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Tubelab Discussion and support of Tubelab products, prototypes and experiments

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Old 22nd February 2019, 04:38 PM   #91
Tubelab_com is offline Tubelab_com  United States
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The Tube World pictures in the link from post #58 clearly show two Ericsson tubes, both with gold pins.

The "Amperex" tubes are marked made in USA. I didn't think Amperex made tubes in the US, so who actually made them?
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Old 22nd February 2019, 05:23 PM   #92
randytsuch is offline randytsuch
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Another interesting pic
5842, Tube 5842; Rohre 5842 ID5904, Triode, vacuum

Shows a WE marked JW5842, but you can see 417A at the bottom.

Randy
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Old 22nd February 2019, 05:55 PM   #93
w5jag is offline w5jag  United States
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GEC CV3789 / 417A
| TubeDepot.com


Pic of GEC 417A with gold pins.

I'll try to dig out my RCA's and get a pic later this afternoon / evening when I get home. Can't find anything but Raytheons here at the office.

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Old 22nd February 2019, 06:56 PM   #94
Tubelab_com is offline Tubelab_com  United States
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Quote:
Shows a WE marked JW5842, but you can see 417A at the bottom.....and some WE417A's were dual marked 417A/5842.
That's pretty common. Many of the tubes I sold were marked like that, so was the Mu 43, 43, or 50....or maybe somewhere in between. I imagine that it wouldn't make much difference in the RF circuits that these tubes were intended for.

The TSE loads the tube with a CCS, so the only AC load on the tube is R15 or R26 and the Crss of the mosfets. I am testing some new mosfets that run around 1 pF and have raised the resistor to 1 meg. That gets me a gain of about 40 with a Raytheon 5842. I haven't played the tube rolling game yet, but I will when I catch up on everything else.
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Old 22nd February 2019, 07:59 PM   #95
evanc is online now evanc  United States
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Iíve been playing with the 6AN4 as a first tube in a very simple single ended amp. Driving a mosfet and then a 4d32 output tube no others I tried (including 5842) give me as low a distortion measurement. Plus is they are cheap. Minus might be the 7 pin socket
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Old 23rd February 2019, 12:27 AM   #96
w5jag is offline w5jag  United States
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Two date codes - 1962 and 1966. Clearly marked made in USA, but have the cross seams on the top of the glass, and what looks like Mullard codes etched into the glass. They also have larger digits etched into the glass, similar to Tubelab's mystery tube, but that didn't show up well in the pics.

The Raytheon is a 1985 date code. I found some 1984, also.

I'm still thinking Amperex. But are they 5842's, or 417A's?

Win W5JAG
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Old 23rd February 2019, 01:17 AM   #97
Tubelab_com is offline Tubelab_com  United States
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Quote:
Plus is they are cheap. Minus might be the 7 pin socket
7 pin tubes do seem to be scorned even though there are sockets available.

The minus that you can't see is how many are available. I have access to the inventory list at a popular tube seller, and I can call another to see how many they have. There are less then 200 6AN4's in stock at the place I can check via computer.

Another possible choice is the 6J4. At least there are over 1000 of them in stock. Granted this does not always reflect the availability of the tube in question at other tube retailers, but it's a resource I use when checking into a tube design.

There is another possibility on paper. I don't actually have any yet, so I'm not going to mention it's number.

Twice I have gone down the road for a tube design only to have someone buy up ALL of the available tubes leaving me with a design, sometimes a PCB, and zero tubes for it. There were 7,000 6HB6's in stock until someone mentioned them here, then poof, all gone, to a Hong Kong buyer. Ditto the 13GB5, over 20,000 tubes have been sucked up by a single US customer. Both were on the dollar lists at two popular tube sellers.

I have a new amp design that's the little brother to the 100 WPC 13GB5 amp. This time I was the customer that bought 500 of each tube to hedge my bet before getting a stack of PC board that are useless.
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Old 23rd February 2019, 02:12 AM   #98
tomchr is offline tomchr  Canada
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Maybe this is blasphemy, but how about using a pentode in the input stage? Something like the EF86 should give you more gain than you can shake a stick at. Likely high enough that you could wrap a little feedback around it to stabilize the gain and lower gain variation from tube to tube. Just a thought...

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Old 23rd February 2019, 02:27 AM   #99
Tubelab_com is offline Tubelab_com  United States
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Quote:
but how about using a pentode in the input stage?
I have several pentode driving pentode amps in the works. Two are working prototypes now. The unique thing is the triode curves I'm tricking those pentodes into giving me. The curves ARE evenly spaced. My manual measurements with Harbor Freight measurements are a bit off in the placement of the 4th line.

This "un-triode" is a TV sweep tube that looks like a triode, and eats 550 volts. A pair of them will squeeze out 80 WPC on a regulated supply, and 50 WPC on an Antek toroid. All 8 tubes are pentodes.

The amp shown here is a push pull design. Meet Little Brother from post #97. There is a Single Ended un-triode I call the UN-SET in the works.
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Old 23rd February 2019, 07:57 AM   #100
Parafeed813 is offline Parafeed813  Netherlands
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Quote:
Originally Posted by w5jag View Post
I'm still thinking Amperex. But are they 5842's, or 417A's?

Win W5JAG
In the third picture you can see the code "VK4".
VK is the Philips code for 5842.
The first symbol of the code under the VK4 should identify the factory.
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