FL2100 HF amplifier ' Murphy strikes again !
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- Опубликовано: 15 окт 2024
- This FL2100 hf amplifier was working fine , no problems at all, Now today after just being sat there its not working, Murphy's playing his old tricks again.
Here is a link to a site with info on 'how to make a Capacitor Discharging tool' ..
terrydownsmusic...
Hi! I just bought one of these broken. FL-2100B, the buyer said tubes were probably gone and the amp was not stable at all and could not be used. I have now spend few days recovering it and it's now working, still need a new band switch because 10m contact has arced badly. Otherwise working well, and peaks 800-900W now with original Cetrons. What i found out is that this and its sister amps B and Z are all prone to self oscillating in HF and VHF frequencies. And when this happens, a tube can arc in it. Usuall damage is those 33ohm grid resistors and band switch etc BUT THIS CAN ALSO DAMAGE DRIVING RADIO as HV comes to cathodes!. There is a design flaw in the circuit from Yaesu, W8JI site has plenty of information of this oscillation and how the design should be changed.
So what I did is I repaired parasitic chokes, removed the grid resistors and capacitors and put grids directly to ground (chassis). This is the way grounded grid amps should be done. Biasing have to be done from cathodes now on. Also grounding of the plate capacitor is not well done... I will still add a netralization circuit in it which is very useful with these 572B tubes that are likely to self oscillate if something changes in the circuit a bit. And new ALC circuit as well. Happy to see your amp working, with original design, I just warn that some day it might not and to know where to start looking. 73 de Simo OH5GIO =)
@MM0IMC Thanks, Ive got two off them, This one is In very good condition, The other one is almost as nice but ive got to rebuild the bandswitch, Its been under the bench since mid last year, It also did good power.
In the info on the FL2100 amp above is a link to a site that has the info for you to build a 'Capacitor Discharge Probe'.... So stay safe and be very carefull when working on ANY high voltage equipement.
A so-called 'Jesus stick'.
Thank you for the video - I have one of these and it does the job - I have a fan mounted on the top of mine - just for extra cooling when running PSK or RTTY.
I own 2 of these amps. They are nice amps once you get the known problems worked out. That's an interesting parasitic choke/resister arrangement you have there.
what is the value in henrys of L203 Grid RFC Choke? with the 3.3k Ohm resistor. or
L3 with the 680 Ohm?
Because the bleed off voltage is still drain off whennu shit doen the amp ...so its very posible for the resistor to fail ass the vomtage is draining ...the part can brakedown,then go open ...happens alot actually..... Especially in bleeder circuits, one way to help insure the amp is safe is to make sure thwre are bleeders and always drain caps...inwich the bleeder circuit should do...thosnis why the resistor can fail even after shut off.... Beat of luck..73 from justin
800.tops if thebtubes are perfect and thats asking alot
.. normaly 600-750 is sweet spot 2 572bs..had some flaws on then2100b butbwas decent amp
I see some one has left a thumbs down... Obviously a Cb'er who knows nothing about amps.
Very neat!
73 de VA6POP