Sunday, July 15, 2018

Restoring a TS-430S, or "dry joints and stray RF: a tutorial"

I recently acquired a TS-430S HF transceiver. The seller claimed the FM board and full complement of filters worked, but no display, buttons/LEDs or sound. He said it worked until he sent it in to have filters added. I figured it was going to be something simple. Boy was I both right and wrong.

These rigs have a habit of dry joints everywhere. So, I powered it up to see - yes, no display. Ok - step 1 - check power rails. I discovered there was no 5v line. The IF board has the 7805 regulator, so it is time to check for dry joints.

Oh look! Some very dry joints. I bet these were marginal until the tech installing the filters jostled it about. I fixed these any anything else I could find on the IF board.

I then powered it up. One digit showed up - the optional 10Hz digit - but all the lights and buttons worked.

Now, this rig has a separate PLL board for the main VFO which exports a signal that blanks the VFO output and the display. Amusingly it doesn't blank the final digit though. Ok, so it's likely PLL unlock. The PLL board was getting power, but ... no stable 36MHz base oscillator. That's on the control board. I pulled that out to find more dry joints around that circuit and its connector - so, fixed that.

I fired it up again. The PLL board was still unlocked even though the 36MHz oscillator was now working. I spun the dial and measured the other VFO feeding the PLL board - this is the fine grain frequency selection that gets mixed in to the PLL boards four VFOs to output the final VFO signal. It was moving OK - so the control board and the other PLLs were OK. Next - check the four VCO selection lines - nothing.

The PLL board has four varicap diode based VCOs and a PLL loop. The control board outputs the band select data to the RF board which decodes it and drives the PLL VCO, the relay based LPFs and the receiver HPFs. There were multiple issues - the control board bandpass lines were wrong and the VCO select lines were wrong.

Next - the RF board. Dry joints everywhere. Here is one of many that linked ground planes together.

And this one was on the VCO output connector.

I removed the TTL IC that did the BCD to output line demuxing because it was dead and fixed the dry joints. But the control board was still outputting the wrong band info. It turns out the IO expander IC that drives those four lines had two dead IO lines. So, that needed replacing too.

At this stage the control board was OK, the band select lines and VCO select lines are OK, but no PLL lock. Time to diagnose the PLL board.

First up - the varicap VCO was working. Wrong frequency but working. The circuit takes the output of that, buffers it though a transistor amplifier, shapes it into a square wave and divides it down via a pair of TTL chips and feeds it into the PLL control IC.

Next - the 5v line on the PLL board was ... suspiciously low. 5v was coming in OK, but something was dragging it down to 3.8v in places. That is too low for TTL. I checked each chip and... the 75S112N flip flop chip was running hot. Ok, so that needed replacing. Note it is S and not 74LS - the PLL loop runs from 45 to 75MHz, so it needs speed. With that chip replaced the 5v rail was again at 5v. But, no PLL lock.

So I then traced the PLL loop. VCO was OK. VCO though the buffer amp wasn't. I pulled out the transistor there and it was open circuit. I didn't have an equivalent so I found a close enough one for now and ordered a replacement. But then it was sill not working right - the signal level into the TTL NAND chip was super low. I figured either the transistor I replaced it with wasn't biased right or the TTL chip was pulling its input low. Indeed it was the latter - the input side was shorted to ground. I replaced that chip and the rig sprung to life!

I recalibrated the four VCOs now that I had replaced some parts. It was locking OK on all bands.

But - the receive signal was low. I checked the attenuator switch - no go. I disconnected the attenuator control cable to the RF board - RX sprung to life! A little solder reflow on the switch board and that fixed that.

After that I just did the obligatory filter and finals board check and reflow.

One LPF relay clean procedure and finals alignment later and it's all ready to go. The SWR foldback protection needs fixing and I need a 150 ohm dry load to do that, so that's my next week project.

As to how those parts all failed, likely at once? My guess is stray RF fried a path somehow. I'm glad this was the extent of the part damage!


  1. Top notch job. Gave me many ideas to watch for. My TS-430s just has bad audio. So probably it is the audio output IC. Looks like it has been replace before so might be something else too. AM filter has been added which might have caused all the trouble. Anyway, best wishes. Bob KD8VFC

  2. Is it bad audio on just AM? Or SSB too? The default TS-430 with no AM filter sounds .. crap on AM because they routed the AM signal through a sideband filter. Tsk.

  3. Adrean, The problem is on both AM and SSB. I can hear it crack when I turn it on but no rushing noise. The 13.2 rail voltage is low right at the IC 5 audio IC. There are several caps in that circuit that might be shorted or bad. Also the voltage is low at the IC output. I suspect a short someplace. Waiting for parts! Thanks!! Bob Sare KD8VFC

  4. What is a dry joint?
    Kevin Rea

  5. How did you determine which were dry joints that had to be reflowed? There are hundreds of connections on IF, control, Rf, PA boards. Just starting on a 430S myself - one digit only displays, sound on AM, other controls ( RIT, Notch, Squelch, AF, RF gain working. I expect some work is required! Did you change any ICs? or the IF voltage regulators?

    1. visual inspection! ;-)

      One digit only means the PLL is unlocked - the PLL board outputs a "I'm not locked" signal to the rest of the board and oneof the things it does is blank the display. However, if you've done the 10Hz modification it doesn't blank /that/ digit.

      So I'd start with the signals going in/out of the PLL board and maybe try aligning it!

  6. Adrian,
    Consistantly after turning on my ts-430s, in about 15 minutes, the pll unlocks on the 23.000 mhz to 29.999 mhz band. Only the last digit is displayed. Do you have any ideas where to start looking what to check on the radio.

  7. hi! chances are that's the PLL unit. You should flip the radio over, remove the bottom case, see if you can reproduce it with the case off. If you can, go wiggle some connectors on the PLL board (the little board under the radio; theb ig one is the RF board) and see if it comes back to life.

    My guess is that you have some loose connectors, dry solder joints or some dry electrolytic capacitors. Those are the normal aging issues with these rigs.

  8. Hello Adrian,
    Since I last contacted you more problems are happening with my Kenwood ts-430s. I did dable around a bit with the PLL unit to no avail.. I did notice that there is ALOT of wax covering ALOT of components in the area of transistor Q4. I read somewere that after time wax can become conductive?

    In addition to the PLL unlocking (no rx or tx only the last digit lighting up on the display) in the 23.000 to 29.999 mhz band consistantly after about 15 minutes of the radio just being turned on.

    Now on all the bands (00.000.00 to 29.999.99 mhz) as soon as the radio is turned on there is no FM (tx or rx) or AM (rx) but it still will tramsmit in the AM mode. only the last digit will light up. I was able to locate a used PLL board on ebay for the Kenwood ts-430s about a week ago, I still didn't receive yet. I'm going to swap PLL units. I'm wondering after swapping boards will I need to align it? If so' what will I need to adjust? The only test equipment that I have is a multitester to check voltage, resistance etc. I'm not that technically skilled but if I know what frequency to set the radio to and what pots to adjust and for what voltages on what test points, I can do that. I know how to read a schematic. I don't have the PLL board yet but I should get it this week. I'm hoping that I can just swap the PLL units and the radio will be fixed! :-)

    Thanks for your advice,
    John from Pennsylvania

  9. So I'd start with the replacement PLL board and see if that's any better. You can align the PLLs using a voltmeter as they're a voltage controlled oscillator! So, you're basically just checking that for a given frequency the control voltage is a certain level. But honestly, you at least want something like one of the 200MHz Rigol scopes to be able to check that oscillators are oscillating. :-)

    Let me know how it goes! If the replacement PLL board works then I can fix that busted one for you!

    And yeah - that wax can absorb water and make things sad. Take some photos and send em here!

    1. Hi Adrian,
      I received the PLL unit today in the mail. I swapped it out with the original one that was in the radio back when I bought it some were back around 1983. I aligned VCO's 1, 2 , 3 a,b,c,d using my multitester and the Kenwood ts-430s service manual. I adjusted the voltage on all of them. The ONLY thing that I noticed was that it took about a half hour instead of 10 to 15 minutes for the 23.000 mhz - 29.999 mhz band to blank out (no rx or tx , no display, only the last digit). The other issue where after turning on the radio immediately there is no fm (tx or rx) and only am TX (the display does come back on when I transmit in the am mode) but no rx anywere from 000000 mhz to 29.999.99 mhz. One other thing that I noticed is I don't get full power output using the new PLL board. Maybe something else has to be aligned to up the power output. I only get about half the power output, about 50 watts??? So' I put the original PLL board back into the radio and aligned all 3 VCO's. The power output went back up to normal. But these two issues still remain! Were should I look next? I was thinking possibly the Control board? I did snap 3 pictures of the original PLL board that has ALOT of wax on the components near transistor Q4. I don't know how to attach the photos to this message? But it seems like the problem isn't on the PLL unit anyways?