ART-13 filament issue

[KC2TAU]

I'm slowly working towards getting my ART-13 on the air. Everything is working fine except for the filament for the two 1625 multipliers. I'm not sure what the issue might be. I measured pin 1 and 7 on V102 which should be first in line for filament voltage. I need confirmation on which pin is which. On V102, if one is looking at the socket from the control side of the transmitter, I measured 22vdc on the right filament pin (the two larger pins) and 0vdc on the left pin. On V103 I'm measuring 0vdc on both pins. Both 1625's test just fine and have good filaments. I'm a bit confused as to what the problem might be. The battery voltage meter is indicating voltage and every other tube filament is operating properly. Any ideas?

[KM1H]

It sounds like you have a ground between the 2 tubes.

Carl

[KC4VWU]

Hi Mike,
             Make sure the 813's are seated good into their sockets. If I remember correctly, I had the same issue about 2 years ago. It will look like it's seated correctly, but since the socket and hole alignment is so tight, the locating pin on the side of the tube will hit the chassis and prevent it from being inserted all the way. Lotsa jiggling, twiddling, and cursing at this point, but I managed to get said tube seated after removing the rear sheet metal to see what was going on. If you do that, you can also get to the relays pretty easy and clean them while you're there.
             
73, Phil

[KC4VWU]

Sorry, too early in the morning (afternoon)! Now I see he said the 1625's

Been there on that one too. I believe about the same issue; dirty socket contacts or bad solder joint. Have you switched the 1625's around and checked ?

---Phil

[KC2TAU]

The 813 filament lights up fine. I'm getting continuity between opposite pins on each tube (i.e pin 1 of one tube is continuous with pin 7 of the other). That seems okay. A ground may be an issue. Has anyone poked around that area? Is the wire connecting the two filaments on each tube in a particularly tight place?

[KE6DF]

The 1625s are 12..6 volt tubes and the ART-13 runs on 28VDC.

So those two 1625s are in series -- hence you will get zero volts on two pins where the 1625s filaments are connected together -- as well as on the pin that's grounded.

Also, the ART-13 has a complicated system of series and parallel tubes and series resistors to get all the 6.3, 10, 12.6 etc. filaments working off that 28VDC supply.

Most likely cause of your problem is a bad connection (or broken wire) at one of the filament pins on one of the 1625 sockets.

Note that if one 1625 doesn't light, the other won't either because of the series connection.

[KE6DF]

The 813 filament lights up fine. I'm getting continuity between opposite pins on each tube (i.e pin 1 of one tube is continuous with pin 7 of the other). That seems okay. A ground may be an issue. Has anyone poked around that area? Is the wire connecting the two filaments on each tube in a particularly tight place?

IIRC the 813 is in series with the 811 filaments (2 x 6.3v + 10V) with a dropping resistor and a parallel resistor to make up for the different currents and voltages.

In fact, you can seen these wire wound resistors next to the 813.

That's a separate circuit from the 1625s filaments.

[KC4VWU]

Yes, I believe the rear tube is the second in the string (V103), and one contact should show ground to chassis. the other should show continuity to one contact on the other (V102 - front) socket; the other contact - full fil. string voltage. Make sure the contacts in the socket are tight. Go in and carefully re-tension the contact fingers for the fil. pins on both sockets.

---Phil 

[KC2TAU]

Very good. I'll take a look at things when I return in a few days from vacation. Are there any tricks in accessing the tube sockets for the 1625's from the bottom of the transmitter?

[KE6DF]

Very good. I'll take a look at things when I return in a few days from vacation. Are there any tricks in accessing the tube sockets for the 1625's from the bottom of the transmitter?

I'd try wiggling the tubes first and see if you can make the filament light.

If so, you would know you were on the right track.

Then, try cleaning the tube pins first as that's easy.

Then, perhaps try a little contack cleaner thru the holes on the sockets.

If all that doesn't work, then you have to take it apart and that is a PITA.

[KC4VWU]

It's a PITA! Do not remove any of the autotune stuff for access because I understand that it is also a pain to deal with; as in removing the osc. module to gain access.

Let me pull mine out and take another look. It's been stowed away for well over a year since my move and I haven't had time to play with it any. As a matter of fact, I have 3; the working unit being the worst of the bunch, purchased as a ratty parts rig.

You get that rig rolling, Mike, and I guarantee you'll love it! Not a powerhouse by any means, but coolness factor is at least a 10.

---Phil 

[Bill, KD0HG]

As has been mentioned, the 12 volt heaters of the two 1625s are in series.
Pin 7 of V102 should have 24 volts on it. Pin 1 of V102 connects to pin 7 of V103, and both should 12 volts present. Pin 1 of V103 is grounded.

So why is there 24 volts on pin 7 of V102 and 0 volts on pin 1? A short to ground on pin 1? (or a short to ground at pin 7 of V103?) That would put 24 volts on V102 and its heater would be way brighter than it should be. You don't really need to read voltages from underneath to determine what the problem is. Look at how bright V102 lights up. If it's way bright, then there's probably a short as I mentioned which you can check with an ohmmeter at pin 1 of V102. You can also wrap a fine wire around the pins of each tube to read voltages from the topside.

Bill

[KC2TAU]

Bill, neither 1625 lights up. Both tubes test good. What bothers me is that both 1625's slide into the socket too easily. I tried wiggling both while DC was applied but nothing happened. You're right, I have 24 volts at pin 7 and the battery voltage meter is operational so I should at least see V102 light up. I'll perform some ohm readings as well. I'm hoping it's just that the sockets are too loose to obtain firm contact of the filament pins.

Phil, can the fingers for the pins be adjusted from the top side? If I remember correctly I was finding that pin 1 of V103 was grounded to chassis so that's good. I'm not going to remove the auto tune, don't worry! The auto tune works great and so I want to leave that alone! I love the rig already. I've put a fair bit of time revising the power supplies that were supplied with it and so this is just part of the adventure.

[KC4VWU]

Hi Mike,
            I managed to get to them from the top, but it's not easy. You'll probably need an assortment of small picks bent in different angles. Harbor Freight and a lot of the auto parts stores sells them. It would probably be best to remove the audio amp, MCW unit, and the sheet metal facia from that end for access as well. Just go easy on them.
             The heater pins may be so loose that one may not be making connection at all. Bill just gave a good idea; wrap some small gauge wire around the pins near the base to make the test measurements. That way, you'll know the pin to contact fit is good underneath the test connection. 

73, Phil

[KC2TAU]

Phil,

Any tricks you used in getting a grasp on them? They look to be down a ways and set into the pin. How did you manage to pull them out? I have a variety of small tools at hand. I'm curious as to how does removing the audio amp, MCW unit and sheet metal fascia help?

[KC4VWU]

Well, for me it made it a little easier to get down to the sockets and gave more flexibility in maneuvering the tools around at different angles. Harbor Freight has a small pick set (4 pcs.) that works well. Just don't go overboard; all it needs is a little tweak to re-tension the contacts.

---Phil

[KC2TAU]

Oh! Those pictures help make things much more clear. I'll definitely need a proper pick set then now that I see how the pins are arranged. Thank you for the pictures!

[KC4VWU]

They will slightly rotate side to side also, since there is a single rivet holding the contact to the base. Some may have two. Eventually though, you know what will have to be done: this is really just a bandaid repair. Get it rolling and maybe you can catch the OMRN in the morning on 3885 kc.

73, Phil   

[N8ETQ]

   I can't recall the details but is that filler panel installed.
I thought there was an "R" on that to complete the fil
string when not using the LF VFO.

Just a thought.

/Dan

[KC2TAU]

Hello Dan,

This one has the LFO installed and its 1625 is getting filament.

Phil,

Your tips are invaluable. Thank you.

[KC2TAU]

Well, it turns out the tube socket issue was a case of operator error. I went searching to see if I could tighten the sockets and so I started to remove the bottom back panel in order to see what access was like it. While taking out one of the screws I heard the "plink" of a nut falling off behind the panel. Great, so now I absolutely had to take the panel off. I ended up turning the transmitter over onto its back and removing the bottom panel so that I could access a small steel tab that was connected to one of the relays. Space was extremely tight to reinstall the nut but what I did was use a pair of needle nose pliers in my right hand to hold the nut. I then had a small eyeglass screwdriver in my left hand that I used to gently push the screw up against the tab. I used such a small screwdriver so as not to put so much pressure of the screw that it would push the tab away and prevent the screw from threading through the tab. I then put the needle nose pliers down and behind the tab and searched around for where the leading end of the screw was. I knew I was about there when I saw the screw head just push out a bit. I started tightening with the screwdriver and was very lucky to get it on the first try.

With that sorted I looked inside to see if I could locate the tube sockets for the 1625's. They are quite hidden under the capacitors for the multiplier section. Fortunately the pins I needed to tighten were actually in view. After trying a bit to tighten them with the pick set I wanted to see if this had made any difference. So, balancing the transmitter on my knee to keep it at the correct angle and inserting the 1625 into the socket with my left hand I noticed something funny. When I thought the tube was in its socket I realized that the pins weren't even seated into the socket yet! Pushing a bit harder seated the tube firmly into the socket! I hadn't been pushing hard enough! After I reassembled everything and put it back together I was pleased to see filament light from the 1625's.

Everything seems to be working quite well except for the fact that the output power is low. With about 1300v on the plates I seem to be getting about 90W at best. Battery voltage is within specification, grid drive is good with the needle moving to the middle of the shaded white area and the antenna is resonant. I don't seem to be getting enough plate current. At the moment I'm seeing a little over 60ma of plate current. I can't seem to get it to go any higher. I would expect that through proper loading I would be able to increase the plate current to where it needs to be but I can increase only up to 60ma. When I tune the final off resonance the plate current doesn't spike much more than 20ma. Also, is it normal to not find a plate current dip when the loading is set lightly? When coarse loading control C is set to 1 or 2 and antenna tuning control D is set at 0 I am unable to find a dip. When control C is set to 4 or 5 I start to see a dip.

I'm using the transmitter with an external air variable loading cap provided by the previous owner. It looks to be three sections at roughly 365pf though I'll see if I can verify that this evening. This should give me enough capacitance on 75m. I'm finding that maximum output occurs with it 1/2 meshed. I've tried taking my tuner (Heathkit SA-2040) out of line with the transmitter but that does not help matters. I know that the ART-13 should be capable of at least 125W, if not more.

The modulation looks good on the scope. I need to make a 1/4" to .206 adapter so that I can run my mixer controller SM-58 through it so that I can shape the audio at least to some degree. The D-104 I have with it sounds, well, not how I'd care for it to sound. The modulation looks clean, though, and that is what matters.

[N8ETQ]

  Damn !

     I have found the ART-13 power output is more sensitive to changes
with the LV rather than HV. but if it looks good on the scope 90 to
125 w is insignifegant.  More drive plus higher screen "E" on the 813
will make it perk up a bit.

Glad you got er' done.

/Dan

With that sorted I looked inside to see if I could locate the tube sockets for the 1625's. They are quite hidden under the capacitors for the multiplier section. Fortunately the pins I needed to tighten were actually in view. After trying a bit to tighten them with the pick set I wanted to see if this had made any difference. So, balancing the transmitter on my knee to keep it at the correct angle and inserting the 1625 into the socket with my left hand I noticed something funny. When I thought the tube was in its socket I realized that the pins weren't even seated into the socket yet! Pushing a bit harder seated the tube firmly into the socket! I hadn't been pushing hard enough! After I reassembled everything and put it back together I was pleased to see filament light from the 1625's.

Everything seems to be working quite well except for the fact that the output power is low. With about 1300v on the plates I seem to be getting about 90W at best. Battery voltage is within specification, grid drive is good control C is set to 4 or 5 I start to see a dip.

I'm using the transmitter with an external air variable loading cap provided by the previous owner. It looks to be three sections at roughly 365pf though I'll see if I can verify that this evening. This should give me enough capacitance on 75m. I'm finding that maximum output occurs with it 1/2 meshed. I've tried taking my tuner (Heathkit SA-2040) out of line with the transmitter but that does not help matters. I know that the ART-13 should be capable of at least 125W, if not more.

.

[KC2TAU]

It's significant to me as it's quite a bit lower than what others have reported seeing. In addition the previous owner sent me a photo of the transmitter loaded to 160W on 75M. I'm taking that with a few grains of salt but even so...

I'm going to run it into a dummy load and see if the problem is with the antenna. I'll verify the LV as well.

[N8ETQ]

 Yeah, they can keep up with a Valiant, I have 2 of em here. One makes
about 75 W and the other about 90.  You can try 500pf exra "C" on 75.
Hook it between that "Load Coil" terminal and the bottom plate. It helps
a bit.

GL

/Dan

[WU2D]

90W is normal at 1300V. How is your grid current? In the paint?