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Author Topic: Kenwood 830s frequency drift  (Read 2897 times)
N4WFK
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Posts: 6




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« on: May 09, 2008, 05:19:13 PM »

I know this subject has been discussed before and I have seen some mods out there to help this common problem on the 830's.  However, I have not seen anything written on what is considered normal or "as good as it's going to get" information on the drift problem.

I turned my 830 on this evening and set the VFO to 7242.0.  It was operated at room temperature, only on recieve, no transmitting.  Here are some recorded changes.

7241.9 @ 4 minutes after power up
7242.0 @ 15 min
7242.3 @ 30 min after power up
Turned heater on at this point
7242.3 @ 32 min
7242.4 @ 33 min
7242.8 @ 43 min
7243.1 @ 1 hour after power up
Heater off
7243.4 @ 1 hour 10 min

My question is whether or not any of the published mods would help nail this down solid, or is this typical for an 830, even with the mods?

Someone said using the external VFO-230 would keep the display and frequency right on the money.  Can anyone offer any advice?  Thanks
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K7UNZ
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Posts: 691




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« Reply #1 on: May 09, 2008, 05:54:04 PM »

Well, maybe it's just me, but I don't see a problem in a 25 year old radio that "drifts" 1 khz in over an hour.  I've seen a few newer radios that do worse.

In normal operation, you would have most likely changed frequency a few times during that period, and never notice that little change in frequency.

As for the VFO-230, I personally prefer the '240.

73, Jim/k7unz

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N4WFK
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Posts: 6




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« Reply #2 on: May 09, 2008, 06:21:11 PM »

Hi Jim,

I agree on it not being a lot of drift but I had seen articles describing fixes and just wanted to know if my particular radio falls into what would be considered normal or within manufacture's spec.  I have been getting away from the newer rigs and would just like to use the 830 as my main station.  I do a lot of listening on some particular 40 and 80 meter spots and would like it to stay put when I set it.  

I have neither the VFO-230 or 240 at this time.  Other than being a little less expensive, is there an advantage to the 240?  

Thanks,

JP
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K7UNZ
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Posts: 691




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« Reply #3 on: May 10, 2008, 07:36:39 AM »

Hi JP...

I too find I am falling back on the older rigs these days.  Just not too impressed with the "new" stuff, and frankly DSP, in my opinion, still leaves a lot to be desired.

Luckily, for me, I have a closet full of the oldies, so I get to enjoy them whenever I want (hi).

Have two complete sets (SM-220 and all)of the TS-830S, which I have always loved, and still do.  Also both a Drake "B" and "C" set of twins.

As for the VFO's, I have two of the 230's and two of the 240's.  The only "advantage" to the 230 is the digital display, and the memory capability.  However, as the remote VFO function frequency is displayed on the 830 itself anyway, there is nothing much to be gained from the digital display on the 230.  And with a manually tuned rig, the memory function is of limited use as you're not gonna be jumping all over the place.

To me, the big disadvantage of the 230 is that it has it's own power supply, and sometimes the display hangs-up, which requires you to unplug, and re-plug the unit from the mains to get it going again.  The 240 simply plugs into the 830 with the one cable, and that's that (hi).  Might just be my units, but the 240 also seems a bit more frequency stable to me, which I attribute to the lack of a heat generating power supply.

Bear in mind, this just my opinion, and the fact is.....the 830 itself is just a darn good radio and I rarely need/use the extras.

73, Jim/k7unz
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W4HRC
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Posts: 15




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« Reply #4 on: May 10, 2008, 08:44:48 AM »

Check out Phil's (K4DPK) VFO stabilizer at the link below.

http://home.comcast.net/~k4dpk/pep_adapter.htm
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KA5IPF
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« Reply #5 on: May 11, 2008, 04:58:21 PM »

Just a note. The VFO-230 is a digital VFO using a PLL. The VFO-240 is an analog VFO, same VFO as in the 830, just in a case by itself.

Clif
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K0ZL
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« Reply #6 on: May 19, 2008, 02:30:01 PM »

You can remove the VFO from the 830 and clean the back contact on the variable cap; be careful not to loose any of the hardware, it's hard to find that stuff.

Pull the top display unit out; then flip the rig and remove the two philips head screws that hold the bottom bracket to the chassis. Now, using METRIC allen wrench (3MM I think), remove the four cool-looking screws from the front of the VFO. It should slide out a bit; then, unplug the two cables from the back of the VFO and pull the vFO clear out.

Remove the VFO cover locking nut on the back, then the VFO can. Save the three spacing washers that are inside on the cover stud....

Now use a good contact cleaner such as DeOxIt on the rear contact of the variable cap. Then put a drop of good synthetic motor oil (I use MobilOne 5W-30, has a nice silky feel to it) on the FRONT capacitor bearing, and also a few drops on the VFO running gear.

Now, temporarily plug in the VFO and check operation by firing up the rig and turning on the calibrator (you'll need external speaker). Zip the VFO from one end to the other and check that the CAL signal is "clean" (nice, clean "swoops" of audio beat note), all across the band (band doesn't matter). Don't worry about drift or instability now; the cover's off!

Before you put it all back together, unplug the rig and resolder all the VFO connections that go to components that are not on the PC board. This will "relax" the wiring. You may even hear or see the wires or components move when you resolder them. Now plug in the rig and re-check the VFO to see that you didn't mess something up.

Put it all back together (don't forget the spacer washers on the back of the cover stud!) and check your drift again.
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K0ZL
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« Reply #7 on: May 19, 2008, 02:34:35 PM »

By the way, most 830s I have seen drift only a few tens of hertz from room temp to operating temp.

1-2 khz is too much.
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N4WFK
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Posts: 6




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« Reply #8 on: May 19, 2008, 05:41:33 PM »

Hey guys,

Thanks for all the input.  I did see a kit for VFO drift before and I think it was the same one that was mentioned here on this thread.  I think I am going to try the route just mentioned and see what that gets me.  I will set aside some time soon and pull down the VFO and see if that helps.  By the way, thanks for all the detailed information on the tear down process.  I may need it.  

I am bouncing between three radios at the moment.  My 930, the 830 and the 520.  I wanted to buy accesories for at least one of these rigs but can't make up my mind.  The 830 seemed to have a bit of a handicap with the drift issue, so hopefully if I can get that straight, it will make deciding even more difficult, and fun.  I am keeping all three though.  One other thing to all you Kenwood guys, I never had a 520 before recently.  What a wonderful rig.  

73's and I will report back soon.  
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KC9MWW
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Posts: 2




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« Reply #9 on: March 23, 2009, 08:29:50 AM »

Thanks so much for the tip!!  I did as you described and it fixed the drifting problem of the radio.  Now, it only drifts about 100Hz in 1/2 hour, which is well inside of the Kenwood spec.
Thanks again for your good directions.  I had just bought the rig (my first rig) and I didn't want expensive repairs.  All is well now except last night the radio went a little funky and started to chirp badly when sending CW.
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NO6L
Member

Posts: 179




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« Reply #10 on: March 26, 2009, 01:34:58 AM »

Not related to VFO problems, You should also take the covers back off and re-solder all the tube socket pins. To get to the pins for the 12BY7 socket you have to lift the IF board out of the way and remove the cover underneath. While you're under there, resolder the bandswitch pins, too.

Trust me, these solder joints will need to be re-soldered. If you don't, one or both of the output tubes, 6146Bs, could loose bias, over heat and short, possibly destroying the power transformer.

This should be done for all hybrid Kenwood and Yaesu rigs that have printed circuit boards under the outputs and drivers.
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KE4DRN
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Posts: 3714




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« Reply #11 on: March 26, 2009, 05:55:15 PM »

hi,

here is the yahoo group for ts-5xx/8xx fans,
it was founded by K0ZL Bill recently a SK.

http://groups.yahoo.com/group/TS-520_820_530_830/

73 james
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