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Yaesu FL-2100Z, last updated 2018-11-13
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The Yaesu FL-2100Z is a compact desktop linear amplifier for amateur HF bands (including WARC bands) and will easily deliver the UK legal power limit of 400W on SSB and CW.  It uses a pair of 572B/T160L output valves in a grounded grid configuration, a succesful formula used in other amplifiers such as the Heathkit SB-200 and in quad form on the current production Ameritron range.

Configuration Class AB2, grounded grid
Frequency coverage 160m - 10m including WARC bands
Plate input power 1200W PEP SSB, 1000W CW, 400W AM/FM/FSK
Plate voltage 2400V (no load)
Drive requirements 100W PEP for full output
Input impedance 50 ohms unbalanced
Output impedance 50 - 75 ohms unbalanced
3rd order distortion products 31dB or better at 1kW PEP
Tube complement 2 x 572B/T160
Cooling system Forced air
Power requirements AC 100/110/117/200/220/234V 50/60Hz
Current consumption (100-117V) 18A
Current consumption (200-234V) 9A
Dimensions 157H x 345W x 326D
Weight Approx 20kg

This unit was bought untested and had not been used for some years, the seller advising me to have a good look over it to make sure it was OK.

The output valves were drawing 40mA during standby which looked like a biasing fault, or maybe a gassy valve.   During soak testing, the unit failed about 45 minutes into the test with excessive current draw from the HT supply (plate current meter off the end of the scale).

24-Oct-2004: This is the culprit, a 33 ohm / 3 watt resistor used as a grid stopper.  As you can see, it had started to disintegrate and finally went open circuit causing one of the 572B output valves to "latch up" and short the HT supply.  The other resistor of the pair measured 64 ohms so both were in need of replacement.
This is a pic inside the top of the unit (click on the picture for a larger version).  Not much to write home about except it looks tidy with no signs of flashover, cooked components, or any other horror stories.
29-Oct-2004: All fixed, there is now no current draw in standby.  Testing under power is giving good results, so the unit is now "in service".
The drive from the FT-990 on PSK with the power at minimum, is 8 watts giving a healthy 80W output. 16W of drive gives 150W out, I don't have the facilities to run up more than this right now - 150W is pushing the little Palstar ATU as it is...


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