[Amps] FL-2100 Problems

Tue Oct 28 15:22:59 EST 2003

Sometime back, I had a problem with an FL 2100, I dont know the series, but 
it really opened a can of worms (problems of design) to the FL 2100.   My 
first symptoms were a cracked 2 watt carbon series resistor, I think putting 
bias to the grids.  Replacing this, I found that the one 572b plate became 
Red hot very quickly, even in idle, and there was high Ip.   Removal and 
inspection  of the tube revealed a roughly 3/8" hole in the grid wires, with 
each wire crossing the hole burned back, with a ball of melted grid wire 
hanging at the tip of each grid wire.   (Look at your own tubes by looking 
down/up the axis of the tube..you can see quite a ways up the grid structure 
that is beneath the plate)  No doubt where all the cathode current was 
pouring through, heating the plate.  Further research revealed a Svetlana 
Mod by George Badger  W6TC, that doubled the standby DC bias to the grid, 
with information that the original bias was only marginally cutting the tube 
off in idle.  Newer tubes apparently had more gain, and the increased bias 
was a fix.  Additional testimonials to big bangs suggested further 
instability problems with that amp....

73, de Pat AA6EG

>From: "Peter Frenning, OZ1PIF" <oz1pif at get2net.dk>
>To: "R_Davis" <WD8JJA at arrl.net>,"H & W Electronics" 
><info at handwelectronics.com>,<amps at contesting.com>
>Subject: Re: [Amps] FL-2100F/B
>Date: Tue, 28 Oct 2003 09:39:00 +0100
>
>I can't comment specifically on the "F" version, I have never seen it or 
>the
>documentation.
>I wondered about the same thing Rick, but can only report my findings. As
>stated by R.Measures, it probably was the end result of some major glitch
>(thinking back, I did have one - while tuning up on 10m, a BIG bang ocurred
>causing my XYL to come running from the other end of the house! and a split
>anode on one of the tubes (that was the end of my first set), as reported I
>never got the second set to work satisfactorily).
>The reason for the two decoupling caps, is probably poor RF characteristics
>of the electrolytic cap (remember that the design is more than 30 years
>old!)
>
>Vy 73 de OZ1PIF, Peter
>
>**********  OZ1PIF **************
>email: oz1pif(no-spam-filler)@get2net.dk
>http://hjem.get2net.dk/oz1pif
>Ph. +45 4619 3239
>Snailmail:
>Peter Frenning
>Ternevej 23
>DK-4130 Viby Sj.
>Denmark
>***********************************
>----- Original Message -----
>From: "R_Davis" <WD8JJA at arrl.net>
>To: "H & W Electronics" <info at handwelectronics.com>;
><Fox_Tango at mailman.qth.net>; <amps at contesting.com>
>Sent: Tuesday, October 28, 2003 2:51 AM
>Subject: Re: [Amps] FL-2100F/B
>
>
> > Very interesting, Peter,
> >
> >  Actually, the question was proposed by "H & W Electronics" on another
> > reflector; I have a 2100B with the similar symptoms, while he asked 
>about
> > the 2100F.
> >
> > The 2100B schematic calls for a 220pF on each grid. If only one went 
>bad,
> > wouldn't I see a different response by using only one tube and switching
>it
> > from one socket to the other?
> > What do you think about the disc/electrolytic combination between the
> > bias-set resistor and the RF choke? This may be just a filter for the
>ripple
> > on the half-wave rectified bias, but they are common to both tubes. so 
>if
> > one was leaking, wouldn't it pull both grids down by the same amount?  I
> > can't read my schematic very well, but it looks like they are a 0.01 uF
>disc
> > to ground in parallel with a 2 uF/25V electrolytic to ground (although 
>the
> > parts list calls it a 2.2uF/50V - more likely).
> >
> > The 2100F is laid out a little different, with a 10uF on the
>relay/grid/bias
> > board.
> >
> > All comments appreciated.
> >
> > Rick, WD8JJA.
> >
> >
> > ----- Original Message -----
> > From: "Peter Frenning, OZ1PIF" <oz1pif at get2net.dk>
> > To: "R_Davis" <WD8JJA at arrl.net>; "H & W Electronics"
> > <info at handwelectronics.com>; <Fox_Tango at mailman.qth.net>;
> > <amps at contesting.com>
> > Sent: Monday, October 27, 2003 3:32 AM
> > Subject: Re: [Amps] FL-2100F
> >
> >
> > > Hi Rick,
> > >
> > > Check very carefully the two caps tying the grids to ground, I believe
> > they
> > > are C8-9 220pF in your version.
> > > I had exactly the same symptoms in my FL2000B, with a set of new
>bottles,
> > > and not until I took it completely apart for conversion to a QB4/1100,
>did
> > I
> > > find that one of these caps had blown - split completely open, but
> > invisible
> > > from the outside!
> > >
> > > Vy 73 de OZ1PIF, Peter
> > >
> > > **********  OZ1PIF **************
> > > email: oz1pif(no-spam-filler)@get2net.dk
> > > http://hjem.get2net.dk/oz1pif
> > > Ph. +45 4619 3239
> > > Snailmail:
> > > Peter Frenning
> > > Ternevej 23
> > > DK-4130 Viby Sj.
> > > Denmark
> > > ***********************************
> > > ----- Original Message -----
> > > From: "R_Davis" <WD8JJA at arrl.net>
> > > To: "H & W Electronics" <info at handwelectronics.com>;
> > > <Fox_Tango at mailman.qth.net>; <amps at contesting.com>
> > > Sent: Monday, October 27, 2003 4:15 AM
> > > Subject: [Amps] FL-2100F
> > >
> > >
> > > > Copy to AMPS reflector.
> > > >
> > > > H & W Electronics <info at handwelectronics.com>:
> > > >
> > > > Did you get a satisfactory answer to this, yet?
> > > >
> > > > I have an FL-2100B with similar symptoms.
> > > > I used to have normal (~.090) bias, was able to drive it to > 
>500mils,
> > and
> > > > it put out 700 - 800 watts peak normally (more if I crowded it).  
>Now
>I
> > > get
> > > > only about 60 mA bias, can only drive it to 250-300 mA, and get 300
> > watts
> > > > out, at best.  Also, driving it real hard, the LOAD control stays at
>or
> > > near
> > > > 0.
> > > > Those are my symptoms.
> > > >
> > > > Possible related causes: One time, I accidentally was tuning into 
>the
> > > > internal dummy load of my Dentron MT-3000A which is rated for 200
>watts
> > > and
> > > > is protected by an internal fuse. I popped the fuse, but quit as 
>soon
>as
> > I
> > > > saw the SWR skyrocket.
> > > > On another occasion, and I cannot remember if it was before or 
>after,
>I
> > > > heard a "TINK" from the amp.
> > > > Neither time did I notice these symptoms immediately, but it has 
>only
> > been
> > > a
> > > > few months since the blown fuse and the "TINK".
> > > >
> > > > Is the concensus that the tubes are now soft?  Funny thing, I 
>checked
>it
> > > > with one tube at a time, and with either tube in either socket, I 
>can
> > > drive
> > > > it to over 200 mA, maybe even 250 with my FT-101E.  But I can't get
>500
> > mA
> > > > with both tubes in. HV still looks good @ 2400V, dropping to around
>2200
> > > > under load.  ALC action looks normal, but at only about 300 watts 
>out.
>I
> > > > haven't cut the ALC line yet to see if it is holding it back.  I 
>don't
> > > think
> > > > it is since I.C. on the exciter looks normal.
> > > >
> > > > Any suggestions before I by a new set of bottles??
> > > >
> > > > Rick, WD8JJA.
> > > > ----- Original Message -----
> > > > From: "H & W Electronics" <info at handwelectronics.com>
> > > > To: <Fox_Tango at mailman.qth.net>
> > > > Sent: Monday, October 20, 2003 11:29 PM
> > > > Subject: [Fox_Tango] FL-2100F
> > > >
> > > >
> > > > > Hi All!
> > > > >    Anyone ever had low reading on the bias current? This one does
>only
> > > > > .06 while spec is .09. What gives?
> > > > >
> > > > > Now, more than ever, QSL.NET is in urgent need of your financial
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