[Swan] 700S Power Supply Requirements?

[Robert Balonis]

While I've not seen or worked with neither the HS 700S (nor the 700C as 
I mistakenly typed in previous message) nor the PSU-3A equipment, I had 
thought the 700S has the same power requirement specifications (and 
probably less in actual operation since I believe it has a reduced DC 
HV input power specification and uses more low powered solid state 
circuits than the 700CX).   Don't think I've ever previously heard of 
RF power output limitations due to power supply model discussed during 
the on-air nets or on the internet reflectors.

Are the specifications (or more importantly, the actual output 
voltages) from the PSU-3A different from the 117X and/or are the power 
specifications different from the 700S from the 700CX?  What are the 
voltage/current capacity differences that require the PSU-3A rather 
than the 117XC for full output from the 700S?

Note that in the mid to late 1970s Swan advertised the PSU-3 (whose 
cabinet looks like the 117XC) as their "fixed station power supply 
designed to provide all the voltages necessary for operation of most 
Swan vacuum tube type radio transceivers.  It provides power for the 
Swan amateur radio transceivers Models 240, 250, 350, 400, 500, 700 
series, including the 750CW." It appears that coincidental with the 
introduction of the PSU-3, the 117XC was deleted from the equipment 
line-up, but the 117X was still available as an "economical AC power 
supply without a cabinet or speaker" for base station operation (and 
more importantly for mobile applications with one of the inverters).

It seems highly unlikely that Swan would intentionally change the 
specifications of the 700S so that the PSU-3A would be the only supply 
that would provide full output from the 700S.  Given the competition 
for the Asian manufactures, its hard to think of that sales strategy as 
other than one that would alienate potential buyers!

Regards, Bob  NB3W


On Aug 26, 2006, at 2:39 PM, Soundval wrote:

> I believe that the PSU series (PSU3, PSU4)  were built to match some 
> commercial units. Then for matching looks to the ham sets there is the 
> PSU3A.
> The Swan 700's required the PSU's for full output.
> The 117's (or 230's) power supplies just didn't make it.
>
> Gene WB6SZS