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Help with TR-7

N

N2LWD

Member
Nov 10, 2008
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This is not easy to explain. Here is what i have. The power output of the transceiver cannot be controlled. The power amp works fine when I test it on the bench and drive it with a signal from a signal generator. The output is clean on all bands when observed on a spectrum analyzer. The signal from the transceiver exciter is clean and can be controlled (reduced) with the drive control. When I connect the power amp to the exciter I get full power output with spurs across the entire HF spectrum and cannot reduce the output power. The power supply shuts down due to excessive current.
Has anyone run into this problem and what did u do to fix it. i am posting this for the person that is working on my TR-7. any help would be greatly appreciated.
Sal N2LWD
 

Just to be clear on this....your tuneup procedure is as follows

Tune up the amp properly for max power out into a dummy load.

Adjust the exciter's drive level for the desired power output level.

If you want to run lower power, that is the correct way.

If the exciter can't be dropped, and exceeds the amp's power out, you are doing it wrong. Get a different exciter or modify the one you have.

You don't control power output by adjusting the amp, only the drive into the amp after it has been tuned for max rated power out.
 
We are not trying to tune the rig up. we are trying to repair it. stated was what is happening when the fellow working on it "connects the power amp to the exciter he gets full power output with spurs across the entire HF spectrum and cannot reduce the output power. The power supply shuts down due to excessive current."

P.S. SR385, the Drake TR-7 is a broadband transceiver and does not need to be tuned-up. IMHO it would be better if u read the complete post before u jump in with useless information.

N2LWD
 
N2LWD said:
We are not trying to tune the rig up. we are trying to repair it. stated was what is happening when the fellow working on it "connects the power amp to the exciter he gets full power output with spurs across the entire HF spectrum and cannot reduce the output power. The power supply shuts down due to excessive current."

P.S. SR385, the Drake TR-7 is a broadband transceiver and does not need to be tuned-up. IMHO it would be better if u read the complete post before u jump in with useless information.

N2LWD
Click to expand...

I know exactly what a Drake TR7 is. I was trying to point out that a step is missing or you left out major details as your posting doesn't make any sense otherwise.

If you want to believe CBer witch doctor nonsense about driving an amp, be my guest. I was giving the benefit of the doubt that there was a misunderstanding about how to drive an amp or missing details.

Good luck.
 
SR385 said:
I know exactly what a Drake TR7 is. I was trying to point out that a step is missing or you left out major details as your posting doesn't make any sense otherwise.

If you want to believe CBer witch doctor nonsense about driving an amp, be my guest. I was giving the benefit of the doubt that there was a misunderstanding about how to drive an amp or missing details.

Good luck.
Click to expand...


The ham working on the TR-7 is a ham for 40+ years. he is also an electrical engineer for Bell Labs in N.J. and has been working and fixing ham radio gear for 30 some yrs.
That u dont understand what is written does not mean that there is a step missing or that major details were left out and the post doesnt make sense.
To call him a CB witch doctor only shows ur ignorance. Please keep ur post to urself as it is obvious that u don't have a clue.
 
Guys, he's talking about the exciter and PA stages inside the radio....not a transceiver/amplifier combination.

There's a really good Drake board on Yahoo with some top notch techs:

DrakeRadio : Drake Radios

I did a quick search on the Forum for "ALC" and came up with this:

"The most reliable way to limit your TX power would be to adjust your ALC control (beneath the high-pass filter assy.) to 50 watts."

I'd get a service manual and start looking at the ALC circuit. It would appear it is not doing its job. Or someone has messed with the control...the TR7 was legendary for having lots and lots and lots of overdesign in the final, and some people liked to take advantage of it.

PS. I've always loved the TR7...built like the proverbial brick outhouse with a receiver second to none. I saw one on eBay just 3 or 4 months ago...brand new, still in the box, never powered up. The seller used to run a ham radio shop back in the early 80's and kept some of the unsold inventory for himself but never got around to using it. He had a whole 7 line up for sale...man it was pretty.

The radio, amp, and tuner (all New in Box) went for around $3k if I recall. Much too steep for my meager change....
 
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