Kenwood TS-930SAT Vehicle repair satisfaction note template.

As author of the TS-940 page, I have been studying this for some years. I believe the TS-940 was made between Oct 1985 and June 1992. This agrees with the serial numbers started with 5xx for the first production run and then went to 6xx, 7xx, 8xx, 9xx, 0xx, 1xx and finally 2xx. I do not believe the year minus 2 decode rule applies to the 940. EB5AGV's Kenwood TS-930S page. Kenwood TS-930SAT. It was a 504xxxxxx serial number (so made in April 1984). At least it was not a first series model, which seems had more troubles. 2/10/2000 After some days, the rig finally arrived to Valencia. I went to pick it up and found a very nice packaging job (thanks, Tony!) and everything as. Kenwood serial numbers come in 2 formats. The original format used from the initial production up until approx. August 2008 is as follows: All numeric - First digit is Year code, add 1998 to get year. If first digit is 0 add 10 to 1998. Next 2 digits are month code starting with April (beginning of Japanese tax year) as 01.

Ts 950sdx Serial Number Data

Welcome to the Kenwood TS-930SAT 'On-line restoration' page. InitiallyI planned to update this page as my restoration advanced. But I have been lucky enough to repair therig in short time so you will get the full picture already. Anyway, if you want to contribute anything,please, feel free to send me a message. Thanks!

TS-930SAT Repair Notes

10/9/2000

All of this started when I saw a message in the uk.radio.amateur newsgroup about somebody selling aTS-930SAT for 'repair/parts'. I am always looking for gear to fix, so I found this could be my next'winter project'. I offered a reasonable amount for it and the deal was made. Preliminary informationabout the set revealed it had some trouble with the power supply section. As I fastly found, the powersupply is not one of the best thing Kenwood did in the 930. It is, in fact, a poor design, lackingprotection and convenient heat dissipation. More on this later.

Rig was offered along a hand microphone (MC-43S), User's Manual and a very interesting spare digitalboard. This last is really nice to have as another flacky point of this set is the through hole viasin the digital board which, when fail, produce a full array of troubles. Owner bought the spareboard thinking the fault was there but he swapped it and found it did not help. The rig came alsowith an optional AM filter (Kenwood 6kHz) but no extra CW filters.

It was a 504xxxxxx serial number (so made in April 1984). At least it was not a first series model,which seems had more troubles.

2/10/2000

After some days, the rig finally arrived to Valencia. I went to pick it up and found a very nicepackaging job (thanks, Tony!) and everything as promised in a large box, which contained another onewhere the rig was. It included also an interesting 'Technical Information' booklet (about 40pages long), depicting the most important features and circuits of the one time 'top of the line'Kenwood. It is a technical report, very interesting to read. I have put it online here: TS-930S Technical Information

Here you have the cover of this document:

So I rushed to my shack and put the rig on the workbench. I had been told that it was not workingand only the dial light worked.. so I connected it and, yes, anything else worked. Front panelmultimeter indicated about 15% deflection. Of course, no display nor any signal on the speaker.So I had a winter project!

I got to the power supply unit, not an easy task, as you need to move the power supply transformer,fan cage and some brackets and all is connected with heavy gauge wire along some tiny connectors.In this picture you can see the power supply unit and its location in the rig:

As you can see, power supply unit is in a crowded zone:

But well, I could reach the PS unit and found some hint of what could happen to the rig: there weresigns of bad soldering joints in the rectifier diodes, which had lead to some burning in the printedcircuit board. I also found a dead transistor in the same board and I guessed it died because ofthe intermitent contact in the diodes. This last transistor controls a 22VDC supply to a zeners /resistors array which in turn generate unregulated 16 and 8 VDC to the digital unit. As the transistorwas faulty, the digital unit would not work so the rig was dead. Dial lamps lighted and 28VDCmain voltage was present, so the power transformer seemed to be in good shape.

So I replaced the offending transistor (2SC2235) with an european BC639, as characteristics wereclose enough. Everything else checked right in the PS Unit and also in the associated circuits.So I applied power and got the rig working!!!. Display lighted, all keypad functions and knobsworked, the rig received signals.. I was really surprised for the easy repair. I had partiallydismantled the rig to get to the power supply circuit so I put it back to place. I found some screwswhich were loose, so I tightened them. Then I powered the rig again. and nothing!. Displaywas dark. Only the S-meter lamps glown. I thought about the digital board not reseting. So Iunpowered the rig and powered it back. And then I got the common noise you get when somethingburns. Dismantling again the power supply circuit I found the recently changed transistor wasdead. And also the 24V zener diode it had associated. Although it passed the diode test,it seems power transistor (2SD843) was gone. And, as I discovered later, also zeners inthe fan cage were gone. Well, not bad at all.. dial lights still lighted ;-)

So I needed to rework the power supply. And had some questions:

• Should I replace the lousy (and unprotected) 2SC2235 based 24V power supply with a 7824 IC,which would drive the 2SD843?. It seemed this was an easy improvement.
• Of course, I had not on hand any 2SD843. Here in Spain japanese transistors are really scarce and,if found, they are expensive. So I needed to find an european equivalent. Main trouble was it hasa TO-220 capsule but with a larger power handling than usual. So I finally located a suitablereplacement, a BU807. Main difference with the 2SD843 is that the BU807 is a darlington. This meansthat I would get a bit lower voltage output but also that its driver will need less power to manageit. As the driver circuit was not protected, this could be an advantage.
• About the broken zeners, 7V8 seems not too common so I put 8V2 zeners. That way unregulated voltageswould be 0.4 and 0.8V higher than standard but, as this voltage is not used directly but regulated,I did not find a reason to worry.

Of course, there was a chance I had damaged something else with the 22VDC going 28VDC. I was afraidI did. So I left everything prepared for next day and went bed thinking about what I had donewrong..

5/10/2000

To fully understand this message I am afraid you will need the TS-930S Power Supply Unitschematics (for rigs with S/N bigger than 309xxxx). So I have put it here in case you need it:

I replaced the 2SC2235 (Q6) transistor with a BC639 (a bit lower voltage rating but similarparameters otherwise), the 2SD843 (Q3) with a BU807 (it is a darlington in TO220 capsule,8A nominal Ic max, diode protected output). I also replaced surrounding 2SC2235 components(24V zener, 22uF capacitor). Zener diodes in the fan cage were also replaced with 8V2/1.3Wzeners (I had not 7V8 zeners available). A preliminary unpowered check was good so I poweredthe rig with the digital board power connector disabled. Voltages came fine enough: about 22Vfrom the BU807 collector and good zener regulated voltages. So I powered down the transceiver,plugged the digital board power connector and checked again. Again, all was fine. Display didnot light, as I expected (too much luck is not good for winter projects ;-) )

Disconnecting connector J9 in the digital board, which carries the UL (UnLock) signal from thePLL board to the digital board produced the result I was looking for: dial lighted, showed infoand tuning and rit knobs worked. Band change buttons were also operative. No audio from speaker,as PLL was not working. Some functions, as attenuator, did not work (relays were not heard).

Up to this point, it seemed 7818 regulator in Signal Unit had opened. Reason for this should bethe momentary 28V in the 22V line, when the 2SD843 shorted. Good thing is that GOOD 78xx regulatorsuse to die that way; they get open. Beware with this, as there are not so good 78xx regulatorsin the market. In the company I work for we got a batch of them some time ago..

So I powered down the rig and had a dinner :-). Then I came back, put the DVM in the BU807 output,powered the set.. and got only 4V!. Checking again PS board I found BC639 was dead. It seems thepoor designed 24V mini-supply failed on startup. I then thought about adding a collector resistor(about 20-50 Ohm) to limit the power surge on startup.

So the rig was not working yet, but I got interesting results, which I summarize below:

• Power supply design is not the best of this rig ;-)
• Kenwood put a 120V transistor (2SC2235) because there is need of it IF the circuit is kept as is.I am almost sure things will improve if I limit intensity on startup.
• Digital unit seemed fine.
• 78xx regulators saved the rig from suffering larger damage.

7/10/2000

As the PS Unit was faulty again, I replaced all faulty or suspicious components in the 22V supply:rectifier diodes (I put a pair of 1N5408 replacing the U05Bs), control transistor (2SC2235; Ireplaced it with a BC639), power transistor (2SD843 replaced by a BU807) and zener diodes(7V8 replaced with 8V2)

Preliminary checkings showed it was working fine. But still no signals heard and I shoulddisconnect J9 in digital board (so disconnecting PLL Unlock) to get the display lighted, as beforelast PS fault. Something was wrong at the Signal Unit.

So I put back power transformer and PS circuit in order to be able to put the rig on its side andto look at the bottom side, where the Signal Unit is located. I checked the input to the 7818 18Vregulator to find 22.5V at about 900mA. So the regulator was not opened, as I first thought.. Timeto get out signal unit!. About a zillion screws later ;-) I got it hanging on some wires.. andthen I located the culprit of all my troubles!. It seems previous owner, trying to get the rigworking, dismantled lot of covers and assemblies. I know this because there were lots of screwswhich were not tight. Well, he had put a long screw (the ones used to fix the digital board)instead of a shorter one to fix a cover in the upper side.. so the screw was shortcircuitingone pin in the signal unit (pin 14 of IC11; just the power input to the chip!). I thought thisshort could have ruined some parts. But once the offending screw was removed, I put back allpieces and powered the rig, to find it was working fine in all of its functions, transmissionand automatic tuner included. Hooray :-)!

Summing up, now the rig worked fine and was able to do my first contact with it.

So I took all the knobs and carefully cleaned them. Here you have the rig without any knob..curious, isn't it?

Once the knobs were again in place, I checked sensitivity in several bands using my trusty HP-8640Bgenerator. I got lower than usual readings in all bands.. So I suspected about a common switchelement (sometimes I get good ideas).. and found that cleaning the rear panel 'RX ANT SWITCH'completely cured the problem. It was as sensitive as my fully aligned Collins KWM-2A.

Kenwood Ts 530s Production Dates

24/10/2000

Kenwood Ts 940s Review

I have only added one component, a 47 Ohm resistor in the 2SC2235 (a BC639 in my case)collector (opening the trace from J7 pin 1 to R23 and inserting it there), to protect the transistorfrom power surges and dangerous V*I products. And have done also a simple change in the PS circuit,puting the PS fan always on, connected to the unregulated 8V supply. This way it runs slower thanwith nominal 12V, but it prevents components temperature cycling as it happens with originalthermistor controlled circuit. I have thought about adding a 7812 in the fan cage and allowingselection of 'standard' and 'low' fan speed by means of a switch. Next time I need to open the rig,I will probably install this mod.

Here you have a picture of the rig working, still without covers.

Kenwood Serial Number Lookup

By now, this is the end of the story.. I will add more information if I work more on the rig. Thanksfor reading!Go back to Main Page