6M Amp Status (W9DR Estate)

[Charlie Young]

Not planning to do anything with this until my work backlog is caught up, but I brought it out of the storage garage into the sunlight for a close inspection prior to Hamvention.  This is in case we see some part missing or damaged. we could scour the flea market for any needed part.  I did not see anything damaged or missing, at least in the main RF deck. 

Two pictures are sent as separate messages.  

The front and rear panels have been repurposed but the rest of the chassis metalwork was new construction.  it looks like they are powder coated.  The amp really looks good.  The old front panel markings for a HF bandswitch can be seen; these were covered by a plastic callsign sign which his XYL removed.  I will have one made with N8RR to cover this up. Otherwise there is no evidence of the repurpose. 

Unless there is unseen component damage, this amp should play as-is or close to as-is.  Not a bad $500 investment. 

The design of it looks great also.   It uses a big air variable for the tune capacitor, and a Jennings vacuum variable load capacitor.  The lead lengths are very short to minimize stray capacitance.  The tube is likely an MRI pull, but it does not show signs of excessive heat.  The tube is mounted correctly, using Eimac components. 

How was he using this, and how much power will it run?  It is obvious he was not running anywhere near the power level the tube is capable of.   The evidence is the meter ratings on the RF deck and power supply.   The plate current meter reads 1 amp full scale.  The HV meter on the power supply reads 5000 volts DC full scale.   That and the fairly light weight of the supply indicates the system is likely capable of running   4 to 5 KW OUTPUT as equipped with the existing power supply.  He was not running  7 to 10 KW.    He might have been running at or near legal limit.   He did blow up the feedpoint on a single 6M9 M2 yagi with it.  3 or 4 KW could do that, but he might have been testing.or the feedpoint connection may have failed.   Anyway, I am OK with the power supply as-is, it is more than capable of doing anything I need it to do.   Legal limit with no time restriction is all I need.  This is one Heavy Duty legal limit amplifier.  

The amp has a couple of enhancements compared to the normal 6m conversions we see. 

It uses 2 copper coils in the output circuit for better impedance matching and harmonic suppression.   The builder knew what he was doing.   It has a filament variac  and a filament voltmeter on the front panel.  Controlling the filament voltage extends the tube useful  life. 

There are still some unknowns.   I have to remove the bottom cover to inspect the components and wiring down below.  Not sure what it is running for a TR relay or for the bias circuit.  Given the other observations, whatever he used is likely adequate.

Anxious to try it out but that will have to wait until we move some other stuff out of here. 

Thanks again to KD8GWH for riding with me, and to N8DX for the tip on the amp availability. 

 73 Charlie N8RR

[Larry Fravel]

That is one good looking amp Charlie.  Nice and clean.  It should run FT-8 for you all day long at legal limit.  

Larry K8YYY

 Truth is like the sun. You can shut it out for a time, but it ain't goin' away. 
–Elvis Presley

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