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Kenwood TS440S Too high voltage in VCO 5 (7.8v versus 5v)

If you had another radio capable of receiving on all of the IF frequencies, you could sniff each oscillator to see which one is moving.

Edit: The inversion suggests a mixer input is sweeping past its designated frequency which flips what comes out of the mixer. I think thats what we are seeing here. I just don't know where yet and brain too foggy to think right now.
 
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I'm not sure what your using there to create that but its amazing!

I haven't had much of a chance to look at it today other then briefly monitoring VCO 3 and VCO 4 TP voltages when first turned on doing the above 3khz sweep thingy and both TP start low at 3v and very slowly rise up to 4 to 5v. While those VCOs were rising VCO 5 was stable at its 5v, will check VCO 2 TP tomorrow as well as any other TPs on this PLL board. I dont know if that info helps.

It would not take long for me to recap the rest of the electros on this PLL board, was thinking about doing that shortly.

I still have to compare the AM/SSB volts from Tech 5 diagram (its on tomorrows to do list!) re: CF1 but did use the diagram to confirm the ssb trace does get power on auto, but on manual wide the ssb trace power is lost so it looks like manual wide does bypass CF1. That murata filter is pricey, about $100 second hand to my door so I'm hoping its not the problem. I decided to inspect/resolder CF1 but didnt see any problems there. Someone had previously touched them up (not from factory) so someone was previously trying to work this out is my guess.
 
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The program is called Friture. It is a free linux program that lets you watch the sound card's output spectrum in real time. It can be used on other input sources too.

Definitely swap all the caps and check for any victims of the old sonybond. Since there is audio (to me it sounded half normal at 1:55 into your video), I am now thinking its just a frequency issue, not a filter issue. Save your money for now.

Hopefully a recap settles these other VCO's down. If not, we will have to figure them out one at a time.

I haven't had much time to look at the schematic, but I do know that the VCO directly under #5 in the schematic does the detecting. 91MHz is divided by 20 in IC2 and then by another 10 in IC3 to produce 455kHz (CAR) for final mixing to audio at D19-D22. But it really don't matter which ones do what, we want them all to behave.
 
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Re: Friture I downloaded it today, it can run on windows as well. I have to experiment with it.

Started the PLL board recap today, just did one of the VCO's, there was countless halo/dry/cracked solder joints under its rf shield on solder side. This ts440s is worse on solder joints then my ts430s. Its like the whole board did not enough solder at factory.

Thanks for heads up on schematic. I was looking at all that area today as well. I dont think theres any sonyblond victims left but will keep an eye out for sure. I actually did a lot of work on the RF board due to sonybond eating legs of things including the centre conductor of jump grey coax to tx mix bias etc.

Gotta admit I get a bit of eye strain too with my age and sometimes need to walk away from the problem briefly to refresh myself. I think we're all feeling like that over the inductor the wrong way around.... :)
 
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I recapped the PLL Board with no change to the problem. VCO 3 & 4 still voltage drifting on test points (start low and rise slowly) with same 3khz audio sweep.

Decided to go check out VCO 1 on the RF Board (I had replaced a few components that had legs eaten off previously) as I read below on another forum which I thought might be relevant:

"The fault was caused by one of the varicap diodes on the R.F. board, it tunes one VCO-2 and is diode D-48. It tunes from about 53 to 58MHz. The diode was going leaky with more than about 4V reverse bias on it and shunting the bias on all the other diodes in that part of the circuit."

I found D49 was shorted (not a varicap) and replaced with 1n4148. Also replaced c192 with correct capacitor (previous person put a 22uf when it should of been 47uf). c170 on this VCO 1 was replaced as part of rebuild I did earlier. All other electros still original in this VCO 1. Attached pic for replaced items in yellow.

I'm wondering if I should take out those varicaps (no shorts but maybe leaky? D44,D46,D48,D50) in VCO1 and test each one or do you think I should be back looking at the PLL board?

Also did the receiver band pass filter diode check as per kenwood SB974 which showed no problems/leaky diodes.

I guess I'm just trying a few ideas...
 

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Take a look at the block diagrams
Screenshot Capture - 2025-09-15 - 15-14-50.png


Screenshot Capture - 2025-09-15 - 15-14-31.png

If you want to receive 27.355MHz, the VCO must mix something with it to get the first IF of 45.05MHz. X - 27.355 = 45.05MHz. Solving for X gives 72.385MHz. This tells us that VCO4 should be active when the band dial is set to 10/11m.

Q17-Q20 on the RF unit do the VCO band switching, providing power to the VCO with the correct tuning range for the chosen band. They should not be on at the same time, only one.

Take a look at the test voltages from the service manual when the radio is receiving 14MHz.
Screenshot Capture - 2025-09-15 - 15-24-52.png

Q19 shows voltage here because the radio was on 14MHz when the test points were measured, so VCO2 (52.55-59.55) is needed since 14MHz + 45MHz = 59MHz.

The service bulletin says the diodes for the bandpass filter selection can go bad and throw off the signals that control these VCO power switches (Q17-Q20).

If all the diodes in the BPFs check out, I would take a look at these switch voltages to ensure only one is on at a time. On 11m, VCO4 should be active, but the other three VCOs should not have power at their collectors.

Lets make sure the correct VCO, and only the correct VCO, is running before moving on.
 
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Thanks for mentoring me Brandon. I was wondering what VCO was on vs frequency. I can now do the calculation based on your example.

Rechecked the BPF diodes again (ok). I actually tested every other frequency range today instead of just 14,000mhz and its working great, its matched the service bulletion frequency ranges with no voltages where they should not be.

At 14,000mhz , Q19 matched the above diagram and when I change to other frequencies it changes. Eg Q17 is the only one running on 10/11 meters.

Q17 - Q20 look like they working correctly as well.....I think....

Only one of them 'on' at a time. I've attached the image for the transistors to make sure I'm not stuffing up here?. I'm seeing the 12v on the base (right most pin) when a transistor is running, and the middle pins (collectors) have 7.7 for all of them at once and left pin (emitter) get its 7.7 when base has its 12v. One anomaly is I see is 0.1v on Q17 emitter when not in use (due to frequency range). All the others show 0v on emitter when not in use.

I've also been starting to check those divider ICs you mentioned on the PLL Board a while back. Checking pin voltages etc, check to see if they are locked etc. Still working on this bit.

I thought maybe some drifting voltage might be supplied to the PLL Board via a connector but all voltages are stable when checking all wiring loom pins etc. VCO 3 (TP2), VCO 4 (TP1) start at ~3v and then drift up to ~6v on startup. Takes a few minutes to go from 3v to 6v.
 

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  • Q17_To_Q20_DTC143TS.jpg
    Q17_To_Q20_DTC143TS.jpg
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I will look at the schematic later tonight at work to see if that 0.1v means anything.
The 4 VCOs I was referring to are on the RF board, not the PLL board. The VCO's with the test points are the ones on the PLL board and they do different things.

I am about to head to work, Ill get back to this later tonight when I get some time. We need to figure out what each of the VCOs in the PLL do, because whichever drifting VCO is furthest from the speaker is the one closest to the problem. I gotta get ready to head out.
 
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Glad you corrected me. I was still looking at the PLL VCO's. I know the one your talking about on rf board. Thats the one I found d49 shorted and replaced and done a bit of work on it from the sonybond glue. I will look at that today and report back :)
 
Work had colored pencils, but things got really messy. I plan to do this better tomorrow and hopefully do the rf schematic too. I have to manage color combinations better so they have meaning and reflect paths because these colors are random. Not sure if I will get further tonight though.
1000004112.jpg
 
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Brandon I think your doing too much for me! - I really appreciate your help but also I don't you to waste too much of your time based on my lack of knowledge. I enjoy having a go at this stuff but yesterday I had a new feeling come over me along the lines of......."would it kill me to sell a few of my radios and just buy a radio that works...." :) Now thats a crazy thought...hehe

Just got my HG finals in for my ts430s which in way better condition then this ts440s. Looking forward to installing them but I'm trying to keep my mind focused on the ts440 before swapping back to the other radio.

Also the ATU does not work on the ts440s. I have seen some videos that say basically while ever the VFOs are playing up the ATU will get into a muddle as its not sure what its trying to tune.
 
When you said AM works fine, are you saying that because you were able to receive stations and verify that they were on frequency, or because the static sounded normal compared to SSB? Has this radio properly received anything?

You said that VCO 3 and 4 are drifting. I wouldn't expect VCO5 to drift in SSB as that VCO is for FM modulation. But what is the test point for VCO2 doing? Is that drifting or pegged to one of its rails, or does it seem locked at some middle voltage? The reason I ask is because all 4 of these VCO's utilize the same reference signal, and if that reference is missing, it could cause this. Q21 on the PLL board is an oscillator for 36MHz. IC13 divides it by 4 and provides 9MHz reference to these PLL chips.
 
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VCO2 produces 100kHz steps, and since its test point is also off, I think it is safe to assume that none of the VCO's are working properly. This strongly points toward a missing reference signal.

I re-colored the PLL block. This time the fill colors represent parts of the signal chain. The color the block is circled in is random, but the matching color leaving that block traces out the signal to the next stage.

I think you need to check out the oscillator (pink fill circled in teal at bottom right). This is amplified by the buffer (pink fill circled in purple, which goes to another buffer (circled in red) before IC13 (circled in green on bottom left). The 9MHz leaves this IC and follows the green traces to the PLL reference inputs. If any part of this pink-filled path goes down, none of the VCO's will lock.
20250923_214330.jpg

20250923_215214.jpg
 
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Thanks Brandon, I didn't realize you were on when I deleted that video showing static on key up but after I posted the video I suddenly had full clear audio being received 95-100khz high on ts440s. ie transmit on navaho cb on 27.405AM, received on ts440 at 27.500AM onwards for 500khz.. Basically it was doing what the first video showed I deleted but now with full clear audio so I go to take another video and its back to no audio received on 440 again.
 

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