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Project TS-930S

...over the years I repaired a couple of TS-930, and I'm very happy to see that people still love this radio... this is how I got in touch with the inside of the great TS-930...

When I got my license more than 10 years ago I struggled to get a radio - not that easy with 25Eur pocket money a month :-). Now, time passed by and I had the possibility to play with lots of different gear, mondern and post modern. As a CW-guy I really fell in love with the TS-930 I got when I was 15 years old. Ever since, this transceiver gave me pleasure on the bands. Now, after years of operation, it died the electronic death.
There is no display, I can not switch to transmit. If I change bands I can not hear a relay as I was used to. There is NO reaction of anything. But the reflection meter on the front is always at the end, on the far right side.
Download the Service manual in high resolution (93MB) from WE0H's Website here
First of all, I checked the voltages at the Power Supply. 28V were present, but no 21V. So I opened everything and realized that the pre-owner already did some modification. Obviously he knew about the W6NL-modifications because there was already a 7808 and a 7815 attached to the heat sink. What I wondered was that one of the Tantal-Cs was soldered the wrong way... it didn't blow up because it was never used (why???)
Anyway, I got the Power Supply Unit out and renewed everything what seemed to be burned.

1. Original Power Supply

2. Modification with one C the wrong way

3. Desoldered the big Cs and already exchanged some parts
I replaced every electrolytic capacitor I found, I replaced all the Zener Diodes and some other diodes, I replaced Q6 with an BC639, I added an 47-Ohm-R in the collector branch of it and replaced the Q3 at the heat sink. The pre-owner replaced it with an BU806 and so did I. I replaced D1 and D2 by 1N5408 and replaced D8 with an series of 3 1N5408 to get something about 2V.

What I replaced: (you can see the power supply schematic here)
D3Zener 12V / 1.3W
D5Zener 18V / 1.3W
D7Zener 33V / 1.3W
D83x 1N5408 in series
D10Zener 24V / 1.3W (I haven't had 22.5V)
C14n7 ceramic, 500V
C24n7 ceramic, 500V
C32200u, 50V
C42200u, 50V
C62200u, 50V
C1110u, 25V
C12100u, 25V
C1322u, 25V
C1322u, 25V
Q3 (heat sink)BU607

4. What a mess!
Now I measure 28.2V on the both right connectors and 22.7V on the very left (first) connector. No, this isn't a typo. It's really 22.7V. I don't know where this 1 Volt is coming from but at least it's not 0.5V anymore.
Okay, I connected everything back. I switched on the Transceiver after connecting everything and - nothing happened!. So I got the digital unit out and resoldered every through hole connection. I inserted silverplated copper-wire.

5. The digital unit

After putting the digital board back in place and connecting everything I switched it on - nothing. No Display, the Meter is still at 120% and I can hear a continious beep out of the speaker. What the hell is going on in there?
I disconnected J9 and now the meter shows a 0, when I switch to transmit I can see the 'transmit-lamp'. Okay, but no display, no sound out of the speaker. Means that there is a PLL-problem as well...
I started measuring the voltages to compare them with the service manual. Here my results
I don't know why I get hose values. I also don't know why they are all about the same. I'm also not sure if the connection on Picture 4 between pin 2 and 3 (from the right) has to be... If it really has to be - why is it such a thin wire then?

6. Measuring the current of the 15V-branch.
Okay, another day another idea. I checked the 78xx again and realized that one is blown: the 7808. I exchanged it and - voila - again blown. KE3WD suggested me to disconnect everything from the digital unit and measure the current going into the board. So I did - and I measured 1.6A in the 8V-branch and 350mA in the 15V branch. To exclude the possibility of a thermal dead of the regulator I mounted them on an external heat sink and controlled the temperature. The 8V from the 7808 on the heat sink are going directly to the digital unit (connector 1) and to an 7805. The small heat sink where the 7805 is mounted was hot. Mmmmmh, why didn't I check this earlier? Anyway, now I know that the problem is on the digital unit. I unsoldered the 7805 and checked it seperately - it worked just fine. Also with a load and 500mA. No problem. The regulator seems to be okay. I measured the resistance between 5V and GND - I have a short somewhere. Should I made this by myself while resoldering the board? Lets see, I will determine that tomorrow...

7. Disconnecting all jacks but the power supply.

8. A short on the digital unit in the 5V-branch.

9. Bridges the bad through-hole-connections under an IC where I can not solder.

10. I hope that the broken thing is not somewhere here :-).
I found the short in the 5V-branch! It's an unexpected failure: IC29, a 7475, was defect. I don't know if an internal diode was the problem. I exchanged the latch and now everthing worked. I read 400mA in the 8V-branch.
I started to adjust the PLLs according the the service manual. Although I had no display the TX was working and I could figure out on what frequency I'm sending with an simple frequency counter.

11. adjusting the PLL (VCO-2 and VCO-3)
I connected everything back, also the UL-signals, but I still haven't had display! So I measured again...
digital board, connector 1 pin 3 showed 0V. Why? There should be some 24V, generated by an potential divider on the heat sink. I checked this divider (a resistor) and saw the all the wires were unsoldered from the heat. And it also lost its color. So I replaced it (33Ohm, 2W) by 33Ohm 10W and measured the current. 1.3A - wow! I checked everything around T1 on the digital board and detected a problematic part: Q15. I replaced this 2SC2274 by an BC639 and I had display!. I also replaced Q15 to be on the safe side.
I checked the PLL-voltage again, re-adjusted a bit and switched out everything. It was 2 in the morning. Luckily I'm a student, so I can spend an hour or two more in the bed the next morning.

12. it is working!

I want to refer to Thread in QRZ-Forum and to say tnx to KE3WD, G4COE and W9GB.