[Amps] 4-400A and QB4-1100 amp - TSPA

[Bill Fuqua]

That gives me an idea. I have a Thunderbolt and if I go to solid state 
rectifiers, a capacitive input filter and then wire up the 866A's in 
parallel but in series with the filtered  output I would still have the 
light show and more output. Just have to have higher voltage filter 
capacitors and bypass the filter choke.

73
Bill wa4lav


At 09:17 AM 9/1/2004 -0600, John T. M. Lyles wrote:
>The 1960 vintage Heathkit Chippewa amplifier model KL1 was a dual 4-400A 
>amplifier which worked well in class AB1. It was described in Electric 
>Radio magazine a few years back, with some modifications to improve it. I 
>believe that there is an online index to ER which you can look up, and 
>order a back issue. I believe that earlier W6SAI Radio Handbooks (like 
>21st edition) elaborated on the craft of building tetrode amplifiers. 
>About that time the 3-500Z was really becoming a favorite, as a grounded 
>grid zero bias (low bias) class B amplifier. Setting up tetrodes for best 
>IMD and linear operation requires a bit more care, as you have both a 
>screen and control grid bias voltage to deal with. Some have found that 
>grounding the grid and screen for RF (and applying the DC bias to both) 
>and driving the cathode is a good way to handle a 4-400A. The Johnson 
>Thunderbolt amplifier had 4-400As but it ran them in AB2 at too low an 
>anode voltage, leaving it short of output and prone to being overdriven 
>(causing IMD).
>
>I have a Chippewa that I am going to restore someday, as it got "modified" 
>by someone. I saw another one that had been converted to grounded grid, 
>but wasn't interested as it had been too modified from original, and for 
>that an SB220 or Drake L4 would be adequate. Problem with Chippewas is 
>that they had a separate huge power supply chassis with 866As and it is 
>usually missing or burnt up.
>
>73
>john
>K5PRO
>
>
>
>>Message: 1
>>Date: Tue, 31 Aug 2004 18:23:08 +0200
>>From: "ON5KM" <on5km at planetinternet.be>
>>Subject: [Amps] search 7527A design
>>To: <Amps at contesting.com>
>>Message-ID: <005601c48f76$d160a020$a284efd4 at computer>
>>Content-Type: text/plain;       charset="iso-8859-1"
>>
>>hi ,
>>who has a link or info to a good stable design using 1 or 2
>>7527a's (qb4-1100 or 4-400) ??
>>all info welcome .
>>tnx on5km stef
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