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Old sweep tube getter

5

543_Dallas

Sr. Member
Jul 25, 2011
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What are you guys doing with NOS sweep tubes from the 60s? Do you let the heater run for an extended period of time or are these more like a 3-500z where running the heater only doesn't get the getter material hot enough.

The only old tubes I've dealt with have been the Russian tubes. With those I ran the heater for a solid 24hrs before turning on the HV.
 

I ended up letting the filament run for a few hours then put them to work. One dud out of seven isn't too bad.
 
ExitThirteen said:
What were the numbers on the tubes?

~Cheers~
Click to expand...

36kd6. I reworked a golden eagle 1k for a friend. All the tubes were junk and I used what I could get cheap. It now has two 30mb6's driving six 36kd6's.

I had never even used one of these old sweep tube amps before he brought this over. I wasn't really sure what to expect. The only glass tubes I own are 3-500z's. It's normal for the anodes in them to glow a dull red but the locals tell me that's bad for a sweep tube...I don't have a clue as to what is normal operation for these things.

It's up and running now. There are still some things that need to be cleaned up and the meters work intermittently...well, they work occasionally. It's had a lot of hands in it over the years.
 
Ahh yes, I am familiar with those tubes and amps. The locals are correct when they say that red plates on sweep tubes are bad... the plates are paper thin and will literally burn holes thru them. Hopefully, your friend uses it primarily for SSB and not AM. :p


~Cheers~
 
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Unfortunately he's an AM guy and long winded. I told him I'd run it around 125 carrier and 600 -700 pep to save the tubes. Since the plates are like rice paper even that may be too much for them. I'm really hoping he will sell this thing and find something that suits him better.

How much power fluctuation is normal for these things as they warm up? When the tubes are warm it's doing 150 carrier and about 1000 pep. Leave it idling and come back in 15 minutes you get 75 watts carrier and 750 pep until things warm up again. Is that acceptable for something with 8 tubes in?
 
Yeah, you will see some variance considering that there is a fan in the amp. The variance seems a little bit excessive, but it's not uncommon to see the variance itself. Normal variation is about 100W or so PEP, 30-40W deadkey.

If he's long winded on AM and he runs it all the time, prepare to have the amp back to you in a few years or so... the tubes will go flat fairly quickly. Nothing is harder on a sweep tube than AM and FM modes.

At 150W deadkey, he's running the tubes around 55% of their max plate dissipation the whole time he's keyed up. Doesn't seem like a lot on paper, but then again, a sweep tube isn't designed to take and make RF either.


~Cheers~
 
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In the early 70's me and a high school buddy used to build three-tube amps from parts and 6lq6 sweep tubes we could find in junked TV sets at the local dumps. 4 watts in and about 125 out and we'd get those tubes to glow! You could heat a 10x10 room in the winter with little effort. Pop a tube, which happened frequently, just run to the dump and find another TV or buy a new tube from Radio Shack fro $3.50.
 
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I ran a pair of 6KD6's in a home brew amp which are the same as 36KD6 but with a different filament voltage. There were times the plates were the same colour as the filaments. LOL They worked well for sweep tubes.
 
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One or both driver tubes was causing the large variance in power. Both were marked around 85%. I put in 2 different driver tubes and it only drops down to 100 watts carrier from 150 when it cools down.

When I got this thing it had 20lf6 tubes in it. I checked the filament voltage and found 28v. The complaint was that it kept blowing tubes, blowing fuses, and making strange noises after the fuse was wrapped in foil. There was also mention of a fireball coming out the front when one of the filter caps let go. A couple tubes had been so hot the sides were sucked in. Some of the filament leads in the tubes had been so hot they were drooping.

The resistors for the parasitic suppressors were way out of tolerance, they measured from 47 to 125 ohms. The diodes on the HV board were crispy looking and not all the same. It's been an interesting experience but I'm not going to make a habit of doing this.
 
Good job on getting the old tube amp running again (y)

Ha, I hear a few locals running there stuff MAXED out, then it burns out and they wonder why. They get the old sweep tube amps because they're generally much cheaper than the newer transistor amps. Knowledgeable operators let them go while holding onto the transistor (pill) amps, myself included;)

Actually, I feel for the equipment, but it does make for some good CB drama.
 
RatsoW8 said:
In the early 70's me and a high school buddy used to build three-tube amps from parts and 6lq6 sweep tubes we could find in junked TV sets at the local dumps. 4 watts in and about 125 out and we'd get those tubes to glow! You could heat a 10x10 room in the winter with little effort. Pop a tube, which happened frequently, just run to the dump and find another TV or buy a new tube from Radio Shack fro $3.50.
Click to expand...

I have an amp from 1969, a WRL 6706 that has a pair of sweep tubes inside.
 

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