Bring the insulatedwire NEAR the receive antenna connection of a second receiver tuned to thecarrier frequency, and make fine adjustments to the null, with the POWERcontrol set at MAX. For the best final measurement, take a piece of insulated wire, bare oneend, and stick that end into the antenna socket of the 850. It ispossible to get so far off on VR8, that VR9 has no effect.Ĩ. Make sure that BOTH of these controls are going through minimums. Push the SEND switch on the TS850 and adjust VR8 and VR9 for minimumindication on the voltmeter.Ħ. Connect a sensitive DC voltmeter between the diode andground.ĥ. Construct an RF voltmeter by sticking a silicon diode, such as 1N914 intothe antenna socket. On the TS850: PROCESSOR OFF, MIC GAIN MIN, FREQ 14.2, MODE USB, POWER MIN.Ĥ. On the IF unit, locate VR8 and VR9 (near the little Murata filter).ģ. Kenwood has service bulletins out on some boards, where theypoint out 30 to 60 feed through for shotgun re-soldering of eyelets with a barewire fed through the eyelet hole when re-soldering and then clipped off.Ģ. Ican believe that story, but they still suffer from very poor QC with regard toinsufficients, cold solder, and lack of eyelet properly done before solderingon the older PCBs. This plant is on a coastline and the boardssuffer from salt air corrosion problems, so the solder does not wet properly. Then they areshipped to a plant where maybe 6 months or even years later the PCBs are usedfor a small run of the units. The PCB blanks are all made at a plant atone time for the estimated life production run of the rig. The followingcomments are from an ex Kenwood service person: The history we were givenregarding the solder quality is that amateur gear is a very low priority, lowquantity production run at Kenwood. I was able to reusethis chip on another board and it came up and worked fine. I noticed when replacingthe chip that there wasn't a lot of solder on the IC pins. It is possible that one of my DDS chipfailures was really due to a poor solder connection. Three is onlyabout 10 components on the board - and they should be cheap to replace fromDigiKey or Mouser.
KENWOOD SERIAL NUMBER DECODER PC
I will probablyreplace the components on the little pc board to fix the problem as Kenwoodprobably wants too much money for the replacement board. My next stepis to see if doing this makes the receiver function again. I could jumperthe RXB signal to 8 volts and make the oscillation go away. Without thisvoltage - there is no way the receiver is going to work. This is generated on the IF board on one ofthose little modules that stand vertical on the board. The biasfor the diode comes from the signal RXB - which should be around 8 volts whenin receive. I checked the two diodes that steer the output of Q28to either the receiver or the transmitter - and saw it working FB for thetransmit condition, but not so good for the receive condition. I looked for the signal coming into the first mixer - whichis a pretty high frequency from the LO1 signal - buffered by Q28. My attention shifted back to the front end - where I saw all of the strangeoscillations. I wasat my work and my TS850 at home, so measuring the voltage was out of thequestion. So I concluded that my PCB was working ok, butthat the input voltage in my TS850 was low (maybe got lower with aging). The problem got worse with lower input voltage and the dc-dc convertorstopped working at about 11.9V. When I checked the oscillatorsignal on C625 (output of oscillator) it fell regulary out and started up again. At an input voltage of 12.43v,the output voltage started to go down and up. But when I lowered theinput voltage strange things began to happen. I fed the DC-DC convertor with12.5 V at L605 and it worked fine, output was -6.2v. I checked C626 and C628, they were wrongon the schematic but they are OK on the PCB. So I removed the PCB with the dc-dc convertorand put it on the testbench at work. I checked my TS850and it had still that problem. My TS850 developed the ALC problem about3 years ago, but I did buy a new rig and the TS850 was put in reserve status.Then I found on your website information about this problem. Transmitter power drop off andburning smell when in transmit. Reduced receiver sensitivity and transmitter output asyou increase frequency Receiver overloaded by AM broadcast stations. Passband tuning erratic while on SSB, okay on CW.People tell me I am off frequency. Monitor function does not work on SSB and/or CW, or isvery distorted. ALCvoltage problems - ALC action seems very unstable (did Kenwood put caps inbackwards?).įrequencydial calibration a quick checkand adjustment procedure.įrequency display is all dots - and radio sends'UL' in CW over the speaker.
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