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Author Topic: Kenwood TS530/830S RF Board X44-1360-00  (Read 2881 times)
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KA2PTE
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« on: May 26, 2021, 12:30:42 PM »

I own a TS-530S and it took a zorch back through the front end because I was feeding my Thunderbolt linear with it improperly.

Removed the RF board, Isolated Q1 (3SK73) shorted, but after replacing it, it shorted again on power up.

After checking Q6/Q7 (3SK73) they were shorted also. Am about to replace all them again but I see still a 100-200 ohm short on the B+ line from connector (7) pin 1 which is the 12V feed. Q5 checks ok, Q3/Q4 seemed shorted but when removed they check ok. D2 checked ok but replaced it anyhow. I have pulled alot of the 0.047uF disc caps such as C71 which seem to be on the 12V line for surge protection , but so far none read short. There's still one tucked away into a tough to get at spot near the bread slicers - but other than this, am I overlooking anything else?


* x44-1360-00.jpg (300.63 KB, 1307x846 - viewed 259 times.)
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W1RKW
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« Reply #1 on: May 26, 2021, 03:44:59 PM »

see if you can isolate the 100-200 ohm short by lifting the various inductors on the 12v line.
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Bob
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« Reply #2 on: May 26, 2021, 08:24:50 PM »

And the T2 12v line also connects to pin 2 on connector 6. I’d disconnect it to be certain the problem isn’t elsewhere.
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KA2PTE
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« Reply #3 on: June 13, 2021, 02:19:12 PM »

For now I set that board aside as I have another, and continued work on my spare which pretty much had similar issues. I replaced all the 3SK73's as they were all shorted with motorola 3N201's. I had to install pin sockets for the leeds as their pin configs are a little different.

Powered up and seems to be getting some local noise, and the CAL signal is heard fairly strong and the IF shift sounds like its working so I guess the IF section is working.

Removing the antenna makes no difference, nor does moving main the RF bread slicer tuning array via the driver knob, so I guess theres still an issue in the front end.
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KA2PTE
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« Reply #4 on: June 14, 2021, 01:52:58 PM »

Forgot about the antenna relay in the chassis, was something I meant to check a long time ago, so went about the process of removing it for test. Not easy as its buried below the final cage. P-N on the cover is: 321D012

After I unsoldered it, I popped the plastic cover off, and clearly one sides common contact was stuck to the
N-O side and the other set of contacts was set resting to the N-C.

A little prying dislodged the frozen contact loose to go back to its normal position.

Most likely its the side that goes to the antenna connector. Had experineced intermittent rx / low rx
months prior and I had replaced the relay on the IF board to no avail, so makes sense it was dirty.

I can only guess that relay contact was getting pretty hot, being stuck in the TX mode like that.  The linear seems to have a high power VHF parasitic that came back in, and it took the front end FETS out but if indeed this is the antenna side, it would have had to jump a pretty good gap to get to the other side as this one was stuck.
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KA2PTE
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« Reply #5 on: June 14, 2021, 08:38:54 PM »

After fixing the relay same thing except cant hear the CAL signals anymore.

I started checking for loose wires and when I moved the pin type coax connector to the VCO output from the pll board to the RF unit, started to sound like the antenna signal was coming in. After reseating both ends could not
bring the signal back tho.

I started putting my finger near the VCO jack on the PLL board and could near a noise level. Narrowed it down to R36 on the base of Q7. If I put an antenna wire there, I get what sounds like a normal noise level, and I think I heard some CW as the band switch was set to 40m. The S meter reads, but theres what sounds like a nasty background noise, possibly my fluroscent lighting all over the band. The AGC fast, slow, off makes no difference.  I guess maybe putting an antenna there is the same thing as mixing RF right into the PLL which I guess is the local osc? That would mean my IF works, but the other gate of the RF mixer fet is still not seeing the antenna inut from the regular jack. Schematic in the SM here:

https://www.mediafire.com/file/u4ok2meob0j6635/TS-530S_Service.pdf/file


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KA2PTE
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« Reply #6 on: June 18, 2021, 07:04:51 PM »

Ok got it!

Turns out I had the RF mixing FET in wrong.
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