ART-13 Dead on Phone

[W7SOE]

My ART-13 has worked FB for over a year, since I finished the PS.

Now I have no output.  There is no indication of grid or plate voltage either in the tune or operate settings.  The transmitter works normally in the CW mode.

The relays sound the same in either mode.  I think the PS is ok since it works in CW mode.

Before I dig into it I thought someone else may have experienced this particular failure.

Rich

[KA0HCP]

sounds like a mode switch problem, since the tubes are getting power and producing output in CW mode, and the T/R relay is working even in Phone.

I would inspect the switch(es) for proper operation, corrosion, burned or loose contacts, or maybe broken wires or solder joints. 

Good luck!

[N8ETQ]

 Hi,

     I would think since you said there was no "Indication of plate voltage",
I assume you ment "Current".  You should still see Modulator resting current
indicated on the plate meter even if the 813 was dead.  There are 2 large
relays mounted to that lower half of the rear panel, I thought one of those
did the AM/CW switching.  I can't remember if you could get at em enough
to clean them from the bottom but 6 or 8 screws vs. about 30 , you may want to give it look see.  The relays I'm refering to are about under the 811's.

See if it does anything in "MCW" first.

GL
/Dan

"Proud owner of "TWO" disfunctional ART-13's !

[KB2WIG]

I feel your pain.

Check to see if the filamints are on in yer audio section... if not, why not?

Plug in a set of cans into the sidetone out jack and yeahalow into the mic...  If ya hear something from the cans, check the audio driver or the mod stages.

If ya hear nothin, check the Speech amp of the Audio Amp unit.

This will give you a few things to do...... of curse, the mic do work, do it?

gud luck,

klc

[KM1H]

You will still get a carrier even with the 811's pulled.

Id start with the relay and switch and be careful when its turned on.

[Opcom]

I got a spare mod xfmr not in use, if it's open or the like.

[W7SOE]

I got a spare mod xfmr not in use, if it's open or the like.

Thank you very much for that offer, so far I have no indication of a bad mod transformer.  And thanks to the rest for the ideas.  I hefted the rig off the shelf and will start digging into it, time permitting.  The mode switch looks good and I hear the bottom side relays clacking when it is operated.  I will take the bottom plates off to inspect next.

BTW, the plate and grid currents are normal both in CW and MCW.

Rich

[KE6DF]

Possibly a loose or dirty connector on the bottom of the speech amp module where it plugs into the main chassis???

Just a thought ...

[W7SOE]

Upon studying the ART-13 schematic it looks like the final B+ runs through one of the modulator transformers secondaries.
That winding, I think, is shorted out in the CW mode.

So if that winding is open I would have no B+ to the final in voice mode.

(You ART-13 experts will correct me if this is wrong)

Egads, let's hope it is a relay or something.    

Rich

[N8ETQ]

Hey Rich,

   It's cool, Relay K103 "Shorts out" the mod xfmr primary in CW
but the plate voltage is still present to the 813.

   K103 is de-energized in "VOICE" and K104 is energized
in "voice". K103 does Switch HV but only to the 811's.

   This is almost to stupid to mention, I began a "Head Scrathin' "
session on one of mine because the "A" ,"E" or the "C" knob was not
"Acurately" aligned with the mark on the Front Panel. DOOH!
I wanna say the "C" knob was the culprit but don't recall.

   If it hasnt been all "Mod'ed up" it looks like K103 is the guy.
The pix look great so I dont think thats the case. I seem to recall
the lid interlock just kept the dynomotor from starting.  That
other mod xfmr secondary is for the 813 screen. should have
LV on it.

"quote"
"BTW, the plate and grid currents are normal both in CW and MCW."
"End"

   Is that to say that the plate current went up to that yellow area
on the meter.?  If so, It's not broke, Just wheezing.



GL again
/Dan

[N8ETQ]

  Sorry, after posting that I read it and found that last line vague.


"quote"
"BTW, the plate and grid currents are normal both in CW and MCW."
"End"

   Is that to say that the plate current went up to that yellow area
on the meter in  "MCW"?  If so, It's not broke, Just wheezing.

/Dan

[W7SOE]

   Is that to say that the plate current went up to that yellow area
on the meter in  "MCW"?  If so, It's not broke, Just wheezing.

/Dan

Not sure I follow that... 

It sure looks like the secondary is shorted in CW and B+ is passed through on voice.

Rich

[N8ETQ]

The secondary is the one connected to plates of the 811's. the other
winding is a "tershiary: (sound it out, I cant spell) winding for the screen
of the 813.

bottom line OM, does the plate current meter read in the yellow area
of the plate current meter labled "MCW" when you hit the  "key" or
test sw. in "MCW" ?

  Shorting the secondary of any XFMR is never a gud idea, an ART-13
mod xfmr is "tough as nails" and unless its been all "hammed" up
and run at 1.5 kv I should think its ok.  The secondary has a Center
Tap where HV is applied. follow the lead to K103 and you will see that
HV is removed from that lead while the other relay takes the PRIMARY
out of the plate lead to the 813.

"   K103 is de-energized in "VOICE" and K104 is energized
in "voice". K103 does Switch HV but only to the 811's."

Be that as it may the key point here is"

 Is that to say that the plate current went up to that yellow area
on the meter in  "MCW"?  If so, It's not broke, Just wheezing.

/Dan

 

[W7SOE]

K104 it is!  After much digging I found an open coil on the K104 relay.  This relay turns on the HV when the mic or test switch is keyed.  The HV is on all the time in CW mode.
I opened up my power supply and could see the HV relay turn on in CW mode but not when the ART-13 was keyed in voice mode.  If I held the test switch over and manually pressed K104 closed the HV relay in the PS closed.  After removing the back covers and one wire from the relay coil I measured no coil resistance and applying 30VDC had no effect.

I find the schematic included in the manual MADDENING!   A prime example of why schematics should be split into sections.

Anyone have an ART-13 K104 relay lying around?   

Rich

[W7SOE]

The secondary is the one connected to plates of the 811's. the other
winding is a "tershiary: (sound it out, I cant spell) winding for the screen
of the 813.

bottom line OM, does the plate current meter read in the yellow area
of the plate current meter labled "MCW" when you hit the  "key" or
test sw. in "MCW" ?

  Shorting the secondary of any XFMR is never a gud idea, an ART-13
mod xfmr is "tough as nails" and unless its been all "hammed" up
and run at 1.5 kv I should think its ok.  The secondary has a Center
Tap where HV is applied. follow the lead to K103 and you will see that
HV is removed from that lead while the other relay takes the PRIMARY
out of the plate lead to the 813.

"   K103 is de-energized in "VOICE" and K104 is energized
in "voice". K103 does Switch HV but only to the 811's."

Be that as it may the key point here is"

 Is that to say that the plate current went up to that yellow area
on the meter in  "MCW"?  If so, It's not broke, Just wheezing.

/Dan

 
Not to beat a dead horse buuut I am not talking about pins 7 and 8 of the mod xfmr (which do go to the 813 screens), I am talking about pins 4 and 5 which are in series with the 813 final plate choke and are shorted by K103 in CW mode.



Rich

[N8ETQ]

Hey Rich,

You are right, I got my "Transformer Terminology Transposed" sorry for the
added confusion.

"Not to beat a dead horse buuut I am not talking about pins 7 and 8 of the mod xfmr (which do go to the 813 screens), I am talking about pins 4 and 5 which are in series with the 813 final plate choke and are shorted by K103 in CW mode.

Rich"

         Anyway, glad it is diagnosed. It's always cool when the logical assumption is confirmed by a dead part!  I supose any DPDT 28V relay
would do. You could just poke the wires through those holes and leave
it hang out the back until a correct replacement is found.


73 GL

/Dan
     

[W7SOE]

Thanks Dan.  That is really a good idea about mounting the relay on the outside until I can find the proper replacement, I didn't think of that.

Rich