[TenTec] Orion II Repair Questions

[Bob, W3IDT]

Some time ago I asked about an issue I was having with my Orion II:
The RX would stop after TX with FT* or SSB above about 10 watts (CW at 
100 watts was fine). Only a power down/up cycle would unlock the RX. RFI 
was suspected, but it is not the cause.

Steve, NY3A, with a complete test shop, has been digging into the issue.
He has discovered two problems. I am asking for any knowledge or advice 
on either one.

1. The problem almost never happens if the input power supply is below 
about 13volts. Almost always happens at 14.5volts. So, there is 
something that seems very input voltage sensitive, though the various 
voltage regulators all seem OK.

2. The proximate cause of the RX shutdown is the "REF-IN" signal from 
the CPU going "low"... As Steve says,
---------------
VCO1 and 2 are unlocking. The reason they're unlocking is their 
reference is going away. The reference is a DDS, direct digital 
synthesizer. The reason it's going away is the REF_EN signal is going 
low. This removes a crystal oscillator reference signal from the DDS. 
This REF_EN sig comes directly from the microprocessor board.
--------------------

Steve's complete message (and earlier messages) copied below.

Does anyone have a clue as to the cause of the REF-IN signal going low? 
OR about the voltage sensitivity?

Any advice greatly appreciated.

Bob, w3idt

.......
. Robert F. Teitel, W3IDT
.
. w3idt at comcast.net
. w3idt at arrl.net
........


-------- Forwarded Message --------
Subject: 	RE: Status /Orion II
Date: 	Thu, 25 Aug 2022 21:42:30 +0000
From: 	Steve S <NY3A at hotmail.com>
To: 	w3idt at comcast.net <w3idt at comcast.net>



Made progress today.

VCO1 and 2 are unlocking. The reason they're unlocking is their 
reference is going away. The reference is a DDS, direct digital 
synthesizer. The reason it's going away is the REF_EN signal is going 
low. This removes a crystal oscillator reference signal from the DDS. 
This REF_EN sig comes directly from the microprocessor board.

This happens only at higher Power Supply voltage. I've been testing it 
at 14.5-14.7V. The manual says the upper limit is 15V. It unlocks is 
either rcv or xmit at this higher voltage.

So why is the micro pulling this sig low at higher PS voltage? Sometimes 
there is a PLL unlock signal which if true, triggers radio shutdown. I 
see no such signal from the PLL. Bottom line is I don't know right now. 
If Ten Tec was around I'd send email that software guy would eventually 
see, and he could tell me.

I started signup for Ten Tec group on Groups.io forum and will ask what 
triggers Ref En shutdown and will see if anyone knows. Odds are slim, 
but hopeful.

Possibly there is A/D monitoring PS voltage through voltage divider 
somewhere, or micro PS may have issue. This seems unlikely since micro 
seems to be running fine otherwise.

In any case, standby...


-------- Original message --------
From: "Bob, W3IDT" <w3idt at comcast.net>
Date: 8/25/22 4:49 PM (GMT-05:00)
To: Steve S <ny3a at hotmail.com>
Subject: Re: Status /Orion II

Thanks for the update.
Hope you're considering it a technical challenge.
Certainly far beyond me.

Should I post something in the Orion reflector?
Maybe someone else has had this issue.

Bob, w3idt

.......
. Robert F. Teitel, W3IDT
.
. w3idt at comcast.net
. w3idt at arrl.net
........

On 8/25/2022 1:59 PM, Steve S wrote:
> Hi Bob
> 
> Just a note...
> 
> I replaced final amp caps, no change.
> 
> I've noticed running at higher PS voltage, 14.5V, will make unit unlock 
> quickly when xmit SSB,CW or even occasionally even in RX. Lower PS 
> voltage, 13V, never seems to unlock.
> 
> I've checked input 1st stage voltage regulators on PLL, and looks ok. 
> Almost all of PLL is double regulated so those should be ok. Mystery 
> right now why PS voltage influences unlock if PLL Vregs don't change. 
> Wondering if PLL control getting messed up somewhere else.
> 
> Ten Tec has info in manual on PLL control details in manual, per band. 
> I'm just starting to get into PLL details to see if I can learn more. 
> e.g. which VCO is unlocking and why.
> 
> Next Wed or Thurs I'm heading to NC for Shelby hamfest, then continuing 
> to FL for relative visit. Should be back in couple weeks.
> 
> 73
> Steve