Hello All,
I was told by a ham during a QSO that if I buy a matched pair of 6146b's, I
would not need to neutralize them?? Is that true?

Thanks KB3IBT

"KB3IBT Dan K" wrote in message
news:6vNvi.1387$hK5.1064@trndny02...
Hello All,
I was told by a ham during a QSO that if I buy a matched pair of 6146b's,
I would not need to neutralize them?? Is that true?

Thanks KB3IBT


No.

On Mon, 13 Aug 2007 00:22:26 GMT, KB3IBT Dan K wrote:

I was told by a ham during a QSO that if I buy a matched pair of
6146b's, I would not need to neutralize them?? Is that true?

No.

"KB3IBT Dan K" wrote in message
news:6vNvi.1387$hK5.1064@trndny02...
Hello All,
I was told by a ham during a QSO that if I buy a matched pair of 6146b's,
I would not need to neutralize them?? Is that true?

Thanks KB3IBT


So why should I get a matched pair?
I could save some money if I don't.

"KB3IBT Dan K" wrote in message
news:nc6wi.1578$jU4.1482@trnddc02...

"KB3IBT Dan K" wrote in message
news:6vNvi.1387$hK5.1064@trndny02...
Hello All,
I was told by a ham during a QSO that if I buy a matched pair of 6146b's,
I would not need to neutralize them?? Is that true?

Thanks KB3IBT


So why should I get a matched pair?
I could save some money if I don't.


Matched pair implies the tubes will be drawing equal current for a given
grid bias; there is no way to "balance" the tubes in most rigs.

Neutralization is used to cancel unwanted capacitive coupling between
the internal tube elements, which varies by manufacturer and tolerances.

Usually you don't need a "matched pair"; I'd go with new tubes of the
same manufacturer and relatively close production dates. In other
words, don't mix a used RCA 6146A with a new imported 6146B
and expect the tubes to last.

Oh, wow, thanks for the explanation Uncle Peter. I really appreciate it! I'm
gonna stick with new tubes. I hope my TS-530 will be able to tune up. Its
been sitting almost a year collectin dust next to my beloved TS-870.
I tried tuning the 530 this past Sunday and it wouldn't budge. Nothing at
all. It still receives pretty good.

Again, Thanks!



"Uncle Peter" wrote in message
...

"KB3IBT Dan K" wrote in message
news:nc6wi.1578$jU4.1482@trnddc02...

"KB3IBT Dan K" wrote in message
news:6vNvi.1387$hK5.1064@trndny02...
Hello All,
I was told by a ham during a QSO that if I buy a matched pair of
6146b's, I would not need to neutralize them?? Is that true?

Thanks KB3IBT


So why should I get a matched pair?
I could save some money if I don't.


Matched pair implies the tubes will be drawing equal current for a given
grid bias; there is no way to "balance" the tubes in most rigs.

Neutralization is used to cancel unwanted capacitive coupling between
the internal tube elements, which varies by manufacturer and tolerances.

Usually you don't need a "matched pair"; I'd go with new tubes of the
same manufacturer and relatively close production dates. In other
words, don't mix a used RCA 6146A with a new imported 6146B
and expect the tubes to last.

On Aug 13, 8:55 pm, "KB3IBT Dan K" wrote:
Oh, wow, thanks for the explanation Uncle Peter. I really appreciate it! I'm
gonna stick with new tubes. I hope my TS-530 will be able to tune up. Its
been sitting almost a year collectin dust next to my beloved TS-870.
I tried tuning the 530 this past Sunday and it wouldn't budge. Nothing at
all. It still receives pretty good.

It's not so obvious that a transmitter that doesn't "budge" obviously
needs new finals. If the last time the transmitter was used there was
a big puff of smoke from the final compartment and a lot of blue
flashing, maybe, but I've smoked far more plate chokes and HV coupling
or bypass caps than finals over the years.

Does it show any plate current at all? The finals are biased for AB1
or so and probably should draw 50 mA or so (see your manual for
details) when keyed up and no signal. If so, as you tweak the bias
(not sure where it is in a TS-530 but there must be a final bias pot)
does the current behave semi-linearly?

If you have bias which behaves right but no signal out, I'd suspect
something in the drivers, not the finals.

If you're sucking major current when there's no signal, then the tubes
might be gassy or maybe the screen current is out of whack or you've
got some super-nasty parasitics (which actually comes back to the
neutralization you asked about).

If the bias isn't behaving right, I'd suspect plate choke/bias
circuitry/screen supply/plate supply.

If it sucks current but fails to load up, then a bad coupling
capacitor or bad bandswitch or pi-network variables.

Tim.

On Aug 13, 8:55 pm, "KB3IBT Dan K" wrote:
Oh, wow, thanks for the explanation Uncle Peter. I really appreciate it! I'm
gonna stick with new tubes. I hope my TS-530 will be able to tune up. Its
been sitting almost a year collectin dust next to my beloved TS-870.
I tried tuning the 530 this past Sunday and it wouldn't budge. Nothing at
all. It still receives pretty good.

I gave you a lot of places to look in my other post, but suddenly the
"Nothing at all" rings a very clear bell. Replace the driver, a
12BY7A, first before suspecting the finals, and especially if the bias
current in the finals is doing the right thing.

Tim.

Tim Shoppa wrote:
On Aug 13, 8:55 pm, "KB3IBT Dan K" wrote:
Oh, wow, thanks for the explanation Uncle Peter. I really appreciate it! I'm
gonna stick with new tubes. I hope my TS-530 will be able to tune up. Its
been sitting almost a year collectin dust next to my beloved TS-870.
I tried tuning the 530 this past Sunday and it wouldn't budge. Nothing at
all. It still receives pretty good.

I gave you a lot of places to look in my other post, but suddenly the
"Nothing at all" rings a very clear bell. Replace the driver, a
12BY7A, first before suspecting the finals, and especially if the bias
current in the finals is doing the right thing.

Tim.

May be worth checking the SG switch, I've had a few in for repair that
had it switched off.

Steve H

In message . com, Tim
Shoppa writes
On Aug 13, 8:55 pm, "KB3IBT Dan K" wrote:
Oh, wow, thanks for the explanation Uncle Peter. I really appreciate it! I'm
gonna stick with new tubes. I hope my TS-530 will be able to tune up. Its
been sitting almost a year collectin dust next to my beloved TS-870.
I tried tuning the 530 this past Sunday and it wouldn't budge. Nothing at
all. It still receives pretty good.

I gave you a lot of places to look in my other post, but suddenly the
"Nothing at all" rings a very clear bell. Replace the driver, a
12BY7A, first before suspecting the finals, and especially if the bias
current in the finals is doing the right thing.

Tim.


If the TS530 is like the 520, one sign that the PA stage may need
neutralizing is that when, during tune-up, the maximum power output does
not coincide with the plate current dip. Another side-effect may be that
the receive pre-selector peak does not coincide with the transmit RF
drive peak.

If all seems more-or-less OK with the new tubes, you can probably leave
things alone.

However, if your 530 doesn't tune up at all, you'll need to look for
more than neutralizing (as suggested by Tim).
--
Ian