The NEC V360 TRPA page and photo's

Since getting back on the air in South Australia ( VK5 ) I have generally run fairly low power (25- 100Watts) on 144MHz but while living in Alice Springs I had built or converted serveral valve amps for 144MHz. I have through the kindness of others been able to buy back my original single 8874 triode amp but have not been able to get up the courage to excite the HT on that amp, it requires a bit of work around the HT rectifier and capacitor bank, so in the main part have not had an amp to use.

During the work on my LARCAN modules for 50MHz I went wild and bougth an LDMOS module from ITALAB in Italy but swore I would wait until the LARCAN was going on 50MHz before I dedicated any time to the new 1KW amp for 144Mhz.

Around this same time the NEC V360 amplifiers from a Channel 5A TV transmitter started to appear in local shacks, so I asked about getting one and in due course one appeared.  I am not sure why I did this as I had the LDMOS module there on the shelf waiting to have DC put onto it.  Oh well it is done now, maybe I will use it for something or give it to some one who needs an amp.

Well a need arose where I knew it was going to be benificial to have a bit more power and be able to off load the heat from the ICOM 275 multimode into the external amp so the evaluation of what needed to be done had to become number one priority in March 2014.

Power Supply

These NEC amplifiers need a healthy supply of 28V to operate and I only had 12V and 48V high current supplies.  It turns out that the switchmode PSU's that had powered these NEC amplifiers were also out and about, so I enquired about sourcing two (one for backup as I have had problems with switchmodes before and other projects).  

These supplies were run on multi phase input supply and require a little bit of modifcation to run on 240Vac single phase.  In reality, I replaced the old input connector with a fused and filtered IEC socket I bougth from Jaycar (photo later I hope).  The removed the original NEC output connector and used the exiting heave output leads to fit some Anderson Power pole connectors.  I have these power poles configured with + and - stacked above each others so no 12V leads will fit into them, just to avoid those frenzied moments when the wrong lead is plugged into the wrong PSU.

Drive power, too much drive power

As is typical in these sort of amplifiers the input level needed to drive them is very low and presents a problem of how to disperse the extra power from a modern day transceiver to meet the low power level needed.  In the case of the V360 if you look at the internal layout you will see there is a multi stage driver stage to take the low input power up to a level required by the output stages so why go down in level then back up again?  When talking with Colin, VK5DK he alerted me to this option and had already converted his V360 in a similar fashion. {Edit - Col had actually injected one stage earlier than me to get more gain}  Thanks Colin, you saved me a lot of trouble.

Input combiner, drive goes in here

V360 P.A input splitter, high level drive goes in at the bottom of this after you lift the hard line coax's off

Connections to the V360

The V360 uses a DC connector on its rear panel that I have not seen for many years and have no idea where you would source one to use for the DC input as well as control and alarm voltages out.  Having no hope of getting one of these it seemed obvious I needed another way to get power into the module.  After some poking and proding I decided to drill two holes in the rear panel to allow some heavy DC leads to be connected.

NOTE:   While investigating the centronic connector I undid the screws for the socket on the V360 and pulled it forward to see what was connected.  This led to the two wide tinplate steel strips that come down from the PA's deck comming into contact and they did not seperate after I pushed the connector back in.  I was quite shocked to find the module now had a dead short on the B+ to ground.  Sigh, nearly another tradgery as I was about to turn the power swtich one to do some tests.

V360 Rear panel

Original rear panel of the V360 showing the muti fuction DC connector

RF out of the V360

Getting power out was very easy, after deciding on the high level drive configuration, I piped in 5Watts from my FT-817 via a coax fly lead, applied the needed 28V and connected a power meter and dumy load the output connector (shown in the photo below). I was immediately rewarded with over 50Watts of output power and the Alarm LED went off now that there was some output, time for a cuppa to evaluate my victory : -)

V360 front panel

part of the V360 front panel (top 1/3 rd) showing the standard output connector and the Alarm LED

V360 documents

V360 CCT pdf   V360 manual extract (30pages pdf 1.9Mb)  V360 manual extract (22 pages pdf 810Kb)
Long view

Looking across the RF section of the V360, output is to the right.  Oh the big blue things are circulators (black magic)

Main PA

Looking down on the otput stages of the PA, output is at the top where the two blue circulators meet

Where to now

Since my initial run up and tests, I have been using the amp on SSB and digital modes.  It needs no extra cooling in SSB or CW operation and gives a smooth 300W PEP.  Digital modes can be run at 200W out (according to my Bird 43) without any undue stress but the module could do with some fan cooling at this level.  This has all been done in Winter, so in summer a fan is definitely warranted for any digital mode in a non air conditioned shack.

Yet to do

1.  remove BIAS on Rx to reduce idle current / heating on standby
2.  fans on heatsink for summmer / digital mode
3.  tidy my mounting of the coax relays
4.  fit a SWR / Power out display to be driven by the internal coupler

This web page was last edited on 6th May 2014 by vk5pj