[Amps] Amps Digest, Vol 44, Issue 84
Edwin Karl
edk0kl at centurytel.net
Fri Aug 25 14:31:49 EDT 2006
Re: AL-80B
Mike, first I would check the bias on the tube. It sounds like the tube is
idling
in the "on" position. There should be a relay that biases the tube to hard
off, i.e. no
plate current or a solid state circuit. When you transmit this cutoff
disappears in favor
of bias from a zener.
Having once had a similar problems with a. a Kenwood TL-922 and b. an
SB-200. By the
way in both cases the Hardbach keying module failed. The result is the tube
is in standby
drawing 150 ma or so current. I believe Ameritron uses some sort of
electronic bias switch
that could also be the culprit (see Harbach above).
Sounds like the tube takes off after being seriously overheated by high idle
current, no drive and
thus no output. That also explains the 300 volt drop in plate voltage when
in "standby".
Good Luck, we're all counting on you ...
ed K0KL
-----Original Message-----
From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
Behalf Of amps-request at contesting.com
Sent: Friday, August 25, 2006 11:00 AM
To: amps at contesting.com
Subject: Amps Digest, Vol 44, Issue 84
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Today's Topics:
1. Sell: Heath Sb201 RF Deck Components (w2cqm at juno.com)
2. 1296MHz amp kits available (Rod Adkins)
3. AL-80B Trouble (Mike Schlamp)
----------------------------------------------------------------------
Message: 1
Date: Fri, 25 Aug 2006 13:38:17 GMT
From: "w2cqm at juno.com" <w2cqm at juno.com>
Subject: [Amps] Sell: Heath Sb201 RF Deck Components
To: amps at contesting.com
Message-ID: <20060825.063834.5614.774032 at webmail02.lax.untd.com>
Content-Type: text/plain
Offering the following components removed from a Heath SB201 15-80m
amplifier. All parts are in like new condition:
A. 15-80m Tuned input assemblies complete with bandswitch. Fully wired.
Removed intact no cut wires.Both components $35
B.Heath 15-80m tank circuit/coil/bandswitch assembly with air variable plate
tune capacitor and auxiliary mica loading capacitor. No RF burn marks ready
to drop in. Will handle 800w. $65
C. SB200/201 HV plate/parasitic choke assembly with HV bypass cap,
resistor/coil parasitics. $18
D.Six (6) OEm 30K 7W bleeder resistors $8
E.Six (6) OEM solderin Nichicon 125mFd/450VDC power supply filter capacitors
Heath Part 25-34. Tested A-OK. Removed from working equipment. $28 All items
+ shipping from zip 18426. PayPal OK if not a credit card transaction. Ron
W2CQM/3 http://swap.qth.com/segamida/549445.jpg
________________________________________________________________________
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------------------------------
Message: 2
Date: Fri, 25 Aug 2006 08:28:57 -0700
From: "Rod Adkins" <adkins92rod at earthlink.net>
Subject: [Amps] 1296MHz amp kits available
To: "Amps" <amps at contesting.com>
Message-ID: <380-220068525152857640 at earthlink.net>
Content-Type: text/plain; charset=US-ASCII
A kit to produce 30W at 1296MHz has been engineered by members of the San
Bernardino Microwave Society http://www.ham-radio.com/sbms/ and the San
Diego Microwave Group http://ourworld.compuserve.com/homepages/edmunn/ :
- power gain 10 - 13dB (so budget for 3W i/p) - uses a PTF 10021 FET
- 28v dc supply; current drain about 2A (or use 24v & lose <1dB power
o/p)
- cost $45 + $5 s&h (shipping USA; kit does not include heatsink,
connectors or T/R relay)
For full details, assembly & test info, and to order a kit, email
1296amp at cox.net
Note: this kit contains surface mount components; familiarity with handling
these is helpful (BUT: it just ain't that hard - see comments below)
For pic of completed amp, see
http://kahuna.sdsu.edu/~mechtron/hamshack/1296Amp/1296Photo1a.jpg (note: you
do not have to erode the heatsink as much as our brave beta-tester did <g>)
Personal comments from a builder:
- I have successfully completed one kit, with a second on the way;
splitters/combiners also under construction
- I used a Model 99 heatsink from Communications Concepts ($22 + s&h)
http://www.communication-concepts.com/heat_sink.htm
- to accomodate the FET height vs PCB thickness, I chose to use a sheet
of 0.032 in thick brass beneath the PCB instead of washers or bending the
FET tabs; I used item #253 from K&S Engineering www.ksmetals.com. Many hobby
stores have a display area with K&S products.
- I decided to use a 4in x 6in slab of copper between the FET and the
aluminum heatsink to better distribute heat. I bought mine from Industrial
Metal Supply Co., who sell metal offcuts by the lb http://www.imsmetals.com/
locations Irvine, Riverside, San Diego & Sun Valley in CA
- thermal grease: to use or not to use? There are many opinions. Advice
I have had is that use of grease prevents getting a good rf ground - leads
to possible oscillation & thermal runaway.
- I found the bias adjustment pot somewhat fragile, so, being ham-handed
(sorry!), I am using a 10-turn encapsulated pot in my Mark II version
- the clearance holes in the PCB are large enough to permit the use of
#6 machine screws (NOTE: must use #4 for mounting FET); having broken a #4
tap recently, which stuck in the project... need I say more
- power relays; for brick amps,I have standardised on an NTE SPDT, 12v
coil, 40A contacts, encapsulated relay from Mouser http://www.mouser.com ;
$7.25 ea @5-off; part # 526-R51-5D40-12F. Spade terminals and easy mounting
with a #10 screw.
- rf relays; I use Transco SPDT, SMA relays from DEM
http://www.downeastmicrowave.com/ $45ea guaranteed working; I have been told
they will tolerate 80W COLD-switched at 1296. They are nom 28v, but DEM
sells neat kits for operating from 12v (which I use)
- connectors; I used right-angle SMA, PCB-style; I found I needed to
file the pins slightly to achieve a sliding fit; pyrojoe claims SMA is good
to 400W, so have at it...
- surface mount parts; I use demagnetized tweezers & a fine Weller
soldering iron bit; if, like me, you suffer from the "slippery little
suckers" syndrome, a la "Pretty Woman," spread a sheet on the floor & work
directly on it. Sounds daft. Wait 'til you're searching for an SMD cap on
your workshop floor...
Now make some noise on the 1296 nets:
- WSWSS http://www.wswss.org/ Tues & Fri evenings
- PNWVHFS http://www.pnwvhfs.org/ Sun am
Any info on other reflectors you think this email should be listed on,
please advise the writer off-list
Rod Adkins WI6M
------------------------------
Message: 3
Date: Fri, 25 Aug 2006 08:28:05 -0700 (PDT)
From: Mike Schlamp <w5cul at sbcglobal.net>
Subject: [Amps] AL-80B Trouble
To: amps at contesting.com
Message-ID: <20060825152805.4720.qmail at web83007.mail.mud.yahoo.com>
Content-Type: text/plain; charset=iso-8859-1
Hi all,
I am having my first problem with my AL-80B and I need some help in
isolating the trouble, along with some signal tracing data that is not
covered in the manual. Below is a synopsis of what is happening.
AMP: 3yr old AL-80B, Amperex 3-500ZG Installed, 110Vac Primary, does
not have the QSK kit installed.
SYMPTOM: With the standby switch in standby, band-switch set for
80M, AC power applied to Amp, the meters read ~2700Vdc (normal is
~3000Vdc), 150ma Ip, and the Ig is showing a negative draw. The Ig meter
buries itself to the left. After 2-3 minutes in this condition, the plate
is glowing reddish orange. With the standby switch placed into operate, RF
applied from the exciter, the exciter complains of High SWR and there is no
RF power being produced by the Amp. With the band-switch placed in any
other position, the same symptoms apply.
ASSUMPTION: The 3-500ZG has a short, and or the tube is not
receiving the proper bias voltage during off periods . The glowing while
in standby is due to the current draw across the plate; dissipating ~400W.
HELP: Is my assumption too far fetched? If the tube is shorted, what
could have happened to cause this, considering the tube is only 3yrs of
age? My fear is if I just replace the tube, I will end up back to square
one over time. Is there any trouble shooting guide regarding the Amp? I
am looking for a document or notes indicating voltages, along with tips of
what to look for.
Thank you,
Mike
W5CUL
------------------------------
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