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Author Topic: Ft101e giving me the blang band switch near tank coil. Cant neutralize tubes  (Read 3779 times)
KG7HVR
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« on: August 31, 2017, 04:50:36 AM »

I picked up this radio a year ago. 2 wires were smoked on the tank coil. I replaced them very carefully with Teflon  coated wire.
I see about 90 -110 watts out on 40  with various tube sets. But on 20, 15, and 10 the band switch arcs out to ther brass rod with the nut that holds the entire assembly  of water switches together. I cleaned it and replaced the damaged insulator but still arcs once I.C. gets  near 200millamp.  There is not unusual dip on either side of the plate. So i cant neutralize  the tubes even on 20..
Tubes are Sylvania also have a G.E. set. All work perfect in my 101b radio that has no issues. But this 101e is no go.[/img]
I have changed to a 10pf cap and see some improvement adjusting the nuetralize cap but it always arcs eventually.  I get like 10 watts out on 10 meters same tubes make 130 in my 101b. I've also switched the drivers around in both rigs and they make no difference.
The switch is jumping to the post when it arcs. Not a bad contact.
Sorry for the bad grammar. Not easy posting from my phone.
Thanks
« Last Edit: August 31, 2017, 04:56:07 AM by KG7HVR » Logged
KG7HVR
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« Reply #1 on: August 31, 2017, 04:56:58 AM »

The band switch arcs and smokes. Why Cant i edit the subject line of this thread.
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N4MQ
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« Reply #2 on: August 31, 2017, 11:40:56 AM »

arcing over is due to high voltage, get a meter to verify the inductance of the coil to see that it is in the anticipated range.  There may be changes that dont match your expectations.  Could the capacitors be off or replaced out of spec?

Have you tried loading a dummy load to see issue is in the box and not the antenna system?  Conquer and divide the problem into smaller pieces.  Enjoy, Woody
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KG7HVR
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« Reply #3 on: August 31, 2017, 11:54:31 AM »

arcing over is due to high voltage, get a meter to verify the inductance of the coil to see that it is in the anticipated range.  There may be changes that dont match your expectations.  Could the capacitors be off or replaced out of spec?

Have you tried loading a dummy load to see issue is in the box and not the antenna system?  Conquer and divide the problem into smaller pieces.  Enjoy, Woody
It did it before the cap change. I'm using a dummy load
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HAMHOCK75
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« Reply #4 on: August 31, 2017, 05:49:00 PM »

Since you have a working "B", did you check when you replaced the two wires to the pi-network that the placement is exactly the same as in the "B"?

The pi-network transforms the 50 ohm load up to match the plate impedance of the finals. If it transforms up too much, the output rf voltage will be higher than normal. The tap position can affect that.
« Last Edit: August 31, 2017, 05:52:07 PM by HAMHOCK75 » Logged
KG7HVR
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« Reply #5 on: August 31, 2017, 06:07:50 PM »

Since you have a working "B", did you check when you replaced the two wires to the pi-network that the placement is exactly the same as in the "B"?

The pi-network transforms the 50 ohm load up to match the plate impedance of the finals. If it transforms up too much, the output rf voltage will be higher than normal. The tap position can affect that.
yea I pretty mulch had to because the wire was burnt to a crisp and it was hard to see where I had been. I checked  for debris in between windings too. I can use the radio on 40m  but anything higher and it arcs bad.
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AC2EU
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« Reply #6 on: August 31, 2017, 08:08:11 PM »

I would try that radio with an external power/swr meter into a dummy load.
You probably won't be able tune it to 1:1, which brings us back to the plate circuit and pi network.
Someone may have mucked with the capacitor values in that area, trying to make the ultimate CB mod, no doubt. Very common. They may have even re-wired stuff there, seen that too!
Check all of the caps that are connected to the pi network via the band switch.

Depending if those are the original tubes or not, you may have to reduce the series cap in the neutralizing circuit to bring it in the proper range. I think the originals were made by NEC or toshiba? Any of the others have different inter-electrode capacitance.


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HAMHOCK75
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« Reply #7 on: August 31, 2017, 08:20:04 PM »

Can you tune up normally at lower power on those bands? If so, then neutralize on 10M where it has the strongest effect. I have Sylvania tubes in mine too. I had to change to a 10 pF cap to neutralize. With the factory 100 pF, the neutralization trimmer was set to min and still could not do it.

The 10M and 11M wires to the pi-network were also fried. I suspect from CB use with higher carrier power than allowed. Also, mine had only one 10M crystal. The other crystal slots contained CB crystals which was were for European CB. Back in those days CB'ers could do DX with a 101, lol.

I had problems with my relays, both RL1 and RL2. RL2 is controlled by RL1. If for some reason, it does not close, the finals will be looking into an open which can cause arc'ing.

The previous poster is correct about CB'er's getting in there. I found someone had cut a high voltage cap out the driver screen supply because there were two mysterious wire leads just hanging in air. Also, a cap had been moved to an rf ground when it should have been chassis ground. Then there was a cold solder joint from that connection that caused all sorts of grief.

Restoring FT's that had been converted by CB'er's has to be twice the work of a normal unit.
« Last Edit: August 31, 2017, 08:22:43 PM by HAMHOCK75 » Logged
KG7HVR
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Posts: 59




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« Reply #8 on: August 31, 2017, 09:10:25 PM »

Can you tune up normally at lower power on those bands? If so, then neutralize on 10M where it has the strongest effect. I have Sylvania tubes in mine too. I had to change to a 10 pF cap to neutralize. With the factory 100 pF, the neutralization trimmer was set to min and still could not do it.

The 10M and 11M wires to the pi-network were also fried. I suspect from CB use with higher carrier power than allowed. Also, mine had only one 10M crystal. The other crystal slots contained CB crystals which was were for European CB. Back in those days CB'ers could do DX with a 101, lol.

I had problems with my relays, both RL1 and RL2. RL2 is controlled by RL1. If for some reason, it does not close, the finals will be looking into an open which can cause arc'ing.

The previous poster is correct about CB'er's getting in there. I found someone had cut a high voltage cap out the driver screen supply because there were two mysterious wire leads just hanging in air. Also, a cap had been moved to an rf ground when it should have been chassis ground. Then there was a cold solder joint from that connection that caused all sorts of grief.

Restoring FT's that had been converted by CB'er's has to be twice the work of a normal unit.
I'm using my mfj 989c tuner for dummy load and watt meter. I never use 101 meter. this radio doesnt work on power reading ..only I.C.  and Alc work for some reason.
The last 2 wires on the tank coil were cooked  thats 11 and 10 . The arc jumps from the 40 meter section of the wafer to the rod next to it. I triple checked the 101b and 101e tank coil and I see no weird mods. I don't have a reliable method to test picofarad caps. My fluke meter only reads microfarads. Nothing looks odd.  Could it just be the switch? Seems it shouldn't be able to arc no matter.
And yes it has the the 11m xtal. 20 arcs too. 40 rarely. I can use 40 and peaks 90 watts on ssb.
Could someone have tried to align this . I got the radio from some half baked pot smoker who just got his tech. I think he picked it up at a swap and tried to fix it.
I'm at a loss.  The tubes dont run away when it arcs all the time. Messing with the trimmer can cause them to run away.it also can minimize arc. If i stay under 150ma it rarely arcs. But once at 200 or 300 arc and smoke time. I have no idea what to do and really like this radio..exvellent rx just like my 101b
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HAMHOCK75
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« Reply #9 on: August 31, 2017, 10:11:28 PM »

That's RL1 causing the meter not to read ALC and power. It's the first thing I had to take care of when I got mine. Its worth it to spend some time cleaning RL1. Do not use any abrasive like sandpaper. Listen to this guy. http://www.w8ji.com/relay_cleaning_and_life.htm

RL1 controls virtually everything in the FT101E ( mine is the EE so I don't have the speech processor ). I recommend getting that fixed before continuing. Hard to know if it is partly responsible for what you are seeing.

It's pretty easy to take RL1 in/out with pliers like this



If you want to narrow it down to which contact is the problem, I do this. Take the cover off and put the relay back in. Then use a plastic tuning tool to nudge the contacts until it works.



Isn't 90 watts peak kind of low? I get more like 140 watts peak on 40M. I don't use a meter though. I have a high voltage oscilloscope probe so I measure right at the RL2 output.

These are fun to work on if you take your time. What tools do you have? Scope, spectrum analyzer, multi-meter?
« Last Edit: August 31, 2017, 10:31:51 PM by HAMHOCK75 » Logged
KG7HVR
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Posts: 59




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« Reply #10 on: August 31, 2017, 11:16:16 PM »

Ok I'll pull it. Alc reads. Just power out doesnt read.
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KG7HVR
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« Reply #11 on: August 31, 2017, 11:32:09 PM »

Ok I'll pull it. Alc reads. Just power out doesnt read.
I pulled it. Looks ok. So I'll swap the 101b one in and see what happens.
90 is low yes. I get 140-160 on the 101b
I have a Tektronix 100mhz scope and a couple bench frequency counters  but nothing else special
I have the soft of tubes in it now in case something bad happens. Hence 90 watts on 40
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HAMHOCK75
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« Reply #12 on: August 31, 2017, 11:54:37 PM »

It could be the selector switch for IC, power out, ALC. I tried that first but it turned out to be RL1 for me. Don't forget there is a potentiometer on the backside to adjust the sensitivity of the power out reading.

I would swap too since you have known good one. I noticed when testing RL1 with an ohmmeter, the contact resistance when it is not working bounces all over the place. I assume you tested with an ohmmeter with the relay in both positions.

Since you have a scope, you can monitor the "R" ( receive ) and "T" ( transmit ) line. One set of contacts on RL1 controls both. They go low to enable as I recall. So "T" goes to zero volts on transmit, "R" goes to zero volts on receive.
« Last Edit: August 31, 2017, 11:57:55 PM by HAMHOCK75 » Logged
KG7HVR
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« Reply #13 on: September 01, 2017, 12:21:59 AM »

It could be the selector switch for IC, power out, ALC. I tried that first but it turned out to be RL1 for me. Don't forget there is a potentiometer on the backside to adjust the sensitivity of the power out reading.

I would swap too since you have known good one. I noticed when testing RL1 with an ohmmeter, the contact resistance when it is not working bounces all over the place. I assume you tested with an ohmmeter with the relay in both positions.

Since you have a scope, you can monitor the "R" ( receive ) and "T" ( transmit ) line. One set of contacts on RL1 controls both. They go low to enable as I recall. So "T" goes to zero volts on transmit, "R" goes to zero volts on receive.

No difference. Alc pegs out till you modulate.  It now seems to arc for a second on initial key up  in tune mode
No amount of adjusting the nuetralize cap stops the arc. I'm guessing that the arc is because the tubes are oscillating basically I can't get much more than 10 watts out and it still does it but even if it didn't tell him I said neutralize this thing when there is no real peak or null to adjust for ? Yaesu description on how to neutralize the tubes is vague at best I don't see anything abruptly changing
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HAMHOCK75
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« Reply #14 on: September 01, 2017, 12:50:45 AM »

I noticed in my notes that I had a problem with something affecting the high voltage supply that caused what sounded like arc'ing except it was not arc'ing but noise from the speaker.

I was trying to recall what the symptom of of poor neutralization was. It was that if you tune for a dip in plate current, then tune for maximum output power, the two are not coincident. When neutralized they are the same.
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