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KW TS-930S PS trouble




 
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KA2PTE
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« Reply #25 on: January 19, 2023, 05:26:11 PM »

With the 28V power disconnected from the PA, the ALC meter is still pegged,
so off to the big main pcb.

That resistor you mentioned, its on the foil side I guess?


Simple test, Disconnect the 28 volt power from the final unit to disable it. If the ALC meter goes back to Zero in transmit then the final unit is oscillating.

If it stays peg out in TX with the final unit disabled, then the problem in the bottom main board.

All this is providing that the ALC zero pot on bottom main board is adjusted correctly to zero out the meter

The ALC signal is from the directional coupler circuit in the low pass board. The forward ( D-15) diode provide rectification (VSF) to ALC circuit and ( D-16) reverse diode (VSR) for SWR protection.

Same basic circuit setup used even today on the newest radios.
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ki4nr
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« Reply #26 on: January 19, 2023, 09:20:19 PM »

Have you tried zeroing out the ALC Meter with VR-11 ?? someone may have fooled with it possibly.

The negative voltage resistor is  R-400 1.5k it's right next to plug 28 in the rear middle of the board.  The 12 volt zener is D-210 that is by plug 14 middle right on board between the two metal shields. All parts on on the component side of the board.
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KA2PTE
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« Reply #27 on: January 19, 2023, 11:00:37 PM »

Just tried VR11, does not change the meter at all regarding ALC in tx mode.

Tried to locate that resistor, still looking. I found R399 over in the corner on the drawing
near Q71/72 , thinking R400 would be closeby but I dont see  it. 3070025 is the SN,
so its an early one.

As I inspected things more, I saw what I thought was a RED LED glowing.
Turns out D67 on the main board is now an LED. Red is shining thru the
glass. But I guess a false alarm, those diodes normally are suppose to do that...
very odd.

SM I have shows no schematic of the signal unit, also have a hires scan of the interconnect but
also leaves the signal unit empty.

After more research, found this PDF where it describes corrosion under the local unit as the cause
of the pegged meter in ALC mode. Theres also a video link on pg7, and the description in the video details
is exactly what I see, full power then a drop off with the meter pegged.

So I guess its time to remove the local board for a peek. I also will need to confirm all the plugs are in the proper
locaitons, as the doc sites its possible to place some where they dont belong and do some damage needlessly.



* kenwood_ts-930s_repair.pdf (2994.38 KB - downloaded 40 times.)
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ki4nr
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« Reply #28 on: January 20, 2023, 12:12:23 AM »

Corrosion is a possibility, who knows were it was stored. Although I never seen corrosion on the rigs I worked on, it could happen. Pull the board and inspect it. Here are the schematics for the bottom signal board and over all interconnect. Should make your life a bit easier.

* TS930 208xxx-309xxx Signal Board.pdf (4301.52 KB - downloaded 50 times.)
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ki4nr
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« Reply #29 on: January 20, 2023, 12:15:45 AM »

Here's the Interconnect board schematic, plus this might be a better service manual than the one your using. It's the later one with both old and new serial numbers radios.


https://www.kg3m.com/sitebuildercontent/sitebuilderfiles/ts930_service_manual.pdf

* TS930 208xxx-309xxx Interconnect.pdf (3185.55 KB - downloaded 50 times.)
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KA2PTE
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« Reply #30 on: January 20, 2023, 12:54:40 PM »

Thanks for those diagrams.

In the PDF I posted, he I guess removed the DC side of the power switch
and jumpered it? Had read about that in my travels, but not sure if it really makes much difference?
They do switch the neutral side of the AC plug, and I hear thats not a desirable situation, so would it be
better to move it tot he line side? This one has the AC relay.

Was able to pull the local board, (attachment2)and the foil side looks like a modding madness episode. I guess the yellow jumpers are KW factory, as probably are some others. There is a black MOV near the long heat sink, plus a trace is cut. I see some foil burned near where you were saying that resistor is near,  and that was indeed R400. It measured 2.7K so it was shot. I had new 1/4w 1.5K's in stock so put them in series, then parallel to form 1.5K 1W.

1st photo shows some mods, a 2SC2458 tacked in with what look like may be shottky diodes?
Some others nearby look like they are using thermistors, or MOV's.



* X57-1000-11.JPG (908.79 KB, 1942x1572 - viewed 92 times.)

* X57-1000-11_mods.JPG (1703.19 KB, 2319x1796 - viewed 96 times.)
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ki4nr
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« Reply #31 on: January 20, 2023, 10:55:01 PM »

All those mods are factory changes. The radio had many, many updates and changes over the years. Then at 310 serial number they incorporated all mods into a new board.

I changed R-400 to a 1 watt small type resistor just so it looked correct on the board, what you did is fine.

Nothing wrong with the AC side of transformer. It has a fuse, relay to do high current switching and computer cord with chassis ground. All works fine, No safety issues  & no need to re event the wheel.
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KA2PTE
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« Reply #32 on: January 20, 2023, 11:34:00 PM »


Ok then I will leave those things alone.
I read that R400 causes loss of AM power, but is it also
the reason for the ALC pegging the meter?

Since I messed with VR11, I will have to do the ALC calibration in the manual.
I believe you have to inject a strong signal into the mike connector?
At this point I may as well do a complete alignment and not assume
anything.
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KA2PTE
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« Reply #33 on: January 21, 2023, 07:54:01 PM »

Signal board is back in, but now there are new problems.
VFO does not change freq, no audio.
Thought maybe the batteries I had in glitched the memory, but still the same after I removed the batteries.

Turned out the Dlock switch got hit, so now the VFO works.

Have a humm in the audio thru headphones I can hear with the vol all the way up and some sorta scratchy noise.
RF gain control only makes the meter read about half way when fully turned. Tuned to a local AM station, comes
in a bit lower than usual.


Dunno if this is due to me fiddling with the ALC potentiometer? Didnt try any tx yet.


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ki4nr
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« Reply #34 on: January 22, 2023, 12:10:15 AM »

You need to be sure you have negative 12 volts, that runs many circuits in the radio. One side of R-400 will have approximately -40 volts, the other side should have -12 volts. The -12v is regulated by D-210

Was the receiver working ok before the power supply problem or was the rig a Non working basket case ??
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KA2PTE
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« Reply #35 on: January 22, 2023, 12:45:28 AM »

I will check that resistor for that voltage and look for D210.

Rx was fine before I removed the local board, the 12V regulator
on the PA was a mild short causing almost 1A draw on the PS, so it got warm
but the rx seemed to be quite good when I put it on my station antenna.

I moved the wire bundles around while listening, almost sounds like when
you have a mike with a loose ground someplace , that rustling and popping type noise.
I have also heard the same noise when an electrolytic cap goes high esr in audio circuits
or there is a poor ground. But I guess improper 12V could also produce the same effect.
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ki4nr
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« Reply #36 on: January 22, 2023, 01:43:46 AM »

You probably notice you have to use quite a bit of force to unplug / plug back in the wiring harness plugs. Many times you can create a new problem by cracking the solder on the board header pins, cause poor/no connections or intermittents. Kenwood soldering was not great in those early years. Also check the TMP connectors on the mini coax's and board plugs, verify you have all wiring plug back in correctly.
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KA2PTE
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« Reply #37 on: January 22, 2023, 04:50:54 PM »

Con (30) pin 4 has 13.5V, Con(26) pin 5 has -44v. so that looks good.

I vibrated the board in lots of places, wiggled on the connectors while
listening, no difference.

There was one of those solder lug screw down terminals on my bench after working with the board,
looked like it was not ever soldered on the lug side. There is like a yellow wire with a lug down near the
wire bundle near the filters area, its secured with its proper terminal, otherwise have no idea where this one came from.

I can hear the marker signal, very very faint loudest on 7mc on the dot....and the humm in the audio is loudest there, most discernable on AM. Meter on ALC reads about half scale, same if you go to proc. RF gain moves the needle only a little bit, and the audio humm comes down a little but its not deaf.

Figured I would trace back from the RF gain pot, heads into Con (19). Have zero on pin1, 5.2V on pin 2, 18V on pin 3 but nothing on pin 4. Pin 5 is like 2.4V but if I move the RF gain control it varies a little.

Someone definately spliced the grey wire on the conenctor to pin 5 at one point. Feels sort of flimsy, so cracked the shrink tubong open and the wire came apart. I respliced it, and still only 2.4V on that pin. If I unplug that connector, hum gets crazy loud, so I guess its because the AGC is disconnected. I saw they said to have it in a sideband mode with the RF gain max, so when I moved it to side band and put the gain to max, I have 18V now on pin 4. Pin5 reads 18V with the AGC sw in slow, and -2.5V in Fast and off.
 





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« Reply #38 on: January 26, 2023, 02:22:03 PM »

All this 930 talk got me to realize that my TS-930AT is sitting here, gathering dust. It works, but it's obvious that the filter caps need to be replaced. I'm not in for the job, so I think it's going up for sale. What is the going $$ for 930's? I know I could probably get more for it as parts, but I hate to kill a working radio. EBAY prices are no longer a reliable source of worth
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« Reply #39 on: January 27, 2023, 01:17:04 AM »


Havent removed the board yet but I saw a Service Bulletin no. 875 from KW about C642 being in possibly backwards.
Hard to know what direction it belongs. https://www.qsl.net/bg4aaf/book/kenpic/ASB0875.JPG

The one I have has the + side of the cap facing the IC3 on the board. I think thats the proper way but wanna be sure.
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« Reply #40 on: January 28, 2023, 02:10:20 PM »

Removed the local board again, went over it and made sure the ground points were clean, but still same problem.
Hear the marker signal best on slow agc, otherwise its very weak.

If I hit the DIM button, the S meter reads a much higher signal level, and the audio comes up almost normal.
I see the DC/DC converter on these are known issues, perhaps thats loading down a voltage line?

So on Con (1) of the Digital unit should have 5,12 and 24V on the pins. I have 9,17 and 24V.
Con(9) pin1 is good with 12V.

Not sure where the D6-D8 zeners are located.

Con(29) on the local board is suppose to have 23.7V on on that pin which seems ok, so I guess there
are problems with the Zeners, if I can find them.

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« Reply #41 on: February 07, 2023, 12:12:51 PM »

So the zeners are not in this radio, they I guess are suppose to be in that big resistor module behind the ATU.
I opened it up and just the resistors are in there.


After recapping the digital board and resoldering it, still had the same problem.  Also bench tested the 5 and
12V regulators ok on the heat sink.

I found out I messed up my R400 and it was really 6K because I forgot to tie one end closed.
I put (2) 3.3K/0.5W resistors in there for about 1.6K which ought to be ok.

But upon powerup, R29 (330ohms) on the digital board smoked. I dont have a short on either side
of my new R400, and I read a diode in reverse polarity on one side, which is probably the 12V zener,
so its not shorted.

The DIM button was out when that resistor smoked.

Turns out someone put a jumper on the foil side to make the trace that seems to be open
that ties one side of R29 to pin 5 of con(2) so I saw it was shorting to ground and redid it,
and replaced the resistor. Now the meter swings all the way to the left pegged, no display.
Wrong voltages now on R400. I will have to look at it again and confirm R29 is going to the
right pin.



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« Reply #42 on: February 15, 2023, 11:53:44 AM »

Ok so looks like D210 the 12V zener was breaking down under load. Now the -12V line is stable
and no more s-meter abnormalities. Rx seems back to where it was and the 28V line is still reading good.

So I went back to the tx tests, and now there is no foldback to 10W, but its never hitting the 100W
level like it use to , no matter where the CAR control is set. Most output is about 55W cw into DL,
with either TUNE or CW set, it wont go past that level. The 28V line goes down to about 27.8V in tx,
not sure if thats acceptable?

Re-checked and set idle currents, output from the new 12V regulator is rock solid. 50W
is about 7A PA current draw. I have 2.31V as per step2 in the tx voltage setting for the ALC.
I saw I missed a nearby ground screw close to that spot on the board, so I put it back. Voltage still ok,
but now the most power out is 10W.

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« Reply #43 on: February 19, 2023, 03:37:05 PM »

Well after alot of troubleshooting, some of it due to a bad coax
on the output of the PA, now have 100+W on the output finally.
12V reg is rock solid. Did some SSB tests and got great audio reports.

If I throw a long carrier into the DL, sometimes the s-meter scale for current
reading jumps around and seems not to settle in. As the PA warms up, current
goes up almost 1A from 8A, then the fan brings it down a bit. I notice when you put it on
the next day the power out is past 100W when you set it there prior, and you have to
back the CAR control down again, not sure if thats normal?

Have not tested FSK, I think thats a higher duty cycle than SSB? Never used that mode.

I will recheck the idle currents and monitor them during the fluxuating current to see if
its the drivers or the finals. I felt the part of the heat sink where the new 12V reglator is mounted
and it seems hotter than the rest of the heat sink, so maybe its working near its limit....I think
we could put some heat sink compound on the ears of the PA heat sink where it mounts to the
rest of the frame to give it a little more headroom.

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« Reply #44 on: February 21, 2023, 03:18:32 AM »

Just my opinion:
Short answer is yes a higher duty cycle but can be easier on the finals.

TL;DR:
FSK is a 100% duty cycle. It's technically the same as FM voice, except the FSK frequency changes in a square-wave fashion from 'mark' frequency to 'space' frequency, instead of smoothly according to the modulation by an audio signal.

The beauty of FSK and FM voice is that the linear P.A. runs at its highest efficiency when set to full power.

The caveat is that if you reduce output power, the efficiency on FSK suffers for the same reason that it suffers at carrier-only level on AM. On many transceivers, only for SSB is the internal fan and heatsink close to adequate.

It may be worthwhile to aim a small 12 Volt centrifugal/squirrel cage blower directly at the heat sink no matter what you want for a mode.
If nothing else it is a quiet helper and should reduce heat, prolonging the life of the equipment. Something like this is what I use on a TS430-S:  https://www.amazon.com/12VDC-Squirrel-Cage-Brushless-Blower/dp/B00HWZ5XGC  but anything will help.



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KA2PTE
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« Reply #45 on: March 01, 2023, 12:42:27 PM »

Thanks Patrick for the info on FSK.

Well the display developed a problem after running the rigg a couple of weeks.
The last digit was more brightly lit than the others in either dim or regular mode,
no matter what frequency, and the red pointer that follows the vfo to tell you what part of
the band you are on , had another pointer appearing 200kc apart from where you were,
lighting up gradually as you approach an even frequency like 14.000 with zeros in it,
then it would fade out as you went higher.

After shooting the digital board with heat and cold spray, no difference. I took the digital board out
again and redid more solder connections, no help. Vibrated the board and specific IC's and wiggled the
cables, no help. Even took down the display board with the display, cleaned, defluxed it and resoldered,
still no help.

That was last week and today when I fired it up, still a problem but after I went to different bands,
moved the VFO up and down the bands many times, the brightly lit segments slowly faded back to normal
intensity and its ben running like that about 1 hr. I shot it again with cold spray and vibrated the board
but no change.

Do VFD's GAS like vacuum tubes maybe?


 
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