I am not sure if the Drake L4-B qualifies as a suitable topic for this
newsgroup, but it does use tubes and the power supply could be used as an
anchor for a small boat.

Are the Chinese 3-500ZGs a drop-in replacement for the Eimac 3-500Z in the
Drake L-4B?

John, N9JG

John,

They are direct replacements but they aren't very good. K3FK had a QRO
amp with a pair of 'em a few years back and we had to resolder filament
pins on one or the other of the bottles several times. We dropped in a
set of Eimacs and the problem went away.

I've heard very good things about the Ampex variants with the carbon anodes.

Dave Heil K8MN

John N9JG wrote:
I am not sure if the Drake L4-B qualifies as a suitable topic for this
newsgroup, but it does use tubes and the power supply could be used as an
anchor for a small boat.

Are the Chinese 3-500ZGs a drop-in replacement for the Eimac 3-500Z in the
Drake L-4B?

John, N9JG

Thank you very much for the pointer. As I understand it, Eimac doesn't make
this tube anymore, but Ampex is a good brand. Hopefully a Google search will
find out where to buy them.

"Dave Heil" wrote in message
nk.net...
John,

They are direct replacements but they aren't very good. K3FK had a QRO
amp with a pair of 'em a few years back and we had to resolder filament
pins on one or the other of the bottles several times. We dropped in a
set of Eimacs and the problem went away.

I've heard very good things about the Ampex variants with the carbon
anodes.

Dave Heil K8MN

John N9JG wrote:
I am not sure if the Drake L4-B qualifies as a suitable topic for this
newsgroup, but it does use tubes and the power supply could be used as an
anchor for a small boat.

Are the Chinese 3-500ZGs a drop-in replacement for the Eimac 3-500Z in
the Drake L-4B?

John, N9JG

I just bought a pair of Chinese graphite-plate 3-500ZG and they work
just fine. I think the Chinese have come a long way in their quality.
Not to give them a 100% pass, however, a few years ago we (our Agency)
had a 100% rejection rate for 6146's that our contracting personnel went
for low-bid despite warnings.

John N9JG wrote:
I am not sure if the Drake L4-B qualifies as a suitable topic for this
newsgroup, but it does use tubes and the power supply could be used as an
anchor for a small boat.

Are the Chinese 3-500ZGs a drop-in replacement for the Eimac 3-500Z in the
Drake L-4B?

John, N9JG

They are direct replacements but they aren't very good. K3FK had a =
QRO=20
amp with a pair of 'em a few years back and we had to resolder =
filament=20
pins on one or the other of the bottles several times. We dropped in =
a=20
set of Eimacs and the problem went away.

I had the same problem with an Eimac 3-500Z, though once only.

Tony, I0JX

Do you mind telling me who you bought your tubes from? I am trying to place
an order through Tom's Tubes, but his computer is sick and is being operated
upon.

"K3HVG" wrote in message
...
I just bought a pair of Chinese graphite-plate 3-500ZG and they work just
fine. I think the Chinese have come a long way in their quality. Not to
give them a 100% pass, however, a few years ago we (our Agency) had a 100%
rejection rate for 6146's that our contracting personnel went for low-bid
despite warnings.

John N9JG wrote:
I am not sure if the Drake L4-B qualifies as a suitable topic for this
newsgroup, but it does use tubes and the power supply could be used as an
anchor for a small boat.

Are the Chinese 3-500ZGs a drop-in replacement for the Eimac 3-500Z in
the Drake L-4B?

John, N9JG

In article , K3HVG wrote:
I just bought a pair of Chinese graphite-plate 3-500ZG and they work
just fine. I think the Chinese have come a long way in their quality.
Not to give them a 100% pass, however, a few years ago we (our Agency)
had a 100% rejection rate for 6146's that our contracting personnel went
for low-bid despite warnings.

Depends on the tube, basically. The 3-500Z is a well-implemented design,
but the 6146es still don't meet original spec. And the Chinese 6550
specifically says on the data sheet not to put more than 250V on the plate,
which effectively makes it unusable in anything designed for the 6550.
But on the other hand, the Chinese 211 and 833 tubes seem just fine.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:



Depends on the tube, basically. The 3-500Z is a well-implemented design,
but the 6146es still don't meet original spec. And the Chinese 6550
specifically says on the data sheet not to put more than 250V on the plate,
which effectively makes it unusable in anything designed for the 6550.
But on the other hand, the Chinese 211 and 833 tubes seem just fine.
--scott

Is this true for all the Chinese tubes? I note there are at least a
couple factories (Liuzhou, Shuguang-Samsung) and at least a few
different brands of the 6550 (ValveArt, Groove Tube). Can they all be
considered as equals?

Tnx,
Bill

-ex- wrote:
Scott Dorsey wrote:

Depends on the tube, basically. The 3-500Z is a well-implemented design,
but the 6146es still don't meet original spec. And the Chinese 6550
specifically says on the data sheet not to put more than 250V on the plate,
which effectively makes it unusable in anything designed for the 6550.
But on the other hand, the Chinese 211 and 833 tubes seem just fine.

Is this true for all the Chinese tubes? I note there are at least a
couple factories (Liuzhou, Shuguang-Samsung) and at least a few
different brands of the 6550 (ValveArt, Groove Tube). Can they all be
considered as equals?

As far as I know, all of the 6550 tubes, as well as the fake KT-88 that
is not even remotely a KT-88 design, are made all in one factory.

Then again, I thought the Shuguang plant had been bulldozered a few
years back, too.

But everyone and is brother are importing the things... they show up on
this shores under dozens of different names. I've even seen them sold
as Mullard and Amperex... and now there's some guy selling fake Genelex
paper logos that you can glue on them, and fake Genelex boxes to put
them in.

And none of them even come close to meeting the original 6550 specs.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Antonio Vernucci wrote:
They are direct replacements but they aren't very good. K3FK had a QRO
amp with a pair of 'em a few years back and we had to resolder filament
pins on one or the other of the bottles several times. We dropped in a
set of Eimacs and the problem went away.


I had the same problem with an Eimac 3-500Z, though once only.

Tony, I0JX

I've seen it a couple of times during the time that the Eimac tubes were
manufactured. I suspect that in all of these instances, the amplifier's
cooling system was not quite as it should have been. It is much more
likely to happen in an amp which relies upon fan cooling and less likely
in an amp using the Eimac Air System sockets and chimneys.

The Chinese tubes that K3FK had problems with were of the Penta brand.

Dave K8MN