FT-101 - Finals crackling when receiving a strong signal

Someone gave me a basket case 101 awhile back that I put back on the bench and I ran into a strange problem. The notes he gave me when I first got it was that it had weak output on 20 meters and below, even with new tubes. Just in case, I put some toshibas in that I know are good and tuned up into a dummy load and saw that it indeed had low output on 20 meters (maybe around 20 watts max) but it was also low on 80 and 40 (around 40 watts).

My first thought was I should neutralize the finals because I need practice doing that anyway and in the service manual it says to put it on 10 meters (10C) @29mhz. After moving the dial to 29mhz, I decided to turn on the internal calibrater to make sure I was exactly on frequency. When the tone began to be received the audio began to crackle and I saw arcing taking place in the final section. I immediately powered off the rig.

I’m not sure where to go from here. The service manual doesn’t seem to describe anything like this. I’m not even sure why the finals would be doing anything at all when I wasn’t keying anything up.

I do have the riser boards so I was thinking maybe I just leave the heater switched off and just start going through and checking voltages. One possible culprit on the fault tree for low power out is PB1180 high frequency IF unit - maybe there is a short?

 

UPDATE: I took a look at the air variable neutralizing cap on my working 101 and saw that it was in a completely different position. I figured it wouldn’t hurt to just eyeball the cap in the basket case rig into the same position and see if anything changed. The good news is I didn’t experience any crackling on receive and I seem to have better output on 80 and 40 meters but I still have the original problem of low output on 20.

I know this sounds like a weak tube issue but I’ve now tried 3 sets of tubes and get the same problem. The weird arcing thing has me nervous too, seems like everything I’ve been working on lately wants to explode.

does it make sense to just start going down through all the boards checking voltages?

 

I gave away my basket case FT101, along with the riser boards I bought for it and everything else a few years ago. I put a couple hundred dollars into it trying to make it work again and it was still a basket case. Maybe it's the same one.

 

If you completely remove the finals do you still get this mysterious crackling on receive?

Other thoughts...can you make the crackling go away by turning the tuning/loading controls? Is there a relay in that area?

 

Firstly, on these rigs if the output is fine on at least one band, low output on any other band will nearly always be down to the various Trimmers underneath needing adjustment.

Don't try adjusting them as per the Handbook (this is a stupid method that you would only use if the rig had just come off the assembly line) - find my suggested method on this website.

If any of the Trimmers peak the signal at Max or Min, then you may have a faulty padder capacitor across that trimmer.

Also - the Neutralisation on these rigs very rarely needs adjusting . . . and even if wrong, it would only cause a slight problem on 15 or 10m. (I have never known it cause any instability or anything like that, and certainly not low power output . . . all you see is the Dip in PA Current not corresponding to max RF Output)

Regarding your "crackling" in the PA companment . . . Does it occur with the Heaters off? (The HT is obviously still there)

With the heaters warmed up, what happens when you switch to TX with NO drive - does the PA Current move?

Perhaps the main PA RF Choke has burnt windings? Leave the lid off the PA Compartment and see where any arcing is occuring. (I have personally never known any issues with arcing on these rigs)

Roger G3YRO

 

The crackling seems to have stopped for now, but I’m wondering if something has burned up because now receive is very low.

The crackling sound hasn’t reoccurred since I adjusted the neutralization cap but something might have been fried because now I have low receive. I switched back to the tubes that came with the rig, because I’d rather not (if I didn’t already) fry my nec tubes.
Nothing looks fried or burned anywhere in the pa compartment, the windings look good, the inside isn’t even dusty, which is a first for me.
Now I have low transmit and receive. The internal calibration signal only goes up to about 3 on the meter max.
I suspect the rig is out of alignment, however the factory markings that they make on the caps seem to indicate everything is still set at factory settings.

Is there a thread or a webpage that has a start to finish checklist to go through when going over these rigs? Like a systematic process of elimination for working out common problems and things like that? I’ve been learning a lot fixing these rigs but would love to have a standard procedure I could follow until I get more experience and a better understanding of these radios.

I’ll search the forum for your alignment procedure, but I’d like to make sure I don’t have any faults before aligning.

 

Another detail I just noticed is that the meter doesn’t react at all to the calibration signal unless it is in LSB. The tone is just as audible in USB and TUNE, and AM you can hear that the signal is received, but the meter doesn’t move at all.

 

Sorry for the rapid fire posts, but it seems that the problem with the meter has been solved by switching out PB-1183C with a spare I had. The receive is also louder now, but the meter only shows about a 3 on all modes now.

 

Ok, another update: The low receive was caused by the noise blanker unit. Nothing looks burned or anything on it and it might just be adjusted wrong, but a spare I had cured the low receive and now she sounds pretty good. Output on 80-40 is now around 100 watts and 20 etc is around 25. I’m thinking now that receive is working and she hasn’t crackled at me all night I’m going to have a look at alignment now. I’m starting to wonder if the person who had this went wild adjusting random stuff, but as I said before the alignment caps underneath are still seemingly in factory positions.

 

I followed Rogers guide to peaking the power and noticed that on 20 meters I almost had to go to full carrier output to get 100ma on the IC meter. I’m currently using the tubes that came with the rig, and while I was told they are good I don’t know so I’m going to switch back to some tubes that I know work and hope the crackle doesn’t come back.