I am pretty sure that all of those other Larcan amps are working
reasonably well. The one that went to Good Buddy Ron had a hex put on
it in an attempt to cancel the hex that GB Ron put on me and K3SK. I
learned that trick from a Jamaican girl friend last year. I met her in a
bar in Berwick. She was driving taxi.
I would add that you should never buy an MRF151G from China. They are
all made out of Chinesium and will not work. Most likely relabeled
junk. Only buy it from a reputable source here in the US of A. I have a
FM TX that has 2 X MRF151Gs in it. I was going to put it on 144, but
decided to save it for the FETs. I am working on two more amplifiers
here. One is a 1000 watt unit and the other is a 1500 watt unit for
KF0M. I am adding filtering and VSWR protection circuits. That is one
of my winter projects.
I am wondering if the problem is a parasitic oscillation that
intermittently appears. The 500 watt amp has a similar bias bypass as
the 1500 watt amp. I believe it is a .01 chip. Possibly adding a .001 in
addition might be a good idea. Maybe a chip on the drain rail as well. I
am just guessing here.
Dave K1WHS
On 10/24/2024 12:03 PM, Ron Klimas WZ1V wrote:
Thanks to all who replied.
If anyone else got a self-igniting amp like mine from Good Buddy Dave,
Here's the link to the correct schematic so you can repair it:
https://www.mmra.org/larcan/15kWhidocs.pdf
Replacement non-exploding chip caps are available from Mouser,
the values on the output network of each FET are -
30 pF in parallel with 27 pF, 39 pF x2, and 6.8 pF,
example Kyocera 800B270JT500XT for the 27 pf.
https://www.mouser.com/c/passive-components/capacitors/ceramic-capacitors/mlccs-multilayer-ceramic-capacitors/multilayer-ceramic-capacitors-mlcc-smd-smt/?capacitance=27%20pF&voltage%20rating%20dc=500%20VDC
There is no reason these caps should have shorted and burned up.
I suspect I was just unlucky and got a Larcan lemon.
Just a heads up on the FET's - they are all not created equal,
SRF3943-2 was the original part, beware of Chinese fake knock-offs.
73 Ron WZ1V
----- Original Message -----
From: David Olean <k1whs@metrocast.net>
To: newsvhf@mailman.qth.net, vhfcontesting@contesting.com, "222 >>
222Activity@groups.io" <222Activity@groups.io>
Date: Wed, 23 Oct 2024 15:05:51 -0400
Subject: Re: [NEWSVHF] 222 activity night
Wow, Ron that is quite a list and I see a new call or two there, which
is great. It is funny how the power level works. When I went from 170
watts on 2M to 1500 watts I was sure that my grid totals would soar
during the contest. They did not. All I saw was an increase in the # of
contacts made. That sure surprised me. 120 watts will still do a lot of
work!! I worked 15 of the 20 stations that you worked. I missed N2SLO,
WB2ONA, K and W1GHZ. Other stations worked here include N1GYT, WA1LWC,
K3SK and two others for the same total of 20 QSOs.
The excitement of the evening was working WA3EOQ on CW. We set up a sked
and I saw a big blip just off frequency and about 20 dB out of the
noise. I tuned it in and it was Howard calling me on CW. I gave him a
559 and he passed along a 569. I never missed a dit, and that was the
strongest I have ever heard him on a Tuesday night. Knowing that things
might be up a bit down the coast, I tried FT8 with K3SK. He decoded me,
and I could tell he was there, but did not decode him. Normally we
hardly ever makea contact on FT8. We switched to Q65B-30 and worked
quickly. -22 here and I was -20 there as I recall. By about 00:50the
East Coast was quiet so I quit and listened on 28 MHz for a few minutes.
Between about 01:15 and 01:30 I could work JAs and VKs on FT8. I saw no
CW activity. Imagine JAs coming in so late in the evening. The SSB HF
contest will be Bedlam I am sure.
I was really having fun hearing actual QRM early in the evening. There
were QSOs on top of QSOs. In short it was a huge amount of fun. Why
can't a VHF contest provide the same excitement? That is an
interesting question.
73
Dave K1WHS
On 10/22/2024 9:00 PM, Ron Klimas WZ1V wrote:
Limped along at 120 Watts on 222 tonight, but logged:
WB2VVV FN41, WA2LTM FN20, K1PXE FN31, WA3NUF FN20,
WB2ONA FN20, K1WHS FN43, N2SLO FN30, AA2SD FM29,
KC1DWH FN31, W1AIM FN34, W1GHZ FN34, N1SV FN42,
WA3EOQ FM09, WA3SSG FN20, K2RMX FN20, WA1RKS FN32,
WA1MBA FN51, WB2RVX FM29, and K3TUF FN10.
Anyone know where I can find a schematic and or parts list
for a Larcan High Band VHF 500 Watt driver amp ?
Having tough time repairing by guesswork.
73 Ron WZ1V
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