[Central-Electronics] 600L Question

[Jim Candela]

Donovan,

    My 600L has been quite reliable, but a few issues to mention:

I had trouble with the 812 screen regulator tube. The filament would go 
out, so the amp would power up in a fault state. My spare 812 had 1/2 
the filament dark, so instead of a 'W', I had a 'V' shaped filament. 
Look for a spare 812 as these are getting scarce. I'm using an 808 right 
now, a miss-match, but it works solid. This has a 7.5v filament running 
on a 6.3v winding. My original 812 came back to life after resoldering 
the pins on the socket, so I have a spare.

The 0A3/VR-75 is also a good tube to get a spare for. This is part of 
the bias supply. I replaced the selenium rectifier with a 1N4007 in 
series with a 750 ohm 5 watt resistor. I also replaced the two 20 uf @ 
450v caps with 47uf/450v. Since the rectifier is half wave, ripple is a 
problem, and does lead to a little 60 hz grid modulation. Increasing the 
capacitor values helps cut the ripple, but I wouldn't do that if the 
selenium rectifier stays in there.

The HV rectifiers, type 816 are getting scarce and expensive. Always let 
these warm up several minutes at least before turning on the HV. In fact 
I'd let them run at least an hour the first time before you key the 
600L. When they go they will flash over internally, and that might take 
out T2. Consider one of the drop in solid state replacements such as the 
1N6237:

http://amfone.net/Amforum/index.php?action=printpage;topic=25830.0

I was lucky since my 600L came with SS rectifiers.

People get funny about the power cord issue, but a two wire power cord 
is really dangerous. Consider a good flexible 3 wire cord that is 14 awg 
or bigger wire (12).

My 600L had a replacement output couplet on the 813 plate for 80m. 
Whoever did it added a sheet of G10 circuit board material from the 
chassis side and the 80m couplet. The clearance was ~ 1/8". Maybe that 
is why the original failed?

As others have said, be anal about making sure the 600L sees a good 50 
ohm non reactive load impedance. If you have to key up to tune a tuner 
for low SWR, do so with another exciter transmitting. Doing this extra 
step will save you from a fatal flame out inside the 600L.

Maybe others have more experiences to add.

Oh, for AM, NEVER run more than about 60-70W carrier since the PEP power 
on AM is 4X the carrier. As it is at 70W, the 813 plate is a dull red in 
color. Someone else said 200W am. I presume that was 200w PEP, so that 
means 50W carrier. This is a good and safe power for AM on the 600L. 
Also on AM, the RF box gets pretty HOT. I have a square fan laid over 
the RF cage  (above 813 tube centered over the plate cap) blowing UP to 
help pull the hot air out the top.

I also use my 600L as an amplifier for my Retro75. Takes 2.5 watts up to 
about 65W AM. I had to load the input with a 75 ohm 2W resistor since I 
had too much drive. So if a Retro75 at 2.5 watts can overload a 600L, 
just thing what a 100V can do! :-)

Jim
WD5JKO






On 10/7/2011 7:04 PM, Donovan W. Case wrote:
> Folks,
>
>
>
> I am new to the group, and a recent recipient of several nice CE units
> including three 20A's and a 10A.  I have a couple more coming including a
> 600L.  I am wonder what 600L owners have found to be the most troublesome
> parts in a 600L?  I keep looking at the 45uF / 1800V oil-filled cap thinking
> that would be a tough one to find today, but perhaps there are other parts I
> should be focusing on that are prone to failure in a 600L?
>
>
>
> Best Regards
>
> Donovan Case
>
> VE1BDC
>
> ______________________________________________________________
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>
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On 10/7/2011 7:04 PM, Donovan W. Case wrote:
> Folks,
>
>
>
> I am new to the group, and a recent recipient of several nice CE units
> including three 20A's and a 10A.  I have a couple more coming including a
> 600L.  I am wonder what 600L owners have found to be the most troublesome
> parts in a 600L?  I keep looking at the 45uF / 1800V oil-filled cap thinking
> that would be a tough one to find today, but perhaps there are other parts I
> should be focusing on that are prone to failure in a 600L?
>
>
>
> Best Regards
>
> Donovan Case
>
> VE1BDC
>
> ______________________________________________________________
> Central-Electronics mailing list
> Home: http://mailman.qth.net/mailman/listinfo/central-electronics
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Central-Electronics at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>