Quest for knowlege

[KB2WIG]

I'm looking to replace my 6L6GCs in my Ranger.

Who would like to comment on substituting  Philips/ECG  6BG6GA for 6L6? 

Michael at SMD has these botels fer a good price.   I cant seem to find anyone who wants to get rid of the '6GCs.

klc

[Tom WA3KLR]

Hi Kevin you ol' rascal,

Very rarely do I order tubes , but I came across this additional (new for me) source recently:

http://www.dougstubes.com/

[w4bfs]

as I recall the plate voltage in the ranger is a little high for 6l6gc .... if you want a plug in replacement use a 1614 or 7027 or 6550 ... the 6bg6 are fb with the plate connection above the chassis ... even a el34 is good .... bias adjustment will be necessary with some ... I would suggest adding a 10 ohm resistor in each cathode to check idle current/balance

[KB2WIG]

Right now, i'm running the plates at 440v; the Design Max is 450V ... yes, its still a bit too high.... the Ranger came with the GCs, so thats whatt I've been running.  The 6550 or the 7027 s are a bit to expen$ive for me. But i'd still like to find a few of them.

The Philips tube is purported to be  "  ABSOLUTELY IDENTICAL to the Sylvania 7027A/6L6GC because they were made  with exactly the same components.  They have the larger 35 watt plates found in only the 7581A/6L6GC or 7027A which means they will work in ANY 6L6 or 7027A application.

http://www.vacuumtubes.com/6l6.html "

On another note, my audio out of the Ranger 2 is 'muddy' and needs more audio.... so i'm plugging in new tubes to see if that will help.

klc

[k4kyv]

The 1614 is just a metal 6L6 that was specially selected from QC tests.  I have seen tubes labelled "1614" on the envelope, but "6L6" engraved on the bakelite base.

[KE6DF]

There are other modern tubes that would probably work.

Sovtek offers 5881WXTs and 6L6WXTs which are Russian military tubes.

The audio types claim both work well at 500 volts with long life.

Of those the 6L6WXTs have higher PD ratings.

They are available new from ebay or amazon.com

Dave

[KA2DZT]

6550s pull more filament current of a 6L6, 1.6 amps each.   Metal 6L6s are rated for about 360 plate volts.

I run 6550s for my single 6146 rig.  650 plate volts.  The 6550s need about 30-35 volts bias.  At that voltage limit the idle current to about 80 ma.

Fred

[KB2WIG]

Thanks fer the input(s).

I'd like to run 6550s like the Tron, but these things sound real expensive...... 


I'd forgotten about the el34 .....  Ive got two 6CA7s in the 500 Watt modulator (that has not been married to the 813 rig). But I'd rather keep them where thay are. They have nice pictures of some kid blowing a horn on 'em.

The price on the 6BG6GA is very, very reasonable......

After replacing the 12ax7 and 12au7, the Ranger still sounds muddy, so the next (easy) thing to do is replace the modders.

klc

[ke7trp]

I have swapped in everything that will fit into my ranger about 5 years back. 

Dont over look the 8417.

C

[Steve - K4HX]

If the rig sounds muddy changing tubes will make little difference. You have some sort of restriction of the mid and/or high frequencies. Fix that before worrying about the modulator tubes.

After replacing the 12ax7 and 12au7, the Ranger still sounds muddy, so the next (easy) thing to do is replace the modders.

klc

[KB2WIG]

" If the rig sounds muddy changing tubes will make little difference. You have some sort of restriction of the mid and/or high frequencies. Fix that before worrying about the modulator tubes."

S, Yer right... I shuda left out the "muddy" part and added the "needs more audio".

klc

[Steve - K4HX]

Ah, mo betta. Can't go wrong with the 6550s.

[KM1H]

The 1614 was a production 6L6 that was tested for RF at 6-8mc, stamped a 1614 and charged more money.

Its just like Eimac and some of their Y* tubes.

If a pair of full emission 6L6's of any flavor cant modulate a Ranger something else is wrong.

Carl

[N4LTA]

One thing to be careful about - and I buy several hundred of these tubes a year - they are not NOS and they do not necessarily meet the old tube specs.

They are guitar amp tubes  - not Russian military tubes as often advertised - they are made in three facilities (two in Russia and one in the the Czech Republic). Some are also from China.

Some  are packaged in a pretty Mullard or Tung Sol box and are essentially the same tube that sells for 50% less not in the pretty box. The box is the only thing they have in common with Mullard or Tung Sol.

The whole guitar amp tube business is a bit scammy and often reject tubes hit the market at low prices. Recently, I could not get any Sovtek 5Y3s because a giant shipment of likely rejects came in and every one had glass chips rattling in them.

I built a  40 meter transmitter with 6L6s last year and was amazed at how the different tubes performed. Some guitar amp tubes were OK and some were awful - the best by far was a 6550 10 years old made by Svetlana before they went out of business. It was better than several NOS 6L6s that I tried.


Pat
N4LTA

[ke7trp]

The 6l6 is rated at 375 volts max. The 1614 is rated at 550.

[KM1H]

And both will hi-pot the same. RCA had to do something to get the big bucks for the 1614 and that was write new specs.

[ke7trp]

All we have to go on is the published data from the manufacturer.  Anything past that is just speculation. 

C

[Opcom]

In all this, the only real complaint is that the sound is muddy. What has been done to find out if the modulator (or mudulator in this case) is actually able to fully modulate the transmitter? Output tubes are seldom responsible for poor sound unless they are bad. Muddy sound is usually a frequency response problem or lack of enough modulation.

Considering the modulator B+ supply is fixed, there can only be so much voltage swing transformed to the RF stage.

Changing tubes won't fix that unless you change to some that can deliver more plate current at lower screen voltages than the stock ones. Then you might get a little more swing towards zero on each plate at the point where the tube is saturated. The so-called "sweep tube" is a good candidate.

The plate dissipation is not as important as cathode current capacity. This is because it is intermittent voice service.

[KB2WIG]

Welll..... I did ask if anyone had comments 'bout the Philips/ECG  6BG6GA.  The price is very gud; I'd like to grab a few if they really are any gud.

I've been told that the % of mudulation was around 50%. When pressed for a critical report, the sound was reported to be muddie.

I swapped the D10-4 leads around so the peaks point the right way, this made a few happier.

I swapped out the 12ax7 and 12au7 and it didn't seem to do too much. I don't know if the mod tubs are gud. I didn't have spares, so I didn't change the mod tubes. I do have a pair of ruskies on the way. (where is Tolly?)

The interesting values for the 6l6gc are, plate 480, screen 290 and the grid -25.   (the book wants 28V, but this keeps the mod curent down around 60)


klc


 

[Steve - K4HX]

The Ranger should modulate at or near 100 percent, even with 6L6s. Might be time to take a critical look with a scope.

[The Slab Bacon]

Rangers quite often sound good right out of the box, and dont have any problems making 100% (or at least real close to it).

Mod resting current and grid biass should reflect AB1 (or AB2) operation with a lot of current swing. (Munky Swing)

Early Rangerz used cathode biass on the modders and the later ones had a biass supply. If ur audio is low and / or distorted, check the cathode resistor for the modders, it may have gone high on you. Or ur schreen supply may be sagging.

As far as mods to the audio section go, there are more recipes than grandpa's BBQ sauce. So a little reverse engineering may be in order.

Sounds like you're due for some voltage and resistance tests........

[KM1H]

All we have to go on is the published data from the manufacturer.  Anything past that is just speculation. 

I tend to believe those that worked with them when new and TCA members.

[KB2WIG]

"Sounds like you're due for some voltage and resistance tests........ "

C     Problem is, they are mostly within 'specs'.  Ergo, the head pounding.  I've got a new pair of 6l6GCs to plug in sat afternoon.  Oh well, its probably something easy and I'm just a bone head who can't see it.


klc


... but I have value

[K5WLF]

... and was amazed at how the different tubes performed. Some guitar amp tubes were OK and some were awful - the best by far was a 6550 10 years old made by Svetlana before they went out of business. It was better than several NOS 6L6s that I tried.

Pat
N4LTA

About 20 years ago, I was working in a recording studio and we were ordering a lot of Russian tubes. Again, this is before Svetlana went out of business. We found that the Sovtek brand tubes had a very "hard" sound to them, and the Svetlanas tended to have a much warmer, 'rounder' sound. So, we tubed up a guitar amp with Sovteks for rock tracks and the Svetlanas were a natural for a country lead.

[KM1H]

Im sure that a careful use of a distortion meter while rebiasing can make any tube sound hard or soft.

In the ham world hard means splatter.