Viking II Blowing fuse

[k5kab]

My Viking II turns on fine during the tune procedures as soon as I throw the plate switch fuse blows. Where do I start?

[WA1GFZ]

remove the HV rectifiers and see if it will come up.

[K9PNP]

I'm presuming you are in CW mode.  Pull the 2 HV rectifier tubes [5R4's] and see if it still happens.  If it does trouble is in the transformer or AC and transformer wiring.  If not, it is in the rectifiers, finals, or modulators or the HV circuitry.  Check the 5R4's, 6146's, and 807's for shorts.  Have had 807's cause this.  Do you have a manual on the rig?

[KM1H]

Also check the 5R4 sockets for carbon paths, aka Pecker Tracks in the Navy We had lots of problems with ceramic sockets arcing when using 5R4's at over 700V in the radar displays.

Carl
KM1H

[WQ9E]

I second Carl's advice.  I ran into this with the 5R4 sockets with both my Viking 1 and DX-100.  I sub-mounted the sockets on my Viking 1 to take care of the problem.

[k5kab]

I'm presuming you are in CW mode.  Pull the 2 HV rectifier tubes [5R4's] and see if it still happens.  If it does trouble is in the transformer or AC and transformer wiring.  If not, it is in the rectifiers, finals, or modulators or the HV circuitry.  Check the 5R4's, 6146's, and 807's for shorts.  Have had 807's cause this.  Do you have a manual on the rig?

You guys are awesome, the 5R4's was the problem. I never would have checked them they were new tubes. Thanks a million this board is great !!!!!!

[K9PNP]

Glad we all could help.

[WQ9E]

It is unusual to find a new tube to be defective but it does happen.  Even simple pilot lamps can be defective-a new one nearly took out the wiring harness in my Viking 1 because of a dead short in the lamp base.  The 6.3 volt line got very hot before I killed the power.

Check again to make sure that there isn't a crack or any carbon tracking in one of the sockets.  The 5R4 sockets are in parallel in the the Viking so it is likely only one tube is defective.  Also be sure the locating pin isn't damaged on one of the tubes since this could allow the tube to be inserted improperly.  If you decide to replace the 5R4 tubes with SS rectifiers you can make a single replacement and put it in either socket leaving the other blank since any reasonable SS diodes will handle the current without needing a second one in parallel.

[ka3zlr]

It is unusual to find a new tube to be defective but it does happen.  Even simple pilot lamps can be defective-a new one nearly took out the wiring harness in my Viking 1 because of a dead short in the lamp base.  The 6.3 volt line got very hot before I killed the power.

Check again to make sure that there isn't a crack or any carbon tracking in one of the sockets.  The 5R4 sockets are in parallel in the the Viking so it is likely only one tube is defective.  Also be sure the locating pin isn't damaged on one of the tubes since this could allow the tube to be inserted improperly.  If you decide to replace the 5R4 tubes with SS rectifiers you can make a single replacement and put it in either socket leaving the other blank since any reasonable SS diodes will handle the current without needing a second one in parallel.

Hello Roger,

What diode would you suggest for the replacement of the 5R4's


73

Jack

[KB2WIG]

FWIW, I use 1N5408's .....  3A  1KV

theys cheep

klc

[WQ9E]

Jack,

The same as KLC, 1N5408.  I bought a bunch of them from Mouser several years ago and they are very cheap in quantity.

When replacing the rectifiers in older gear (SB-220, etc.) that use resistors and capacitors across the rectifiers then you should remove them as they are not necessary or desirable with modern rectifiers.

[KM1H]

And if you are building a big PS the 6A10 (6A @ 1000V) is only a few cents more than the 1N5408 but it gives a huge safety factor in surge survivability.

Carl
KM1H

[ka3zlr]

Thanks Guys..

73

Jack