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Oops, fat fingers... no, it was on 7025, 40m.

Steve, K0XP

On 2/15/2024 6:14 AM, Bob wrote:

Thirty meters? 1150w?

Bob W4JFA?

On Wed, Feb 14, 2024, 8:18 PM Steve <k0xp@...> wrote:

If they are the ones in the wattmeter bridge circuit, they're 1N5711, a fairly common Schottky diode that I've used before (and may even have some in my stash). They used to be available everywhere, I dunno about now, I'll hafta look.

I just chased 8R7X on 30m and am pushing it to 1150W output; and lo and behold, the very first reflected LED is popping up dimly but reliably at that output power and frequency; no others, just that one. I've decided I really don't like this scheme of using LEDs as a meter; they just don't seem to give very reliable information all the time even if they're much cheaper to implement.

Mine seemed to fail either when I turned it off this morning, or when I turned it back on after a couple hours (or possibly in-between??). I didn't disturb any coaxes in between those times, just snuck off and took a nap for a couple hours after chasing early morning Asian DX. And this happens when I come back... We had clear skies and very little but high cloud up there at all. Humidity perhaps around 30% or so, temp around 40 degs F when I turned it back on. Odd. I really hate to drag it out to remove the cover and poke around when I don't yet know what, specifically, to look at, because this thing is so heavy and big that I'll have to lug it across the room to get access to all 19 of the screws, then lug it back to plug in and try it again. Maybe I'll do that just to try reseating all the Berg connectors, in the hope...? And I need to check what the 22-ohm cathode resistors are on mine, anyway... I don't think mine has had Glenn's (George??) upgrade to three resistors per tube installed.

AFTER the DX contest, of course? 8-D

Steve, K0XP

On 2/14/2024 4:07 PM, Al wrote:

?Hi Steve,
                 My 8410 took static hit just before Covid started. I talked to Alpha just before they went silent and the sampling diodes are known to blow under your and my conditions. I am currently traveling so I can’t give you the diode numbers but you will find them on the schematic. Like yours mine has full output power but no power out display. With the diodes blown the computer interface has nothing to read. I could not find diodes during Covid hopefully you will have better luck. Let me know how you make out.
73 Allen N3JOC

On Feb 14, 2024, at 10:44 AM, Steve <k0xp@...> wrote:
?I have an 8410; however, according to the schematic(s), it appears as if
it probly uses the same wattmeter as the 9500.

The other day, I encountered intermittent flashover in my external
antenna tuner while running around 1100 watts on 160; it would cause all
the reflected power LEDs on my 8410 to light up. I managed to finish
working someone, let the amp cool down for five mins, then shut it down.
All front panel indicators appeared to work properly at that time
(although I've never, ever, seen a grid current LED light up, nor the
FAULT LED even though I once did have a real fault where I thought that
LED SHOULD light... but it didn't). The output power and reflected power
indicators have always been very accurate and worked fine.

Later that day, I fired it up again... and was chagrined to find NO
output power indicated on the front panel LEDs... neither forward nor
reverse. But the amp was still amplifying normally; output power on an
external wattmeter indicated full power out. I fired up the AE9K Alpha
Monitor program and it, too, shows no output power. But the amp does
still have full output power; so something common to both forward and
reverse power that drives the front panel display failed in my amp. When
the tuner flashed over, my external LP-100A power meter usually
indicated something really high like over 2500 watts momentarily.. once,
I think I saw 2932 watts indicated  ===8-O  Since then, I've fixed the
tuner problem... but have no output power indication on either the
amplifier front panel, nor with the AE9K Alpha Monitor program, even
though the amp is actually still correctly putting out full power.

I'm now printing out all 19 pages of the schematics, but an eyeball
perusal in Acrobat hasn't yet identified exactly which connector carries
the output of the tube deck to the TR system and what it plugs into on
another schematic page. Meanwhile, I thought I'd ask here, in case
someone else has already "invented the wheel" and fixed this kind of
problem. Any help?

TNX,

Steve K0XP

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