Discussion in '"Boat Anchor" & Classic Equipment' started by W4JJA, Apr 13, 2012.
Where can I buy a new pair of 6146B tubes for my Kenwood 530S?
All you are likely to find are new old stock...
RF parts is one of the most reliable sources.
There are several suppliers that can be found by doing a "google" on "vacuum tubes". There are, at least were very recently, some Russian and Chinese companies manufacturing 6146B/8298A tubes. I haven't "run into" any of the Russian tubes so cannot comment on their quality. However, I have had 2, or 3, units come in for repair with Chinese tubes in them. Like certain other Chinese manufactured tubes, I am NOT impressed with either the quality or performance.
You can find a number of sources for 6146W tubes. Those are identical to the 6146B/8298A.
I bought a used Kenwood TS-520S last fall for a great price and while it seems to put out full power it still has the original Japanese finals (S-2001A ?), so I started searching around for NOS 6146B or 6146W on-line and on E-bay. Prices are all over the place and with NOS you never really know what you are getting. Anyway after many months I found a NOS RCA pair for around $30 with 1988 date codes, so I'm happy. Haven't tried them yet but they certainly look to be unused, they will sit on the shelf for now.
Where is the best place to obtain 6146B tubes? What is the best brands? What brands should I avoid?
IN your backyard ....
At your AES store in Florida!
AES-Orlando stocks 6146B and some common tubes
Ken Kemski, K4EAA is in Sarasota, FL
Ken will have virtually anything you need for that Kenwood hybrid!!
Ken stocks the 12BY7A Driver tube
RF Parts (California)
K4EAA FAQ about Kenwood Hybrids
How can I tell when my finals (6146's) are getting "soft?"
Tubes go "soft" when their cathode emissions begin to drop. That means that for a given set of circumstances, plate voltage, screen voltage, drive level, etc., fewer electrons make it from the cathode to the plate. When this happens, plate current begins to fall off, output power starts to drop, and we start to increase the LOAD control and re-dip to maintain the power output.
As we increase the LOAD control, and more heavily tax the finals, the tuning starts to get broad, with a much less pronounced "dip." This can occur gradually over time, so we tend to overlook it.
Finally, we're seeing 70W out on 20M with very broad plate tuning - It's time to replace the finals. Fortunately, for Kenwood, this can take over 35 years, depending on your operating habits, as#I get lots of rigs with the original S2001 tubes in place, almost as good as new!
Why Can't I Successfully Neutralize my 6146A's?
The Kenwood's were designed around the 6146B, which was significantly different from previous 6146 and 6146A versions. You should not use the 6146, 6146A, or 6146W built before the mid-1960's in the Kenwoods. After the 6146B was introduced in 1964, the 6146W's gradually were migrated to the 6146B design, and later versions of those tubes are fine. The neutralization circuit employed in the Kenwood hybrids was designed around the 6146B, and may not be able to successfully neutralize the older versions - That can lead to instability in the finals.
Nebraska Surplus has at least three different ones listed on their webpage.
Unfortunately, Nebraska Surplus generally thinks that what they sell is platinum plated, not just gold plated!
When you do a "google" on "vacuum tube", there are several vendors that "come up" on the first page who handle the 6146 family of tubes. Also, their prices are usually very close to the same.
As for brands: RCA, General Electric, and Sylvania are usually the best, Raytheon tubes are not bad. Amperex is the best of the off-shore brands. The Japanese 2001A tubes are the same as the 6146B/8298A and are usually pretty good. However, the Japanese tubes are not that common in this country. There were/are a couple of Russian tube manufacturers that make/made an "OK" 6146 family of tubes. But, stay well clear of any Chinese 6146 family of tubes.
I have some good used ones pulled frpm some refurbished and stored military gear, they put new ones in before storage, these tubes test 100% right out of the equipment.
While Hicksville, NY is on an island I wouldnt call it offshore.