Re: RS-320 - Keeps blowing FET's

[m II]

Jim wrote:

> Anyone else having problem with Ten Tec Rx-320 blowing front end
> FET's? Any mods to prevent this or is there a replacement FET with
> less tendency to short out? This is definitely a design fault, as I
> have 3 receivers in parallel on same antenna and the R320 is the only
> one blowing FETs.

Mine is #08C104XX with no problems in about three years. What are the
chances of static build up in your antenna?

mike

[Sherman D.]

If you are handy with a soldering iron, you might consider solding an rf
choke coil to the antenna input connect to ground. This would provide a DC
ground while allowing the radio frequencies to pass thru unaffected..

"Jim" <wd...@cox.net> wrote in message
news:aj78a0lopb8ronbg2...@4ax.com...

> Anyone else having problem with Ten Tec Rx-320 blowing front end
> FET's? Any mods to prevent this or is there a replacement FET with
> less tendency to short out? This is definitely a design fault, as I
> have 3 receivers in parallel on same antenna and the R320 is the only
> one blowing FETs.
>

> I sent it to the factory and they were supposed to perform a mod to
> prevent this, but it never worked. Wasted $50.00.
>
> Called factory again, their latest solution - - - sending me a bag of
> FET's so I can replace them myself.....

[Rob Mills]

"Jim" <wd...@cox.net> wrote in message
news:aj78a0lopb8ronbg2...@4ax.com...

>>> Anyone else having problem with Ten Tec Rx-320 blowing front end
FET's?<<<

I've never had the problem my self but have heard others complain about
having problems. One individual said that TenTec soldered a resistor across
his antenna to ground (don't recall value) when he returned his for a blown
FET.
I purchased mine just after TT put them on the market and never leave it
connected to an external antenna while I'm away from the house and always
ground myself before messing with the antenna. RM~

PS, Wonder if having all those radios connected to same antenna (if I read
you right) at the same time might be a contributing factor?

[William Everhart]

On Thu, 13 May 2004 20:30:49 -0500, Jim <wd...@cox.net> wrote:

>Anyone else having problem with Ten Tec Rx-320 blowing front end

>FET's? Any mods to prevent this or is there a replacement FET with
>less tendency to short out? This is definitely a design fault, as I
>have 3 receivers in parallel on same antenna and the R320 is the only
>one blowing FETs.
>
>I sent it to the factory and they were supposed to perform a mod to
>prevent this, but it never worked. Wasted $50.00.
>
>Called factory again, their latest solution - - - sending me a bag of
>FET's so I can replace them myself.....

Find out the max current handling of the FET and then put a fuse in
line with the out that's rated at that current. You'll just have to
replace fuses once in a while. Don't forget to put it in an easy spot
to get to.

[m II]

William Everhart wrote:

> Find out the max current handling of the FET and then put a fuse in
> line with the out that's rated at that current. You'll just have to
> replace fuses once in a while. Don't forget to put it in an easy spot
> to get to.

A fuse may be too slow to react. A diode or two may be of use. Here's
one set up using a single pole double throw switch to remove the antenna
from the set when not in use AND give protection when connected. Static
protection only, not lightning.

This lets the antenna be grounded when not in use. OA, OC and BO are
terminals on the switch. D1 and D2 are diodes. and are continually
connected between OC and OA. The antenna wire is always connected to common.

antenna in __________
is common | >
to ground | to ant. | <
------------OA | BO-----------| Radio >
| OC to gnd| <
D1 |--|<--| |------|_________ >
D2 |-->|--| | |__|
|
to ground |
--------------------------------|

mike

[WShoots1]

Rob: << PS, Wonder if having all those radios connected to same antenna (if I

read you right) at the same time might be a contributing factor? >>

That's probably it. One time I had my DX-392 and B&H connected to the same
antenna. While tuning the 392, the Bellow & Howl screeched and the FET in it
died.

Unfortunately, a replacement FET, actual or sub, is not available, so I just
used what I had plenty of spares of, with resulting reduced sensitivity.

Bill, K5BY

[RHF]

MII,

TRY BUILDING AN [EXTERNAL] ANTENNA "GIZMOE" CONNECTOR BOX:
Most Shortwave Radios can benefit from one of these little
External Antenna "GIZMOE" Connector Boxs
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/message/7

GIZMOE BOX's Antenna Input Connector Plug or Two Terminals:
[ Metal {Plastic} Utility Box ]
- One for the Antenna Connection.
- The 'other' for the Ground Connection.
+ Solid Heavy Duty Hardware for Grounding Point.

A = Antenna Connection Point
G = Ground Connection Point {& Plug/Terminal}
* = Space {Blank Space Indicated}
R = Radio/Receiver Connection {Plug/Terminal}
NOTE: Diodes 1N914, 1N4148, ETC.
S = Switch Medium Duty Toggle Switch works best.

G**********A = External Antenna
|----o)----| = NE-2 Neon Bulb or Gas Discharge Tube {EMF Pulses}
|**********|
|-->|-->|--| = Forward Diodes {Minor ESD Discharges}
|**********|
|--|<--|<--| = Reverse Diodes {Minor ESD Discharges}
|**********|
|--/\/\/\--| = 10K Ohm Resistor / Potentiometer {Static Bleed}
|****^******
|****|******
|****------|
|**********O
|**********S = Switch {Antenna Connection and Dis-Connect}
|**********O
G**********R = Radio's External Antenna Input

GIZMOE BOX's Antenna Output Connector Plug or Terminals to
match-up with the Radio/Receivers. Can use a short piece of
Coax Cable or a set of short wires between the Gizmoe Box and
the Radio/Receiver with the proper Plug/Terminals on the end.

Hope this helps ~ RHF
.
.
= = = m II <ohmwork...@spots.ca> wrote in message
= = = news:<vIVoc.5034$j6.209@edtnps84>...

.

[m II]

Jim wrote:

> Anybody have a part number for the FET's in question?
>
> While I have it apart I plan to put a pair of back-to-back diodes
> across the input; that's an old remedy.

Later models of the set may have had the diodes installed at the
factory. I can't find any references to a part number..

http://lists.contesting.com/archives/html/TenTec/1999-07/msg00194.html

Some interesting stuff:

I haven't tried any of this, so I can't comment on the difficulty of setup.

http://g7ltt.dyndns.org:8010/drm/rx320mods/
http://www.tu-darmstadt.de/fb/et/uet/fguet/mitarbeiter/vf/DRM/DRM.html
http://groups.yahoo.com/group/DRM-L/

mike

[ohmwork...@spots.ca]

This message was cancelled from within Mozilla.

[m II]

m II wrote:

>> G**********A = External Antenna |----o)----| = NE-2 Neon Bulb or Gas
>> Discharge Tube {EMF Pulses} |**********|
>> |-->|-->|--| = Forward Diodes {Minor ESD Discharges} |**********|
>> |--|<--|<--| = Reverse Diodes {Minor ESD Discharges} |**********|
>> |--/\/\/\--| = 10K Ohm Resistor / Potentiometer {Static Bleed}
>> |****^****** |****|****** |****------| |**********O |**********S =
>> Switch {Antenna Connection and Dis-Connect} |**********O G**********R
>> = Radio's External Antenna Input

What the heck....must be something to do with line length/line
feeds...strange..I wrap my lines 72 characters per inch. Your original
post had everything looking fine, in a vertical ladder diagram manner..

mike

[j_nospa...@comcast.net]

You might also want to head over to Yahoo groups. There's a pretty
active RX-320 group over there. They may have some suggestions as
well.

hth,
jeff

On Thu, 13 May 2004 20:30:49 -0500, Jim <wd...@cox.net> wrote:

>Anyone else having problem with Ten Tec Rx-320 blowing front end
>FET's? Any mods to prevent this or is there a replacement FET with
>less tendency to short out? This is definitely a design fault, as I
>have 3 receivers in parallel on same antenna and the R320 is the only
>one blowing FETs.
>