Well, my Kenwood TS-790E
After last repair, I noted there were some trouble with the ON AIR indicator, as it sometimes didn't follow the PTT: from time to time it kept lit even in RX and also the opposite (off on TX). I found also some other problems.
Summing up this is what I had found:
Thanks to my friend Mario EB5HRZ, I got on the bench another TS-790 to be able of doing some side-by-side checks. and, yes, if I swapped CONTROL UNITs from one 790 to the other, the problem followed the CONTROL UNIT. So at least I was sure the fault was on it!
Then I checked signals at the CPU. RESET signal worked exactly the same in both. Oscillators were also the same, starting immediately after power on. But all the I/O activity seemed frozen in the bad unit, until about 5 seconds passed. Checking control lines at the CPU, there was one long delay since first WR signal was generated until the next ones, in the bad CPU, but none in the good one (I mean WR signal was switching fastly on good CPU, since first moment)
I checked voltage rails with oscilloscope, and were perfect.
It seemed there was some problem in the data bus as, what happened when LEDs did weird things is that the command from the main CPU to the display CPU had some error on it so it was interpreted as another commmand. In fact, when for example LOCK LED was lit during tuning, frequency on display remained the same but there was a change in frequency. So I guessed display refresh command was corrupted and the damaged transmission was interpreted as another command.
Next day, I continued with the CONTROL BOARD resoldering I started the day before. It took about 2 hours to get it done completely.
But then, after reassembling it in the rig, it did not power up, even waiting for the 5 seconds it used to take :-(. Well, I was sure there were no soldering bridges in my work (it was done with lots of care and I am soldering since I was 9. now I am 40 ;-)!) so I thought what happened is that something was now worse than before, reinforcing the idea of a soldering or PCB trace problem.
While I was measuring with the oscilloscope, finding that CPU clock oscillated and there was address and data I/O from the CPU, it suddently came back to life, but with the same old problems (LOCK LED lighted from time to time when rotating dial and such). I powered it off again and then I got a silly idea. my guessing was that the problem could reside in some input to the CPU which was waiting for something to be ready. so I carefully touched with my finger around the CPU pins. and rig came back to life again!
Looking at the schematics they were all signals to and from (!) the fluorescent display (FIP). I fastly reduced the focus to the FIP BY signal (pin 4 of the CPU). It was low on start up and, as soon as it got high, rig started to work. And, yes, placing a 1k pull-up was enough for the rig to power up always immediately :-)!!!
JOSE
Nov 22, 2013 I never ran into a Kenwood TS-790 before, but I was surprised by its nice design and spacious PCB layout. The reported defect didn't leave much to my imagination: the radio didn't lock on 2 meters. All I probably had to do was to focus on the VCO. With the service manual in one hand. Get the best deals for kenwood ts-790 at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items! KENWOOD NETWORK COMMAND SYSTEM Radio VoIP Program ARVP-10 Version 1.03 (Free) August 2018: TS-480HX/SAT KENWOOD NETWORK COMMSND SYSTEM Setting Manual (PDF:560KB) January 2019: PC CONTROL COMMAND REFERENCE FOR THE TS-480HX/ SAT TRANSCEIVER (PDF:124KB) December 2003: TS-480HX/SAT IN-DEPTH MANUAL(PDF:2.25MB) April 2004. View and Download Kenwood TS-790E service manual online. TS-790E transceiver pdf manual download. Also for: Ts-790a.
has given me some more problems. read on to see how I got through them!After last repair, I noted there were some trouble with the ON AIR indicator, as it sometimes didn't follow the PTT: from time to time it kept lit even in RX and also the opposite (off on TX). I found also some other problems.
Summing up this is what I had found:
- Variable delay to power up display and keypad input from POWER ON: from 2 to about 5 seconds. and getting worse!
- Inconsistent ON AIR indicator (sometimes it does not follow PTT!)
- LOCK LED lights from time to time while changing frequency (but LOCK is NOT activated)
- DISPLAY refresh fails: frequency changes in the unit but change is not displayed.
Thanks to my friend Mario EB5HRZ, I got on the bench another TS-790 to be able of doing some side-by-side checks. and, yes, if I swapped CONTROL UNITs from one 790 to the other, the problem followed the CONTROL UNIT. So at least I was sure the fault was on it!
Then I checked signals at the CPU. RESET signal worked exactly the same in both. Oscillators were also the same, starting immediately after power on. But all the I/O activity seemed frozen in the bad unit, until about 5 seconds passed. Checking control lines at the CPU, there was one long delay since first WR signal was generated until the next ones, in the bad CPU, but none in the good one (I mean WR signal was switching fastly on good CPU, since first moment)
I checked voltage rails with oscilloscope, and were perfect.
It seemed there was some problem in the data bus as, what happened when LEDs did weird things is that the command from the main CPU to the display CPU had some error on it so it was interpreted as another commmand. In fact, when for example LOCK LED was lit during tuning, frequency on display remained the same but there was a change in frequency. So I guessed display refresh command was corrupted and the damaged transmission was interpreted as another command.
Next day, I continued with the CONTROL BOARD resoldering I started the day before. It took about 2 hours to get it done completely.
But then, after reassembling it in the rig, it did not power up, even waiting for the 5 seconds it used to take :-(. Well, I was sure there were no soldering bridges in my work (it was done with lots of care and I am soldering since I was 9. now I am 40 ;-)!) so I thought what happened is that something was now worse than before, reinforcing the idea of a soldering or PCB trace problem.
While I was measuring with the oscilloscope, finding that CPU clock oscillated and there was address and data I/O from the CPU, it suddently came back to life, but with the same old problems (LOCK LED lighted from time to time when rotating dial and such). I powered it off again and then I got a silly idea. my guessing was that the problem could reside in some input to the CPU which was waiting for something to be ready. so I carefully touched with my finger around the CPU pins. and rig came back to life again!
I was able to do this several times and found a zone of about 4-5 pins which consistently started the rig when touched. suspicious, right ;-)?
Looking at the schematics they were all signals to and from (!) the fluorescent display (FIP). I fastly reduced the focus to the FIP BY signal (pin 4 of the CPU). It was low on start up and, as soon as it got high, rig started to work. And, yes, placing a 1k pull-up was enough for the rig to power up always immediately :-)!!!
Of course, even with the pull-up, rig continued to produce random problems. but I knew I was close!. So I traced that control line to the connector which go to the DISPLAY BOARD and, yes, there was no continuity :-)!!!. I tried to find the faulty via but as it goes below the CPU itself and the service manual PCB is not clear enough on that zone to follow the trace, I decided to run a tiny wire (wire wrapping kind) from the CPU pin to the connector, fixing it as it was made in the old PC mainboards, with small drops of adhesive spread along the wiring route (tape is only until adhesive cures)
And, YES!!!, rig started AND behaved perfectly on next power-ups. so it was FIXED!!!
Wow, how great is to find an obscure fault :-)!
Thanks you all for the patience to read all these ramblings. I hope they could help in the future to some other troubled TS-790 users.
Best regards from a very happy camper,
JOSE
Description
Best photo printer for mac high sierra. Rocksmith pc crack by skidrow password. You are buying a Kenwood TS-790A Transceiver from Jahnke Electronics.
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Serial number 80300025.
This radio is in outstanding working condition and outstanding overall condition – check the pictures! Unit transmits at 40 watts VHF and 35 watts UHF.
A new battery with a holder has been installed. A fresh alignment has been completed. This radio does not come with the 1.2 Ghz module.
This TS-790A comes with a power cable, mic and the manual as shown in paper and also on CD. Also, the original Kenwood double box set with styrofoam inserts.
Free shipping applies to customers in the USA and please email for shipping rates elsewhere.
Please know that when you purchase this transceiver, it will come to you carefully packed and as if it were new. It will not be dirty inside or out or have any adverse odor. It will have been cleaned and tested fully and lubricated to work as quietly as possible so that when you provide it power, it will operate as intended. Please do compare our guarantee with that of other sellers and check our feedback on ham radio sites. Udemy app for mac.
Kenwood Ts-790 Service Manual
This unit will come to you UPS Ground or USPS Priority Mail – fully insured and warrantied as fully operational. Our technical staff is very well versed in this equipment and they have inspected, tested, lubricated and repaired (if necessary) your purchase before it was listed for sale. As such, we assure you that your equipment will arrive fully operational and we will guarantee it for 30 days against any defect whatsoever. If you have ANY problem, we will take the unit back and repair or replace it immediately.
Kenwood Ts 590s Manual
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