[Icom] Ic-2100H

Mon, 2 Dec 2002 07:44:48 -0600

Roger,

  Yes, the IC-2100H is known for final module failures. Icom used a final
design that produces a clean signal but that is also relatively inefficient
(generates a lot of heat). They didn't use a fan and in many mobile
applications (especially if you're a long talker), the large heat sink just
isn't enough. Even a couple of 3-minute transmissions at the 5-watt level
will get the heat sink nearly hot to the touch. HOWEVER, the radio has one
of the best receivers I've seen recently in a 2m mobile.

  I had an IC-2100H that had a final module that would fail intermittently.
I wasn't sure whether the failure was related to the switching transistor or
the module itself. Here's some of the information I used to troubleshoot the
problem.

  There are four pins on the Icom RF modules. From left to right, they are
1) RF input, 2) "gain control"? (this is driven by the TO-220 switching
transistor), 3) B+ (supply voltage), and 4) RF output. Pin 3 should always
be at the supply voltage whether in TX or RX. Pin 2, however, should be at
0v in RX and should be around 6v or so at 5w TX (it will be a little bit
higher for the higher output levels -- the guy at RF Parts just said it
should be above 6v at 55w).

  In my case, when the radio was transmitting real RF at 5w, pin 2 would be
right around 6v when in TX, 0v in RX. When the radio got hot and failed, pin
2 would go up to about 12.5v in TX. This inferred, to me, that the load at
pin 2 was reduced because some of the pin 2 connections inside the RF module
"opened-up" during RF module failure. I confirmed this by checking the
voltage at the pin 2 PC board pad during transmit with the RF module lead
disconnected from the module when the radio was operating correctly -- the
voltage was very close to 12.5v confirming that something is opening-up at
pin 2 inside the RF module.

  If the switching transistor was failing, I would have expected to see near
0v during transmit at pin 2 of the RF module. According to some emails I've
received, the TO-220 switching transistor is on the bottom of the board near
the RF module (I couldn't see it from the top of the board).

  Last time I checked, the RF module costed $55 plus $7.50 S/H (RF Parts).
Also, the cover comes off of the RF module relatively easily, I know a
friend who found a crack in one of the traces in an intermittent module and
simply flowed solder over the crack -- it works for now! Also, in regards to
seeing nearly 80 watts out of the radio, perhaps the previous owner had
cranked-up the drive level on the high power setting (not a good idea on one
of these radios)...

   73, Michael N9BDF

====================================
Message: 17
From: "Roger Peterson" <[email protected]>
To: "icom" <[email protected]>
Date: Sat, 30 Nov 2002 19:46:01 -0500
Subject: [Icom] Ic-2100H
Reply-To: [email protected]

I aquired an Icom IC-2100H and the finals I believe fried. My question is:
Is this an a problem with these radios or is it that mine had a weak final.
It is an almost new rig. I was transmitting and the power supply was set at
13.6 volts and it was drawing about the current it should have been. The
only thing is it was showing 80 watts out. Thought that was a bit high.
Checked my swr and it was well below a 2 to 1. When they blew it wasn't
drawing excessive current.The power supply made a sort of grunting noise for
2 or 3 transmissions and then the output dropped to driver output. Can
anyone help me with this problem.

Tnx es 73

Pete Kc8qr