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 Post subject: Yaesu FT-101E tubes heaters question
PostPosted: Sep Sun 26, 2021 11:29 am 
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Joined: Jun Wed 19, 2019 11:07 am
Posts: 68
Hi this set was wired for 220v, which was the voltage my country had in the past. There is also a sticker (220v) at the back of the set.
Nowadays in Europe we use 230V. The set works on 230v ok but of course the heaters voltage and the output power goes up.
The heaters voltage is within limits (checked from the datasheet) but at the edge. The limit for the finals, from the datasheet, is 13.8v and my set has 13.69v. This is just about true for the driver tube.
Shall I worry about fast tubes deterioration or am I ok because the voltage is barely within limits?

I could rewire the set, but I like the extra output power, if it does not hurt. Bias is set correctly and monitored form the front panel meter to 60mA or less.


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 Post subject: Re: Yaesu FT-101E tubes heaters question
PostPosted: Sep Sun 26, 2021 12:04 pm 
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These sets run quite hot because there is a lot going on in a small amount of space. Life of all components is reduced by excessive heat and the small increase in power has NO significant impact at the receiving end.

Rewire the transformer primary tap to reflect the actual voltage and your set and bank account will both be happier over the long run. With lower power tubes, running the filament at design center or slightly lower (but within spec) is the desired operating point. With high power transmitting tubes, follow the tube spec sheets because many high power transmitting finals require the filamentary cathode to be fed with rated voltage as a minimum and very slightly over as a maximum in order to avoid significantly shorted tube life. Lower power tubes are more forgiving but heater life drops dramatically with a small increase in voltage and the increased heat in the tube makes other issues more likely (more issues with gas liberated from overheated elements, secondary emission from the control grid due to increased heat, less of a safety factor when accidental mistuning or short term overload due to antenna problems, etc.)

For sweep tube sets like this one where the finals are no longer cheap, it is highly desirable to load the rig to rated power and then reduce power 10 to 20 percent below this level by decreasing mic gain and carrier level (dependent upon mode). Loading the rig to rated power is needed in order to avoid excessive screen grid dissipation from light loading and to keep distortion low on SSB and then reduce drive to final. Tube life is greatly increased with no perceptible impact on received signal strength.

I have a Drake C line that was heavily used for contest and DX operation for a couple of decades. It is now in semi-retirement but still gets used and it has the same Sylvania "sweep tube" finals in the T-4XC that I installed shortly after I bought it used in 1983. Slightly throttled back, it still has no problem driving a SB-220 to its rated input and when used with my homebrew triple 4CX800 grid driven amp it is loafing along at 40 watts output. By using marginally lower than rated input along with a final cooling fan provided for very long tube life in this set.

Rodger WQ9E


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 Post subject: Re: Yaesu FT-101E tubes heaters question
PostPosted: Sep Sun 26, 2021 1:21 pm 
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Joined: Jun Wed 19, 2019 11:07 am
Posts: 68
Thanks Roger!
Like everything in life, so in electronics.

"The light that burns twice as bright, burns half as long - and you have burned so very, very brightly, Roy."
Blade runner 1982


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 Post subject: Re: Yaesu FT-101E tubes heaters question
PostPosted: Sep Sun 26, 2021 8:30 pm 
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Joined: Jun Wed 19, 2019 11:07 am
Posts: 68
But look what I have found
http://w8ji.com/filament_voltage_life.htm
He mentions that when operating filaments within their rated limits is ok for HAM radio purposes.
I operate them on 13.69v and the limit is 13.8v


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 Post subject: Re: Yaesu FT-101E tubes heaters question
PostPosted: Sep Sun 26, 2021 8:41 pm 
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You are dealing with more than just filament life here, the overall heat budget is important in transceivers that were designed to fit into a small space with the minimum cooling necessary.

Very seldom will you need to replace a final amplifier tube (or audio output tube or other high power tube) because of an open filament. It will likely fail due to gas, heater to cathode short, or other failure mode. The reason for keeping the filament voltage close to design center is to keep the overall heat budget within reasonable limits. The other components that live in the set with the final and drivers will thank you for your kindness. Running a rig at its limits to get the maximum capable output power is useful only when taking product photographs for advertising copy, like any other "machine", running it at a slightly more conservative rating will increase its service life and in the case of a transmitter the penalty is not detectable in terms of communications performance.

Rodger WQ9E


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 Post subject: Re: Yaesu FT-101E tubes heaters question
PostPosted: Sep Mon 27, 2021 1:00 am 
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Posts: 12210
Location: Ohio 45177
The 101 has a constant running cooling fan on the final output cage that would alleviate a bit of extra heat, probably not a problem in an air conditioned domestic environment. I added a computer fan to the cage of my T4XC that is not high RPM to keep noise inaudible, but it keeps fresh air moving thru the finals which has to help. The shortened lifespan of the sweep tubes in the Yaesu is substantially due to mistuning or excessively long key down for tuning. Those tubes should last quite a long time. Especially if there is not extreme compression or constant carrier output. I have a set of good used Japanese finals for mine and also some NOS GE brand tubes as a last resort, which requires a minor mod to use. It has the finals that came with it when I got it. This ARF linked supplier of tubes in Ohio got me a proper set of the correct NOS finals for my Drake at much less than ebay prices: http://www.findatube.com

_________________
Reddy Kilowatt says; You smell smoke? Sorry about that!


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 Post subject: Re: Yaesu FT-101E tubes heaters question
PostPosted: Sep Mon 27, 2021 1:55 am 
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The FT-101 transceivers definitely need the final cooling fan but it was an option even on the FT-101E and not just the EE "economy" and EX "extreme economy" versions. Most sold in the U.S. originally came with a fan but not all of them have it and that was particularly true for some of the JA export markets so if your rig doesn't, it should have a fan added.

As to the voltage, since Yaesu kindly provides taps for 100/200, 110/220, and 117/234 volt operation; it makes absolutely no sense to run it with the wrong tap for 230 volt mains. Yaesu didn't specify a transformer with these fairly closely spaced taps just for the hell of it, they meant for the operator to choose the closest tap to actual line voltage for proper operation and if your line voltage is centered on 230 volts then the 234 volt taps are the correct choice. Getting a few extra watts from excessive voltage is not the way to treat equipment that is approaching half a century old.

Rodger WQ9E


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 Post subject: Re: Yaesu FT-101E tubes heaters question
PostPosted: Sep Mon 27, 2021 2:37 am 
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Joined: Jun Sun 15, 2014 5:37 pm
Posts: 1395
Location: Montreal, Quebec
The first time I saw an FT-101, I'd seen ads, was Field Day 1972. Someone took advantage of the handle and brought it along.


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 Post subject: Re: Yaesu FT-101E tubes heaters question
PostPosted: Sep Mon 27, 2021 12:51 pm 
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Joined: Apr Wed 01, 2020 7:22 pm
Posts: 334
sv3ora wrote:
But look what I have found
http://w8ji.com/filament_voltage_life.htm
He mentions that when operating filaments within their rated limits is ok for HAM radio purposes.
I operate them on 13.69v and the limit is 13.8v



Yes, but W8JI is mainly referring to EIMAC RF transmitting tubes, not TV oscillator sweep tubes...Any additional headroom you can provide to those 6JS6C and similar "sweep" tubes will add to their life expectancy...!!!

73...Jordan VE6ZT


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