[ICOM] 2SC1972 drivers?

[Dave]

Greetings;

In response to several request regarding the results of replacing the 
original drivers in the 756 Pro2 with the 2SC1945 the following has been 
my experience:

The transistors were received from RF Parts. Instructions accompanying 
the transistors recommended the installation of a 15 ohm resistor 
(swamping) between the bases of the two transistors. Also recommended 
was the reduction of the feedback resistors to 100 ohms each. In this, a 
quite late production, the feedback resistors were of the proper value.

Tests performed:

RF was monitored through the 30dB port of a 1KW attenuator terminated in 
the 50 ohm input of an IFR COM 120A communications monitor.

4 hours continuous key down at half power (50 watts)at 14.025 MHz. Heat 
rise in the drivers were within what I would consider nominal limits. 
Full power of better than 100 watts was obtainable on all bands except 
at the high end of the 10 meter band. Output at 29.500 was 95 watts CW.

Based on Icom specifications, two tone tests did not produce any 
excessive artifacts or spurious emissions.

Results of CW tests performed at app. 20 wpm  produced clean envelope 
rise and fall times.

IMHO the 2SC1945 transistors appear to be acceptable substitutes for the 
2SC1972.

Comments are welcome.

Dave, W5WP



ZL2AAA wrote:
> Please let us know if they work ok as would be very helpful for others 
> Morrie
>
> ----- Original Message ----- 
> From: "Dave" <dave at wpaperman.com>
> To: "ICOM Reflector" <icom at mailman.qth.net>
> Sent: Friday, February 05, 2010 7:55 AM
> Subject: Re: [ICOM] 2SC1972 drivers?
>
>
>   
>> I have reviewed the specifications of several transistors and have gone
>> with 2SC1945 from RF Parts.
>>
>>     
>> Dave, W5WP
>>
>>
>>
>> ----
>> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
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>
> ----
> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
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>
>