks).

Found an eBay listing which had some pics VINTAGE 1960 039 s KAY MODEL 752 GUITAR AMPLIFIER SILVERTONE | eBay
 

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If the speaker is any good, that may be the value. ya, my fujiya also has the 35w4 along with a 12av6 and 30a5 - spec claimed 1-watt !
 
arcaxis said:
It's a 50C5 power output tube. My old Hickok tube tester didn't list a 50C3, so I got suspicious. the 50 is the filament voltage and usually the last number signifies the number of elements in the tube, 3 or 4 is usually a rectifier and 5 or 6 is a pentode which the power out tube would generally be. The filaments of the tubes are likely run in series (50+35=85 volts) with an additional resistor (250 ohms in schematic) to drop another 40 volts. The 50C5 and 35W4 were common tubes in old radios and should be found fairly easily online, but not at a music shop. If the amp has a two wire cord, which I'm guessing it does, get it converted promptly to a proper 3 wire grounded one (unless you enjoy getting shocks).

Found an eBay listing which had some pics VINTAGE 1960 039 s KAY MODEL 752 GUITAR AMPLIFIER SILVERTONE | eBay
Click to expand...

Oh, thanks! That's great news. I was starting to think I'd be shit out of luck if anything ever happened to the power tube.

And actually, the Reverb listing you linked to is the exact amp I bought. That's not the listing (that ended 11 months ago), but it's the same amp (someone bought it and is selling it now I guess), and the same exact pictures were used for the listing.

Evidently, they're pretty rare amps!

And yes, I will definitely be replacing the power cord with a 3-prong. I did the same with the Gibson Skylark GA-5 I had years ago. That was an awesome little amp and one I wish I still had. But things got a bit tight, and I had to sell it. :(
 
Also, I was curious. I was actually able to track down the Kay catalog that lists this amp (see attached). Regarding this amp, it says it's "a combination of the best features of tubes and Solid State Circuitry."

Since there are only two tubes here --- preamp and power amp tubes --- I'm guessing this must be referring to a solid state rectifier?
 

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The schematic shows a single transistor for the preamp stage in the frontend followed by the power amp tube, so it's a hybrid.
 
Oh, I see that now. So what's the 35w4 tube, then? The rectifier? (Please forgive my ignorance; I'm still trying to learn about tube amps.)
 
famous beagle said:
I'm sorry? I'm not catching your drift apparently.
Click to expand...

Though the evidence has been edited, earlier one spoke about the 5 and the 6 suffix and how one could be pentode, etc. They also mentioned the 3 & 4 were often rectifiers . Do you remember the implication about how c03 could be a power tube - because it had a 3 at the end
 
I'm curious to hear this amp, Beagle. Please post some recordings of it when you can.
 
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