I don't really care that much about actual readings. Really, who cares if it
reads 2600 or 2700V? I didn't look REAL close it might be 2675. The output
wattmeter is a Bird 43 so the output reading is fairly accurate.
This amps PS has a Heathkit Shop upgrade board.
The AC line typically runs about 244 V here.
73, Stew K3ND
________________________________
From: K9sqg <[email protected]>
To: [email protected]
Sent: Friday, May 24, 2013 10:48 PM
Subject: Re: [DrakeRadio] Re: What is the differences between L4 and L4B amps
Stew,
Those voltages are higher than virtually every L4, L4B, and L7 amp I have ever
owned or serviced, except for an X model designed for export that had slightly
higher voltages. A calibrated meter needs to be used to get accurate
measurements; I have measured the voltmeters and found them to be off by as
much as 10%.
After I rebuild the supplies, I typically get 2500-2600 volts unloaded with
about a 75-100 volt drop when it goes into transmit, with no audio. Very
little drop on severe voice peaks but I use 330 mfd caps in the supplies, not
the 200 mfd standard.
High plate voltage should always be investigated. Why? It might be indicative
of high line voltage which in turn leads to high filament voltage which in turn
leads to lower tube life.
Enjoy those Drakes.
73,
Evan, K9SQG
-----Original Message-----
From: GALE STEWARD <[email protected]>
To: DrakeRadio <[email protected]>
Sent: Fri, May 24, 2013 10:32 pm
Subject: Re: [DrakeRadio] Re: What is the differences between L4 and L4B amps
Plate V is about 2700 no load and about 2400 under load (key down). Power out
in this condition is about 1150W on 40M.
Don't worry too much about actual numbers. I just tune mine for maximum output.
I normally drive it with a TS-850S (100W).
Working the WPX contest right now on 40M with it.
73, Stew K3ND
________________________________
From: slowcountry1 <[email protected]>
To: [email protected]
Sent: Friday, May 24, 2013 8:39 PM
Subject: [DrakeRadio] Re: What is the differences between L4 and L4B amps
Stew,
What plate voltage is indicated on your L-4 no load? I have not seen a
reference to what it should be. My meter indicates almost 3KV. I do not have
access to a high voltage probe anymore; I would love to know if this is
accurate. I ran a dedicated 220VAC line to my shack and if memory serves, its
about 235 or 240VAC. If the taps are supposed to be 220VAC, the line increase
would explain a little elevation on the plate voltage.
Do you follow the tuning procedure in the manual to .585 IP and 220 IG? It
seems as if Drake instructed the operator to tune so those values were present
on CW/TUNE as an absolute requirement. I tune for maximum power which in turn
results in lowest IG. It seems that I've read several places that one should
run the lowest IG. I advance the loading cap a little past maximum output
power to load a little more heavily. On a whistle in SSB setting I derive
somewhere just under 700ma IP and 160 IG. If the plate voltage were correct
this would yield like (2900*.700)*.65 = 1395 watts output. Therefore, either
my plate voltage is not what is indicated or my W4 and MN-2000 are out of
calibration. I try to run the set around 600 -700 watts when I use the amp.
Your thoughts?
Regards,
Doug N9XTF
--- In [email protected], GALE STEWARD <k3nd@...> wrote:
>
> Also, the L4B had a built in watt meter where the L4 had only a relative RF
> output indicator. The RF decks are identical. I have one of each and my main
> amp (the L4) puts out 1100W with the stock supply power supply on 80-15M.
> It's a bit less on 10M. Your tubes might be a bit soft.
>
> 73, Stew K3ND
>
>
>
>
>
> ________________________________
> From: Doug <dcoffman@...>
> To: "[email protected]" <[email protected]>
> Cc: "[email protected]" <[email protected]>
> Sent: Thursday, May 23, 2013 9:01 PM
> Subject: Re: [DrakeRadio] What is the differences between L4 and L4B amps
>
>
> I own an L-4. The differences I am aware of is the L-4 has the ALC pot on the
> back of the RF deck instead of the front panel, does not have a standby
> switch and came with 3-400z instead of 3-500z tubes. As far as I know mine
> has he original finals and produces 900 watts + - with about 85 watts drive.
>
> For longevity concerns, I rebuilt the power supply about 10 years ago. I have
> recently replaced the foam seal on the air compartment, oiled the fan and
> installed two 12VDC fans to move air through the PS. Other than thinking of
> adding a soft start I don't know what else I would do to it.
>
> One could and have made it legal limit by building a new PS but 900 watts vs
> 1500 just doesn't seem like a big deal and may push the components closer to
> their tolerances.
>
> I'm more concerned about finding out if there are any other components that
> should be changed out due to their age.
>
> Doug -N9XTF
>
> Sent from my iPhone
>
> Sent from my iPhone
>
> On May 23, 2013, at 19:35, "KG0MN" <kg0mn@...> wrote:
>
> > I assume the B model is newer and has many improvements made to it. Can a
> > L4 be made into a B-model without out spending an arm and a leg? Is the L4
> > a decent amp without any major faults?
> >
> > Thanks and 73
> > Kevin - KG0MN
> >
> >
>
> --------------------
> PDSWireless
> Quick and Simple Internet Access
> http://www.pdswireless.com
>
> [Non-text portions of this message have been removed]
>
>
>
> ------------------------------------
>
> Yahoo! Groups Links
>
>
>
> [Non-text portions of this message have been removed]
>
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