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Author Topic: Blowing fuses in the TS-830S  (Read 3245 times)
HS0ZFQ
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Posts: 118




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« on: January 02, 2013, 05:39:13 AM »

Greetings and Happy New Year to all:
     I have a TS-830S that was repaired by a friend and I love it. It beats the heck out of my IC-706.Recently it has developed a problem of blowing fuses.I have taken my Palstar antenna analyzer and antenna tuner and run tables on swr and frequencies used so I don't think the problem is there. I am going to go throlugh the antennas and feedlines again. I have two S9 verticals with two BalunDesigns baluns.
     Could a kind soul give me suggestions as to where to look in the radio system for the problem.After a few minutes of operation the fuse will blow. I do not want to operate the 830 and damage it.
     Any help will be highly appreciated.
Yours Truly
Richard Vincent
HS0ZFQ
ChiangRai, Thailand
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KA4POL
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Posts: 2028




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« Reply #1 on: January 02, 2013, 06:31:31 AM »

Happy new year to you too.
You need to specify under which conditions exactly the fuse blows. The SWR will most likely not have an influence. How do you power your rig? Does the fuse have the correct value?
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AC5UP
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« Reply #2 on: January 02, 2013, 06:33:26 AM »

I doubt it's an antenna issue, a leaky electrolytic capacitor in the HV power supply is more likely.

Does the fuse blow in RX? If the fuse only blows in TX I'd definitely look at the HV supply for a leaky filter cap or shorted rectifier.
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KA4POL
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« Reply #3 on: January 02, 2013, 06:39:22 AM »

According to the manual for 120 V you need a 6 A AC fuse. So, if I am correct, you got 220 V in Thailand. A 3 A fuse should be right.
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AA4N
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« Reply #4 on: January 02, 2013, 07:41:06 AM »

My TS-820S was doing that when I first bought it, 4 years ago.  It was an ebay bargain.

The rig would blow it's main fuse after a few minutes of transmitting.  If you watched the plate current in CW mode.  It would slowly increase from it's normal idle current value after 30 seconds or so in transmit (without key down).  The current increase would get faster and faster.  Then the fuse would blow just before the needle pegged out.

After a week or two of futzing with it.  It turned out that the brand new shiny Chinese (or maybe it was Russian) tubes that the previous owner had installed were gassy.  After I replaced them with a pair of slightly used American 6146's.  The problem disappeared.  The rig has worked beautifully ever since.

Just something you might looks at...

73,  mike
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HS0ZFQ
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« Reply #5 on: January 02, 2013, 07:47:57 AM »

Thanks for the quick replies. The 830 only blows the 6A 250V fuses on transmit. I never have a problem on receive. I got the fuses from K4EAA who specializes in these hybrids so I figure I am safe on the fuse rating issue.
I power the rig  with a transformer.The receiver end of the transformer is 130 Volts and the other end goes into the wall 220v. To the new reply I have brand new matched 6146 and a new 12BY7A ?? rectifier that I bought from the US. They are all American NOS tubes. I looked  at one just now still in the box and it is a Phillips ECG from RF Parts.com
Richard
HS0ZFQ
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K8AXW
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« Reply #6 on: January 02, 2013, 08:31:56 AM »

ZFQ:  The 12BY7A isn't a rectifier but is the driver for the 6146 finals.  Even though the tubes are brand name, they are still NOS.  I would consider them suspect #1.

Since the radio is approximately 30 years old, any number of parts can be giving it up.  If the power supply was crapping out, as in a bad filter cap, then the plate current wouldn't go up but go down.  What does the HV do while this plate current is moving upscale?

Have you removed the radio from the case and done a visual around the final area looking for hot and or failing components?


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AC5UP
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« Reply #7 on: January 02, 2013, 09:20:17 AM »

Someone should mention that since the 6146's are in parallel it's possible to TX with only one tube. You won't see full output, but, if one of the tubes can fly solo while the other cannot I'd take that as a clue.

Mandatory Disclaimer:  Any tests in or near the high voltage section should be approached with caution. It can take a minute or more for the filter caps to bleed down to a safe level. A power cord unplugged is better than a power switch turned off. Always assume the radio is capable of tickling your fancy because someday it will......  Tongue
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AC5UP
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« Reply #8 on: January 02, 2013, 10:23:10 AM »

One More Thot:   When the 6146's were replaced, are we reasonably sure they were neutralized ?
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KA5IPF
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« Reply #9 on: January 02, 2013, 12:34:43 PM »

Someone should mention that since the 6146's are in parallel it's possible to TX with only one tube. You won't see full output, but, if one of the tubes can fly solo while the other cannot I'd take that as a clue.

Mandatory Disclaimer:  Any tests in or near the high voltage section should be approached with caution. It can take a minute or more for the filter caps to bleed down to a safe level. A power cord unplugged is better than a power switch turned off. Always assume the radio is capable of tickling your fancy because someday it will......  Tongue

The filaments are in series, can't remove just one tube.

First I would look at the 4 20 ohm cathode resistors and replace them. Use 1/2w carbon comp. Then I would replace the main filter caps.

Clif
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AC5UP
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« Reply #10 on: January 02, 2013, 12:52:17 PM »

The filaments are in series, can't remove just one tube.

I did not know that...........

And I'm glad to hear it as I have a small stash of NOS GE 6883's. Same characteristics as a 6146, but with a 12.6v filament for mobile application. Couldn't bear to throw them away because of the NOS thing, but didn't have a plan for them until now. Ought to pull them out to look for an 'A' or 'B' after the number.

BTW:  If the plate cap on one of the 6146's in a TS-830 were to become disconnected, would the remaining tube still work at reduced output power ?
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KE4DRN
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« Reply #11 on: January 02, 2013, 04:52:12 PM »

Hi Richard,

KA5IPF gives great service info.

please join other Kenwood Hybrid 5xx and 8xx fans here

http://groups.yahoo.com/group/TS-520_820_530_830/

owner and service manuals in pdf no cost

http://www.n6wk.com/kenwood/

Here is a link for the dim bulb tester, it will protect the transformer
when you are testing the radio.

http://antiqueradio.org/dimbulb.htm

73 james
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K4EJQ
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Posts: 101




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« Reply #12 on: January 02, 2013, 08:50:57 PM »

Richard. Never operate any Tetrode tube ( 6146 in this case ) with screen voltage but NO plate voltage applied ( plate cap removed ). To do so will cause the screen grid to act like the plate and draw damaging current VERY QUICKLY. The screen grid is not as heavy duty as the plate and will burn out quickly if powered from a "Stiff" source. Good luck with your trouble shooting. 73 /HNY-Bunky. K4EJQ
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G3RZP
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« Reply #13 on: January 03, 2013, 12:22:46 AM »

There was a UK military tx with a pair of 4-250A in the final. The 600 volt  screen grid line was fused, and was also plate supply for the 5894 driver. The 5894 screen was fed from separate supply, and if the fuse in the 600 volt line went, the 5894 lit up like a light bulb - but not for very long!

Never run screen volts without plate volts.
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WN2C
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Posts: 466




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« Reply #14 on: January 03, 2013, 07:03:02 AM »

The filaments are in series, can't remove just one tube.

I did not know that...........

And I'm glad to hear it as I have a small stash of NOS GE 6883's. Same characteristics as a 6146, but with a 12.6v filament for mobile application. Couldn't bear to throw them away because of the NOS thing, but didn't have a plan for them until now. Ought to pull them out to look for an 'A' or 'B' after the number.

BTW:  If the plate cap on one of the 6146's in a TS-830 were to become disconnected, would the remaining tube still work at reduced output power ?

Yes it will.  Had that very thing happen to me one time.  Had tuned up the radio and was talking to some local guys and then not then the radio blew the fuse.  Replaced the fuse and fired it back up.  It stayed running bu at reduced power.  I opened it up and found the plate cap had come un-soldered (must have been really hot or just old connection) so I soldered it back up, fired it up and it worked fine after that.  It will work on one tube, but I wouldn't work it long that way.

Rick  wn2c
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