Gonset #1 maul report

[N3DRB The Derb]

got it into place and fired it up. Operation good, sharp dip and good loading and we got up to 350 ma with full drive until we went for the gusto and flipped the tune operate switch to operate while we was unkeyed. Upon key down we got lots of zots. After that anytime the amp
was turned on we got nothing but zots. At one point during the trip home, Glo had to brake suddenly and the amp went sliding off the rubber mat. about 3 ft into the front part of the truck bed. I'm thinking the 811's took a hit and we might have a fil to grid short somewhere. As soon as you turn it on now it just zots.

I'm going to dump the 572B's in it in the morning and see if it works without any other changes. Too late and too ragged out to mess with HV now. The keying circuit seemed to work very smooth before what ever let go went.

We'll attack it in the morning.

[The Slab Bacon]

Take a careful look and see if the impact jolt might have shifted the tank coilz or bandswitch straps around. Rememba that all of that stuff just kinda hangs in the breeze with no real support. Especially look where that one strap comes kinda close to the bandswitch through bolt.

Howeva, if it zotted once and now continues to zot, look for a possible carbon track, or
A SMALL METAL DEPOSIT ON SOMETHING closing up a working gap somewhat. I wus a little apprehensive of sitting that thing in the back of ur pickemup. Oh well, sh!t happenz.
 


                                                                       the Slab Bacon

[N3DRB The Derb]

One of the 811 plate caps is BLUE. The other ones are normal silver looking. we may have a winna here.

lemme take a pix.

notice difference in solder color -  plate cap on tube on left normal looking, tube on right = blue.  Confirm or deny?

I'm going to go ahead and move that strap out a bit while I'm in there.

Watcha think Slab? bad solder on that plate cap?

[N3DRB The Derb]

Slab - we took a another look at the band switch. the 2 front contacts going to the fixed caps are fried to a crisp, and these were ones I just replaced because they have screws.  Don't think it had anything to do with the ride home.

the amp worked just fine until you give it the full HV, then those contacts just sizzle. There was no evidence of instability on tune mode it just sat there and made power @ 350 ma until I gave it the full HV.  The tank circuit in these things are gay.

I'm thinking more and more that the tank assy just cant stand the juice. Buying another one and single banding them on 160, 75, an 40 is starting to look better all the time.

I'm going to give it one last try here, and if I burn up any more switch contacts I'm just going to single band the amps 160, 75, and 40 using 3 of those tapped inductors. Screw band switching.

[Opcom]

One of the 811 plate caps is BLUE. The other ones are normal silver looking. we may have a winna here.

lemme take a pix.

notice difference in solder color -  plate cap on tube on left normal looking, tube on right = blue.  Confirm or deny?

I'm going to go ahead and move that strap out a bit while I'm in there.

Watcha think Slab? bad solder on that plate cap?

Dear sir,
That blue color is something I find on ye olde molde military stuff. I'd say it's a good one, or was at one time.

[N3DRB The Derb]

normally that blue color means the plate wire is arcing inside the plate cap and needs resoldered IME.

[The Slab Bacon]

Just FWIW the one cap that is blue, I marked it with a blue sharpie when I tested them. IIRC it had a little less emission that the other 3. I used a blue sharpie cause it was laying on the table at the time.

Timmy,
         Like we discussed at the fester, I still dont feel that that wimpy assed band switch is up to the job on AM. For SSB, it is prolly ok, but with the 100% duty cycle of the AM carrier it is definately somewhat puney. A more scroteful bandswitch or monobanding may be the only way out.
 
                                                       The Slab Bacon


Hmmmm............ Just an afterthought, I wonder if the jolt of sliding around in the back of the truck was just enough to lessen the grip of the contact in order to make it loose contact and start to zorch??

                                                       

[N3DRB The Derb]

yeh I think I am heading towards that conclusion as well. The contacts are the type that have the 2 spring fingers with the slot in the middle - and the contacts are always arcing away on the thinnest part of the fingers.

I have some solid contacts off of some other wafers that dont have those tiny little fingers to compress the contacts.They are solid all the way through and the only hole is the rivet hole. I think a retrofit to those solid contacts might help.  I am going to
try when I get home later today. I need to try out that air rivet gun. I assume aluminum rivets of the right size.

if the solid contacts do he trick, then it is a circulating current issue in the tank circuit. That plate tuning cap is half assed for am.

I also have to build a dog grooming gizmo for the wife too today or tomorrow. May not get to it for a day or 2.

[Steve - WB3HUZ]

The bandswitch may be PW. But others have used the Gonset on AM for years w/o a problem. So maybe there's more to it.

yeh I think I am heading towards that conclusion as well. The contacts are the type that have the 2 spring fingers with the slot in the middle - and the contacts are always arcing away on the thinnest part of the fingers.

I have some solid contacts off of some other wafers that dont have those tiny little fingers to compress the contacts.They are solid all the way through and the only hole is the rivet hole. I think a retrofit to those solid contacts might help.  I am going to
try when I get home later today. I need to try out that air rivet gun. I assume aluminum rivets of the right size.

if the solid contacts do he trick, then it is a circulating current issue in the tank circuit. That plate tuning cap is half assed for am.

I also have to build a dog grooming gizmo for the wife too today or tomorrow. May not get to it for a day or 2.

[WA1GFZ]

my warped mind is dreaming of weird things going on with your poor dog. Keep the drive low

[WBear2GCR]

bandswitch?

we don't need no stinkin' bandswitch!

Derb-o, consider a hard wire bypass for the bandswitch for 75m operation??
You have two "mauls" and if the other is for 40m, then ur all set??

Worst case it will take the stupid contacts out of the equation for testing porpoises...

Also consider the Rich Measures' "fuse" technique for the plate line - that ought to be a fast, cheap way to protect the rest of the thing... see his site for the details, it's easy. 

                      _-_-bear

[N3DRB The Derb]

Bear,

The plate tuning cap has 2 fixed 500pf padders that are switched in one at a time as needed because they used a half assed plate tuning cap with not enough stuff for 80 meters. There's a 80A, a 80B, and a 80C, with adding fixed capacity in each case.

The 2 fixed caps only come into play on the B and C positions. The only thing I could do would be to change out the plate tuning cap to one that has more pf and spacing, which would probably be a good idea anyway.

I had a lot of time to think about it today. I have 2 whole amps, and I only care about 160 and 75. Starts to make more sense to just start considering them as homebrew single bander projects.

I am going to try one more time with these solid silver finger contacts and my new wafers, and if they zorch, then we go single band if those dont do the trick.

right now, it's got to be 110 degrees in the shack. I'm not going to do anything in there until it cools off.

[N3DRB The Derb]

since I am going to order 2 of Measures kits for both the amps, I was curious to know how the resistors in the original parasitic suppressors had fared over the 40 + years. I cut the inductor and measured.

#1 - 211 ohms
#2 - 170 ohms
#3 - 214 ohms
#4 - 117 ohms

value was supposed to be 100 ohms each. So even low value carbon rx's go up in value randomly.

[WBear2GCR]

Not sure you need more than an old toaster to do the Measure's trick... just nichrome wire.

Anyhow, the Measure's thing I was talking about is the fuse for the HV.
One can't zorch a switch unless the current goes above a certain level.
So, zorch the fuse first...? 

As far as switching in padder caps?
You don't need to switch in padder caps if you are working into a dummy load.
You can clip lead them in, as you go to find if you need them on the part of 80 that ur testing on - or else test on the part of 80 that doesn't need them??

So, get the thing keying properly into a dummy load with the appropriate padder hard wired in place. Then worry about if you need to switch it in or out in the "real world" on the real antenna.

The shift of the carbon comp resistors may be just due to old age, or else it may be due to heating from parasitics, or both. The actual resistance isn't critical as the purpose of the resistor is to reduce the Q of the supressor coil. Of course if the innards are fried enough then they won't handle any current, and then the Q will go wacky, which is NG.

              _-_-bear

[N3DRB The Derb]

I had always been thought that he higher the value of the old resistor, the more the upward drift over time. Not sure about that now. 2 of those rx had more than doubled in value. Prolly not critical for the usage they were in, but a interesting test.

Measures is just about convenience, he supplies everything you need in one shot enough to do 3 or 4 amps. Well worth the cost methinks which is $16.50 per and 6.50 for each other amp. I could go find a toaster, but I dont wanna be like Sanford and Sons ham radio, know what I mean? I be poor, but not that poor.

[WBear2GCR]

Heck, I scrounged an old toaster just to have random nichrome wire around...

Probably easier to tin the virgin nichrome though... special methods may be needed to get slobber to adhere...

If there is a wholesale appliance shop you can get a whole lotta nichrome wire for that money, even today...

Fwiw, those new flat surface electric stoves appear to use flat corrugated nichrome ribbon... embedded in some sort of ceramic or clay like substance - I saw one at my favorite appliance store dumpster (yes I do look there from time to time), but I failed to grab it, and it was the last time I saw one like that! Flat corrugated nichrome ribbon!

Pure sex in a high power rig! 

Well not withstanding any other comments about him reading W8JI's site is worthwhile.

And yeah the carbon comp resistors go wacky over time.
I was speculating that the ones you have might be internally cooked, so they don't hold any current - which they need to do in the event of a parasitic.

Think about it - they're supposed to hold the Q low, and also eat some heat (that nasty parasitic energy), but if they go *high* once you apply juice, then the Q of the supressor coil goes *up* and perhaps forms a nasty resonant circuit, the opposite of what you want.

I still vote for the Measures HV "fuse" and then hardwire the bandswitch, and other fried/fryable connections and run it into a dummy load and have at it to see what is doing what... that should make it easy enough to trouble shoot the thing for parasitic oscillations.

One nice technique that I have seen once or twice, but don't know a whole lot about is a hunk-0-ferrite standing on a rod (grounded) near the plate of the tube... not sure how it works, but is supposed to somehow suck parasitics to ground... probably someone who actually knows something about RF engineering around here can explain that one - but it might work for your Gonsets...

         _-_-Warshington Bayer Twuo Greek Chariot Races

[Opcom]

Just FWIW the one cap that is blue, I marked it with a blue sharpie when I tested them. IIRC it had a little less emission that the other 3. I used a blue sharpie cause it was laying on the table at the time.

so, faking the military coating!!! I seen clear, yellow, red, and blue-green covering solder connections over the years.

[N3DRB The Derb]

I cover solder connections that i dont think will ever have to be touched again with a cover of GC red insulating varnish. I've done it ever since I worked at the radio store, it made it easy to spot customers who got their hands into radios after we fixed em and then brought them back as non working and wanted free repairs. 

the stuff also makes a damn good removable locktite for tiny nutz n boltz.

[N3DRB The Derb]

Pat, I got some (well, 250 of them) ferrite beads made out of number 43 ferrite which start to suck RF @ 25 Mhz and go up to 250 mhz. think I'll throw a few of them around each side of the new parasitic suppressors. should have zero effect at 3.8 Mhz.

I'm going to sprinkle them liberally around likely trouble spots. I'm going to work a bit on it today, and maybe put some more new lytics in yaesu #1. I took a break for a few days because I was feeling burned out.