Drake TR-4Cw output problem

[n5ama]

I have a Drake TR-4Cw that is giving me a problem on 15m output. All the other bands have 100w+ except 10m with 90w output. The 15m band has no output but receives well. I'm assuming the eliminates the 35.5mhz crystal. I've checked the band switch and it appears ok. The manual isn't any help on trouble shooting and says Drake is "good stuff" and recommends sending it back to Drake if a problem is encountered.

Anyone have any suggestions on where to start looking?

Thanks,
Tom N5AMA

[WQ9E]

Tom,

Are you able to get an increase in plate current on 15 meters when increasing drive?  If so, the problem is likely a switch contact for the final tank coil. 

If you can't increase the plate current on 15, then it is in the driver section.  But since the receive and transmitter largely share the driver stage coils as the receive input coils, I suspect your problem is on the output network side from the final which only is used for transmit.

Rodger WQ9E

[n5ama]

Hi Roger,
Thanks so much for the reply and place to start looking for my problem!
There is no plate current regardless of the drive control position.

I'll look at the output network associated with the finals.

Thanks!
Tom N5AMA

[WQ9E]

Tom,

When you say no plate current, is it not even showing idling current on 15 meters?

If it shows idle current but you can't increase it with the RF tune or xmtr gain controls like the other bands, then the problem is in the exciter (probably driver stage).

I just got home from teaching a MBA course but I will take a look at the schematic and try to give you better directions in the morning.  It is very odd that it will receive but not transmit on 15!

Rodger WQ9E

[Dave K6XYZ]

I have a Drake TR-4Cw that is giving me a problem on 15m output. All the other bands have 100w+ except 10m with 90w output. The 15m band has no output but receives well. I'm assuming the eliminates the 35.5mhz crystal. I've checked the band switch and it appears ok. The manual isn't any help on trouble shooting and says Drake is "good stuff" and recommends sending it back to Drake if a problem is encountered.

Anyone have any suggestions on where to start looking?

Thanks,
Tom N5AMA

Sometime back I had a similar problem with my TR4-CW/RIT.
It turned out to be....
Drake wire wraps several wires on the same terminal on the band transformers....in the driver section.
Over time these wires wrapped on top of each other go high resistance or open and cause failures in the driver.
I put liquid flux on these wire wraps and securely soldered them all.
no more problems.
I don't have that rig or the manual anymore so I can't be more specific....but the above is what I did to fix it.
Use the manual schematic and trace the ckt and you'll go right to it.

[n5ama]

Ok, thanks to all for the help. I found L7 open. The fine wire used in the coil disconnected from the top of the coil form. It was impossible to see but it checked open and sure enough it was loose on one end. after adjusting L6 and L7, I now have some plate current and some 15m output. I can't set the idling current to 100ma. It won't drop below 250ma. Also the 15m receive is way down compared to 20m. I adjusted L5 on the front end.

Not totally up to speed but making progress.

Happy Thanksgiving to all!
Tom N5AMA