Restoring a small transmitter

AM Radio discussion. Directional arrays are FUN!
Patrick De Landsheer
Posts: 5
Joined: Thu Nov 27, 2014 3:21 pm

Re: Restoring a small transmitter

Post by Patrick De Landsheer » Mon Apr 25, 2016 12:16 pm

I m sorry to have taken so much time to reply. The small transmitters and the linear amplifiers were modify and custom made by Mr Cunningham for a friend who gave them to me. I will look for the brand of those amps. They are Ham radio amps and the power is 400 watts no 2000. A friend provide me with 1mhz crystals. As I said before, I need to change frequencies. From 1620 ot 1610 khz to 1000 khz AM.

COMMENG
Posts: 80
Joined: Wed Dec 18, 2013 4:30 pm
Location: Midwest

Re: Restoring a small transmitter

Post by COMMENG » Tue Apr 26, 2016 4:44 pm

The previous owner had attempted to retro-fit a replacement power transformer, which put about 750V B+ on the 6DQ5 plate instead of the circuit recommended 450V.. I got that figured out and was able to get it down closer to the 450V
No worries about high voltages with the 6DQ5. It's the 6V6 and the 12BY7 that might have flashovers with that voltage. One can increase R3 and add a resistor for the 6V6 to get higher power at higher voltage.

I would recommend replacing the electrolytics C1A, C1B, C2, and C10 since the prior transformer may have damaged them.

Also note the Pi-output network. C12 and C13 were set/selected for the frequency of operation. if going down in frequency, you may have to increase those capacitor values. And you may also have to move the coil tap as well.

Lastly, if you are feeding any type of Ham Linear do not feed it with more than 15 to 20 Watts from the Cunningham exciter.
They are Ham radio amps and the power is 400 watts
Is that input power and are the Linears Tube type or Solid-State?

Phil

Patrick De Landsheer
Posts: 5
Joined: Thu Nov 27, 2014 3:21 pm

Re: Restoring a small transmitter

Post by Patrick De Landsheer » Thu Apr 28, 2016 7:27 am

Sorry for having taken so long to answer. A friend gave me a few 1 Mhz CRYSTAL to help with the frequency changing, I know some modifications are needed but I not sure where to start. Any help? I want to switch from 1610 or 1620 to 1000 khz. Thanks.

Patrick De Landsheer
Posts: 5
Joined: Thu Nov 27, 2014 3:21 pm

Re: Restoring a small transmitter

Post by Patrick De Landsheer » Thu Apr 28, 2016 7:31 am

The linear amps have tubes

COMMENG
Posts: 80
Joined: Wed Dec 18, 2013 4:30 pm
Location: Midwest

Re: Restoring a small transmitter

Post by COMMENG » Thu Apr 28, 2016 11:13 am

Patrick De Landsheer wrote:Sorry for having taken so long to answer. A friend gave me a few 1 Mhz CRYSTAL to help with the frequency changing, I know some modifications are needed but I not sure where to start. Any help? I want to switch from 1610 or 1620 to 1000 khz. Thanks.
There is a Master Tune-Up Chart in the manual.

For 1MHz it says use Full Coil (48 Turns) and add 230 pF to the Plate Loading capacitor.

How many and what are the tube types in the Linear?

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