The AM Forum

I picked up a Tbolt cheap.  I am going to go through it at some point and if I ever have the room, Use it with my ranger and SX100 for a complete station.  The Tbolt has no power cable.  Any ideas where I can get this twist lock type plug?  If you found one that fit, Would you please tell me the part number so I can order one?

I plan to use it on 240 volt.

Thanks..

Clark

The mate for the chassis connector, if original, is Hubbell 7565 C Connector Body
This ebay listing just ended several days ago but this guy has 3 for sale: http://cgi.ebay.com/Hubbell-7565C-Insulgrip-3Wire-Twist-Lock-Connector-Body-/180532853246

THanks.. I emailed him to see if he has them.

Pete, The manual states neutral wire and two 115 volt lines.  My 220 Volt outlet is ground and two 115 volt hots.  Will this work? Sorry for my igorance about this.

C

Clark,

As was common at the time, much of the vintage gear tied neutral and ground together.  The NEC requires ground and neutral to be bonded together at the panel but kept separate until then.  You can either modify the equipment to lift neutral off ground and have separate neutral and ground (4 wire plug) or ignore the newer NEC.

To use the 3 wire plug, you need to connect neutral to the third contact (I assume you are going to run the Tbolt on 240) and since this line is grounded internally neutral will then be connected to ground.

A LOT of vintage gear is still run as originally wired.

The 60 amp 240 wall socket is 4 wire.  But the adapter box I built to plug in here, Then provide two 240 volt 20 amp plugs (for linear amps) use 3 wire plugs.  This is Ground and two hots.

Should I just hook this up to that 240 volt 20 amp plug and then plug it into the box?

C

usually a a 4 wire socket is for three phase. I wonder why they installed that type of socket? You should be good to go if you have the amplifier wired correctly for 240.

What do they have in there? Two grounds?  If you do have three phase, just use two hots and the ground.

You need a 4-pin arrangement to support hot / hot / neutral / safety ground.

If it were my T-bolt (and I am not mod adverse at the expense of safety), I would mod the power arrangement on the T-bolt for the correct 4-wire connection.  As I recall, the T-bolt does require some 120V even if wired for 240V on the HV transformer.  Therefore it needs hot / hot / neutral to support both 120 and 240V feeds.  The 4th connection, safety ground, goes to the chassis and should never be wired to carry current.

My 2 cents.

73, Bill   N2BC

Ok.  Does the Ground have to be the house ground or can it be my station ground which is an 8ft Copper rod into the earth with a number 6 into the shack?

Its going to be a real pain to rewire all this crap for the Tbolt. The 220 volt 20 amp plugs I have now are all three wire..
Running a new circiut just for this Tbolt is just nuts. If I cant run it three wire or use my station ground, Then I will sell it off and not even bother.  I just thought it would be neat next to the ranger.

 

C

Clark, I would continue just like you were going to with the three prong adapter plug. If you want to add a safety ground, you could run a separate wire and ground it to the outside of the amp somewhere. I would hook the forth wire to the house wiring.

Now if it were at my place, I would just go with the three wires and be done with it.

The wire with #6 hooked directly to the back of the amp might serve you well if your going to use an antenna tuner. Good RF grounds are where it's at. Now some people wouldn't agree with what I just said if they are using a bunch of pro audio gear and are running into ground loop problems but that a story for another time

End of story ;D ;D ;D

Alright already,

The proper care & feeding of a Tbolt can't be that difficult! I'll hazard a guess the back of the Tbolt has the same male end as a Johnson Desk. Leviton still makes the non-NEMA twist-lock female connector. Purchased one not too long ago, along with a standard cloths dryer cord/3wire #10AWG.

Power neutral (white wire) I believe goes to the keyed/sort of L shaped slot on the female side. Your earth ground/8 foot rod (what ever color) connects to the chassis.

73's,
Craig

PS: Just about any good electrical supply business should have it in stock. Take Tbolt with you to test.

ADDED Later: Clothes dryer cord could be RED/BLACK/WHITE maybe RED/BLACK/GREEN

Craig,

The connector isn't a problem and shouldn't be difficult to find.  The only issue is whether you want to "upgrade" the older Johnson gear (Desk KW, T-bolt, Viking 500) to meet current NEC.  The original wiring has neutral connected to the grounded chassis in multiple places (at least in the Desk KW).

So you can either rewire, use the ground lead as the neutral return, or have ground and neutral tied together at the transmitter/amplifier.  My personal opinion is that option 2 or 3 is probably less egregious than many of the wiring mistakes and shortcuts commonly made in home and a lot of commercial construction.  From recent reading it sounds like a burning CFL or lightning exploded corrugated gas line is more likely than problems from using a 50's wiring style vintage rig.

Wait a minute. Are you saying that your NOT using the service neutral that enters the house from the pole, but instead using the house safety ground as the neutral connection in your cords to your equipment??? No this is wrong, dangerous, and you need to correct it. You need two hots and the neutral on the cord from the outlet. The ground to the chassis can be braid, or heavy wire to your station ground.

I got the plugs for my old tbolt and invader 2000 at Graingers. Donno if you have one of those near you or not. My J500 doesn't use a plug as its hard wired to the power supply chassis. Two hots and neutral on the terminal strip and a ground lug on the chassis for station ground.     

Sorry for stiring up a bee's nest here guys.   I just dont have the electrical experience for this and that is why I am asking for help :)

The 240 volt plug on my wall that the electrician installed is 4 prong.  Two hots, a neutral and a ground.

This line powers an SB200, and various other SSB amps that I own. 

This 60 amp plug (Dryer type) has a three wire cord with two hots and a Ground that runs to a dual outlet 220 volt 20 amp style plug for the amps.  This is two hots and a ground.  The neutral is not used and stops at the wall. It does not carry down to the amps.

The only oddity here is the Tbolt as it has two hots and a neutral.  The ratio is 50/50.  4 people saying hook the Tbolts neutral to the ground and go on.  4 saying you cant do that and you need four wires.  I am just confused.

w1atr..  Can you unplug your Tbolt and tell me the NEMA number on that plug so I can go and get one or order one? It seems nobody is willing to simply tell me what they used.  I had a Friend bring his Desk KW cable over and it wont fit. The Desk KW plug is MUCH larger.

Thanks guys

C

I told you in my first post the type of connector that is used with the mate (if original) in the Thunderbolt.

Yes Pete, thats it. I just checked mine and it's this one.

http://www.grainger.com/Grainger/wwg/search.shtml?searchQuery=7565+c&op=search&Ntt=7565+c&N=0&sst=subset

And here's one for less.

http://www.onestopbuy.com/leviton/7565-C-2655.asp

and another,

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260494397837&rvr_id=&crlp=1_263602_263622&UA=WXF%3F&GUID=dac4270e1270a02661f16b91fffa48e9&itemid=260494397837&ff4=263602_263622

So far we're down to 17 bucks. Maybe I'll find a free one if I keep looking haha.

Yes, we have a winner! The connector issue is solved. I don't believe a Home Depot or Lowes will carry them. Another faster option is a local electrical supply business.

As to 3 wire or 4 wire; for years clothes dryers were a three wire appliance. Wonder how may wifes were zapped? Ain't my ball of wax, but my 500 & Desk are wired as a 3 wire boatanchor same as it left the factor, plus a good heavy ground wire from chassis to ground rods outside the shack.

Clark, some of the stuff in the tbolt runs on 120VAC. Most likely fans, low voltage transformers, filament transformers, maybe a relay, etc. The 240VAC might be just for the HV plate voltage, I don't have a skizmatic for the tbolt.

Craig,

Clark,

The fans used in the T-bolt are the same ones used in the Desk KW and Viking 500 and they are prone to shorted motor windings.  They make a lot of smoke when this happens but there shouldn't be any collateral damage.  But I would suggest properly lubricating the bearings before you put it into service to reduce the chance of failure (due to excess heat from dragging bearings).  You may need to remove the fan assembly to get the front bearing.  I use a hypodermic loaded with the same synthetic oil required for the purge blower motor in my central heating system.  Also remove the dust/dirt on the fan assembly.

I would leave it wired as is and connect a safety ground to the chassis.  Only the plate transformer runs off 240 volts; the fans, filament, and screen supply transformers are connected for 120 volts.

Ok. So you cant run the Tbolt on a 3 wire system.  I will just ditch the thing.  I am not going to pay an electrician to run a seperate line from the box for this amp alone.

Thanks for the links on the connectors!  I was looking for the nema number of the modern part so I can just go down and buy one. 

Thanks alot guys!

Clark,

You CAN run the tbolt on a 3 wire system. A separate heavy ground wire from a 8 foot ground rod is connected to the chassis.

Nothing more is needed, simple.

Craig,

I got three emails stating you cant do that and I am going to either burn the house down, Shock and kill myself and or the Tbolt will have 240 across everything and blow up.. LOL!

I am going to try it.  I dont see any reason why this thing cant run on three wires. I ordered that plug.  It should be here next week at which point, I will fire it up

Its my Bday today!  Going to try to get some AM in on 40 this morning.


C

Happy Birthday and don't blow yourself up  ;)

You will be fine with a 3 wire system plus safety ground connected to the chassis.  Notice all of the three wire Johnson gear still around?  It didn't blow up or burn down with the house or it wouldn't be around still.  There is a much greater chance that your laptop battery or CFL will blow up before you have a problem with the Thunderbolt.

I have a Desk KW, Thunderbolt, 6N2 Thunderbolt, and a Viking 500 that are all connected as originally designed (along with an additional ground wire to the chassis). 

Clark,

When you get ready to wire the plug: Using a volt meter, hot to hot should measure around 240VAC. Either hot to neutral should measure around 120VAC.

Look at the skizmatic: It should become clear how the plug, new cord, etc.; will mate up with the male connector on the back of the tbolt. Also check out the color of the screws in the plug, betcha two of them are gold in color, hot connects to these. Only one of the screws will be silver in color, neutral connects here.

Sort of like cutting a piece of wood, measure twice, cut once.

Craig,

Or just simply reconfigure the jumpers under the chassis and run the whole thing on 120. Short sweet and simple!!

I've done that with my T-bolt years ago!!

All rewiring for 120V does is make the HV tranny look  like the other 120V components.  Neutral will still be connected to the chassis - doesn't make it much worse (there will be more current flowing on the neutral however), doesn't make it any better (safer).

You had best hope that the neutral and safety ground are wired properly all the way back to the entrance panel. 

The 'right' fix is still to separate neutral and safety ground.   

If you are not going to do that, make sure your outlets & wiring are proper. 

Also, be darn sure that everything else in your shack - or at least within reach of the t-bolt - is always securely bonded to safety ground.

It is such a bad practice to knowingly connect the chassis to neutral.  With a roomful of boatanchors, worked on by who-knows how many people with who-knows what skill levels.....   bad, bad idea....

73, Bill  N2BC

that is easily enough done while your reconfiguring it. It just involves moving a couple wires around in the power supply. Takes all of 15 minutes to do it. While you have it out of the case gives a good opportunity to give EVERYTHING ELSE a good thourough inspection!

Unless you want a T-bolt just for collector value, it is one of the lowest power to weight amps out there and really not worth putting in all of that work and the cost of a hernia truss for an amp that is only gonna give you 150-200max watts carrier.

R U still alive ??? ??? ???

As a famous AM'er once said.  "Are you on narcotics ?"    ;)

God Bless Mel Gibson ......

Yeah he can walk it right in to the supply house up on his shoulder like one of those giant 80's ghetto blaster radios.  ;D

Actually it's very easy to remove the AC receptacle from the back of the chassis and the wires attached to it. That's what I took when I went to the local electrical supply house. He looked at it, mumbled something to himself, walked to the back, and came back with three matching plugs (at one time I had two HF Thunderbolts and a 6N2 Thunderbolt).

I got the plug off the net.  I guess I will have to rewire the 240 volt line to the shack.  What a pain.  Every other amp, and transmitter I own uses 3 wires.

I am going to match the Tbolt up to my Valiant and or ranger once I have a large enough shack to hold it.

C

My Junkston desk weighs in at about 400 lbs. Not that stupid, took the plug off of the desk and then to an electrical supply house. Piece of cake ;D

Craig,

I ran my Thunderbolt off 120 AC for years without any problems. It's still wired for 120 today. All my linears run off 120 AC.

Its ok.. I want to run this in my new ham shack with a valiant and ranger sitting next to it. I want it on 240 volt. I have a feeling its going to run alot better on 240 and thats why these amps have rep for low power. People plug them into wall sockets at 120 volts.  Its not something I am going to use all the time. Its just an amp that I have wanted for years and I finally go it :)

C

Clark,
         It would be OK paired up with a ranger, but you wouldnt accomplish much pairing it to a valiant. Paired to a valiant would be a waste as the t-bolt is only good for somewhere around 150-200w of carrier out and a barefoot valiant can do 125 or so.

On 240 its going to do more then that.  300 should not be a problem.  My Valiant has adjustable Screen volts using a 6aq5. I thought of using a T connector and putting a Cantenna on the floor to help reduce the ranger and Valiant.

C

Ok, on 240 it will do 201 watts  ;D  ;D Their good for somewhere around 6-700w PEP out.
Do the math, divide by 4 for AM carrier to have the headroom for modulation peaks.

The biggest problem with them is the low (2000v) plate voltage. and the plate tank wont take much more without zorching over.

the only hope is to change the tubes to the unobtanium PL-175s and kick up the screen voltage. Basically a big waste of time. If you run it at 150w of carrier with good peaks, you can beat the piss out of it forever, but thats about it.

Frank's on the mark with this rig. Big brute tank-looking rig but, on AM, works like a little pussycat with little to no claws. On SSB, it gives you some leverage over a SB-200 linear, but with a SB-200, you can carry it under your arm if you have to move it from place to place.

Hmm..I think you guys ran them on 120 volt.  I talked to a few people since I got the thing and they told me that with SS rectifiers and 240 volts. The amp comes to life and will do 300 am. There are loads of pages showing 2400 to 2500 volts on the plate in this config and there are saying 1200 watts out pep.  I see no reason it wont do 300 watts on AM.  The valiant all the way up does 130 watts with about 450 pep so its going to double the power of the valiant and take a ranger way up. Its rated for 800 watts input on AM. So thats near 300 watts.

I really just want the thing to sit there on the table with my johnson gear. I wont use it much. But should be a nice piece for the collection.  Time will tell and I will test it out.  I am into this thing right so its worth it to me to at least try!  Most of these where snatched up by Cbers so I feel lucky to have a decent one here.

C

When I received my first Thunderbolt, it had solid-state rectifiers in it and was wired for 220V AC so my initial testing was done at that voltage. Even at that, plate voltage was no more then around 2250 volts. Don't remember what the AC line voltage was at the time. Also used an external measuring voltage meter to read plate voltage.  In the AM mode, plate current should be no more then 375 ma if you follow the manual. I remember trying this thing on the air and pushed the plate current to about 400 ma; line voltage was about 232V AC. Blew apart one of the coarse loading caps and bubbled one of the six electrolytic capacitors in the HV power supply. I think the coarse loading caps are rated at 2500 volts. I was driving it with a Ranger.

Clark,

Run the beast on 240VAC. Then remember that 800 watts AM rating was when power was measured as INPUT. So you are looking at 800 watts PEP input. Do the math and 200 watts of carrier output might be a MAX (about) figure.

Still a good pair of shoes for the Ranger ;D

Craig,

PS: Something else I've noticed with the NorthWest group on 3.870; using a SB-610 and watching a trapz pattern will get the driver & linear loaded correctly and sounding gud.

Ok. I was also thinking of using it with my BW 6100 for vintage SSB net.  Also, If I can get one of you guys to help me with this CE20v. I could use that. 

I thought the 800 watts AM was input rating for carrier.  I dont think they used PEP back then.  If it was rated like the rest of the johnson gear then it works out to be 250 to 300 watts.  Either way, Its going to spice up the ranger and look neat sitting there on the table!

C

Look at the ads in the old ARRL handbooks, even the Johnson KW Amplifier had a 2000 watt PEP input rating if used in SSB service. The early desk ran AB1 in the SSB mode, figure the efficiency. Later ones were modified by owners, (if they purchased the kit from Edgar) to run AB2 with 4-400A's to make more smoke as a linear.

Craig,

PS: For grins & giggles, I broke out some of the advertising claims. The Ranger was said to be able to run 65 watts input on AM. Who knows what comes out the other end. Then going to the claims of the Tbolt; using a Ranger as the driver, power increase is 5.7 times. For what it is worth.

They mention "PEP" in the first paragraph of the manual for SSB rating. Also, make sure you add an external relay to switch between the operating bias and the blocking bias. This is also covered in the manual. The manual is pretty specific on tune up procedures depending on the mode. I would follow that closely until you get the hang of what they're telling you to do and the various meter readings. If your Thunderbolt came already wired for 220V AC, you probably don't need to do any internal wiring but, if it was used on 120V AC, you're going to have to rewire several primary leads on several transformers. The bias-screen transformer and the filament transformer only run on 120V AC. See page 2 of the manual.

Roger that, Pete.

C

Be careful what you ask for... you just might get it :-)

But, let's be realistic...  that thing has a pair of 4-400's?  Ok.  Regardless of what tubes are in the final, the math will eb the same.  Easy as P=IE! 2000v @ 300mA = 600w DC Input.  Figure efficiency of the Class B circuit at 65% (theoretical, 60% more real-world number'ish) = 390w out.  That's roughly 100w of carrier, if you use the thing as an AM Linear.

Since most reports I see everywhere are that the Thunderbolt produces 750w out in CW, I gotta say that it's more than likely to be running a bit above a kW DC input. (2000v @ 500mA / 2500 @ 400mA - somewhere in there).

So, whatever amplifier you're using, use the 25% figure/rule/law/whatever....  Whatever the total of the linear amp is, figure 25% of that for carrier.  If you get 1000w Carrier out of it, then 250w is where the carrier level should be set for AM.  Watch your scope so you don't over-modulate.  Same is true for solid state devices.  If your ricebox produces 100w carrier output, then reduce the carrier to 25% of that (or 25w) and adjust the alc until it doesn't increase with audio peaks, or reduce the audio gain -just- to the point where you're no longer driving the ALC positive.

If you plan on running the Thunderbolt at 300w of carrier, and then try to fully modulate that signal, then I'm afraid you'll be disappointed in the signal reports.  Overdriven, distortion, "fuzzy" sounding...  Take heart, though... reducing the power output back to 1/4 of the output of a Thunderbolt, is only going to knock you from 300 to 200w, and that's less than 1/2 of an S-unit, and the signal would then be -clean- (as long as it wasn't over-modulated).

73 = Best Regard"S",
-Geoff/W5OMR
(/m5 Baja Spring, TX)

Clark,
        just FWIW, the primary on the plate transformer is just split into 2 windings.
Series for 240v and parallel for 120v. The outpoot voltage is not gonna change much other than whatever voltage sag you get at the 120v outlet from the heavier current draw on 120. It should make little or no difference in the outpoot of the amp unless you have bad line sag.

As far as replacing the MV rectifiers with solid state, that will also NOT make much / any difference in the outpoot as the voltage drop across the MV rectifiers is only a couple of volts. You could actually use 866s at 12 or 24v and they would work well (I've experimented with it). The big advantage of solid stating them is that you eliminate the zorch over problems if you don't let them warm up long enough to vaporize all of the mercury in the bulb.

You might gain a little something by solid stating the smaller rectifiers in the screen supply. But then change the VR tubes to allow for the higher screen voltage.

Be sure to buy a really good hernia truss when working on it!!   ;D  ;D

My Thunderbolt is paired with a Johnson Pacemaker which, to me, is the perfect match.  It does a fine job on SSB and CW while providing a worthwhile gain on the fairly low power AM output from the Pacemaker.   It would be even better with a low power controlled carrier rig.  For a worthwhile gain from a Valiant you would want something with three 3-500Z tubes or the equivalent backed by a serious power supply and plenty of airflow.

I have a 6N2 Thunderbolt used with Yaesu FT-225/625 rigs but I have never tried it on AM.  It is as painful to move as its HF brother.

Rodger,
          The Pacemaker and the T-bolt would really make a nice lash-up!! Thats a rig that you just dont see many of at festers.

I actually built a piss weak exciter for my T-bolt. A 2E26 (cause I have a bucketfull)
modded by a single ended 6V6------A WHOPPING 7w out!!  ;D  I figgered it was better to have a low powered exciter than to attenuate a higher powerd rig down by heating up a resistive attenuator. The drive requirements of a T-Bolt are so low in the AB2 mode that all you have to do is tickle it with a little RF to get full outpoot.
With many rigs used as exciters that was actually a problem, even if you used the "swamped input" mode.

Once its up and running, I will let you guys know how it works. Its no hurry for me. I have no room for the thing. Once I get my new shack built and I have room, I am going to lash it up to the valiant and Ranger and give it a shot.  One of these 4-400s in the GK500C does 350 carrier and 1200 PEP.  One them in the T3 does 550 carrier and 1800 pep.  The GK500 voltage WAS also low, but once I beefed up the primary wiring, Ran solid state rectifiers everywhere and doubled the Oil caps, The thing came up 500 volts. I dont see why the Tbolt wont do the same.  I realize its not Class C and not  nearly as efficient, but the thing is rated for 300 am.  The guys talking about 100 watts AM are just flat out wrong.

I talked to a guy 3 days ago with a Ranger and Tbolt in California. Off and on was a big difference on the air.  He said he runs his at 275 AM as it seems to sound the best and have enough headroom.  I honestly dont care what it does.  Its a novelty rig for me. Once In a while, I will fire up the ranger and Tbolt and say hello.  I have plenty of other big rigs here to put out a big signal.  But its just idiotic to come on here and say that this amp is only going to make 100 watts.. Jeesh..



C

Slab,

The Pacemaker seems to have a horrible reputation but mine was easy to restore and has held its alignment properly for four years now.  Paired with a RME-6900 it makes a decent all mode station.  The only unusual problem I ran into was a coil with a wire strand intermittently shorting to ground which took a little searching to find.  You do have to ride the VFO a bit to counteract the drift but it is still better than my Eico 753.

These low drive linears are fun to play with and I made a few contacts using my QRP Yaesu FT-817 driving a KL-1 Chippewa.  The 2E26 is a neat little tube, it looks like a compact 6146 and seems to have been more popular in homebrew designs than commercial.

Rodger,
          The 2E26 IS a neat little tube!! Terribly oerlooked by builders. I think of it as 1/2 of 6146. 2 can make 55w of audio in shove-yank with no problems if you push them into a little grid current (AB2). They used a lot of them in older low powered commercial 2-way stuff, and they are pretty good for VHF stuff as well. They are cheap and plentiful, I have a 5-gallon drywall bucket full of them. You can also plug them in in place of 6146s in older 100w rigs to reduce the outpoot to drive a leanyour. Usually they can be plugged in with no circuit mods, making a nice, easily reversable modification.

Clark,
        I / we didnt say they only did 100w, we said somewhere between 150-200w.
I know, I've had one for many years. I've ran it up to 350w or so, and it wouldn't make any positive peaks, not to mention not sound very good. I found 200w was a comfortable operating range.

Unlike class C where you can easily see 60-70+% plate efficiency, in leanyour service expect to get somewhere around 33%. That is why linear AM was not very popular back in the days of the 1kw DC input power limit. Why run 330 wats when you could get 6-700w out in a plate modulated rig. That is also why big screen or cathode modulated transmitters werent built. It was a plate efficiency thing.

you really seem to like the T-bolt, as a novelty rig they are pretty kool, but I just cant get serious about one. If you changed out the plate tank, and ran the Ep up to 3000-3500v they would prolly kick ass and take names. However if a bullfrog had wings, it would never bump it's ass!!   ;D  ;D

It is a shame you dont live closer, I would give you my T-bolt, that way you could have one to szht on and one to cover it up with  ;D  ;D


                                                         The Slab Bacon