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Author Topic: question for w8ji al 800  (Read 4033 times)
W4RS
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Posts: 64




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« on: December 21, 2012, 04:47:29 PM »

tom, i have a al-800 that i use in the philippines. the power grid is 50 cycles, some time 225 volts, sometime 250 volts. if you see they way they wire you would know why!
i would like to protect and extend the life of this wonderful amp. any suggestion, ie: inrush protection, etc. and for others, i have an alpha 89 a, sdx77,henry 2k classic. and i like the al-800 the best.
jim du3/w4rs
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W1QJ
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« Reply #1 on: December 21, 2012, 09:56:56 PM »

Do you have a manual for this amp?  If not, download one from the Ameritron website.  You will notice the amp has a combination of taps on the transformer to satisfy 14 different voltages.  7 in the 120v range and 7 in the 240v range.  See the manual transformer section for the different taps avaialble depending on your line voltage.  Since the amp has a single transformer for HV and filament  voltages are both affected  by line voltage.   SInce your line voltage varies greatly it is hard to select any given tap that will be right at all times.  You will have to select a tap that is a compromise and go with it or else get a 20A Variac which will allow you to adjust the line voltage as it changes.  That would be the simple way to do it.  Short of that any tap is a compromise at some point.  Although the plate voltage is not a big deal it is the filament voltage that is important.  Since the seconday filament current is low for one tube you could install a high power rheostat on the secondary filament line and set the filament voltage when needed and settle for whatever plate voltage you have since it is not that critial.   The amp already has a step start built in so you won't need that. 
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N4BBQ
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« Reply #2 on: December 22, 2012, 03:35:02 AM »


Well I'm not Tom, but just the thought of the filament voltage wobbling around on that particular tube would scare me to the point of shipping it back to the US where its safe and running something not so sensitive to such a change in voltage.

Have you measured the change in filament voltage as the line voltage changes?
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W4RS
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« Reply #3 on: December 22, 2012, 05:08:36 AM »

yes i have the manual. and have adjusted the taps for 240v sort of a compromise position.
the power varies from day to day, i do have a 30 amp varac, i could use it? i tried an auto voltage supply, but it cut the amps available down. the 3cx800 is a strong tube, the filitment voltage does worry me, i have several transformers here, also a peter dial for my 8877's spare!
and if i ship it back, then what do i use? dig out my old 4-400? besides i have 4 new 3cx800 here with me. its spares for the alpha, also have extra 8877's. you can't get them here, so i brought them with me.
thanks for the info, i guess i just need to worry about the fil voltage? a seperate trans with a varaic?
jim w4rs, du3/w4rs
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N3QE
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« Reply #4 on: December 22, 2012, 05:49:50 AM »

Especially in broadcast usage with 24x7 operation, filament emission is the limit on tube life, but in ham operation, if the amp is powered down the vast majority of the time, you are unlikely to hit that limit.

While in absolute terms 25V swing from 225 to 250V sounds like a big number, it's about +/-5% around 237.5V, and that's not atypical of many locations. The Ameritron instructions for setting voltage taps looks like it's more worried about overvoltage on the HV supply than about filament, and for typical ham usage that may be a more realistic limit than filament emission life.
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W1QJ
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« Reply #5 on: December 22, 2012, 05:59:01 AM »

The simple fix is to use a high power variac about 20A set the amp up for a voltage on the primary so that all bases are covered with the variac.  You will have to put in a good line voltage monitor so you can adjust the variac input voltage before you turn the amp on.  I see this as the easisest way to do it. 
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K8AXW
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« Reply #6 on: December 22, 2012, 08:53:23 AM »

As an additional thought, you can gang two 10A variacs to give you the 20A.  It's what I did when I built my amp. (It's necessary to use an insulated shaft to connect the two)
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W4RS
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« Reply #7 on: December 22, 2012, 01:26:21 PM »

ok guy's thanks for the info. the amp is not used all the time, i find the du3 gives a few db all by itself. i think the varaic is the way to go for here. thanks everyone for taking your time to answer my question.
73's good dx,
jim du3/w4rs
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KC4MOP
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« Reply #8 on: December 24, 2012, 04:58:20 AM »

I envy you in the Phils. We visited there 3 yrs ago and it was the time of my life. We were in Cebu, my wife's family. I had a temporary DU license and enjoyed 40M. The QRN is outrageous there on 80 and 160. Almost unusable! Fun talking to many folks with accents and other countries. I had a barefoot TS 50. and a homemade dipole at 30 feet high, thanks to Ace Hardware. The MFJ 259 saved me a lot of up and down trials tuning.
Any way back on topic. The Phils has 60hz power and yes, I cringed at the way they distribute power, especially telephone. The Variac would protect your amp. somewhat. It might starve the amp for the current it needs, but you said it is 30 Amp Variac? And DU3 is very hard to connect with on the East Coast. Fairly easy for Left coast Hams. Grey line is my only hope to get into SE Asia.
It would be nice to PM operating comments in the Phils and your situation there.
Fred
« Last Edit: December 24, 2012, 05:02:17 AM by KC4MOP » Logged
KD0REQ
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Posts: 880




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« Reply #9 on: December 24, 2012, 09:32:06 AM »

instead of jury-rigging a few Variacs and manually adjusting power all the time, why not get a constant-voltage transformer (Sola, Topaz, etc.) and put that between what is laughingly called "the line" and your amp?  there should be some floating around, used to be the norm to put one in front of minicomputers.  only issue would be the 50 Hz thing, but they did make 'em.
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AD4U
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« Reply #10 on: December 24, 2012, 11:54:00 AM »

Not Tom either.

The only thing that concerns me is the 50 Hz power.  The transformer MAY NOT be designed to work on 50 Hz.  The transformer may get too hot and burn up.
  
The 225-250 volts should not be an issue.

Dick  AD4U
« Last Edit: December 24, 2012, 12:19:54 PM by AD4U » Logged
KC4MOP
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Posts: 731




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« Reply #11 on: December 24, 2012, 01:43:30 PM »

The Philippines is 60hz.
2 hot wires that give you something like 220 vac. No ground or neutral there. The center tap of the pole transformer is not run to the house. This prevents confusion with the locals not to accidentally wire their panel for 110 vac.
It is very different there and the way they distribute power from the meter to the customer is really scary!!!
Here's some pics of what I saw in my Photobucket.. And some close engineering of house building there too. Stop lights are sometimes manually operated during the "rush hour" or there are power outages or they are optional. Nice place to visit IF YOU LIKE HOT WX!!! Clik on the picture to get a full view.

http://s1263.beta.photobucket.com/user/mopman6/library/Philippine%20Wires#

Get a little laugh.
Fred
« Last Edit: December 24, 2012, 01:47:14 PM by KC4MOP » Logged
W4RS
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Posts: 64




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« Reply #12 on: December 24, 2012, 07:37:05 PM »

hi guy's yes the wireing is a mess. they do not use nicropress sleeves, or wire nuts, they just twist the wire's together, no copper sleeve, nothing but twist it! i have wired my house the us way when i built it, but the line noise is always s5 to s9. i put my own neutral system in with ground rods. not to worry though if they need to work on the line, they just cut the power off!here i use all yaesu, 1000mp, ft890, ft 847. the amp here is a al-800. i worry about the filiment supply with the ac curent here.its a great amp, i have had this for 12 years, bought new, used in us, shipped here, and never been inside it!
yes it warm, but ole aurthur does not come around very much either. my uniform for the year is shorts and a tee shirt.
anyway i will try to post some pictures of the wireing here. those fred u took is considered good!'
jim du3/w4rs
« Last Edit: December 24, 2012, 07:39:36 PM by W4RS » Logged
W4RS
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Posts: 64




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« Reply #13 on: December 24, 2012, 07:44:06 PM »

oh i forgot, seem like that is happening a lot latley. oh well. i have used a auto voltage regulator, but with not good results. it will be fine at 230 volts, but when you key the amp, it drops to 210 or so, then goes to 250 or so trying to catch up. so i just put the tap on 240 and watch the grid!
du3/w4rs jim
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W9PMZ
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« Reply #14 on: December 25, 2012, 02:23:29 AM »

Ahh....  The strung wires on the poles...
That's nothing.  When I go to Thailand on business it is common to see poles with 200 or more wires. A mix of power, cable and phone. Where I have been in Thailand large wind storms are not common. 

It is truly amazing...

73,

Carl - W9PMZ
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