IC 7000 additional treatment

My good friend Tasos (SV8YM) posted recently a further protection treatment for IC 7000 driver transistor. You can find more details about this in his blog. All these mods were made to my IC 7000 with absolute success. It is working perfectly so far. Tasos is trying hard to do something that ICOM should do in the first place: Make this little machine reliable!

Talking to Yoshiki

“Hi, I am Yoshiki, 9 years old, living in Yokohama Japan.I have JA-call sign (JF1UCV), and QRV in Japan.I am visit KH0 and am enjoying the contesting from AH0BT with my dad/W1FPU.I like contesting, that's very COOL than Nintendo-DS.-------I am planning to join next CQ WPX SSB contest as SOAB Rookie category. Please call me !!!”

That is exactly how he describes himself in QRZ.com. It was a pleasure meet him as KH0UA in the CQ WPX contest last weekend. Personally, I was surprised by his skills dealing with the huge pileups and giving 4 digits numbers. I have a feeling that he will doubtlessly win the Rookie category this year.

Working the test I have to mention the thrill of exchanging numbers with the legendary OH8X, probably the biggest club station in the world!

Good propagation, big numbers!

TEP came back!

I spent last weekend in my second QTH. I am not prepared for 6m band operations there. Shame on me! You can imagine my surprise to hear ZS6NK (Paul) on magic band using my 160m dipole. I worked him as well as ZS6JON (John) with these wires and 50watts. I checked that I could hear them on my mobile antenna too. For a moment I heard Z22JE (Dudley) but not worked him. What a propagation! TEP was missing for years. It seams that it came back for good. If you think how many possibilities has an RF signal to reach your receiver, you can realize that everything is possible.

Schematic taken from http://www.hamqsl.com/solar.html

Spring Ham activities

Last week was too busy. Propagation on upper bands is great recently. What a relief after so may year of quietness. On the other hand a several events and tests took place that are worth to mention. Let start with the QSO between ISS and a Greek school of Athens. I was stacked to 145800 to listen Timothy. J. Creamer KC5WKI speaking to children and replying all their questions. Great signal from the spacecraft up to 59 to a vertical antenna. And great job from RAAG that organized and contribute to make this contact real. These days, Denis (SV8RV), made significant progress in remote transceiver controlling front. He used the TS-480 and the Radio Remote Control 1258MkII by SM2O. The result was totally satisfactory, even with small bandwidth networks. During the test we listened a QSO between VP8LP and SV2KBS in 10m band. This hardware is a really killer product for this type of operation.

Finally my friend Spyros (SV8CS) came back from Montichiari, where he participated in the recent CTU as a lecturer. He has with him his daughter Anna (SW8NAC), who was the younger attendant of the Contest University. More details for the event you can find in this blog. From the left: K3LR and his XYL,IK2QEI YL, SW8NAC and SV8CS.

Vintage taste

This is the oldest device in my shack. It has about the same age with me. It is a signal generator made in fifties by TESTGEAR (ACTON) LTD, a small family business company. (You can find info about them following this link ). It came to me totally unexpectedly. It previously belonged to an Englishman ham who past away recently. A relative of him, who is a good friend of mine, she picked up from his shack and thought to bring it to me as a gift. I have not to say how much I appreciated this gesture. Thank you Moira. It was in a good cosmetic condition but I was curious if it was still working after all these years. So I unscrewed the back to see what it looked inside.  With  a great surprise  I found out that the interior was still in excellent condition too. Shiny tubes and pretty capacitors! Take a look! What a construction? This is the pre-transistor era.

…And finally it is working properly as at the first day out of the box, still producing decent signals. Wow!

Now, there is a real question. What can you do with it when the modern transceivers have a stability of 0.05ppm? Practically nothing. Just admire….

IC-7000 driver unit instability problem UPDATE

This is an update by SV8YM to the recent mod he uploaded to mod.dk. So I have to post it for anyone that could be interested.

“After my first experiences with this problem, I had proposed a simple preventive measure, consisting of adding a gate series resistance to the driver unit, which apparently suffers from instability with destructive results in many cases.This update is the result of further study of the problem. It attacks the problem in a more efficient way,taking more measures to reduce the instability but also taking measures to prevent the destruction of the driver unit.The update consists of two parts, the first about improving the original modification, and the second about taking extra steps to ensure better stability and protection of the transistor in the driver unit. One can perform just the first part which is very simple. The second part is quite a bit more complicated and requires lifting the PA PCB and performing more alterations and additions to the circuits - but it offers considerably more safety.

PART 1: IMPROVING THE FIRST MOD'S EFFECTIVENESS

The first mod required the addition of a 10 Ohm resistor in series with the input (gate) of the PD55015 LDMOSFET in the driver unit. After studying the circuit's behaviour and experimenting, I finally , changed the resistor’s value to 1 KOhm (see schematic below) which offers much more stabilising action with just a modest decrease in power output (~5%). So, if you have already done the first mod, change the resistor to 1000 Ohm. If you haven't yet done it, refer to www.mods.dk for the full description of the first mod,but use an 1000 Ohm resistor , instead of 10 Ohm. Resist the temptation to tamper with the service menu to compensate for the small ~5% loss in output power – it's really not worth it.

PART 2: ADDITIONAL PREVENTIVE MEASURES

The second part attacks the problem from different angles. It requires considerably more effort and skill.  This part is for the more experienced technicians, so detailed instructions (e.g. "lift the PA PCB by desoldering... and then..." etc., will not be given here. Please be extremely careful.

1) Modification of the drain - gate negative
feedback network of the driver unit

Lift the PA PCB and remove the driver unit. The drain - gate negative feedback network flattens the gain vs frequency response of the broadband driver amplifier stage. It uses a capacitor (C101,10nF and a resistor (R102, 100 ). Change the capacitor to   0.1 μF, 50V. This lowers the range of frequencies for which the network provides negative feedback, stabilising the amplifier there also. Apply a thin film of silicone grease to the heat sink's surface and tighten the driver unit's fastening screws well when replacing the driver unit.

2) Addition of an extra bypass capacitor

This part requires adding an extra tantalum bypass capacitor across C305 (470 F, 16V PA UNIT). Locate the capacitor's leads (see photo and schematic diagram) and solder a 47 F / 35V tantalum capacitor across the electrolytic. Observe the polarity!!

3) Addition of a driver unit protection fuse

Adding a fuse to the 13.8VDCline feeding the driver transistor's drain improves the chances that even if the instability occurs, the transistor will survive. (There won't be any fireworks and smoke, in any case!). Locate L302 on the PA UNIT (see the schematic diagram that follow for diagrams and photos).   Unsolder it and transfer it to the of the PAUNIT (as shown in the service manual), soldering only the lead that connects it to the node with C305 and  L301. Then solder an 1.5 A, fast-blow 20mm glass fuse to the free lead of L302 in the way shown in the photo, soldering the other end of the fuse to the PCB trace that L302 used to connect to (it's the "b" line with 13.8V on it). Use a small piece of wire to solder the fuse to the trace. Don't locate the fuse elsewhere using long wires! Do it exactly as shown. Lay the fuse flat on the PCB.Use a small piece of thick paper or plastic sheet to insulate the end of the fuse soldered to the free lead of L302 from the PCB trace under it. After you have finished, cover the fuse with a piece of electric tape to prevent shorting the 13.8V line when replacing the rig's covers.

FINALLY, 4) Lowering the idle current of the driver unit

In order to lower the gain of the class A driver stage, also reducing
its thermal burden without seriously affecting its linearity at the RF
drive level used, we can lower the idle current via the service menu. The service manual procedure sets the idle current of the driver unit at 1A. Reducing it to 0.6 A produces no ill effects on linearity (as measured in a two-tone test in SSB). Follow the procedure at page 4-3 of the service manual, "transmitter adjustment". Set the current at 0.6 A as per the instructions and exit the service routine.

This concludes the mod. Good luck! Enjoy using your IC7000!”

The diagrams that follow refer to the fuse addition

 

Talking to Angelo (W8ERN)

Some QSO are exceptional. And that was with Angelo this evening. It is several days now that propagation permits easy contacts with USA stations in 15m. So it could usually be a routine QSO, but Angelo surprised me. He  answered my call speaking Greek! This excited me enough to have a quick search in the net for his call. What I found, it was a really impressive site of his. Live log in real time, audio clips of QSOs, S-meter watch, statistics and many other interesting info. It is  unbelievable what one can do with internet nowadays. We had a very friendly chat with Angelo and I hope to meet him again soon. As for you I recommend a visit to his site: (http://w8ern.myqsx.net/). It is really worth it!