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32v2 no plate current




 
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Author Topic: 32v2 no plate current  (Read 1792 times)
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W4KJP
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« on: August 16, 2021, 02:04:41 PM »

I have been using my 32v2 paired with a 75a4 for sometime now.  I had to do some rearranging in the radio room and now I am not getting any plate current.  With it set to "TUNE" "Phone" the grid current is 13.5ma.  When I switch the HV to "ON" I can hear the rely of the dow-key click but the red light does not come on and no plate current is observed. Any help would be greatly appreciated!

 
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w8khk
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« Reply #1 on: August 16, 2021, 02:48:03 PM »

Here is a link to the schematic diagram for the 32V2.  Three separate pages, tape them together to view with ease.

http://jptronics.org/Collins/32V/32v2.schematic_8.5x11.pdf

Since you mention the Dow-Key relay is energizing, but there is no illumination of the red light for high voltage, it is a rather simple trace of the 120 volt wires from the power plug to the transformer.

There are only three possible components that could cause that combination of symptoms.
1) Fuse F-302 - 5 amp
2) Switch S-301, the interlock switch that prevents HV when open.
3) Relay K-301, the left-most two sets of contacts on the schematic diagram, in series.

Since you have no high voltage AND the red light does not illuminate, we can safely assume the HV indicator bulb I-302 is not defective.  BUT if you are assuming you have no high voltage BECAUSE the red light is not on, then it is possible that you do have high voltage and indicator bulb I-302 is defective.  Factual, verified symptoms lead to accurate troubleshooting.  I AM  INCLUDING THIS PARAGRAPH BECAUSE IF YOU ASSUME THERE IS NO HIGH VOLTAGE BECAUSE THE LIGHT DOES NOT ILLUMINATE, YOU HAVE A VERY UNSAFE CONDITION WHILE TROUBLESHOOTING INSIDE THE TRANSMITTER.  BE VERY CAREFUL BECAUSE 700 VOLTS IS LETHAL.  DO NOT DEFEAT THE INTERLOCK SWITCH WHILE TROUBLESHOOTING.  ALWAYS WORK SAFELY AROUND HIGH VOLTAGE!

If the Dow-Key relay is energizing, that indicates K-301 is being energized, as relay K-301 contacts set four (counting left to right on the schematic) have the sole purpose of energizing the external "remote" relay.

Have a look at the schematic, highlight the wires from the power plug through the above listed components, back to the primary of the HV transformer, and you will see how to troubleshoot this, or similar problems.

Hope this helps you get that fine rig back on the air!
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Rick / W8KHK  ex WB2HKX, WB4GNR
"Both politicians and diapers need to be changed often and for the same reason.   Ronald Reagan
W4KJP
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« Reply #2 on: August 17, 2021, 01:17:31 PM »

After reading though Richards reply (thanks Richard) I did a little more troubleshooting and determined that the dow-key is not being energized.  There is clicking sound when I flip the HV switch to "ON" but it was not the dow-key like I thought.  Looking through the schematics provided this is making me believe my issue is the F-302 5amp fuse.  I have not had the time to remove the radio from the case so I have not proven this.  When I had the radio unplugged if the remote relay screws 7 & 10 were shorted would this have caused the F-302 5amp fuse to blow? 
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w8khk
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« Reply #3 on: August 17, 2021, 03:12:45 PM »

Hello Kevin,

Neither fuse F-301 or F-302 will be blown by shorting terminals on terminal strip E-308 when the 32V-2 power plug is not connected to the 120 volt AC line receptacle.

F-302 could be blown by shorting E-308 terminal 7 to terminal 10 ONLY if the transmitter is powered on, AND both the main line switch S-304 AND HV switch S-303 are on, AND mode switch S-302 is in either the CW or PHONE position (NOT the CAL position) causing relay K301 to energize, thus closing relay contacts 8 and 9, exposing 120 volt line voltage between terminals 7  and 10.

However, with the unit plugged in, whether any of the switches above are closed or open, there will be 120 volts exposed on E-308 terminals 7 and 8, or 7 and 9, as there should be a jumper between terminal 8 and 9.  These terminals expose 120 volts at any time the power plug is energized.  Thus shorting 7 to 8 or 7 to 9 would cause fuse F-302 to blow if line power is available.  

The jumper above completes the circuit when a 120 volt external relay is used, but the jumper would be removed if you wish to use the associated K-301 relay contacts to control some circuit other than the 120 volt line voltage required by the Dow Key relay.

If your 32V2 is the same vintage as mine, in the factory cabinet, you should not need to remove the transmitter to check or replace F-301 or F-302; they are push-and-turn fuse holders on the back panel.
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Rick / W8KHK  ex WB2HKX, WB4GNR
"Both politicians and diapers need to be changed often and for the same reason.   Ronald Reagan
W4KJP
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« Reply #4 on: August 18, 2021, 08:13:34 AM »

I was finally able to get the 32v2 moved out from against the wall without putting scratches on the new desk!  It turns out the F302 5amp fuse is blown.  No local electronic stores around anymore so I had to place an order.  Hopefully, whatever caused the fuse to blow is no longer an issue. 
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w8khk
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« Reply #5 on: August 18, 2021, 06:41:04 PM »

There has to be some reason the fuse blew.  It is possible that the cover for the terminal strip on the back may have contacted other terminals.  Before replacing the fuse, I would suggest checking for a short circuit on the terminal strip where the relay is connected.  In addition to the AC line terminals mentioned previously, be aware that pins 1, 2, 3, 4, and 5 carry the high voltage, either 600 or 700 volts, depending upon the voltage switch setting.  Pin 6 is ground, so any connection between chassis or the ground terminal and these five pins would likely blow the fuse as soon as the high voltage rectifiers are warmed up.  Since the filaments of these tubes are powered by the low voltage transformer, there would be no delay between switching on the high voltage and the short circuit taking out the fuse.

If you do not find any short on the back panel terminal strip, and the new fuse also blows, I would suggest removing the high voltage rectifier tubes (V-302 and V-303) and then testing again with another fuse.  If the fuse blows again, you will need to troubleshoot the AC wiring to the primary of the high voltage transformer.  If the fuse DOES NOT  blow, then the problem might be a bad rectifier tube, or a short or defective component somewhere in the high voltage circuit.  Again, extreme care must be exercised when working with the high voltage supply in this, or any transmitter.
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Rick / W8KHK  ex WB2HKX, WB4GNR
"Both politicians and diapers need to be changed often and for the same reason.   Ronald Reagan
WD5JKO
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WD5JKO


« Reply #6 on: August 19, 2021, 10:24:52 AM »


No local electronic stores around anymore so I had to place an order.  Hopefully, whatever caused the fuse to blow is no longer an issue. 

The Auto Part stores can sometimes come to the rescue when you need something right now. Napa has a 250v 5A fast blow fuse. See attached image.

Jim
Wd5JKO


* NAPA.jpg (56.49 KB, 1135x426 - viewed 99 times.)
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W4KJP
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« Reply #7 on: August 20, 2021, 06:38:24 AM »

Jim, 

Thanks - I did check NAPA and Advanced Auto first but neither of which had them in stock but they could order them.  I ordered a pack and they were supposed to be delivered Thursday but now its Saturday.

Kevin
w4kjp
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WD5JKO
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WD5JKO


« Reply #8 on: August 20, 2021, 07:19:42 PM »


Kevin,

   Sometimes I will make a fuse adapter to a circuit breaker. The idea is to solder wires to a blown fuse, and connect the wires to an equal rating circuit breaker. With a fuse holder with a cap,

you can add a wire through the inside of the fuse if you drill holes through each side of the fuse, and then run the wires out through a hole drilled in the cap, and solder. Could also use an

automotive cartridge fuse that way.

   At work, on a 3KW RF generator, there is a $10 20 amp cartridge fuse. We have an adapter that uses a 20A breaker, and wires soldered to the fuse

ends. We only use a new fuse when we know everything is working OK.

Heck, you could even use a 100 watt lamp for troubleshooting. Vary the wattage of the bulb depending on the load.

Jim
Wd5JKO
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KD6VXI
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« Reply #9 on: August 21, 2021, 11:59:07 AM »

If you have a harbor freight they have a nice fuse assortment.  It's only a few bucks for 20 plus different sizes.

--Shane
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W4KJP
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« Reply #10 on: August 23, 2021, 12:57:42 PM »

Thank you everyone for the help!  The fuses were delivered and the plan is to get the transmitter hooked back up Wednesday after work. 

I didn't even think about checking Harbor Freight.

Kevin
w4kjp
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W4KJP
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« Reply #11 on: August 23, 2021, 02:42:35 PM »

I decided to go ahead and check for a short across the terminal pins 7 & 10 on the 32v2 and it was open.  Then I checked across the power leads for the dow-key that connects to these terminals and there is a short.  Dow-key gone bad? 

Kevin
w4kjp
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