[TenTec] Centaur Tubes odd ones in parallel

[Rick - DJ0IP / NJ0IP]

I AGREE but most of the members here seem to disagree.
There is a huge lack of information available on hot switching.
People make a big mistake and simply trust the OEMs.

Every time I bring up the fact that Ten-Tec's delay before transmitting RF
is too short for all of the Ameritrons and older amps with open-frame relay,
several guys chime in with "I've never had any problem."   If they run
enough CW and wait long enough, their relay will burn enough that they do
have a proble.  Perhaps they will have pre-mature tube failure and wonder
why.

This topic is ABSOLUTELY ON TOPIC for this reflector.

I asked Jack how they determined that the delay of RF should be 15mS.
He told me he got that number from Ameritron directly.
Indeed, it is even the Ameritron Amp manuals:  average switching time 15ms

So I looked up the manufacturing specs on the relay.
There it was:  "average" switching time 15ms
+ PLUS 2ms bounce time...
+ PLUS another 2ms if you use reverse diode protection (which we do).
15 + 2 + 2 = 19mS, not 15.  

BUT WAIT...  The 15ms is the "average", which means sometimes faster,
sometimes slower.
AND more important, it specifies the time for switching from steady state.
What if the relay is trying to follow CW keying?
It is basically never in a steady state.
Sometimes it is already in motion in the wrong direction.
This means it must overcome the inertia in the wrong direction BEFORE the
starting count for the average switching time.

MEASURED:  22ms is required!
I measured it long ago when I was working in the Rhode und Schwarz lab.
Bob (K4TAX) measured it about a year ago with a brand new AL-80B.
We both came to 22ms.

Ten-Tec delays 15ms in the Orion and OM7 and 17ms in the Eagle.

I discussed this at length with Jack in November of 2013.  He agreed and
promised it would be addressed.  Then 2 months later he announced his
retirement and shortly thereafter sold the company.

THIS is still on the table to be addressed.
I personally use an external keyer when running an amp, and I add 10ms to
the delay.
I have used my own time sequencing control since about 1979.
I home brewed a keyer for that.

When I bought the Eagle, I decided to buy a keyer with adjustable delay
times so that I would have a backup.  In the meantime I'm using that one
instead of my home brew unit.

It's hard to get the hams to understand switching times when most of the
engineers working for the transceiver manufacturers apparently don't
understand switching either.
And that is just for the transceiver.

Switching within the amp also needs to be time sequenced.
THIS is about the only time I am willing to dump my attitude of "KISS" and
say do it right.  It has to be complex here.
You should have two separate vacuum relays and they switch with slightly
different timing. One uses reverse diode protection, the other uses a
resistor instead.  

73 - Rick, DJ0IP
(Nr. Frankfurt am Main)


-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Mike
Schatzberg
Sent: Friday, April 03, 2015 12:11 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Centaur Tubes odd ones in parallel

Yes, indeed. But I only think of their higher power options with two or
three holes of 4cx800 tetrodes. These sorts of ceramics with their high
dissipation are where switching gets more difficult. 

I still believe the number one cause of tube failure is switching. The
triodes are often doomed to fail through poor design in the control board.
They are rugged generally but will not hold up to hot switching. 

That is why I found so much work with Commander. 

Sorry again for too much bandwidth.  

73,

Mike
W2AJI 

Sent from my iPhone

> On Apr 2, 2015, at 3:22 PM, Rick - DJ0IP / NJ0IP <Rick at DJ0IP.de> wrote:
> 
> Not so; QRO had the HF-1000 and HF-2000 with 1x and 2x 3-500z tubes.
> I owned both back in my serious contesting days.
> 
> In fact they still sell the HF-2000.
> It is currently my favorite amp on the market.
> See:  http://www.qrotec.com/
> The first amp shown uses 2x 3-500z.
> 
> They have always had this amp.  Discontinued the HF-1000 because the 
> AL-80x made life too hard for them.  Couldn't compete on price.  I 
> owned an AL-80A at the same time I had the pair of QROs.  Simply no 
> comparison in build quality, though for the price, I think the AL-80B is
now the best amp going.
> BUT, you have to manage your timing with it.  Its open-frame T/R relay 
> is s l o w.
> 
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
> 
> 
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Mike 
> Schatzberg
> Sent: Thursday, April 02, 2015 10:56 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Centaur Tubes odd ones in parallel
> 
> I never use tetrodes myself and that is what QRO uses. 
> 
> Commander may have one of the best RF decks in the business. But their 
> control board is in need of help generally particularly their 
> switching. I have modified many units over the years.
> 
> 73,
> 
> Mike
> W2AJI
> 
> Sent from my iPhone
> 
>> On Apr 2, 2015, at 2:06 PM, Rick - DJ0IP / NJ0IP <Rick at DJ0IP.de> wrote:
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