[AMPS] 6146 splatter help?
J. Bradshaw
ac6tk@cybertime.net
Mon, 1 Jan 2001 16:57:12 -0800
From: "Mark Keith" <nm5k@wt.net>
:
: measures wrote:
:
: > >Is there any way to improve the splatter on my TS830s (low s/n) with RCA
: > >6146B's?
:
: Not sure what you mean..."low s/n" doesn't make sense... If you are
: splattering with the ts-830, that would usually mean you are
: underloaded. This is common with the old hybrid kenwoods, as many will
: tune up in the "tune" mode, and not finish the job in the cw mode. You
: need to fully load the radio in cw mode to ensure proper loading. The
: only problem you should see with some 6146's might be a problem
: neutralizing. If you have no problems doing that on 10m, they should be
: fine. You are pulling the correct appx plate current.
Low serial number. The radio is loading fine in CW and making plenty of power and I think it's nutralized. I used a rcvr through a
pad at the output with the SG shut off, to adjust it.
: > It is already the cleanest radio ever built. .
:
: It's pretty good , thats for sure.
I'd buy that, but I wasn't sure if maybe something was broke.
: > >On voice peaks (p's, t's and ch's) there are burps like key click sup and
: > >down the band about -40-60 db from the intended energy.
: > >It is only barley noticeable up and down with a 10+ S9 signal in another
: > >rcvr (although I hear the same thing coming from my TS130
: > >too).
: But do other people hear this? You may just be slightly overloading your
: in shack rcvr.
My 30L-1 was on line and someone on the air came over to complain, so they heard it. I turned off the amp and it was still there
and even reduced the mic gain and he said it was still there. I got out the IFR and yes it was there too (internal 40 db pad) but
maybe were both too picky
: > >It is clean from the 12BY7 on a spectrum analyzer (FM/AM 1100s). It seems
: > >that maybe the alc just isn't fast enough whenever the
: > >grid starts pulling current.
: >
: > ALC is never fast enough.
I'd buy that
: I don't even pay attention to the alc on a 830. Or any other kenwood for
: that matter.
Huh?
: > >The mics I have tried are Shure 444 (desk)
: > >and 404c (mobile) and they both do the same thing.
: >
: > An electret mic. makes cleaner audio.
: A good dynamic even better I think. I use a audio technica dynamic mike.
: I've never run across a person who says I have bad audio yet. The 444
: has fairly funky audio in comparison I think, and the electrets too flat
: usually. Not bad, but not near as good as the dynamics I've used.
: > >The
: > >mic gain is critical and goes from 0 to full slam scale around 9 o'clock
: > >but less so with the processor on (15 db) about 10 or 11
: > >o'clock.
: In that case sounds like you have too much mike gain. I run mine about
: 12 oclock and still can go plenty farther. I can turn mine up all the
: way, and am still not overly nasty. BTW, I run my compressor, but very
: lightly at usually about 9 oclock. Doesn't even move the compression
: meter unless I started screaming. Shouldn't need any more than that. 15
: db??? uhhhhhhggg....Could sound pretty funky.
I dunno. Maybe the meter is overshooting. It doesn't even swing most of the time.
My first thought was that the balanced modulator didn't have enough carrier and was splattering so I did an alignment. I don't
think anything would have gotten past the speech clipper and the filters- The xtal filter is tight and right to spec. Anyway the
drive looks so good I'm back to the Pa and alc circuits. I'll try a dynamic cardioid I have handy. The Shures are both "controlled
magnetic" but I don't know for sure their impedance. Could it be I have too much carrier? I converted to P-P and used a scope to
set the injection levels. I'll go back and do the re-alignment of the alc metering too.
I see that the 3.6v and 9v lines supply the alc time constant fet, but the 3.6 doesn't make a difference .2 either way. The grid
bias didn't make any differece between 50 and 70 mils and is also set through the alc amp transistor, so I know the B-E junction is
good. I guess all its really does is sense the jumps when the grid starts to conduct so maybe it's gone flat, or maybe there is so
much RC that it slows down the alc action. I would think that some kind of drive limit would be better. maybe I could add a
circuit in, but wouldn't the speach clipper take care of that anyway?
: > >The plate is 750v, the grid is -60v and the SG is 235. I dropped the SG
: > >down to another tap at 210v, but there was no difference
: > >in operation other than Ip went from 210ma to 180ma. Idles at 60ma. I
: > >tried opening the grid chokes on the resistors, (47 ohm) and
: > >tried a standby pair of GE 6146A's but no change at all. The 9.00v and
: > >3.60v are set after doing the power supply mods, and the
: > >vbt/carrier oscilllators have been adjusted for max bandwidth (+- 1.4 kHz
: > >@ -6 db) in ssb (Thanks Rich. The Fcenter on the 455k5 was
: > >a wee off). Most voltages on Q19,Q20 look good, but I can't probe the
: > >alc line without messing it all up.
: > >
: > less ALC means less feculence.
So that's what you call that.
:
: yep, I did the Measures VBT mod on my 830. Works real nice. Also the 210
: mil number just about right. It was ok the first time.
I kind of did the vbt my own way after figuring what was happening. The manual is just wrong. I think they meant it for AM. I
bypassed the 455 filter with .047 across the CF3 opt. diodes and cw3 tap like in the book, but tuned up and down to find the skirts
and the Fcenter of the Xtal filter, then brought the 455 filter back in and peaked it on Fcenter for the xtal filter, then checked
the known xtal skirts for symmetry. Basically the same thing but it gets you a lot closer than starting with 8375.
Also I splurged and bought new pot assy's for both the vbt/tone and IFshift/notch at PCP and put them in, so it's just like a new
radio now.
I hadn't done anything to it for months before I got the complaint, so the only thing I could figure was that I screwed up the alc
with the amp connections, or something went bad in the PA.
Thanks all-
Jim, ac6tk
: >
: > >So is there a problem with the alc or pa or am I chasing ghosts? I love
: > >this radio better than some of my newer ones.
:
: I think you need a new mike. Or reduce the gain from the one you are
: using. The mike input on the 830 is low OR high impedance. It does not
: take much mike gain to drive an 830. If you are near overdrive at 9
: oclock you have a problem there. I'd look at that first. Sounds like the
: rest is ok to me. I bought a gold label 830 about 2 years ago. I did a
: total full alignment, and then the VBT and other mods that Rich has on
: his website. The rig just works fantastic. Best overall receiver I've
: ever used . Period. The audio thru the headphone jack is ultra clean and
: smooth. Plug the same phones into my icom for instance, and you can tell
: the difference right off the bat. To the average ear, the icom would
: sound fine, but compare to the 830, and it sounds fairly ragged. Also
: the compressor or "rf clipper" on the 830 one of the best ever made.
: Can't hardly tell it's on when adjusted properly. MK
:
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