I have a bad roller wheel on a 3K roller inductor. ?Anybody have a replacement or know of a replacement? Lou

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FWIW, CTR Engineering probably has the right one for the job.? Just say'in

Andy? K9ATX

Yes or maybe just get a new fan. They are a not a rare item.

I concur with the others. You should feel a good steady stream of air out the side and whilst it is not loud, you can definitely hear it running.

73, Alek VK6APK

On 20/12/2023 6:08 am, mike repinski via groups.io wrote:

Maybe a little oil?

On Tuesday, December 19, 2023 at 04:59:54 PM EST, Louis Parascondola via groups.io <gudguyham@...> wrote:

It runs at the same speed

On Tuesday, December 19, 2023, 4:16 PM, Bob <W4JFABob@...> wrote:

Does the fan run at the same speed all the time or is the speed thermostatically?controlled?

Bob? W4JFA

On Tue, Dec 19, 2023 at 4:13?PM Louis Parascondola via <Gudguyham=[email protected]> wrote:

You should be able to feel a steady stream of air coming out the side.

On Tuesday, December 19, 2023, 4:07 PM, Bob <W4JFABob@...> wrote:

Hi all,

I'll condense this. A friend just got this AL-80B that had?at one time melted a filament tube pin. The tube socket, the type that the socket is on a circuit board, was burned pretty badly. He got a new ceramic socket. I did what I needed to do to install it including getting the grids grounded, socket properly mounted etc.

Amp works fine now but I noticed the cooling fan is basically silent and seems to barely spin. When holding my hand?on the output?vent I barely feel any air movement. I've never worked on one of these 80B's before so I don't know what's normal, however I feel this isn't moving nearly enuff air.

I know this is hard to put into words?but can anyone give me some kind of idea of how much air can be felt blowing out of the vent?

I know the fan worked normally at one time because the inside of this amp was full of dust etc! Actually it was disgusting! It took me quite a while to get it clean.

Thanks all.

Bob? W4JFA

-- 
"Where the Old Soo crossed the New Soo"
Duplainville, Wisconsin

Web page:  

Youtube Channel:  

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Yes or maybe just get a new fan. They are a not a rare item.

I concur with the others. You should feel a good steady stream of air out the side and whilst it is not loud, you can definitely hear it running.

73, Alek VK6APK

It runs at the same speed

You should be able to feel a steady stream of air coming out the side.

There is a one year on Penta through Penta. ?

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Those are Z5U caps.? They are a poor choice for coupling RF with high current..? No wonder they failed.? Can't believe Alpha would do that. I have repaired several 8410s and I don't even remember those blue caps being used.

They done it; here's the BOM listing:

2 CDX-2221-C 3 C1-2 C7 CAP,CERAMIC DISK,0022uF,6KV 20% VISHAY

Here's the actual parts listing:

CDX-?‐2221-?‐C 3 CAP 2200PF 6K VOLTS 20% .375 L.S. RADIAL

I don't know the vintage of my amp, but it's early enough that it had the VTX-118s in it. I've since bought a pair of 1500s but haven't installed them yet.

?Really should use a cap that is rated for high RF current.? The idea of using six caps for coupling is just bizarre.

I agree; I was flabbergasted when I first saw disc ceramics being used as the plate blocking cap in a high power amplifier in my ALS-800 (in fact, they, too, are blue, just like the Alpha's caps; must be something about blue disc ceramic caps that is attractive like a Siren to amplifier designers? 8-D ); it has a pair of something, I didn't note what they were. I looked in the parts list and schematic but I didn't note whether those are changed for the ALS-800H, which uses a pair of -800A7s for well over legal-limit output power. I doubt they are, though.

Rember: that guy -JI designed the ALS-800/800H, so it's GOTTA be "right", right??? 8-D

? I get that you had them but heck man.? Just order a proper HEC high energy RF cap and be done with it.? The amp will work better and be more reliable.

Perhaps. I've had quite a few of those CDE doorknobs that cracked, though, so I'd probly use one of my few Russian humungously-sized replacements, instead. However, the layout around that area is tight, so there's not much room for a larger cap of any type without lenthening the leads from the plate choke to the input tuning C. I frankly was not very impressed with the layout of the 8410's output section at all. I'm really wondering if the 160m coil's toroids are going to do the same melting-stunt that I've read that K1TTT's Commander HF-2500s have done during a contest.

By the way,? Filament voltage on that 8410 should be checked!? They run very high Fil voltage and if your line voltage hits 250 it could pop those tubes.? I know this because one guy kept losing 4cx1000s.? We found he had high line voltage due to the entire neighborhood being on Solar. In the middle of the day it would hit 260!!? Then Pop the tubes.

I've gotta go do that ASAP; it seems to me that I might be losing a bit of power every time I turn on this thing, which could be from the cathodes boiling away and losing emission. I'm totally off-the-grid here, and presently have to run the Alpha from a 3700 watt Xantrex RS3000M 120VAC inverter, which runs off six paralleled 105 A/hr LiFePO4 batteries, recharged from 2 kW of solar panels. I've measured the inverter's output at 124VAC under 800VA load but that drops to about 118 under 2 kVA load at the AC outlet. Obviously, that is still too high for the Alpha since it spends the majority of its time just idling. But there's no way to turn it down unless I get out my 2.4 kVA variac. That Alpha is a power hog, though... I can't usually run a pileup longer than a few hours before the batteries drop below 50% State-Of-Charge, which, on a cloudy day, might get back up into the high 80s by sundown the next day. I've had it down to 14% (right after the recent ARRL 160m contest) but that day was bright and sunny, so the batts got recharged back to about 75% by sundown.

73,

Steve K0XP

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Hopefully someone will help me out.? I have 3? LD-4513 Traveling Wave Tube amplifiers.? These I think operate around 2400MHz.? I would like to get some information on them.? A search on Google doesn't seem to come up with anything on this particular device.

73, Clint, VE3CMQ

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On Sun, Dec 10, 2023 at 02:46 PM, Dave wrote:

Hello Group, I could use your help!
Looking to pick up a 3-500ZG replacement for my AL-80B.? My choices are:
RF Parts Company: 3-500ZG (6-month warranty). 250$ (China)
DX Engineering: Penta Labs RF Vacuum Tube 3-500ZG (no warranty listed). 300$ (assume China?)
DX Engineering:?Ameritron 3-500Z Replacement Power Tube (All products manufactured by Ameritron have a one-year limited warranty) 360$ (assume China?).
Both vendors have always been reliable for me so my question:
Is the Ameritron tube worth the additional $$ or is it branding?
Is the Penta Tube?worth the additional $$
What would be the best replacement?
(sorry for writing a novel)
Thanks in advance!
73
K5AKM - Dave

Howdy Dave,

Just as an FYI, Henry Radio (yes, they still sell stuff...) has new "Greenstone" 3-500C tubes for sale. They are Chinese (of course), but seem okay, work well, and are "guaranteed"...

I purchased a couple of these a long while back, and they are still running strong. I've run the pair in both my Drake L-4B (that's what they're in now), as well as my Henry 3-KA. They work great, and the price was (I thought) quite reasonable.

Anyway, just another option to consider.

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The AL-80B? does not use real deal plate block caps, but a pair of disc caps.? ?The disc caps are not RF rated either.? ? Any plate block cap needs to have enough pf? so it's reactance (XC)? is 5% ( or less) at 1.8 mhz.? There is barely any RF current flowing through a plate blocker on 160m...... but the current through em progressively increases as freq increases.

As a reminder: I just had to replace all three of the 2200 pF/6 kV disc plate blocking caps on my Alpha 8410:

But there was no smell when these blew; they just shorted the high voltage, causing a plate current fault which, fortunately, shut down my amp before any catastrophic damage occurred. These caps apparently shorted out one by one, cracking independently as each broke down from the high power and voltage (plate voltage in my 8410 is just under 2900VDC). The total capacitance was originally 3 x 2200 pF = 6600 pF; I replaced them with a set of six 1000 pF/10 kV discs I bought a few years back, but unfortunately, I didn't think to take a pic of the installation. However, note that the way the caps are arranged above, the "outside" of one cap is directly adjacent to the "inside" of another, which means you have the full plate voltage between the capacitors. To make certain there would be no flashover between capacitors, I therefore spread the replacement caps out evenly but kept the leads all twisted together as shown above and as short as possible so as to minimize any additional inductance. So far, so good, on my Alpha 8410, which has a pair of 4CX1000As in parallel, far more than what a pair of 3-500s will do.

>Correct component would be a pair of HEC? 500 pf HT-50/58,? 7.5 kv? ceramic doorknob caps in parallel .?

> You can buy those cheap, directly from mfj / Ameritron.? That's what's used in the Ameritron?

>AL-1500 / AL-1200 / AL-82.

If I was not in a hurry to get my Alpha back on the air before I missed out on another pileup, I would have ordered HECs instead of using the disc ceramic caps. In the olden days, pre-COVID and pre-Ukraine, you could buy doorknobs of all sizes and voltages from Russia or even ND2X at dirt-cheap prices and receive them within several weeks (with all sorts of strange and exotic Russian stamps on the boxes). Nowadays, that's neither so easy nor cheap? 8-(

..... all 30 of em test to 15 kv? ( which is the limit of my hi-pot tester that I bought last year from CTR engineering).

High voltage hi-potters are very easy to make and relatively-cheap to boot; just search epay for 10+ kV variable power supplies, perhaps using search terms such as "neon sign power supply", "Tesla coil power supply", or the like. No longer do you need to spend el mucho buxos for shipping a heavy, old, surplus neon sign transformer; now, the Chinese are selling small, adjustable high voltage power supplies, completely self-contained on a single PC board. I bought one, which consists of a small PC board with the circuit on it and an onboard transformer, for about $40 a couple years ago; it operates from 12 volts DC. I tested and evaluated the board, then designed and built my own hi-potter. It's fully adjustable from a few hundred volts to over 10 kV, and my hi-potter includes both a voltmeter as well as a leakage current meter, both mounted on and behind plexiglass to prevent me from touching them while in operation. It actually goes to at least 11 kV and will provide a few tens of microamperes current, which is as much as you want to have arcing around within a leaking tube, and far more than enough to tell whether it's good or not. It's such a small and cute little gadget that it's difficult to remember that it's more than capable of killing me if I'm not careful with it!

73,

Steve K0XP

The AL-80B? does not use real deal plate block caps, but a pair of disc caps.? ?The disc caps are not RF rated either.? ? Any plate block cap needs to have enough pf? so it's reactance (XC)? is 5% ( or less) at 1.8 mhz.? There is barely any RF current flowing through a plate blocker on 160m...... but the current through em progressively increases as freq increases.? ? On 10m, there is loads of RF current through a plate blocker.? ?Reason is.... on 160m, the tube C (anode to grid) is directly in parallel with the C1 tune cap.? ?They are in parallel...via the plate block cap? between em.? ?On 160m, the tube C makes up a fraction of the total required C1 value.? On 10m, the tube C makes up most of the C1 tune C.? ?Think of the C1? tune cap as being a tiny variable padder, in parallel? with the tube C.?

?

Correct component would be a pair of HEC? 500 pf HT-50/58,? 7.5 kv? ceramic doorknob caps in parallel .? You can buy those cheap, directly from mfj / Ameritron.? That's what's used in the Ameritron AL-1500 / AL-1200 / AL-82.?

?

What else that will work is higher V rated disc caps.? Typ the higher V rated disc caps? will also handle more RF current.? I just finished testing a mess of new? .01uf ( 10,000 pf)? @ 30 kv? disc caps.? These are HUGE things at 1.125" diam x? 7/16" thick.? ?These are the blue chinese disc caps that I bought from their ebay store.? ?They tested between 9200-9700 pf..... and all 30 of em test to 15 kv? ( which is the limit of my hi-pot tester that I bought last year from CTR engineering).? ?These things handle stupid amounts of RF current.? ?They come in 10/20/30 kv rated.? They are so cheap, and shipping was cheap, so bought 30 of em.? ?So far, so good.? I can't blow em up.?

Scott

My 922 did exactly what you're describing then I had a plate short.? Plate blocking cap had let go... Cracked and got to ground.? That was the smell. It was only on specific bands too.? I reckon you look for hot spots there.

Aaron

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Jim,