SR failed in PTT. Globe champion. questions

[ke7trp]

The Green SR rectifier died on the champ. Lucky for me, it was on the bench being worked on when this happend.  It was a Two contact unit.  I ripped it out and put a 1000V  1amp diode in its place.  Fast recovery.. Thats all I had on hand.

The Champ now keys again but every once in a while, The Relays Chatter before latching on now..   

1. Should I try a different type of diode?

2.  Should I change the single electrolytics value?  Its a new low voltage unit.

Attached is the schematic.   Its SR4  above the 5U4 on the Schematic.  The Cap, C65 is a new 47UF 25 volt unit. The old one was a 50MF 25 volt paper.  Resistor is a 47k ohms half watt.  Its on the 6.3 Fil line. 

Thanks in advance.

Clark

[Gito]

Hi


Looking at Globe 300 schematic,maybe it's not Relay 2 that is chattering ,because it's a DC relay(use Dc voltage/current to make it work/DC coil),and a DC relays has only two states on or of.(in this case using half wave rectified 6.3 V ac to activate  this relay))

But this relay (RL2)  activated/act as a AC switch  for  Relay3 (bigger relay)that is AC activated relay in this case 110VAC(AC coil) .I think maybe this Relay (RL3)that's chattering, It sometimes happen.when using AC relays.
Sometimes because the AC voltage is lower than 110 v,or some defect/some dirt in this relay.


Gito

[KM1H]

A DC relay will do that if there is sufficient ripple on the voltage. Also remember that a DC relay is an AC relay with a twist.

Ive also had several 24VDC relays used on the tower for antenna stack switching fail yet now work just fine on AC. Must have been the RF affecting the magnetism.

Carl
KM1H

[WQ9E]

Clark,

If the old rectifier was a selenium unit then you have a little less forward voltage drop with the silicon replacement.  You may have enough voltage that the relay is closing too forcefully and the contacts are bouncing.  Check you voltage across the relay coil and add a series resistor as necessary to put it into spec.  If the voltage level is too high you could also burn out the relay coil during an old buzzard style transmission.

Rodger WQ9E

[Gito]

Hi

Carl wrote that if there's enough ripple in the DC power supply than the Relay will chatter it,s true.
but I think not in this case,because Clark is restoring His globe like the "original" circuit ,and I  think the Globe is design so that the Relay won't Chatter  with this circuit.

And if it is caused by the ripple in the DC power supply than the chattering of this relay never stops as long as it's on ,unlles the Relay is defect or not the original Relay.
Speaking of DC relay used in AC circuit,yes of course it can be done if the AC voltage has the right Voltage,I think the AC voltage needed has a "critical" point.that is, if We used it with a lower voltage than needed it will chatter.To much voltage it may burn the Relay's coil.
So my conclusion AC relay is more prone to Chattering if the voltage is lower than it needs.
And I think if A DC relay has not enough DC voltage it won.t work.


Gito

[ke7trp]

Thanks for the replies.  I dont know which relay is chattering.  I did not get that far.. All I know is that I used it in PTT for 2 years. No issue.   Then the SR just up and failed.  I put a 1 amp diode across and now it chatters some times.

I think it might be the bounce.. It sure CLACKS loud now.  Before it was a nice click.   When I get back from my Holliday Trip, I will check the voltage across the relay.  If its to high, No problem.  I have boxes of resistors.

So in short...  this was a ONE part swap.. SR to diode.  Nothing else changed. 

Thanks for taking the time to help me.. I will let you all know what I find.

Clark

[ke7trp]

 I hope everyone had a Great holliday.  Me and Toby the dog made a Car Trip to Nevada so I could be with my family.  Had a great time talking with my 92 year old Grandpa about radio.

I am home now and got a chance to take some Volt meter readings of the champ.

6.43 volts AC on the Filiment supply.
8.30 volts DC after the diode, cap and resistor to the relay.
7.49 volts DC under load keyed.  Still Chattering once every other key down.

So it looks like Rodger might be correct on this one!   Can you suggest a course of action?

The cap is 47 UF, The Resistor to ground is 47K ohms.   The diode is 1kv at 1 amp Fast recovery.

I dont see much if any ripple.  When switched to AC on the relay line, my Digital Fluke rolls around the last few digits. So the ripple is 1MV or less.  Its a steady and solid 8.30 on the DC side.

THanks alot guys!  I hope to get this going today!

Sorry for the ignorance. I am still learning.
Clark

[WQ9E]

Clark,

As a quick test whether the extra voltage is the culprit I would use a couple of additional rectifier diodes in series to further drop the voltage.  Silicon rectifiers drop about .7 volts per unit regardless of current draw so a pair would reduce this by 1.4 volts.   Add the new diodes in series with the one you replaced observing the same orientation.

 

Rodger WQ9E

[ke7trp]

Tried that. The FR107 diodes I have are labeled LOW VOLTAGE DROP on the package. I tested this and found .12 volts per diode. I would need a hell of alot of them.

I just sat down and dead bugged a FULL wave rectifier with 4 diodes and a cap.  I clip leaded it off the fill line and tested it. This got me zero ripple and 7.6 volts DC.  So the ARRL book seems correct about half wave being +.45 and Full wave being .9.  Still.. Its to high.  I put a 10 meg resistor on the input side. That further lowered it. But its still 7.3 volts or so.  I guess all that work got me a volt.  I just dont have a 50Meg Resistor and that seems to be about what I need to Drop it down. 

What alot of work for a failed SR.   I guess I am learning though! The relays are labeled 6.0 volts DC.   

Any other ideas?

C

[WQ9E]

Clark,

What is the DC resistance of the relay coil?  You could measure this with an ohm meter; if you do this remove the connection to one side of the coil just to make sure you are not measuring anything in parallel with the coil. 

Otherwise, remove whatever additional resistors you added and measure the current flow through the relay coil.  Either of these will provide the information you need to choose the correct series dropping resistor.

The needed resistor is only going to be a few ohms and if this is around an 18 ohm coil (my guess) then the needed series resistance is going to be 4 to 5 ohms.

Rodger WQ9E

[ke7trp]

I will try that.. I measured it at 1.8 ohms but the coil is hooked up. I will have to unsolder it. 

I have tried a Full wave.. I made one and clip leaded it in. Still chatters.

I removed the D104.  Clip leaded it straight. Still chatters.

Replaced the chattering relay with a new one. Still chatters.

Put in old style top hat diode with more volt Drop. Still chatters.

Tried two diodes. Still chatters.

Changed cap to 100 UF. Now 0 Ripple.   Still chatters.

Really odd.  I guess I am missing something here.  I will do Ohms law with the Current of the Relay coil and try a resistor.  Thanks for the help man

Clark

[ke7trp]

Voltage Drop resistor did not fix it. Still chatters with lower volts. 

Cleaned and adjusted the intermediat PTT relay.  This provides 120 volts to the plate relay.  No dice. Still chatters.  I am out of ideas on this one.

C

[WQ9E]

Clark,

Can you visually verify which relay is chattering?  This will expedite narrowing down the problem. 

I had managed to forget what a poor job WRL did on some of their schematics and parts lists; it doesn't make the job of troubleshooting as pleasant as it could be.

Larger relays with the spring loaded contacts will often chatter and bounce if they cannot move freely at the pivot point so check that they are clean and operating freely.  Also check/clean the contacts.

The may be one of the truly rare coincidences where the replaced part and the immediate new symptom are not related but it will be surprising.  So check the contacts on RL-3 to see if they are part of the problem.

Good luck!
Rodger WQ9E

[ke7trp]

The realy is the one handling the plate.  I replaced it last year with a PB plastic covered unit.  Plug in.  Worked great until now. Lucky for me, I soldered and mounted the new socket. I replaced it with a brand new PB unit. Same chatter.

I have since cleaned and adjusted the 6 volt to 120 volt relay.  They ran it this way so you would have low voltage DC on the mic.  That relay is 100%.  We are all at a loss as to why this chatters with PTT but it does NOT if you throw the transmit switch.  I measured AC and DC on the relay.  Its a clearn 7.4 volts at the relay.  Solid 122 volts on the plate relay.

I guess I will put a valiant inline until I figure this out.  It really has all of us Stumped.

Clark

[WQ9E]

Clark,

The only difference between throwing the switch and using PTT is that relay OR the microphone PTT switch.  Try another microphone to rule that out and if isn't at fault then the root cause of the chatter is the 6 volt relay. 

Are you measuring 7.4 at the relay with PTT closed or is this open circuit?  If it is 7.4 with the PTT engaged then that is 25% over and too much.  If the voltage is close to 6 volts closed then the problem will be found in the contact controlling the plate relay.

Rodger WQ9E

[ke7trp]

I bypassed the mic jack.  I put a clip lead on the wire on the back of the plug, then Grounded it. This rules out the mic. 

That is 7.4 volts under load.  Do you really think that is to much for a 6 volt relay? 

I put a 10 ohm inline on the DC side.  That did nothing. 

C

[WQ9E]

Clark,

Although 1.4 volts high doesn't sound like much that is about 25% higher than rated and it may be aggravating a spring that has weakened with age in the relay-thus it doesn't take as much force to close the relay as it did 50 years ago.

Since you have a 10 ohm resistor in series, carefully measure the voltage drop across this resistor and that will tell you how much current the relay coil draws.  Then you can calculate the needed resistor to drop the loaded voltage down to desired.  That is obviously a pretty sensitive relay in the Champ with a fairly high resistance coil.

Rodger WQ9E

[WD5JKO]

We are all at a loss as to why this chatters with PTT but it does NOT if you throw the transmit switch.

Maybe the relay is fine, but the problem is with the PTT switch??

Jim
WD5JKO

[ke7trp]

I dont know what you mean by PTT switch.    There is a Transmit switch on the panel. This works fine. No relay chatter. 

The PTT switch is in the D104.  I bypassed that and clip leaded the line to ground.  Got the chatter.

C

[Jim, W5JO]

Clark, did you have the chatter before the Selenium Rectifier opened?

[ke7trp]

No. Ran it two years.. D104 on lap.  Keyin away..   Took it down to stabilize the VFO.   PTT stopped working in one shot..  Replaced SR with Diode.  Now chatter.

C

[ke7trp]

Bear with me here..LOL

According to the text books :"For example, if you half wave rectified 120v AC RMS, you would get 85vDC, and if you full wave rectified it you would get 170vDC"

Then why do I get:

6.43 input AC
Output 8.3 volts DC

With a HALF wave rectifier?

According to the text books.. my DC output should be LESS then the AC input.. THis must be my Champs problem.

C

[ke7trp]

Link to above text

http://wiki.4hv.org/index.php/Diode


Sorry..  I am trying to learn and you guys are really helping  me.

C

[Gito]

HI

Clark have You tried to switch in/test the RL2 alone ,independent than the others relay?Does it chatter ,I don't think so
Looking at the schematic RL2 is the one which "Supply" all the AC relay in this circuit.

Can it be the Switch 1(ON/OFF switch) is "damaged" so there's a "little" resistance or the component around it(RFC7,8).
Logically AC relays chatter when the AC voltage is under the needed voltage.

When the PTT switch  is on, RL 2 is on activating all the AC relays that activated all  the B+ of this transmitter ,meaning there's a 300 maybe 400 watt is loaded to the AC line via Switch 1 ,can it be the ac voltage drops after SW 1.
That makes the AC relays chatter,because the AC input is not high enough

Another option  the AC relay is RL1,RL3 and RL4 ,it can be one of this relay that's chattering.


Gito

[Jim, W5JO]

SR4 is tied to the 6.3 Volt winding on the transformer.  Are you sure of your work when you put the diode in place of the Selenium?  Go back and double check the polarity of the diode and cap.  You are correct, if you put in 6.3 volts you should get about 85% of that out.  The only relay that winding works is RL 3 so there must be a misplaced wire or something.

The only other possibility that crosses my mind is a bad relay (RL 3).  If the coil is fowled up or the cap is low in value, then you could have the same problem.  Do you have a cap checker?  Now are you hearing a chatter than continues or is it contact bounce?  When you hit PTT the relay keeps chattering or does it bounce a couple of times and locks in?