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Author Topic: Kenwood TL-922A  (Read 3954 times)
K7VGE
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Posts: 9




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« on: March 07, 2013, 07:32:56 AM »

Thanks for reading this.  Need help to save time.  Have a TL-922A Kenwood blows fuses when I put switch to SSB.  Have not had time to open amp up yet.  In the CW mode it works with out blowing the fuses.  It put out 2KW in the CW mode.   

Thanks for your help or ideas.

Ed
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W1QJ
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Posts: 1457




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« Reply #1 on: March 07, 2013, 08:08:38 AM »

Does this amp have a step start?  Does it have higher value cpacitors in the PS than original?  Any other mods?  The amp can't put out 2KW in the CW mode, that is impossible,  Does it have the correct fuses?
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K8AXW
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« Reply #2 on: March 07, 2013, 08:32:17 AM »

Perhaps that's 2KW input power (Panel meters I X E) 

If the power supply changes HV transformer windings when going to SSB for a higher voltage, perhaps something in the filter circuit is shorting out or even the transformer itself is defective.
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K7VGE
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« Reply #3 on: March 07, 2013, 09:30:43 AM »

Does this amp have a step start?  Does it have higher value cpacitors in the PS than original?  Any other mods?  The amp can't put out 2KW in the CW mode, that is impossible,  Does it have the correct fuses?


Thanks for the reply your right it can't put out 2KW my mistake.. Should be read as 2KV via the multimeter.   It has the right fuses.  No step start Some mods done bought it used will have to check the logs to see what was done.

Thanks
Ed
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K7VGE
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« Reply #4 on: March 07, 2013, 09:34:51 AM »

Perhaps that's 2KW input power (Panel meters I X E) 

If the power supply changes HV transformer windings when going to SSB for a higher voltage, perhaps something in the filter circuit is shorting out or even the transformer itself is defective.
Thanks for the reply,    HV transformer my be going I know it step up to 3KV for SSB when working right and 2KV for CW mode.  As for the 2KW in my first message should have read as 2KV on the Multimeter.

Thanks for help.
ED
« Last Edit: March 07, 2013, 09:37:37 AM by K7VGE » Logged
W8JX
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Posts: 6030




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« Reply #5 on: March 07, 2013, 10:30:38 AM »

First thing to do is to disconnect plate caps (after using a shorting stick) then see if fuse still blows. If not you have a tube arcing over. If it still blows isolate HV output leads from transformer from power supply rectifiers and capacitors. I doubt it is transformer.







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K6AER
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« Reply #6 on: March 07, 2013, 03:25:24 PM »

I agree with W8JX. The capacitirs are getting pretty long in the tooth. Also chect the equilizing resistors and the caps across the diodes.
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K7VGE
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« Reply #7 on: March 07, 2013, 04:16:52 PM »

First thing to do is to disconnect plate caps (after using a shorting stick) then see if fuse still blows. If not you have a tube arcing over. If it still blows isolate HV output leads from transformer from power supply rectifiers and capacitors. I doubt it is transformer.

The unit works ok in the cw mode lower voltage, but if I flip the switch to SSB its shut down. ok on the tubes would upping the voltage make the tube arc? or would they ark at the lower voltage too.  Did pull the rectifier board check the diodes, and resistors need to get a meter to check the capacitors, all checked out.  Will need to put back together and do your suggestion.


Ed






« Last Edit: March 07, 2013, 04:20:37 PM by K7VGE » Logged
W8JX
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Posts: 6030




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« Reply #8 on: March 07, 2013, 04:31:57 PM »


The unit works ok in the cw mode lower voltage, but if I flip the switch to SSB its shut down. ok on the tubes would upping the voltage make the tube arc? or would they ark at the lower voltage too.  Did pull the rectifier board check the diodes, and resistors need to get a meter to check the capacitors, all checked out.  Will need to put back together and do your suggestion.


When a tube is getting gassy, the higher the voltage, the more likely they will arc. By discounting them and testing it narrows trouble down and rules out tube if problem still exists with tubes out of circuit. 
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W1QJ
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« Reply #9 on: March 07, 2013, 05:36:15 PM »


The unit works ok in the cw mode lower voltage, but if I flip the switch to SSB its shut down. ok on the tubes would upping the voltage make the tube arc? or would they ark at the lower voltage too.  Did pull the rectifier board check the diodes, and resistors need to get a meter to check the capacitors, all checked out.  Will need to put back together and do your suggestion.


When a tube is getting gassy, the higher the voltage, the more likely they will arc. By discounting them and testing it narrows trouble down and rules out tube if problem still exists with tubes out of circuit. 

Thats right, the tube may not go plasma at 2KV but can at 3KV.  I have seen this several times before.
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K7VGE
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« Reply #10 on: March 07, 2013, 09:05:39 PM »

Thanks for reading this.  Need help to save time.  Have a TL-922A Kenwood blows fuses when I put switch to SSB.  Have not had time to open amp up yet.  In the CW mode it works with out blowing the fuses.  It put out 2KW in the CW mode.   

Thanks for your help or ideas.

Ed

Thanks for all your direction on this amp.  I replaced the Mode switch and checked the rectifiers board and took the plate caps off and turn on the amp and it work with no fuses blowing.  Now what.  Put all back together and meter reads 2.1 KV in the CW mode and 3.4 KV in the SSB no blowing of fuses.  Now put it on line with 75 watt drive get about 500 watt out in CW Mode, about 700 Watt in SSB.  So I am on-line with this amp but for how long.  Amp is for back up anyway.  Thanks again. Ed
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W8JX
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« Reply #11 on: March 08, 2013, 06:20:29 AM »

Now put it on line with 75 watt drive get about 500 watt out in CW Mode, about 700 Watt in SSB. 

This is low output for this amp. It suggests a bad or weak tube or tubes if you are tuning it correctly.
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KH2G
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Posts: 306




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« Reply #12 on: March 09, 2013, 02:59:38 PM »

The CW/SSB switch changes taps on the transformer but there are 2 caps in the circuit C2 and C3. If one were to short, it may cause this effect. Also there is a discharge gap device at the antenna relay terminal to take care of any HV developing during relay changeover. (Unless this has been modified)
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W1QJ
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Posts: 1457




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« Reply #13 on: March 09, 2013, 03:42:46 PM »

The CW/SSB switch changes taps on the transformer but there are 2 caps in the circuit C2 and C3. If one were to short, it may cause this effect. Also there is a discharge gap device at the antenna relay terminal to take care of any HV developing during relay changeover. (Unless this has been modified)

KH2G. the C2 and C3 you refer to seem to be capacitors that have a common point on the switch which goes up to the cap filter board.  The other side of the caps go to the CW and SSb terminals of the switch, possibly if one was shorted it could throw a short across the hi/lo secondarry windings?  Lifting then both off the center and trying it will be an easy test. Lou
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K7VGE
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Posts: 9




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« Reply #14 on: March 12, 2013, 06:08:02 PM »

Thanks for reading this.  Need help to save time.  Have a TL-922A Kenwood blows fuses when I put switch to SSB.  Have not had time to open amp up yet.  In the CW mode it works with out blowing the fuses.  It put out 2KW in the CW mode.   

Thanks for your help or ideas.

Ed

Thanks for all your direction on this amp.  I replaced the Mode switch and checked the rectifiers board and took the plate caps off and turn on the amp and it work with no fuses blowing.  Now what.  Put all back together and meter reads 2.1 KV in the CW mode and 3.4 KV in the SSB no blowing of fuses.  Now put it on line with 100 watt drive get about 800 watt out put in CW Mode, about 1250 Watt in SSB 40 meter band.  So I am on-line with this amp but for how long.  Amp is for back up anyway.  Thanks again. Ed
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