[SixClub] SB-200 6 meter conversions

[KB0NLY]

Anyone have a solid number showing what the FL-2100B power supply is capable 
of for plate current??  The stock 572B's have a max of 275mA per tube, for a 
total of 550mA running a pair at max.  The GI7B(T) are rated for a nominal 
plate current of 400mA each.  Meaning a supply capable of 800mA-1A would be 
best.  But I don't know if the FL-2100B transformers HV winding could handle 
that.

If anyone has the answer chime in.  I would love to retrofit the current amp 
with another socket and tube and make it a pair, plenty of room to do that. 
Swap out the fans for a blower or higher flow fans and it would be 1kw amp.

I did consider the GS31B for a future HF amp build.

73,

Scott



--------------------------------------------------
From: "Roger (K8RI)" <50mhz at rogerhalstead.com>
Sent: Monday, May 24, 2010 8:19 PM
To: <doc at kd4e.com>; "World Wide Six Meter Club" <sixclub at mailman.qth.net>
Subject: Re: [SixClub] SB-200  6 meter conversions

> On 5/24/2010 10:02 PM, kd4e wrote:
>> Nice piece of work!
>>
>> I have a GI-6b that I believe is identical to the GI-7b
>> except not good up into the 2m and above range - fine on
>> HF and 6M.  $35. including std USA shipping.
>>
>> doc
>>
>> KB0NLY wrote:
>>
>>> I had an amp on 6m running 572b's, while it would make
>>> power it seemed to oscillate and tuning was very touchy.
>>> After a while of fighting it and talking to many other
>>> conversion owners I determined it was the best I was
>>> going to get out of it.  The tubes just aren't worth a
>>> darn at 6.  They glow red at 10m, pushing them higher in
>>> frequency they would look hot enough to melt.  I tried a
>>> new set of tubes, Taylor 572b's, and they did a little
>>> better, some more mods and adjustments helped some of the
>>> problems.  Eventually I got fed up with it and sold it.
>>>
>>> I then had the opportunity to operate a station that used
>>> a SB-200 converted to a single GI7BT russian triode.
>>> Tuning was nice, clean output, very stable and easy to
>>> use.  I decided to build my own but couldn't get an
>>> affordable candidate for parts by this time.  I ended up
>>> finding a Yaesu FL-2100B that was damaged while being
>>> shipped, the meters smashed, a small dent on one back
>>> corner of the case.  I bought it and started to gut it
>>> and rebuild it.  A couple months of weekends later I had
>>> a half gallon amp that is very user friendly.
> That PS should handle apair of those IIRC.
>>> have one thing I would like to improve on it and that's a
>>> fan upgrade, the current AC fans In there are pretty low
>>> flow and I want to swap out for one or two higher output
>>> muffin fans.  However in its current configuration it
>>> doesn't get too hot to concern me.  I usually only push
>>> it to about 300w for casual use, though I have driven it
>>> to 500w a few times.
>>>
> Some where on the net is a photo of one with a squirrel cage fan on the
> back, pressurizing the under side of the tube compartment.  It's a very
> neat and clean modification. I saw an MLA 2500 conversion using a pair
> of the FI-7B's. it ran around a KW out and also had the same fan
> modification.
>>> http://kb0nly.info/6mqro.html
>>>
>>> One of these days I think I might actually get
>>> adventurous and build an amp using a pair of GI7BT's and
>>> see if I can get a full gallon out of them.
>>>
> You might want to look at the GS-31B. It's rated for a KW with a much
> larger heat sink.  $49 each.1.2 KG with heat sink. Good from 5 MHz to 2
> GHz.I think, but not sure,  the bottom is the same as the GI-7B
> Some with machine shop access have removed the heat sinks from both the
> GI7B and the GS-31B, and build a brass water tank and used water
> cooling.  You still have to put air on the seals, but just think...a big
> amp with no fan noise.
>
> 73
>
> Roger(KI8RI)
>>> 73,
>>>
>>> Scott KB0NLY
>>>
>>
>
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