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Author Topic: phantom 12 tube 6LQ6 500 watt prob  (Read 10962 times)
UNIT503
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Posts: 2




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« on: July 01, 2003, 01:54:38 AM »

i bought this amp in my home town to give as a gift to my ham friend. it powered up fine there. i put it in the trunk and took it home  about 100 mi.
i went to hook it to power to check it one last time before i gave it to him. no power to the fan, tubes  nothing. there is power  i checked the power inputs ,
fuse is fine. there is a spot on the back where it looks like a car fuse would fit.(black rubber holder) if i put a fuse in it and hit power nothing. with a fuse in it hit power then filter it will blow my power srrip...any ideas.
thanks
scott
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UNIT503
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Posts: 2




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« Reply #1 on: July 01, 2003, 10:47:47 AM »

im sorry it 's a 10 tube not a 12 and i found a huge ceramic cap coming off the tune knob that has a black bubble on it. but i don't think this would shut it totally off
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KO4NR
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Posts: 117




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« Reply #2 on: July 01, 2003, 01:21:11 PM »

Not trying to be a wise cracker or something but you should get someone that knows basic electrical troubleshooting to look at it.  No power is a very simple problem to troubleshoot but can also be very dangerous!!  It sounds like a bad connection or power switch to me.

Many of the 6LQ6 sweep tube amps are junk so use good judgement before buying.  I hope you got it cheap.

Be careful!!  Your "Ham" friend could probably fix it if he does any homebrewing at all.
73,
Bill
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KE4ZHN
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Posts: 140




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« Reply #3 on: July 11, 2003, 05:36:40 PM »

Not trying to be a wise guy or anything here, but your ham friend probably wouldnt be caught dead running one of these on the amateur bands! First of all, finding the 6LQ6 sweep tubes this monster uses is nearly impossible, and when you do find any at all, be prepared to pay a left cahoney for them! Plus, these are dirty overdriven trashy amps designed for big power with low exciter drive, meaning they were built for CB use. Sure, many of the older models have a bandswitch on them, but this was only so they could sell them as amateur amps without the FCC shutting them down. As I recall, D&A manufacturing in Scottsbluff Nebraska got shut down several times by the FCC and finally went under, probably from being fined to death. So, for a ham to operate one of these things, he would have to either bypass the drive stage of this thing (meaning 4 of the 10 tubes would be useless!) or run 5-10 watts of RF drive from his rig to excite this thing. Then he will proceed to be run off the bands wherever he may try to operate this thing due to the splatter and crappy raspy audio these distortion boxes generate! TV sweep tubes, never were, and never will be good for linear amplifiers! They were only used as a cheap alternative to REAL transmitting tubes and they fail quite miserably in this regard. Sure, a few amateur amps used them, but they never really made it big in the amatuer world due to the tubes limitations, and the fact that the tubes just cant take the abuse of linear service. And since TV sets havent used sweep tubes in many years, they are all but gone now. Do you and your friend a favor, fix this thing and sell it! Preferably to a CB`er in a foreign country so we dont have to listen to the splatter from this mess! These amps have terrible IMD specs and the drive stage is way too much for the 6 tubes in the final stage. The result is a final stage so overdriven that no amount of tweaking makes one of these sound good and run clean. Keep in mind that power means nothing if its not CLEAN power! Besides, this amp on its best day will only do around 500 watts pep out and most any decent amateur amp will blow its doors off power wise, and clean wise! 4 811`s at $20 apiece will blow all 10 of those sweepers away and sound much better doing it. Not to mention you wont have to worry about your neighbors coming by your house to lynch you for the TVI that those dirty junk amps generate!
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W9GB
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« Reply #4 on: August 09, 2003, 11:10:06 AM »

Scott -

I am sorry to hear that you have purchased this 500 watt unit - I just hope it was less than what the parts are worth.  A bit of education: The 6LQ6 sweep tube (used in tube based televisions) is no longer manufactured (US mfg stopped in the 1980s).
The cost to replace these tubes is more than some of the used high quality amatuer radio amplifiers on eBay (and at hamfests)

US Amplifier still performs repairs on these boatanchors (note his web page is "ba") and has converted a few to Russian or Yugoslavian sweep tubes (which are still produced)
http://www.freewebs.com/skunkworks/ba.htm

Actually if the tubes are good - I would sell the 6LQ6 tubes (look at the nice prices on eBay for used)Lawrence Summerrow, W4EMF has details for high quality Russian surplus ceramic tubes (usually less than $35).  Here is a GLA-1000 conversion (which used 4 6LQ6 tubes)
http://www.nd2x.net/w4emf-GLA.html

w9gb
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KC9SZU
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« Reply #5 on: December 10, 2005, 10:45:03 AM »

i'm sorry that you fools believe that sweep tube are junk, but you're wrong. and sure they are expensive, but i have an old 1 driving 3 6lf6 H.E.C. Holden Electronics Corp. amplifier, and yes it does work fine on 11 meter, but it also works great on 10-12 meter also with excellent results. thing will put out between 150-200 watts, ofcourse a little more if i overdrive it. 900 volts, just over 500mA, and grounded grids and my spurs are far less than some of these palomar and texas star transistorized amps. that's what's trash, but even then with a good filter anything can be cleaned up and corrected. and that there being the key... though you'll have little less power... spurs and harmonics will be attenuated. and dont be surprised if your friend does too like sweep tubes and their amplifiers. just because a few here are too cheap and not in to doing things the old way or the hard way, doesnt mean he wouldn't or isnt.
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K5MO
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« Reply #6 on: December 03, 2007, 04:58:31 PM »

This is an old thread but....

These amps ARE junk...lousy bias so SSB sound lousy and splatters buckshot all over the band, poor cooling , ridiculous layouts. Plus, with each sweep tube costing the same as a Russian GI7B external anode triode, it's ridiculously expensive
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KB4USB
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« Reply #7 on: December 24, 2009, 06:28:14 PM »

I use a D & A Raider for 20/15/17m and get between300-400 watts from 4-6KV6a's and a D & A Maverick using 4-6JG6's and 4-6LQ6's and have gotten great "clean" reports on SSB and no neigthbor complaints... I like these amps as a SSB amp...
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W8JI
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« Reply #8 on: December 25, 2009, 01:25:05 AM »

I use a D & A Raider for 20/15/17m and get between300-400 watts from 4-6KV6a's and a D & A Maverick using 4-6JG6's and 4-6LQ6's and have gotten great "clean" reports on SSB and no neigthbor complaints... I like these amps as a SSB amp...

The only reason you are getting clean signal reports is the people listening to them either don't know how to listen for splatter or have some limitation like local noise or weak levels preventing them from hearing splatter, or they simply want to be nice guys.

The future of weak signal operation on 10 meters is bleak because of the CB junk making its way into ham use.

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KJ4LCM
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Posts: 41




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« Reply #9 on: December 25, 2009, 06:25:43 AM »

I guess that my question here would be that if sweep tubes are so bad, than how did so many REAL ham rigs use them with no problems. IE: ft101 series. These are some of the BEST am rigs from the later years. Not being a SA, just curious.( I use an SB200)LOL.

Merry Christmas Everyone.

Dale
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NB3O
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Posts: 49




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« Reply #10 on: December 25, 2009, 08:58:42 AM »

"than how did so many REAL ham rigs use them with no problems."

Many of us new about their consequences and chose to either change them out (Drake T4X to 6146 conversion), run CW only, or splatter our ham neighbors.

Those of us running the many-sweep-tube amps used them as a platform to retrofit other transmitting tubes or scrapped them for parts to prevent them from showing up somewhere between 25 and 30 MHz.
 
Some of the more benevolent hams assisted newly minted Generals (like myself) to convert them without killing ourselves.

Some of the other locals who chose to put them on 10 meter SSB with disregard generally suffered "other" undesirable consequences.......
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AD6KA
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« Reply #11 on: December 25, 2009, 02:15:39 PM »

>but even then with a good filter anything can be >cleaned up and corrected.

Um, actually that's not true. A low pass filter will not clean up IMD.
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W8JI
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« Reply #12 on: December 25, 2009, 02:32:21 PM »

I guess that my question here would be that if sweep tubes are so bad, than how did so many REAL ham rigs use them with no problems. IE: ft101 series. These are some of the BEST am rigs from the later years. Not being a SA, just curious.( I use an SB200)LOL.

One of the major differences is the basic design. The FT101 and the Drake T4 series use only TWO tubes in grounded cathode with stiff screen and HV supplies. The tubes were neutralized to eliminate unwanted feedback. Drake actually selected a tube that has very good RF characteristics. Short leads, multiple leads on critical elements, modest internal capacitance, and not too bad linearity when in AB1 grid-driven service.

Contrast that to a typical CB amplifier. The CB junk uses multiple tubes in parallel, sometimes as many as 8 tubes in one stage!  Generally the grids are on an intentionally loose supply voltage to make the amplifier "swing". There are often mismatched stages in tandem, RF bypassing is poor, and the supplies often have no bleeders at all making them a death trap. Sometimes LV relays are used to switch B+, tank values are all off, and they are built to drive with a few watts without regard to stability or odd-order IMD performance. Everything that makes them an attractive CB amplifier, like non-linearity that makes the have extreme positive carrier shift on AM (lots of swing), makes them total crap for Amateur service.

Contrary to what people might thing, a filter cannot clean up odd-order IM products or non-linear transfer functions that are often intentionally designed into the CB stuff.

Merry Christmas,
Tom








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N3OQD
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« Reply #13 on: December 25, 2009, 04:14:06 PM »

One's money is much, much better spent on the entry level Ameritron AL-811 than any of the sweep tube amps around.  The only sweep tube amp that I know was reasonably decent was the Ameritron AL-84.  It uses four tubes in parallel.  If my memory serves me, sweep tubes are good for about 75 watts or so (of comfortable) output PEP per tube in a parallel circuit (excluding any drivers or pre-driver stages).  33 watts of plate dissapation and do the math.  Even so, without a mod of some sort to utilize current Russian or European EL-905's, Sweep tubes, these amps are just not cost effective in the long run at all.  As been stated repeatedly on this forum page, the vast majority of sweep amps ARE junk and easly proven with a spectrum analizer.  Just as a small LOUD audio amp does not equate to quailty high fidelity audio, neither does a LOUD "linear" amp equate to a clean signal out.  This is the mindset of most CB'ers.  And since the majority rule there, then this is accepted as the common so called "fact".  Now, in retrospect, if your on a real buget, you could find a Heathkit SB-200 for about 300 or so dollars, purchase and have all the Harbach mods installed and WALA you would have a nice amp good for a solid 600 or so watts output and the two 572b tubes are cheaper than a pair of NOS sweeps AND are in current production.  As for the Phantom, I would strip it for parts and sell the sweeps to recover my losses. PS: W8JI specializes in this area and in this, Merry Christmas.
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KM3F
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« Reply #14 on: December 26, 2009, 02:14:37 AM »

Those of you who are defending the use of sweep tube amplifiers are in need of some education you are missing.
1. Some years back the FCC tightened up the Harmonic and IMD specs on all radios and amplifiers.
2. The amps being produced at that time and before that time could no longer be made to pass the new rules so they were discontinued.
3. Today there are no amplifiers authorized using any tubes but those that will produce a low enough IMD to meet the FCC standards as well as having harmonic outputs reduced.
4. The sweep tubes were never designed for RF service because of their non linearity of operation that produced Inter Modulation Distortion (IMD).
5. IMD in not able to be filtered because it is the results of non linear operation within the tube/device and is not a harmonic per sey.
So harmonic output in not the real reason, it is IMD that can't be controlled.
Look at the list of mfgers that are allowed to market their amplifiers in this country and you will find non that offer a product that does not meet current regulations.
When your told the old amps are dirty the above is the reason.
And NO you cannot hear IMD unless you are familuar with what, where and to check for it.
Just saying an amp sounds good dosen't cut it.
99% of all the amplifiers today use tubes that can meet the present spec such as the 811, 572, 3-500 and some ceramic types.
THERE IS A REASON WHY.
You have no valid argument for using an old type amplifier in this day and age.
As for solid state amplifiers, they are subject to the same rules as the tube amps and must be designd to meet them the same.
Using a cheap CB design will produce a dirty signal the same as an old tube amp so no good hear either.
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