MINI BLOG

HUAGAO SEMICONDUCTORS WROTE TO ME ABOUT THE MRF-485 DRIVERS THAT THEY ARE SELLING ON EBAY. THEY ARE USING AN EXCERPT FROM MY PA REPAIR PAPER IN THEIR AD. I HAVE NOT TESTED THESE NEW DRIVERS FOR BETA (hFe), BUT THEY CLAIM THAT THE CURRENT GAIN (hFe) OF THIS NEW BATCH OF 485'S IS AROUND 30. THAT SHOULD BE OK FOR USE IN THE 930 AND 940S PA's WITHOUT FEEDBACK LOOP MODIFICATIONS. HOWEVER, I WOULD LIKE TO TEST THEM FIRST. They have a different appearance than the ones I've tested (better, actually) - those had a gain of around 22 and they were closely matched. I've had good luck with their products. The ones I used worked perfectly without any mods to the PA feedback circuit.

Huagao has credited the information to me,. and stated that if there are any copyright infringements then they'll take the references off, but as long as they give proper credit, I don't care. This information is all in the name of the "Ham Spirit"

JOHN'S RADIO-ELECTRONICS PAGE

NOVEMBER 2020 UPDATES
     COMPENDIUMS, MANUALS, SCHEMATICS, AND DIY PROJECTS
CREATED: 3/23/2016

Kenwood TS-930S AM issues: If you want to control your AM power using the front panel Carrier control, and you have an older model 930S, it's easier than you think. A paper is below. Also, if you had to replace your older Signal Unit (SU) with a later model one, and you lost your AM, that will not longer be a problem - it's an easy fix.
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In light of recent developments, I've updated both of my papers on the TS-930S power amp.  I recently bought lot of parts and boards from a parted-out 930S on eBay. One of the pieces was a "virgin" Red-Dot PA that worked perfectly - except, it failed tests 1 & 2 in my Anatomy of a Working TS-930S. The forward diode test across the main power leads was perfect, but the reverse was under a volt. Driver Q3 had serious Base-Collector leakage problem.  Fortunately, I had a couple new red dot Motorola 485's lying around. 
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If you need help with a project or you have a question, send an email to me at  w3afc@aol.com and I'll get right back to you. A Revision 9 to the Compendium of Repair is coming along. I'm working  on it right now. But I also see the need to start new tabs. I'm still working on "Anatomy of a Working TS-930S Signal Unit", but in the interim, I've added some of the sections as buttons, below.                                                               
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                                                                                           Visit My QRZ HAM Radio Page                             ​​

SCROLL DOWN FOR KENWOOD and SWAN RADIO INFORMATION.

​​SECO 250 TRANSISTOR TESTER: Click HERE for pictures, the Schematic, the complete Manual, and more.TEST EQUIPMENT
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ADVANTEST R3271A SPECTRUM ANALYZER: Click HERE for pictures and complete info!
​The more I used my FFT function, the more I yearned for an actual Spectrum Analyzer (SA). This was definitely a "want" and not a need. And the more I researched models and features, the more I succumbed to "salami theory". Why buy a SA with a range of 9KHz to 1.5 GHz for $600 when for just $100-$200 MORE I can have one that goes to 13.5 GHz. No, wait! For another $150 I can get one that goes from 100 Hz to 26.5 GHz! Or for a mere $2,500 more I could get one that goes from 30 Hz to 26.5 GHz (HP8563A with all the right options). You get the idea. I had to draw a line somewhere so I drew it at $800-$1,000. Fortunately, I found a super deal from a company called SES Sales (travist_tech on eBay) so I ended up spending less than $600. Check out the pix on the TEST EQUIPMENT page.

​This will be a very useful tool for analyzing the output from the various TS-930S Power Amp options. I just need to read the instructions - all 600+ pages of them. It has a handle, but that's just to prop it up. This thing weighs as much as two concrete blocks.

USING A TEK TDS SERIES SCOPE WITH FFT AS A SPECTRUM ANALYZER: CLICK HERE FOR MORE COMPLETE INFO!
One advantage to a using a scope with FFT is that you can simultaneously display the waveform and the spectral display (FFT), plus the input signal level permitted by a scope is generally much higher than that of a Spectrum Analyzer (SA). Of course FFT is crude compared to a dedicated SA, and the SA is much more precise, but if you can't afford both instruments go for something like the Tektronix TDS 360. They can be found on eBay for $150 or so. Whatever you get, pick something with a high bandwidth and a fast sampling rate.

SIGNAL UNIT SWAP: IT WORKS!

​I was itching to try this. BOTH of my 930S rigs are the "old" style, with the AM carrier control  (VR22) on the underside of the board. With the later models, the carrier control adjusts the AM carrier level. Looking at the two schematics, I could see significant differences between the two boards, not just in the AM area but others as well. So I was aware that I might encounter some issues or areas where some functionality might be compromised. In fact, I might blow something up! But if the important features, such as CW, SSB, and FSK still worked, swapping out the board might be a good way to go if your board is bad and you can't fix it.

The big question was, would the new board work with the existing PLL system or would it need a partial or complete alignment per the Kenwood Service Manual? If the answer was "yes", then a swap might not be the way to go for some HAMs. For one thing, unless an OP knows positively that the replacement board worked correctly beforehand, many hours might be wasted trying to make the defective replacement board work. 

NEW INFO: I tried TWO late model boards in my older "test bed" radio. BOTH work perfectly, and I'm using one of them now. The band switching system, CW, SSB, and FSK work just as though the replacement board was the original. This is in contrast to the first replacement I performed, where I replaced a bad late model board with a similar board. THAT one worked, but I had to perform an alignment to get the band switching to work properly (steps 1-7, PLL, Service manual). Without any mods, the only thing that won't work will be AM. The mod involves simply installing a diode in the switch board that is already there in the newer radios. The older model relied on VR22. Without the diode, there will be no carrier so what comes out will sound just like SSB.

I've worked a lot of contacts with the radio with the newer board. My scope output looks perfect, and I get great audio reports.

THE COMPUDIGITAL (K6IOK) POWER SUPPLY KIT- IT'S THE EASY WAY TO FIX YOUR POWER SUPPLY!

If you need to rebuild your Kenwood TS-930S power supply, but you don't want want to modify your old AVR board, you can buy a ready made kit from Jeff Hilliard of Compudigital that will simplify the process for you.

                     Seriously, it's so simple even a CAVEMAN could do it! (Sorry, GEICO)   Click HERE for my write-up.

The kit has a replacement AVR board that eliminates the need for the various sub-voltage regulators, resistors, Zener diodes, and even the 5-watt PA current sense resistor. For a very fair price you get a BRAND NEW 20/26-amp Phoenix Contact Quint, the AVR/power board, and electrical and mounting hardware. The board contains circuitry to provide all the necessary voltages, reduced-voltage fan outputs, and the Ic and Vc voltages for the IcA and IcB  ("sense") circuit. Trust me, it's worth it.

My installation was slightly different than most because both of my 930s rigs have the old low-serial numbers. I installed the kit in my rusty but trusty Test Bed radio. JEFF is about to release a new version of his board (Ver. 3) and I plan to install that model in my everyday 930S. The new board will have an improved connector system.

The pictures below tell the story, or you can download my write-up from the above link. Click on each picture below to get a huge version. I didn't mount the Quint or​ the new AVR replacement the way Jeff shows in his videos and instructions. But my way works well for me.
​NOTE: My 930s runs ALL DAY, and it remains STONE COLD. No heat whatsoever. As in zero! Right now I'm working on an engineering project and I have Plans and other papers on top of my radio. Again, no heat!

KENWOOD COMPENDIUM INFO

​The first section of the Compendium of Repair describes how to replace your original Kenwood TS-930S power supply with a 24 to 29.5 volt (adjustable) Phoenix Quint commercial-grade switching power supply. There are several models that will fit and work perfectly in the radio, including one that delivers 20-amps nominal, with up to 26 amps in "Boost Mode", which translates to 624 watts. At a voltage setting of 28-28.5 volts, that translates into approximately 22 amps. Data from Phoenix Contacts indicates that the voltage x current relationship is linear. 

Dave Phillips, KB7JS, pioneered the 20/26-Amp conversion. It really performs. I converted both of my 930'S to that model, and I've added my info to a button below and to the Compendium. I've also posted some photos and information on my project at the bottom of this page. That Quint is my "go to" model now.
SPARE PARTS: I would like to extend my sincere thanks to those of you who have donated parts for my experiments. Dave Phillips (KB7JS) has donated two PA's and a Signal Unit (plus several metric tonnes of technical information) and contributor Luis Velazquez (K4BTA) sent me a complete 930S to rebuild and experiment with so I wouldn't have to keep tearing my main 930S apart. And Jeff Hilliard of Compudigital donated a complete 930S conversion kit for testing and review. These donations of time, technical knowledge, and equipment truly exemplify the "Ham Spirit".

The radio that Luis donated  received well but it needed a Quint PS which I already had. I installed a longer RF input cable and extended the TXC wires so now I have a "test bed" TS-930S rig to experiment with. You can see it in the foreground in the picture at the top of the page. With the longer cables I can run it with the various PA's lying out flat behind it, making it easy to measure voltages, check scope patterns, and so forth. Luis included a PA that he rebuilt using 2sc1307's, yet another viable choice for drivers. It had a strange output power problem that turned out to be an intermittent MRF422 final output "pill". I replaced both pills with spares that he included, changed the feedback resistors, and it works great now. Luis had already reduced the voltage to the 1307's using a 12-volt regulator to control the gain, but the increased negative feedback really helped to tame the 215 gain of those 1307's. The increased feedback idea was developed by Merit Arnold (W6NQ). I worked about a hundred contacts during the last two contests with that PA and it's very stable. That solution is now PA rebuild Option 4, below.

KENWOOD POWER AMP INFORMATION

​No supplier, even Eleflow, has "low-gain" drivers for the 930S PA anymore. But that's not really a problem. There are lots of ways to make the newer MRF485's from Eleflow work. Note that I said "from Eleflow". There are a lot of 485's floating around on auction sites that are fakes. Some even have plastic collector tabs. These are total junk. Avoid them like the plague.               

​I now have four PA's with successful solutions, including the use of 2SC1969's as drivers which are described in the PDF below. Option 4, using 2SC1969 drivers is beginning to emerge as the "go to" solution, because it appears that there are several sources for quality 1969's with reasonable prices and hFe levels. RF Parts is one of those suppliers. As before, stay away from auction site stuff unless it's from a reputable place like RF Parts, Dalbani, etc. If you can find quality MRF 485's with a gain of 70-80, Option 3 works well. Both of my 930S rigs use Option 3 PA's.

​I need to make some additions and changes to the Compendium, so there will be a Revision 9. Part of the reason is that I recently repaired a TS-930S for someone. The original plan was to use my own Compendium as a guide to make sure there are no errors or omissions. Unfortunately, his problem was caused by issues with the Signal Unit. But that repair effort prompted me to add a couple sections to the Compendium to cover some of the other issues HAMS might encounter when trying to repair their own rigs, and for that matter, to help them decide whether or not they wish to proceed with the repair effort. As an aid, I've added a button below that describes some of the issues that confronted me when I repaired that radio.

ADDING A PANADAPTER-LIKE DISPLAY TO YOUR TS-930S.

​Click HERE for a write up by Contributor Ed Corse.

DOWNLOADS: COMPENDIUM OF REPAIR FILES​

SIGNAL UNIT FILES (UNDER CONSTRUCTION)

Since I'm behind schedule getting the updated Compendium together, I might as well put some useful information on the site so that owners who suspect that their low or no output problem might be related to their Signal Board. Here are some buttons that link to some future sections of the new Compendium. I also decided to add some of the other sections relating to the VFO, tilt-down front panel, and more.

CONTRIBUTORS' PAGES

HOW OTHERS FIXED THEIR KENWOOD TS-930S RADIOS: The buttons below will open up Acrobat documents that show how others have installed their power supplies or repaired their radios.

OTHER KENWOOD FILES AND SCHEMATICS

SWAN RADIO INFORMATION

TUBE TESTING INFORMATION

TEST EQUIPMENT REVIEWS

​With all the inexpensive test equipment out there, i thought it would be fun to buy a few pieces, test them, and put some "semi-scientific" reviews here. I started with a cheap "Arbitrary Waveform" Sweep-Function Generator, and now I'm adding an inexpensive but popular DMM called the WH5000A that's sold under a couple brand names, including AstroAI, and Kuman. I bought the AstroAI version, which boasted a frequency counter capability of 60MHz. Impressive young Skywalker, but you are not a Jedi yet. 

I also just finished playing with a JinHan JDS2012A handheld oscilloscope/DMM combo. The advertised scope bandwidth is 20MHz, but its response extends far beyond that. In fact, it can display the 44.93MHz First IF frequency of the 930S Signal Unit. The review is below, but I have many more photos of this scopemeter at work to add. I use mine daily.

other useful information

I found a company on eBay that makes very nice nameplates, and they made a couple for my radios. Their name is ​Players Trophies and Awards.