squelching TR751
 

I have a TR-751 2m allmode mobile and when power is first applied you'll
hear about 1 second of USB "hiss" which fades into squelch. Turning the
squelch control does nothing at that poin, it's all squelched. Strong
signals are heard, so I know the RX is okay. Using a dowloaded copy of the
service manual I tried a few things, and while adjusting VR14 "Tight
Squelch" I accidently also touched the chassis (thus it was grounded).
Squelch went away and hiss was normal. Unfortunetely, the schematic is
blurry so I can't trace (or for that matter, even FIND VR14). I was thinking
it might be a capacitor, which would account for the hiss and quick fade
into squelch, but with the blurry schematic - forget it. So, does anyone
have any idea if it's okay to just permanently ground VR14? I realize I
won't have squelch for FM, but I only bought the rig for 2m SSB.
TIA
Woody

squelching TR751
 

I had one with the same problem. I have since picked up another one that is
in mint condition (I do like these rigs).
Anyway, the cheap, cheap, cheap (read junk) pots that Kenwood chose to use
for the volume and squelch controls have a tendency to vaporize over the
years. What you will find is that the center wiper is probably not making
contact with the resistance material.
A good way to confirm this is to hardwire (with a jumper) the center wiper
of the pot to either end of that pot. One position will give full squelch
while the other will give open squelch. I do have an extra 751 main board so
if you figure out which part you toasted I can send you that part.
Don't feel bad..........I went through the same thing with my parts unit
before it became a parts unit. The thing that fooled me was that the squelch
pot is on the front section of that concentric volume/squelch pot.
The rig was in pretty rough shape cosmetically, so it wasn't a great loss
when I scrapped it.

Pete

"Dot" wrote in message
...
On Fri, 24 Feb 2006 17:07:52 -0600, "WBY"
wrote:

So, does anyone
have any idea if it's okay to just permanently ground VR14? I realize I
won't have squelch for FM, but I only bought the rig for 2m SSB.

1) "VR" usually denotes a "Variable Resistor" and it's just likely that
one
end of it's rotation is grounded.

2) Never try to do by modification that which can be accomplished by
adjustment.

Also... check your setup instructions. Some rigs have an S-Meter driven
squelch that can be activated to kill everything below S1 through S9. The
Squelch knob then becomes a centered control that fine tunes above and
below
the "RF Squelch" level.

3) Never do by modification that which is offered as a user setting.

squelching TR751
 

Thanks for the info Pete! I'll try your suggestions.

"Pete KE9OA" wrote in message
...
I had one with the same problem. I have since picked up another one that is
in mint condition (I do like these rigs).
Anyway, the cheap, cheap, cheap (read junk) pots that Kenwood chose to use
for the volume and squelch controls have a tendency to vaporize over the
years. What you will find is that the center wiper is probably not making
contact with the resistance material.
A good way to confirm this is to hardwire (with a jumper) the center wiper
of the pot to either end of that pot. One position will give full squelch
while the other will give open squelch. I do have an extra 751 main board
so if you figure out which part you toasted I can send you that part.
Don't feel bad..........I went through the same thing with my parts unit
before it became a parts unit. The thing that fooled me was that the
squelch pot is on the front section of that concentric volume/squelch pot.
The rig was in pretty rough shape cosmetically, so it wasn't a great loss
when I scrapped it.

Pete

"Dot" wrote in message
...
On Fri, 24 Feb 2006 17:07:52 -0600, "WBY"
wrote:

So, does anyone
have any idea if it's okay to just permanently ground VR14? I realize I
won't have squelch for FM, but I only bought the rig for 2m SSB.

1) "VR" usually denotes a "Variable Resistor" and it's just likely that
one
end of it's rotation is grounded.

2) Never try to do by modification that which can be accomplished by
adjustment.

Also... check your setup instructions. Some rigs have an S-Meter driven
squelch that can be activated to kill everything below S1 through S9.
The
Squelch knob then becomes a centered control that fine tunes above and
below
the "RF Squelch" level.

3) Never do by modification that which is offered as a user setting.