A follow up video on how to neutralize the tubes on a Kenwood Hybrid radio TS-520(s) TS-820(s)

[@williamogilvie6909]

The 520 SE is a nice little radio. I bought one in 1996 from an older ham who was a member of my ham club. I should have done a smell test first because I soon discovered the power transformer was totally smoked. I bought the last replacement HRO had in stock and put it in. After cleaning up the rig, I put it on the air one night, using my 80 meter dipole. I easily raised a station on the East coast, then all hell broke loose. The 6146's started arcing and continued arcing after I unkeyed. So back to the shop. I discovered the cathode resistors ~7 Ohms, had been replaced with 10 gauge wire. That explains why the transformer blew. My ham friends, an older couple, really pulled a fast one on me. I tried several different resistor types. I remember some blew like fuses right away. Eventually I got that radio working as it should and had many As is with it.

[@zigzag3853]

Wow, not a good experience, not to mention that transformer isn't exactly cheap and a pain to change out.

[@williamogilvie6909]

@@zigzag3853 I made it into a good rig, although it wasn't such a bargain when I finished. Sometimes the road less travelled is more interesting.

[@oldgravely]

Smoke test?

[@zigzag3853]

If they try this with the SG switch not turned off, I guarantee more than smoke. I guarantee a door stop! If done as I said, it works quite well. Have verified it.

[@TheColeChannelEagle]

No. No smoke. I've done it this same way on over a dozen Kenwood and Yaesu hybrids. And they're all still talking like they did when they were new. There's always more than one way to do something, and none of them cause smoke, unless you do it WRONG.

[@TheColeChannelEagle]

Yes, if the SG switch is ON...then they're doing it WRONG....lol.

[@TheColeChannelEagle]

Old hammys. Still stuck in 1957.....🥺😖😩😫😜

[@bennydirollo1818]

The same thing with the yaèsu101 ee

[@sparky5247]

Why 28.5 ? The service manual calls for 21.255 . Art W8AEW

[@zigzag3853]

Best to perform it at the higher band since oscillation is most likely to occur there if something is off. Not sure why Kenwood calls for 21.255 when their actual owners manual calls for 28.5. K9TW (A kenwood hybrid tech) gives a more detailed answer below: "It is best to perform neutralization at 28.5mhz to 28.8mhz as at that frequency the Xc (capacitive reactance) is the lowest of the radios bands at approx. 25,000 ohms. Capacitive reactance can be thought of as AC resistance to RF. Xc at 80 meters at 3.750mhz is approx 193,000 ohms. So you can see that the 6146B is far more likely to take off on 10 meters than on the lower bands. In years past with most of the transmitters mfg it was pretty common practice to direct neutralization at 21.3mhz. This was done as an attempt to get some level of neutralizing the inter-electrode capacitance on either side of 21.3mhz. In reality neutralization is only most effective at the frequency that it is performed on."

[@sparky5247]

@@zigzag3853My owners manual (1978 version ) called for 21.3 . I later purchased a service manual which lowered the frequency. Thanks I try 28.5 73's

[@TheColeChannelEagle]

Exactly Zig Zag!! K9TW rebuilt my TS-820S, and he's one of the last Kenwood "guru's" since K4EAA, and ANYTHING he says on Kenwood hybrids, you can take to the bank!!