SR failed in PTT. Globe champion. questions

[ke7trp]

All relays good.. If I key the transmit switch the transmitter keys fine.  This ensures all AC relays are working perfect.

If I PTT the rig via the mic, I get chatter.

This means that the Relay that is switching the AC to the relays might be at fault. I replaced it after adjusting and cleaning. No change. Still chatter.

So.. :

No relays are damaged. All are working.
If switched AC transmitter keys fine.
If I use the 6.3 volt AC to Half wave I get 8.3  volts DC clean.
This makes the DC relay click nice with no arc.
AC relays then Chatter before closing.. About 1 second of BUZZ before it latches solid.

I dont see any voltage Drop. No AC ripple.

Question:

1. If I put 6.43 volts AC input to a FULL functional HALF WAVE rectifier, What DC voltage is expected?

Tomorrow, I plan on unhooking DC relay lines and checking coil resistance, This way, I can do Ohms law and get the resistor value I need to Drop 8.3 to 6.0.  I have inserted a 10ohm 2 watt with no luck.  So my guess value must not be correct.

Gito. Thanks alot for your input.  AC switch is fine.. If I throw AC switch, Transmitter works 100%.   This is fine. I can do that.. However, I like to sit back in the chair with a D104 and rag chew..  Whats broken needs to be fixed

I can only guess (with all of your help) that the 8.3 is just to much for the DC relay.  The forward Drop of the SR was high. The forward Drop of the silicone diode is LOW.


Clark

[WQ9E]

Clark,

The DC voltage from a half wave rectifier will drop more quickly under load than a full wave circuit given similar filter capacitance but both will charge the capacitor to the peak voltage (less voltage drop across the rectifier itself).  So under light load the DC output voltage from the half wave rectifier will be greater than the RMS AC input.

Back to the basic problem:  Applying the principle of Occam's razor if the relay system worked normally before the selenium rectifier was replaced and that was all that was done and now you have relay chatter then it must be directly related to the replacement.  It may well be your relay, RL-3, that is the "driver" of the chattering relay is the true fault.  Perhaps your selenium has been slowly dying and the coil voltage to RL-3 has for years been below the nominal value and once you approach the name plate rating coil voltage rating then you have trouble.  To test my theory, put a variable pot in series with the relay coil and adjust the pot to the point where RL-3 just pulls in reliably when the PTT is activated and see if the chatter goes away.  If this is the case, it is likely for years you have been applying less than 6 volts to the relay coil which has masked the problem.  Use your pot to increase the voltage so that there is 6 volts across the coil and see if the chatter returns.  If this is the case then you need to replace or repair RL-3.

Rodger WQ9E

[ke7trp]

Great Rodger.. Thanks alot for helping me man.

Tomorrow.. I will use my Variable DC supply to kick that relay in.  I will unhook the wires, use clip leads and a switch to safely kick in that relay with 5, 6 and 7 volts ect..    If I get to a lower voltage and it works, Its a simple Resistance measurement to get me to the correct relay.  

Again.. Thanks to all for helping..  There are just some areas where I know when to say when.. This is one of them.  I need help.

Clark

[WQ9E]

Clark,

Glad to be of help.  Think of this as a learning experience that will make it easy when you hit a similar issue in the future. 

I should have been clearer in my previous response about the DC voltage from a half wave rectifier. 6.3 volts AC is the RMS value from the transformer secondary  but at the peak of the sine wave the voltage is going to be about 1.41 times the RMS value (square root of 2 times RMS to be exact) and it will charge the filter capacitor to this on peaks.  So with no load (PTT not keyed) you should have a DC value of (6.3 - rectifier voltage drop) * 1.41 or around 9 volts but this will drop rapidly under load. 

Rodger WQ9E

[ke7trp]

Ok.. Thanks again.. The ARRL book is confusing.  The wikki article is even more.. They are saying a lower voltage.. That caused me to believe my Half wave was constructed wrong.  I am 100% is correct now.  I dont understand what the 47K ohms purpose is other then a bleeder.. But why place a bleeder here?  Maybe it provides some load? 

Thanks again for the help.. I am really enjoying the bands right now.. Lots of AM going on.. I put the old Valiant in line and she is running strong..

C

[WQ9E]

Clark,

I imagine the Wiki article is assuming no filter capacitor so the lower voltage would be correct.  There was a company that used to sell light bulb life extenders that were a half wave rectifier in a button package that you put  into the socket before the bulb was screwed in.  This provided the lower voltage to the bulb extending the life and a similar device was sold for extending the life of the old series string Christmas light bulbs.

But once you add a filter capacitor then you are going to end up with a greater than RMS DC voltage under light loading.  The resistor across the filter cap provides for less change between the no load and full load voltage and will discharge the filter cap when the power is removed.

I will have the Desk KW and Viking 500 on 75 and probably 40 tomorrow night for Heavy Metal.  I have been dealing with a series of phone calls on a consulting project tonight so I have to be tied to the phone and computer instead of the rig.  So much for the holidays   but consulting is where I get my "mad money" to feed my vintage gear habit.

Rodger WQ9E

[Gito]

Hi

Clark ,why don't You try to jumper Rl 2 connection ,the relay connection for Relay 3/meaning by pass RL2/not using RL2,if the chatter still exist,than it must be RL3 ,Since relay 3 is an substitute for Switch 2 and switch 3a and 3b in the schematic diagram When using PTT switch ,If I'm not wrong

Gito  

[Jim, W5JO]

If C 65 is 47 uf. then it is too small.  That cap should be 500 or 600 uf.  I overlooked that value in your original post.

[WQ9E]

Good catch Jim!

I thought only the rectifier had been replaced and didn't realize the cap had also been changed.  The parts list calls for using a 500 uf @ 6 volts but I would definitely bump up the voltage rating to a safer value.

Clark, the best tool for measuring ripple is your scope set for AC coupling.  A meter set for AC will work I guess but the scope trace really shows the story.  To measure the ripple you have to have the PTT engaged so that the supply is loaded by the relay.

Rodger WQ9E

[WD5JKO]

H Clark,

   Boy both Rodger and Jim have both given you excellent advice. I know this must be frustrating for you. Similar things happen to all of us. Some days I cannot make a wire work!

   Here are a few tidbits to toss up in the air:

* A DC relay will not chatter if the coil excitation is pure DC (when PTT is closed, and relay coil pulls current)
* Measuring the AC ripple with either a DVM (AC mode) or scope is best done when loaded. That means measuring when the relay is energized. With DVM, % ripple is (AC measured/DC measured) * 100. Keep in mind that many DVM's lie when measuring AC with a large DC component. A Scope is better.
* When replacing the SR with a silicon diode, it is an easy mistake to get the diode stripe on the wrong side. The Chump schematic shows it right however. When you diode test with DVM, the cathode (stripe) uses the negative
lead (black) on DVM, but in a rectifier circuit like the Chump, the striped side is plus.
* You said you were going to use a variable DC supply to control the relay. That is an excellent idea Clark. A rough guide might be for a 6 vdc relay coil, to pull in at 4-5 volts, and to drop out at 2-3 volts. You can play with the contact gap (N.O.) and spring tension to change those two points.
 * Relay coils like to be pulsed. For example, for a 6v DC relay the initial turn on could be at 12 volts for 100ms, and then decay to 5-6v thereafter to hold the relay down. This pulsing closes the relay quick, an important thing if you run CW with relay(s) switching various things at a CW rate (NA to your Chump). This would require circuit mods to the Chump.

Jim, W5JO is correct that the capacitor filter should be much higher in value than 47uf (> 10X that value at 10vdc is still a very small and inexpensive cap these days.).

Also measure the DC resistance of the coil. Maybe the relay has a normal value already stamped on the coil. There could be a shorted turn, and maybe the relay failed first..taking out the SR..

* After you get this going again, look up diode commutation to suppress the back EMF spike released when the coil current is interrupted (releasing PTT switch).

Good Luck Clark,
Jim
WD5JKO

[Jim, W5JO]

H Clark,

   Boy both Rodger and Jim have both given you excellent advice. I know this must be frustrating for you. Similar things happen to all of us. Some days I cannot make a wire work!
Jim
WD5JKO

Clark with a 1/2 wave rectifier you will get about .45 of the RMS voltage  and normally these circuits are only used in low current applications like you are seeing.  The ripple will be very high and requires a LOT of capacitance to filter.  If you have a 470 uf 16 volt or 25 volt cap, parallel it across the one you have there.  This is the reason I mentioned earlier to check your work after you finish.  It is a mistake I have made in the past and, for us, it was easy to read past the problem. 

[kg8lb]

   Did you say you put a Silicon diode across the dead Selenium Rectifier ? If so, the SR may be leaky with voltage applied and passing a litle AC along .
  Disregard if this is not the case, I didn't read all of the digression regarding AC/DC relay theory so I may have missed a part where you changed the wiring.

[Gito]

Hi

Yes Roger and Jim using a higher value of like 470 uF,makes the ripple small,but after looking at the part list of Globe 300, it wrote that C65 is a 50uf -25 V Cap,can it be wrong.but there is no problem before (no chattering)

And as I wrote before,if it is caused by the ripple ,than the chattering will not stop ,as long as PTT switch is on.
But Clark wrote the AC relay chatter before closing.about 1 second of buzz before it latches solid.,That means the Chattering had stop,after 1 second

I think something is changing in  the HV power supply of this  Globe,like using  higher Capacity (uF) for the original one .Or the filter choke had shorted.Making a capacitor input power supply.

I have the feeling that  the AC voltage ( 110 V) drops for a part of a second when the PTT switch is pressed ,because the surge current/inrush current  present when filling the Capacitors of the  HV power supply.

At that split second ,the voltage is lower than 110 volt,so the AC relays chatter,
After the HV capacitor is filled / the inrush current stop,the voltage get's to it's  normal voltage,It happens only a part of a second.
Of course I can be wrong ,Just an Idea.


Gito

[ke7trp]

I am going to put a 1000UF 16 volt cap across the output of the rectifier and give it a go.  All of this has made me go back over my Globe King 500 Restoration documents.  It seems I went down this path with the king also.  In my notes it stated I used a 500UF cap across the output. Someone here, I cant remember who, Told me to put the cap in. That solved the kings chatter. 

I just cant believe I forgot about that mod on the king.  I can remember anything you ever want to know about one subject, But simple things I have done before, I cant recall. 

Gito.  I have 128 volts at the line and it is not sagging much at all.  I normaly run the rig on a 22 amp variac set at 115 volts  At 115, I get exactly 6.3 volts filiment.

C

[ke7trp]

Really getting Frusterated here.  Today, I cleaned the terminals, wrapped on a new 1000 UF 16 volt cap.  Put a new 1 amp diode. Band towards the cap and DC line.  Still chatters. Its better. But not fixed.  About 30 % of the time, When you key it, The AC relay chatters and buzzes until latching.

If I use the Front panel Switch marked Transmit, The realy never chatters. I can key it over and over.  Key the D104 and it chatters.  I am at a complete loss now.

Clark

[WQ9E]

Clark,

Try the experiment you proposed earlier with the outboard DC supply for the relay.

With the new higher value capacitor, your loaded voltage across the coil will be even higher than it was so check that also.  Those little DC coils won't stand a lot of over voltage without burning out.

Rodger WQ9E

[Gito]

Hi

Clark when You used the transmit Key,than You by pass Relay 3, (Switch 2 and 3A,3B).
Relay  3 is not energize.So there' no Chatter.

Yes the AC line may looks Constant ,but imagine if there's a 1 ohm resistance in this line,and the transmitter needs  400 /500 watt power input when operating,than it needs about 4 A current,that means there's about 4 A flowing in Your line voltage and a drop of 4 Volt.and I believed when You used the PTT switch the inrush current is much higher say 10 A for a fraction of a second ,than there's 10V drop in the line for a fraction of a second.

This also happen  when We switch an electric Drill,or switching on an "old" TV set,Our light bulb will flicker at that time,meaning there's a dropping voltage in our AC line,since the power needed at switching On time is Higher than in running condition.

And I believed there are resistance in AC line in our house,maybe small,maybe a little high ,because the connection of the AC plug ,the length of the cables .

My point is when We put a temporary high load(PTT ing Your Transmitter),the AC voltage at Our transmitter drops for a part of a second because there's an "R" in Our AC line

So at that time the AC relays will chatter.And when the Load is normal again the AC voltage is normal again and all the AC relay  is operating at the right voltage.
Than the chattering is gone.
My conclusion is based at

1.If our friends wrote ,the chatter is caused by  ripple ,than Relay 2 will always chattering  when the PTT switch is on.But it ceased after a while,so I believed that's not the case.

2.And there's nothing wrong with the AC relay.it works normally,after chattering for a while.

So why AC Relays chatter? because a"low" voltage that supply it


Gito

[ke7trp]

The AC relay does click when the Transmit switch is thrown. No chatter.  This realy ONLy chatters when I use the Push to talk DC relay.  Makes no sense to me. 

I have measured Voltage. Very minimal Drop. I cant see more then a volt but I am using a Digital meter.

C

[Jim, W5JO]

Clark, you really don't need over 5-600 uf.  A lot more than that will be a problem like as Rodger has pointed out.  Put a 470 uf in parallel with the 47 you have there.  Provided you have wired everything correctly and do not have a bad wire somewhere then it should work.  When you use the transmit switch you are bypassing the relay so there won't be any chatter because it is not being used.  Try using the switch then key the PTT and see if you hear the chatter.  If you do hear chatter when you key the mic with the transmit switch in the on position, then the keying relay is bad, or you have significant resistance in the keying line somewhere.  The problem may very well be in the microphone.

Sorry about the continuous sentences but this site won't let me put in very many lines before it acts up.

[Gito]

Hi

Clark ,yes the AC relay Clicks ,but which one ,there are 3 AC relay RL1,RL3 and RL4.
If I'm not wrong looking at the schematic,the relay that's clicking is R L! and RL4.
RL3 is not on ,because it's only on when PTT is on(RL2 is Of).
The point contact's is bypassed by Switch 2 (not RL2),Switch3a ,3b (not RL3)'
RL1 and RL4 is feed directly from the AC input via closing SW1,SW2,SW3a,SW3b.

The chattering is present when RL3 is energize via the point contact on RL2,This point  contact  is a switch  for 110 VAC supply  feeding RL3.
As I wrote before in PTT of condition ,to test RL3 ,(not in transmit condition /but must used the PTT switch to transmit )jumper this point contact so RL 3 is energize,without putting RL2 in "action"
Make this jumper as an AC switch,meaning You can switch on and of with this jumper,and see what happens?


Gito

[K0ARA]

Dirty contacts on the D-104 relay?

[ke7trp]

D104 is fine. I put a test clip on the back of the mic socket and then shorted it to the chasiss. Still chatters. 

I dont have a 500 UF cap.  I will have to order one.

I used a 500 on the king. It works fine.

If I Throw the transmit switch there is no chatter.  If I then Key the Mic up I get a nice smooth CLICK of the DC relay as normal. This relay is closing nicely.  There is no arc and its nice and clean. 

The AC relay with the multi contacts is the one that chatters. I can see the arc inside it. Its a clear cover Potter Brumfield. It Arcs of a moment then latches.  If I key this with the transmit switch, It simply Closes with NO arc or chatter.

I measured the resistance of the WIRE that runs from this relay up.. It would not make my Fluke beep.  I looked over at the meter and its reading .900.  I need 1.0 to get the  beep.  Maybe I need to Run a new wire here?  I will try to jump it.

c

[WQ9E]

Clark,

I assume that the .9 on your meter is in ohms which is fine, you don't need a different wire jumper.

With your description of the problem, either relay RL-3 is creating contact bounce due to a coil issue or it has a contact or other mechanical issue.  Since everything works normally when you throw SW-3 that pretty much excludes problems with the other relays since SW-3 is in parallel with the RL-3 contacts and substitutes for it when using manual transmit control.  Since it allows the transmitter to operate normally, then you know the problem has to be in the RL-3 circuit.

To avoid running in circles either connect a known good 6 volt DC supply to the coil of RL-3 and use this to key the relay or you can use a battery holder with 4 AA cells or similar to provide the source.  If you still have problems using this voltage source then you have a problem with the relay (RL-3) itself.  It could be bad contacts or mechanical wear.  But by using a known good source of DC to key the relay coil you can exclude the rectifier/filter capacitor from the equation.  If it works fine with a good 6 volt DC source then you need to add series resistance to make up for the lowered forward resistance of a silicon versus selenium rectifier.

[WD5JKO]

I measured the resistance of the WIRE that runs from this relay up.. It would not make my Fluke beep.  I looked over at the meter and its reading .900.  I need 1.0 to get the  beep.  Maybe I need to Run a new wire here?  I will try to jump it.

   Clark,

    I don't know what kind of Fluke mater you have, but some only beep when in "continuity mode" when the resistance between the probes is less than 100 ohms. I'm not sure, but maybe the .900 you measured was volts, like what you see on the diode scale. Then again maybe Roger is right and the 0.900 means 0.9 ohms, and this is nothing to worry about.

I just cant believe I forgot about that mod on the king.  I can remember anything you ever want to know about one subject, But simple things I have done before, I cant recall. 

Join the crowd Clark. My friends marvel at my memory, yet I am quickly realizing that pieces of my memory disappear with no recall. If I go through the attic looking through boxes of radio parts, each part had a story of why I wanted it, and how I obtained it. Then I look at the part 20 years later, and wow, many of the stories are lost ... NO RECALL! Pretty scary 


Jim
WD5JKO

[ke7trp]

Hmm.. On my meter it is one spot for Resistance. Beep is an optional button.  It autoscales.  I just noticed that its not enough to make it beep. 

Tomorrow, I will jumper the wire just for fun.  If it fixes it, Hey, I got wire..

If not, I am going to Set the bench supply to 6.3 volts DC.  Hook it up with jumpers.  Then fire the rig up and send the 6.3 to the DC relay. If it keys solid.  I have more work to do. 

I think that is the next test that makes sense.  Thanks for ALL the help guys.  A simple problem has turned into a long repair.  The good news is the king is working great. 

C