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 Post subject: Drake T4XC Transmitter Alignment
PostPosted: Oct Tue 05, 2021 9:51 pm 
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Joined: Jun Sat 29, 2013 11:05 pm
Posts: 5
I was recently given a pristine-looking T4XC transmitter with the matching power supply. Everything checks out good when verifying the resistance and voltage charts in the manual. On a dummy load, I can get 100W out on 40m and 80m, although I have no idea where I'm transmitting as I can't find the signals on a nearby receiver, tuning up and down those bands. The 40m band, for example, appears to tune where the dial says 160m, so I'm thinking the alignment is way off. I also had to replace a final, so it probably needs neutralization. The first problem is, the manual calls for aligning the PTO slugs according to the color of the dots. What dots? I don't see any. Can anyone shed some light on this? The manual says the accuracy should be within 1/64". Does anyone have their own alignment procedure that doesn't depend on dots?
Thanks!

Jerry VE6TL
Calgary


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 Post subject: Re: Drake T4XC Transmitter Alignment
PostPosted: Oct Wed 06, 2021 12:21 am 
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Joined: Mar Fri 29, 2013 4:46 am
Posts: 233
Location: Livermore, CA
I've worked on several T4XC and never had the coil forms out of adjustment. Take a machinist scale graduated in 32's, and 64's and rest it on top the card board tube the 1/4" iron rod raises in and out of. Measure the distant to the top of the iron core and see if it matches the manual spec's. All my T4XC's looked like yours no color dot on the cores I'm not sure the white glue counts as a color someone else can chime in on that. Anyway I used the no color spec's to align mine seem to work just fine.

Dave


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 Post subject: Re: Drake T4XC Transmitter Alignment
PostPosted: Oct Wed 06, 2021 1:03 am 
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Joined: Mar Thu 04, 2010 3:09 am
Posts: 133
Do not try to align it yet. I have a T4XC and it is very possible to get it to tune up way out of the band from the front panel and can get full power way out of the bands. I think the manual mentions that possibility somewhere. The multiplier circuits do not function.

For 7.295 khz I currently have the RF tune just to the left of center on the 40 meter white stripe. The plate is straight up and the load into a dipole is to the right of straight up, about 1 o'clock. Start your tune up from there and you will be close.

Rich


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 Post subject: Re: Drake T4XC Transmitter Alignment
PostPosted: Oct Wed 06, 2021 2:42 am 
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Joined: Sep Wed 10, 2014 2:01 am
Posts: 2343
Location: Costa Mesa, California
I have looked at the manual and don't see any mention of dots. The transformers--T4, T5, T6, T7--are the driver, mixer, pre-mixer, plate circuits. The PTO is never adjusted. I use a pair of vernier calipers to set the slug heights for each band. The calipers' inside measurement points work very well for accurately setting the slug heights.

Norm

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 Post subject: Re: Drake T4XC Transmitter Alignment
PostPosted: Oct Wed 06, 2021 2:53 am 
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Joined: Mar Fri 29, 2013 4:46 am
Posts: 233
Location: Livermore, CA
I'm wondering if someone moved the RF tune pointer are all the other bands tuning in the wrong part of the RF Tune scale as well or just 40m?


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 Post subject: Re: Drake T4XC Transmitter Alignment
PostPosted: Oct Wed 06, 2021 3:09 pm 
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Joined: Jan Sat 12, 2008 12:25 am
Posts: 290
Location: Kingwood, Texas
Those slugs look like they’ve never been tampered with. My advise is to leave them alone. I suspect you may have an oscillation. Use a frequency counter to determine what frequency it’s actually transmitting on.

Darrell


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 Post subject: Re: Drake T4XC Transmitter Alignment
PostPosted: Oct Wed 06, 2021 4:03 pm 
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Joined: Jun Sun 19, 2011 2:31 pm
Posts: 8081
It sounds like on 40 meters, you may be tuning up on the PTO output rather than 40 meters. Perhaps your 40 meter range crystal isn't operating? You do have the XTALS switch in the norm position? Cycle it a few times to clean it and leave it in the Norm position.

As Darrell noted, the slugs in the tuning network don't appear to have been messed with. You can check that the RF tuning knob is properly indexed by turning it to its full clockwise stop and at that point all of the cores should be protruding 9/16".

I have several 4 lines from the original no suffix through the C line. For alignment, IF you have a R-4 series receiver then the best alignment occurs with the receiver connected to the transmitter via the proper interconnecting cables. The loads specified in the alignment section are used if the T-4X series transmitter is used without a matching receiver and results in a usable alignment but not as good as when the transmitter is seeing the actual load imposed by the cables and receiver circuits.

The T-4XC will be much happier if you supply a little cooling air for the finals, a small fan works fine and can sit on top of the final compartment. Sweep tubes are capable of sustained moderate dissipation and thus will withstand SHORT heavy overload. Tune quickly and allow cooling between attempts if you haven't yet mastered fast tuning of a pi net transmitter.

Drake also included instructions for using their T-4X series under the old novice 75 watt power limit and for this you readjust the bias control until idling plate current just barely moves the needle. This is a useful setup while testing and getting used to the transmitter because it reduces plate dissipation while testing/tuning. You must reset the bias to normal before attempting SSB/AM operation or full power CW.

Rodger WQ9E


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 Post subject: Re: Drake T4XC Transmitter Alignment
PostPosted: Oct Thu 07, 2021 10:44 pm 
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Joined: Jun Sat 29, 2013 11:05 pm
Posts: 5
Thank you to all who replied.

I took the transmitter over to a friend's place (with a spectrum analyzer and frequency counter) and was able to see the output was from the first oscillator, with a strong first harmonic too. We then used his scope to trace the various circuits and found the crystal oscillator wasn't working. After testing it on different bands, it started to work. Turns out it was the band switch after all - even after I had sprayed it with DeOxit. We sprayed it again and now it seems to be reliable. I never touched the slugs as I took everyone's advice to leave them alone as they looked to be untouched from the factory. And yes, it can tune up out of the band or in band on 40m. The dial calibration seems to be very good, so I'm going to leave that alone too. Now to find out why 10m and 160m aren't putting out any power as the other bands are working just fine (about 100W to a dummy load). Might be more problems with the band switch. And by the way, there are a number of trimmer capacitors on the side but no mention of them in the manual. I assume these are to set the min/max frequencies of the bands. Anyone have info on them?

Jerry VE6TL


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 Post subject: Re: Drake T4XC Transmitter Alignment
PostPosted: Oct Thu 07, 2021 11:03 pm 
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Joined: Mar Thu 04, 2010 3:09 am
Posts: 133
There are very inexpensive digital frequency counters, less than $20 shipped, that make great frequency readouts for transmitters like the T4 to be sure you are tuning up in band. My T4XC's dial is close but drifts as it warms up and being able to see where you are is a great feature. I have a 6 digit and 8 digit version and can get down to an accuracy of a few cycles. It takes just a few turns of wire around the coax to function. Also good for Johnson Rangers etc.

Rich


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 Post subject: Re: Drake T4XC Transmitter Alignment
PostPosted: Oct Sat 09, 2021 1:32 am 
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Joined: Jun Wed 08, 2011 2:33 am
Posts: 12368
Location: Ohio 45177
My slugs are untouched according to the dope on the shafts and I think I checked the settings before I did an alignment. On mine I forget if it is 80M maybe, but it does not peak tune quite where it should. I went thru the whole alignment procedure without touching the slugs. The higher bands are on or pretty close anyway. I decided that if I ever decided it was not up to snuff, I would just send it out to one of the Drake experts that have experience fiddling with that slug tuning especially when they measure right where they should be anyway. I had headaches aligning my FT-101 too. Getting it so the RX and TX peaked in the same place with the preselector settings. 40M was off. I got it better but now 20M RX does not peak in the same place as TX even after going over and over the procedure. Well that is old radios for you. Someone knows the tricks and tweeks that are not in the manual and they are probably those experts. And you have to pay. Curtis Long of Franklin Ohio was the guy that tuned up those T4XC rigs in final assembly and he is pretty much long dead and gone. Maybe he took the information to the grave.

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