The AM Forum

Trouble with tuning up.
Hi everyone. I am having trouble with my 5100. when trying to tune her up into a dummy load when I throw the plate switch to the on position I cannot seem to get the meter to show any dip to minimum when adjusting the plate tuning control.
Any ideas on where to start would be helpful.

Thanks so much.

Cheers

Bill W3KBS,
Havertown, Pa.

Most of us don't have a crystal ball to visualize the steps prior to the transmitter not working.
We need info!
Schematic would be helpful to readers
PA amplifier stage probably a good place to start. Look for open connections, bad connections, broken parts, bad tubes - you know, the typical stuff
DID it work? If so, what band were you on when it stopped working?
What band are you testing on?
Is the dummy load good?
With these transmitters, a 100 watt light bulb makes a great visual dummy load indicator. Back in the "good old days" that's what many amateurs used.
What about the drive? Any meter indication?
When you key the transmitter, can you hear the VFO  signal in the receiver?
Have you measured any voltages in the PA stage?

It don't work; where do I start doesn't instill a lot of confidence in your trouble shooting skills of a transmitter; voltages in there can kill you if you're not careful.

Good Morning Pete.

Thanks for replying to my email. I trouble shoot pretty good was just looking for a place to start and if others had the same problem. The rig did work after I refurbished it several years ago. I moved and the movers. we're not too gentle as there is a pretty noticeable dent on the bottom. It's a small one however. One more thing. If I was a novice trouble shooter and negativity was used, like you did with me, I would not be back to the forum. Pete we are trying to attract new people into the hobby not push them away. Choose your words wisely because just never know who you are talking too. This is a hobby, we are "ALL" supposed to be having fun not criticized. 

Cheers

Bill W3KBS

Hey Bill, since it worked before the movers got a hold of it check to make sure the previous stages are giving you the drive at the proper frequency. Something in the driver stages might have been damaged.

All things considered..... have fun.

Hi Bill

Sounds like something got jostled. 

What are your settings?   For 3.550 Mc,  my initial settings are as follows:

Load   6
Exc    12-
Plate 6.5

If your issue is happening on all bands,  remove then re-insert the RCA connector from the Buffer/Oscillator into the RF Multiplier stage.

Is the XTAL/VFO switch in the VFO position?   

What is the screen grid showing on the meter?

Bill,
Just curious, what's your Grid Current showing in tune, and what's it showing in operate and HV on? 

73
Mickey KF4NU

Hi Bill,
Assuming you checked all the obvious stuff like you are getting grid drive and the frequency of the VFO is correct and the band switch is in the correct position and the antenna (dummy load) VSWR is good. Then it sounds like something in the PA plate pi network may have failed. Typically if you have fixed loading capacitors, not sure on the 5100 if this is true, then check to see if any of these are blown. Since you said it worked before the movers dented it, looked for cracked components and or broken connections in and around the plate matching circuit assuming everything else is Ok.

WA1QHQ