Technical Questions & Answers
For Kenwood Amateur Transceivers TS-520, TS-520S, TS-820, TS-820S, TS-530S, TS-830S, and more!
From the K4EAA Ham Radio Email Logs
PAGE 6
 

Over the years I have received and answered many thousands of technical questions from Ham Radio Operators.  At this juncture, I suspect I have answered every Kenwood question that is possible to ask at least once - And several, many, many times.   While it takes a fair amount of time to add to the FAQ, with pictures and diagrams and the like, the email questions can be copied and pasted reasonably quickly.  That is what I have done here.

I will be adding to these as time permits, as I have over four years worth, after all!   You can either read through the emails page-by-page (like a novel!), or search the site for keywords which will lead you directly to your area of interest.   ENJOY!   Ken, K4EAA


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Ken,

I had emailed you last year asking for guidance on an AGC problem with my 830S and you were so kind as to suggest I look at Q9 and Q10 on the IF Board. (My problem is that my rf gain control is always wide open no matter where the pot is set, and the S meter will peg for 2 plus minutes intermittedly when the rig is first turned on, as well as every time I change the MODE switch from TUNE to CW).

I’ve checked all of the wiring and connectors to and from the rf gain control, agc switch, etc. that I can trace as you also suggested and all connections check out good.

Here’s my question, how can I measure the voltages for Q9 and Q10 (as well as any other voltages on the IF board? The top/parts side of the board is too dense to get a probe tip to the base of the parts. I even tried those little spring loaded clips that clip onto parts leads, but again, there is no room. In addition, the only way to access the underside of the board is to completely remove the board from the radio (which of course means all of the connectors have to be unplugged from the board as well). Thus, I cannot figure out a way to measure voltages on the IF board to see if my problem might be there

How do you do it, i.e., how do you physically gain access to measure voltages on the If board, such as for Q9 &Q10? I’m quite befuddled!

Thank you again for any help you can provide,

Ken R.


Hi Ken;

As you're finding out, half the work is figuring out how to access the boards when the rig is running! For the IF board, you should be able to remove the mounting screws and fold the board over for access to the foil side. Take some newspaper or a magazine and insulate the top of the board so it cannot short against other parts of the radio. It may be easier to stand the radio on its side while getting to the bottom of the board.

You may also find it helpful to clip some of the ties that hold the wire bundles together. One of life's mysteries is why Kenwood chose to orient the stand-up resistors the way they did - Whenever I want to measure (i.e.) a base or collector voltage, the resistor lead that's accessible from the top of the board is always the wrong one - Like plus or ground instead of the base! They do that so consistently it must be by design! My life would be easier if they had installed the stand-up resistors the other way - Then, I could measure almost everything needed from the top of the board. But, that would make it too easy . . .

Best 73's,
Ken


Ken,
Well I guess I messed up trying to help out a friend. I took my radio (830) to his house to let him listen to the well rounded audio of an older unit that the newer radios just don't have.
While I was out at the truck turning my mobile off, he was inside hooking up the radio to the antenna. When I keyed up the radio to tune it all was well. Then I unkeyed and the radio had no recieve (at all). Looking to see what the problem was, I found that he had hooked the keying line from the amp to one of the IF out jacks on the back. I pulled the plug off and told him that we were just going to run the radio. Besides that the accessory cable I brought was for the amp. What did He mess up and is it a very simple fix? Now I don't remember now which one of the jacks he had plugged into. I want to say it was #1 but, not sure.

Any HELP will be welcomed.
73, IRVIN


Hi Irvin;

Well, it looks like both of those jacks are capacitively coupled to points in the IF. There are resistors to ground, and then small caps (47pf as I recall) going to the IF circuitry. The amp probably has a higher DC voltage meant to go to relay contacts for switching. That means that if it zapped anything, it would probably have been because of the transient making it through the little caps. The R's could be smoked, but that wouldn't affect Rx operation.

You can see what parts might be involved here:
http://www.k4eaa.com/TS-830S.pdf

It can't be too bad, those are pretty small caps, but suspect any active part that is electrically close to those connections.
Hope this helps,
Best 73's,
Ken


Hi Ken,

My 830 has been working great until the other day. When I keyed up on 75 SSB I heard a loud pop and lost all drive. Upon investigation R10 on the final board had burned. What is strange is that the R10 that burned, and appears to be the original, is a 6.5K or 6.7 K. I'm not sure if the 2nd band is blue or green through the burn marks. The schematic I have shows R10 as a 4.7K. Was there a change or mod? Which should I replace it with?

73,
Bill


Hi Bill;

I've always used 4.7K (along with the 2.7K) in that divider. That divider is used to read the plate current in the metering circuit. I would check the 20 Ohm cathode resistors as well - That's usually what "Pops!" The 4 in parallel should measure 5 Ohms. Replace them if they're significantly higher.

Hope this helps,
Best 73's,
Ken



Ken,
I was so hoping to figure this out on my own.
I just received my TS-830. The receive is wonderful, the transmit on SSB is not.
It tunes up fine following your tune up procedure. I get all kinds of power. When I switch to SSB (20 meter USB) and key the mic (MC-30S) I get nothing. You can hear the relay click but no transmit power. I do not think it is the mic, it will trip the VOX if it is turned on. I read about a possible bad ground connection on the IF board. I am not clear as to how to apply a better ground. Star washers under some of the screws, or do I need to run a ground wire from a ground trace on the IF board to the chassis ?

Bob


Hi Bob;

After servicing hundreds of these radios, I have never seen the "bad ground" that you refer to. I have never had to place a star washer under any board, and can't even imagine where those popular "remedies" got their start!

I presume the problem starts with the ALC - You can get no ALC deflection with the MIC control up and talking into the microphone? Are you seeing about 50ma of plate current when you key the mic in SSB?

One thing you can try is to turn on the MONI switch, plug in a set of headphones, and see if you can hear your voice. That will tell us how far the audio is/isn't going.

Let's start there.
Best 73's,
Ken


Now Ken I have another question for you: I’ve noticed lately that the audio fidelity from the SP-230 speaker unit sounds a bit “thin” and lacking in low frequency firmness / authority compared with my primary Yaesu FT-2000 radio. This difference is particularly evident when approaching the zero-beat of a CW signal; the LF energy seems to rapidly cut-off / fall away below several hundred Hz. I wonder if you are aware of any common component degradation or failure that may account for this high-pass characteristic that seems to limit the baseband low-end audio response, capacitors C20, C30, etc, for example? Unfortunately the underside of the AF Board is not so easily accessible to check the integrity of suspect components. Perhaps like C24 in the HV power supply, one of these other smaller electrolytics make have also dried out / gone low in value.

On the other hand, maybe the LF response was deliberately tailored by Kenwood to be like this, but I’m certain I’ve noticed a thinning of the AF bandwidth; what do you reckon?
73 Leigh


Hi Leigh;

There are carrier adjustments available through the case on the bottom of the radio - They are marked USB, and LSB. Adjust the carrier until it sounds proper and there is nothing on the other side of zero beat. This is a user adjustment on all the hybrids.

Hope this helps, 73's,
Ken


Many thanks Ken!
This advice was spot-on and remedied the problem; very helpful. The audio sounds much better now; and with the IF Shift knob back at its normal centre-detent position. It looks like there was some small drift in the carrier oscillator(s).

Is there a more definitive adjustment method rather than tweaking the trimmer caps TC2 and TC3 until an incoming SSB signal “sounds proper” with good fidelity / spectral balance as doing this was quite subjective and it wasn’t clear where the maximum AF bandwidth was achieved?

Also I wasn’t completely sure what you meant by “until there is nothing the other side of zero beat”, could you kindly elaborate a little?
73 Leigh


Hi Leigh;

If you use the calibrator signal you can do it by ear pretty darn closely. You know what 60 Hz sounds like, set the bandpass (i.e.) from 60 Hz to 2400, or whatever the passband of your filter is. Do this on both sides of zero beat for USB and LSB. Zero beat is where the audio frequency goes to zero. An alternative is to use a calibrated audio generator or a frequency counter and calibrator signal.

Isn't proper audio sound sort of subjective anyway? Your passband is set by the filters installed in your rig, you just get to select what portion of the audio they are centered on . . .

73's, Ken


Ken:

I am the original owner of a Kenwood TS 520S that was purchased in approximately 1978.
Because of time constraints, etc I did not follow through with my intent of completing the
exams for ham license and accordingly the radio in its' new unused condition ended up in
storage. Because of recent retirement, I obtained my General license in February of this
year and was able to restore the radio to service. It appears to have survived storage and
appears remarkably clean. For the last month the radio has worked perfectly on the
80, 40 and 20 meter bands by the criterion so well described on your excellent site.
At the outset upon setting up the radio thru a MFJ 949E tuner I believe all of the bands
worked although the higher bands have been down as you well know. That is to say that
I was able to receive and transmit initially on all bands.

However, I noted yesterday that the 15 meter band is inoperative both receiver and transmitter
with no drive function or audible cal signal. The other bands remain fully functional and unchanged. Contact cleaner application to all the band switch contacts did not correct the
malfunction.

The manual describes in its troubleshooting section that an individual band malfunction may
indicate that the heterodyne oscillator may not be functioning and requires adjusting along
with antenna coil adjustment. Is it possible that the described alignment would correct the
malfunction? Is the problem more complex, requiring the bandswitch procedure you describe
in your FAQ? Do you think that it would ultimately be necessary to schedule a repair session
in your shop?

I would much appreciate your time and your initial thoughts of my problem. Surely there is
minimal if any activity on 15 meters (?) at this time but of course I'd like to correct the
problem. I would like to purchase from you, if available, a set of adjustment tools ie AL-1,
AL-2 and AL-3. Kindly let me know the total cost with shipping and I will forward payment
to you by whatever method you prefer ie paypal, credit card etc.

73 Richard


Hi Richard;

I would check to see if indeed the HET oscillator is working. Almost all of the transceiver circuitry is used on all bands, the only exception being the bandswitch and the individual tuning coils and caps associated with the bandswitch. In other words, if there's a problem with only one band, it's almost surely located on one or more of the boards containing coils, caps and crystals which make up the bandswitch.

Disassembly of the bandswitch is usually not necessary unless a board has to be removed to get at a bad component. Try tuning the HET oscillator to see if the band suddenly comes to life. Count turns as you twist the core to be able to come back to where it was originally set should the problem be elsewhere.

Best 73's,
Ken


I’ve got a TS830S that has suddenly exhibited the following behavior:

When cold – turn on and let the tubes warm up for 5 minutes or so.

Select Tune and hit send. There’s a delay as the output will climb to about 20W. Looks like the HV starts around 900 and then drops back to 800 and power climbs as voltage drops back. In CW it will climb to 120W then drop back to nothing, sometimes fluctuating. HV is moving around as well. But will then climb up and stabilize.

After about an hour, the HV stabilizes, the wattmeter instantly responds and you get plenty of output without variation and the IP is around 350mA

I scoped the drive into the final compartment and it looked good at all times with modulation.

So I’m thinking that this is probably the HV caps needing replaced. I measured about 8 ohms on the cathode resistance to ground in the final compartment so this explains my higher than normal IP reading.

Would you recommend that I get the HV cap kit and the resistor kit and replace all that stuff?
Tate


Hi Tate;

Since your HV starts at 900V and then drops to 800V under load, I'd say your HV caps are probably fine. The Cathode resistors need to be replaced for sure. You didn't say what your drive (ALC) was doing while the output was fluctuating. Let me know what it reads at low power, if possible. I would suspect the relay, RL-1 at this point, and you will confirm if you say the ALC is jumping around as well.

I'll wait to hear back from you.
Best 73's,
Ken


ken. just found your web site and know you are busy ,so will try to be brief.I have a Kenwood 820s. This rig was given to me by the original owner and is in vary good condition.
it receives well but will only tune up to fifty watts.I sent it off too an outfit in the Dakotas and they wanted $550.00 to fix it .more than I could afford so have been useing it as is. I also have the vfo-820 and the sm220 monitor neither of which i use. your web page led me to beieve it should not cost this much. Your thoughts on this would be appreciated

Thanks David


Hi David;

The final compartment is pretty simple. It you have good tubes, the cathode resistors are OK (5 Ohms total), the plate voltage is good (900V no load, perhaps 750-800V under load), the screen voltage is good (210-240V), the grid voltage is OK (around -54V in SSB), you should have good output!

The supply voltages are derived pretty simply, just rectifiers and filter caps, and the grid voltage can be adjusted - It's what you set for ~50ma when you key SSB with the MIC gain turned full CCW. If you give these values a check, you may find something that's off and we can go from there. It could be as simple as the HV caps, a bad one would halve your output power, and the whole replacement kit is only 24.95.

Hope this helps,
Best 73's,
Ken


Hi Ken,

Subject TS-520S
First of all, thanks for the cathode resistors I ordered. I received them yesterday. Now a new problem. I was trying to hook up a frequency display and managed to short the 13.8v connector. I was able to trace back to the rectifier unit and checked the diodes D8-D11.
D10 and D11 read a dead short in both directions. This is after disconnecting the 13v ac (yellow wire) and 14v (blue wire) from the circuit board.
Would you have the replacement diodes? The Parts list calls for a part # of V03C.
I tried to find a replacement at my local Radio Crack store, but I don't have to tell you how that went.

Thanks,
Ed


Hi Ed;

The V03C is a 3A rectifier. 100PIV should be OK. In that case, a 1N5401 or higher (1N5402, 03, 04) should work nicely. I don't happen to have any on hand, but they are available online for about 10 cents each.  Radio Shack has them, but for considerably more money! I think they get 1.59 each. It's still a pretty cheap repair.

Hope this helps,
Best 73's,
Ken





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