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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Tue 18, 2019 8:24 pm 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
Which knob reduces power? Is it the load knob? Because that one can really bury the meter if I turn it up. I'm using an old crystal that has FT 243 stamped on the bottom. When I last wrote I was tuning on a 40 watt bulb. I don't have any light bulbs laying around. Just for kicks I replaced it with a 500 watt Inca descent photoflood, and the tune up acted a bit different. Seemed.like the chirp was a bit better. But I'm not getting this tune-up bit. The book simply says drive-plate-load all at maximum. But when I read on the net, you're supposed to be looking for dips.


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Tue 18, 2019 8:45 pm 
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Joined: Apr Thu 12, 2007 3:24 am
Posts: 2187
Location: Milwaukee WI
I have seen a lot of posts talking about the problems with the small crystals as a real thing. But in this case, the oscillator type between the Knight and Ranger are different and the crystal may act in a different way.
In most cases max output will track with the dip when adjusting the plate control. I recommend you find a good 50 ohm or close to it dummy load otherwise your readings will be as messed up as they are right now.


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Tue 18, 2019 9:40 pm 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
Well I just did something dumb. Out of curiosity about the above post saying these crystals can be fake, I opened it up. After taking out the 3 screws, the metal top seemed to be stuck. So I gave it a little pry. The top and a spring went flying, and I saw a flat piece of copper. Underneath the copper (I think) were a couple little pieces of square metal that dumped out in my hand. So I put everything back together, hoping everything was in order and turned right, and it worked. Except I notice when I close the key, the tone gets louder in my receiver if I touch the metal top of the crystal. I don't know if it was that way before


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 12:10 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
As long as I'm loading up the thread with dumbest questions, it seems the meter sensitivity switch in back doesn't change the meter reading one bit. And it checks out according to the assembly diagram. As for the cw signal being louder in the receiver when I touch the metal top of the crystal, I don't know if it did that before I stupidly took it apart. But I just took apart the crystal again, and it looks like you'd have to be really stupid not to be able to reassemble it. So I guess the crystal is ok.


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 12:38 am 
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Touching the crystal would make it louder in your receiver because your body is now acting as an antenna helping to radiate a stronger signal.

When you took the crystal apart, if you touched the blank or contacts with your fingers then you should take it apart again and clean those using a clean cloth or paper towel and isopropyl alcohol. The early National HRO manuals contain instructions for properly cleaning these types of crystals which were used in the single element filters in many early receivers.

The switch should definitely reduce the meter sensitivity. With the rig unplugged and the dummy load disconnected, measure the resistance from the center conductor of the RF output to ground and it should drop in the reduced sensitivity setting of the switch. R23 and R25 form a resistive voltage divider and when the switch is in the low sensitivity position, R24 is added in on the load side of R23 further reducing RF voltage to the detector/meter portion of the relative power meter.

Rodger WQ9E


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 1:05 am 
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Joined: Dec Sun 14, 2008 3:33 pm
Posts: 886
Location: Tokyo
Let me interrupt this thread to pick up on Rodger's comment on the Knight T400. To me, it's inconceivable the design team that gave us the T60 and T150 was involved in the T400. That's quite an ambitious and sophisticated rig. I suspect that transmitter was designed by someone with substantial RF engineering experience, perhaps retired, perhaps moonlighting. Allied was clearly in over their heads, yet it took them three years to realize it. I keep a faint hope that the grandchild of that engineer finds his granddad's T400 notes and releases them to the world. Btw, the assembly manual was available for purchase separately ($2, I think) and in 1962, I almost ordered it! I also suspect Allied kept it in the catalog for three years to judge buyer interest. But $400, later $500, was a lot of money in the early 60s, especially for a kit, especially for a Knight kit.

Back to your regular T60 thread.

Rob


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 1:13 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
Aha! There's a rat. I don't know where it is. Connecting my ohmeter as above to the center terminal of the pl259 antenna jack and ground, and flipping the switch makes no difference.


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 1:38 am 
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Rob,

I wonder if you had ordered the manual if you would have actually received one? If so that would be quite the collector's item!

Henry, What are you measuring to ground? Should be around 5K. Most likely culprit is the switch contact itself but it could be your favorite builder made another assembly error or the 100 ohm resistor went open at some point.

Rodger WQ9E


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 1:58 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
I'm reading 5.14 kohms in both positions. After I removed the boob modifications I put things back to original. I guess I could have missed something. But that much looks in order. Explains my tune up woes though. I can't reduce meter sensitivity. The fact I easily bury the needle on CW tune-up tells me the meter is probably stuck in high mode.


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 2:10 am 
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Joined: Jul Sat 28, 2012 9:32 pm
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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 3:39 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
The resistor tests 102 ohms. I wonder if I have a bad switch here. This is a single throw slide switch. One of the outer legs is cut off by the factory. Across the center conductor and the cut off stub I get 814 ohms . When I flip it to where the red center wire to ground connects to the other outer leg going to the resistor, I get the same 814 ohms, unless I push on the black plastic slider. Then it goes to zero. When I let off it goes back to 814. If I flip the switch the other way where nothing is connected to the sawed off leg, it stays 814 whether I push on it or not. Lacking any quick access to a replacement switch I suppose I need to resolder it, take it out of the radio, pry open the tangs and open up the switch for a look-see. I'm dismayed that the designers put the switch on the back of the radio. Because you need constant access to switch the meter. Tuning up in tune mode of the function switch, you need full meter sensitivity. But in CW mode you need it at low sensitivity.


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 3:55 am 
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With an inexpensive open switch like that, if you have some WD-40 spray it where it will get into the switch and cycle it back and forth rapidly several times and you will probably find that it works again. If not it was probably hit at some point bending the fragile contacts and it will likely need replacement because once those internal contacts are damaged bending them back in place just weakens them reducing the already minimal contact tension.

Or if the previous builder put a hole in the area, mount a 5K pot in place of the switch and this will give you a variable sensitivity control.

Rodger WQ9E


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Wed 19, 2019 4:08 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
I fired up the xmitter to test my theory. Sure enough pushing on the switch drops the meter reading. Spray didn't help. The switch is obviously bad. Now I can get back to my chirp. But not tonight. This is actually a sweet little machine. I'm glad I paid my $29 for it. It might have all these design flaws I read about. But I think it's a sweetie pie. Thanks again.


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Thu 20, 2019 4:08 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
Well I've had that switch out of the radio twice. Attached is a photo of the insides, nice and clean. Before all these bright clean contacts were coated with some brown crud, reminiscent of burned-on oil. Under the round part is a spring. I stretched the spring slightly to be sure of good contact. But guess what? The dadgum switch still doesn't work unless I press on the plastic slider.But it does prove that I can reduce meter sensitivity, which is absolutely needed. So I guess I'm going to have to dig up another one.
On another front, being the chirp, today there is no chirp. I guess since yesterday was the first time it had been fired up in who-knows-when, it just needed a little exercise and a good night's rest. Plus I had taken apart the crystal and cleaned it. Now the CW note is smooth as silk, with a touch of hum. So I guess a new 20 mfd 600V cap is in order. I'm trying to get it ready for field day Saturday. Should be some fun, even if all I have is a 7037 crystal.


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Thu 20, 2019 12:49 pm 
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Time for a new switch. That was a really poor design for a sliding contact switch where it relies upon contact between those raised points on both the moving and stationary contacts. Once alignment is slightly off from normal wear then that switch will have issues.

Find the matching Knight model P2 relative power/SWR meter and then you won't have to reach for a switch on the back of the set to switch ranges :)

Have fun with FD operations!

Rodger WQ9E


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Thu 20, 2019 4:35 pm 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
Well here's my little sweetie pie. I jumpered the switch for now just to keep from pegging the meter. When tuning up, what's the big hurry in doing the tune-up on CW and then getting it back to standby? Won't the radio be spending a lot of time in the CW position?


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Thu 20, 2019 8:37 pm 
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Nice looking setup and it looks nice with the matching power meter.

The primary reason to tune quickly in CW is that unlike tune mode, the screen voltage isn't reduced so out of resonance the final draws a LOT of current which can quickly damage the final tube and/or power supply. So when doing the final tuning in CW mode you have to tune it up quickly and carefully to avoid damage.

Also, when actually running CW the final is keyed and so most of the time it is off and the duty cycle is low while during tune up in CW mode you have the key locked so it is at 100% duty cycle and the T60 wasn't designed to run that way for long. In AM mode, it uses a controlled carrier screen modulation system so that the final isn't running continuously at full carrier level like it would in a high level plate modulated rig. A rig that would stand up to 100% duty cycle at rated power would be a lot heavier (and more expensive). But treated like it was intended, the T-60 works quite well on both CW and AM and controlled carrier AM works very well with the great majority of amplifiers that were designed for low duty cycle SSB service and can be run at or near their full SSB ratings. Trying to run most classic SSB amplifiers with full carrier AM near their rated peak power will quickly destroy them from overheating the finals and power supply.

Rodger WQ9E


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Thu 20, 2019 11:55 pm 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
Well it looks like I got something cooking. See photos. My first transmission. If I can believe my little Knightkit meter, my SWR is 1.25:1. I know I must be getting out, because I have to turn the sensitivity on my Hallicrafters with an antenna wire draped over the curtain rod down to practically nothing to keep from overloading it. And as you can see with my trusty frequency counter, I know my Hallicrafters is set at 7037 or very close. Boy my transmitter needs a new big capacitor. Listen to all that hum. But practically no chirp though. I wonder how many toes I stepped on getting everything tuned up. Nobody answers my CQ, but then I probably wouldn't know it if they did,


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Fri 21, 2019 2:28 am 
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Joined: Dec Sun 14, 2008 3:33 pm
Posts: 886
Location: Tokyo
Good looking pair. Just think: if you had gotten a properly designed transmitter, in good condition, you would have missed out on all this fun. Is it not an extremely satisfying feeling to get these problems sorted out and solved? Have you not bonded with your T60 in a way that would be impossible with a modern transceiver?

Rob


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 Post subject: Re: Knightkit T-60 Transmitter Questions
PostPosted: Jun Fri 21, 2019 3:53 am 
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Joined: Jul Sat 28, 2012 9:32 pm
Posts: 249
I'm not closing out my questions on this radio. But a couple of days ago I put out a bulletin in my club that I was looking for old xtals. Today I got an answer from a guy who told me I could come fetch some. It was a pretty good little batch of 40 and 80 meter ones. He gave them to me. Along with a bonus freebee. A Heathkit DX40, in dire need of some healing luv. You betcha. It's gonna get it.


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