Yeepers, haven't worked on this in a while...
Ok, last I fired this up, no RF output but the ammeter on the PS registered
20A. So I pulled the main feed to the PA and put in an ammeter into the
smaller red lead, as per the manual. Current went first to >400mA (supposed to
be 4 to 8 milliamps) before settling down to 10mA. During this time smoke
decided to roll out. Termination of testing.
Pulled the PA and it looks like R8 smoked. R8 is 3.3 ohm feeding Q4. But
Q3/Q4 had no power so not sure why it would smoke. The white/gray wire for
bias is after this 3.3ohm so I'm a bit surprised.
I checked driver and final transistors, without removing them; the final shows
typical diode connections. The driver shows base to collector ok, but the base
to emitter is shunted by 32 ohm (the bias adjust pot apparently). Have not
pulled transistors to test further.
Any idea while R8 would smoke?
The white/gray wire bias, hmm, something wrong there: With no PA installed I
measured 4.5V and rising with the radio in TX. Ah, stupid me, with the PA
removed the bias diode is missing. Clipped in a 1N4004 and I get 0.64V for
bias to the PA.
shawn kb1ckt
On Tuesday, June 12, 2018, 6:40:44 AM EDT, Shawn Upton via TenTec
<tentec@contesting.com> wrote:
Have schematic but have not pulled the panel so I can look inside the box to
verify what wire goes where.
shawn kb1ckt
On Mon, Jun 11, 2018 at 10:15 PM, Rick@dj0ip.de<Rick@dj0ip.de> wrote: Do you
not have a schematic, Shawn?
If not, you can download it here:
www.dj0ip.de/ten-tec-stuff/omni-a-d-manual/
It's not very difficult to determine which transistors are the finals.
They're pasted to the heat sink.
The transistors are Q3 and Q4, MRF 458, and shown in the manual on page 3-52.
The schematic is at the top, a picture (very poor quality) below the schematic.
Unfortunately all of the documentation from back then was strictly black and
white.
73,
Rick, DJ0IP
(Nr. Frankfurt, Germany)
73,
Rick, DJ0IP
(Nr. Frankfurt, Germany)
-----Original Message-----
From: TenTec <tentec-bounces@contesting.com> On Behalf Of Shawn Upton via TenTec
Sent: 12 June 2018 03:09
To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Cc: Shawn Upton <kb1ckt@yahoo.com>
Subject: [TenTec] Omni D final wiring
Working on an old D that someone else has been into... and before I go too far
I'd like to verify the wiring to the final. A quick look on google does not
reveal what I need: verification of what wire (color) goes where. It does not
look like fun to open up the final.
Radio receives good but when I did a power test I got 20A input (per the 252
PS) and nadda for output. PS tripped out on 40m a couple of times too. I'm
still in the beginning stages of debug, and checking wiring seems wise (wires
on the pass throughs have been removed and reattached--hence the question).
Quick check with an ohm meter shows 100ohm to GND on what i think are the
finals (which bothers me but perhaps it's elsewhere in the radio, as I did not
remove 13V wire), and a diode where I think the bias diode is.
shawn kb1ckt
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