30L-1 Performance and Reliability Improvement
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- Опубликовано: 24 янв 2023
- RF section modification of Collins 30L-1 amplifier to use 2X 572B tubes. These fully reversible modifications result in a higher duty cycle and much-improved reliability.
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Ohmite OY series 100 ohm 2W is also a composition resistor and can be used in the parasitic suppressors; available from stock at DigiKey
Great video. We miss watching your videos .
Thanks Tony! We stopped taking in so much service. I need more time for fun things.
@Tom W8JI Yes.
Let me know when you're ready to go fishing. I will take you to West point lake.
thank you for sharing your knowledge, I'm from Brazil and I will implement these modifications. 73 PY5NC
Outstanding!
2 x 572b i'm going to do this...
Many thanks...
73 de K4WRF
Getting ready to get back on the air after a 10 year layoff and I was wondering about using 572-Bs in my 30L-1. I think that when I put it all to bed I had just put a new set of 811-As in, but it's nice to know I can do the switch when those get used up. Thanks!
Very nice video and after watching this, I bought preowned 30L-1! I am interested in how 30L-1 works with 10, 18 and 24MHz WARC bands. How would be SWR between Transceiver and 30L-1.
I have one that i convert to GI7B tubes but i would like to ask you about the transformer, do you use the stock one or something different?
I can't decide if i will use a bigger external power supply or the stock transformer.
Thanks, Chris
Please tell me how to run this amplifier with only two valves!
How are you getting that output if you're only using two valves? I'm confused because doesn't it use four?
Hello, excellent. I have a 30L-1 with 4 811s, but I know of people that replace the 4 811s y 4 572Bs. Is that ok? Better or worst than 2 572Bs? Also, the mods shown at the begining are still valid is using 4 811s? Thanks
The problem with four tubes like the 811 or 572B is they really should be neutralized for stable operation above 20 MHz. Four tubes have too much feed through capacitance to be stable above ~20 Mhz at 1500Vdc, and this problem is proportionally worse as the anode voltage is increased.
Almost everyone, such as the Heathkit Warrior, the Gonset four-tube 811 amplifier, and the Ameritron four-811 tube, neutralize.
Yaesu in the FL2100 eventually had to add a rather poor implementation of neutralization with just two tubes, but this is because of the voltage. Ameritron, in the AL572 amplifier, has to neutralize the four 572.
If proper stability tests are run on the 30L-1 as-manufactured, it will fail miserably. The Dentron Clipperton will fail also. If the neutralization is removed from the AL811H, Heathkit Warrior, or Gonset, they will miserably fail proper stability tests.
I likely have some videos of this.
With that in mind, and because the 30L-1 amplifier components can never make use of the full power of four 572's, it makes absolutely no sense to run tube cost up and amplifier stability down by adding two extra tubes that will not increase useful output significantly but will significantly decrease stability. Maybe three tubes, not four. Three tubes are on the edge of needing neutralization but are more stable than using four.
I personally would never use four.
@@Jerrythenerdful Tom, very thorough reply. Highly appreciated. I'll start by adding the bracket on the back of the variable cap. It makes a lot of sense and can't see any problems. Thanks.
@@CH_Pechiar I have not documented the electrical advantage by actual measurements because they would be so involved. But if the amplifier is shipped, not having the air variable weight hanging on the front sub-panel, and also having that capacitor supporting some of the tank coils, is reason enough. This is the third 30L-1 we have received with a loose tuning capacitor (out of maybe ten or eleven).
I have documented in other amplifiers that wider and shorter grounding paths result in improved upper-frequency performance. It is almost always the sum of many small things that makes the difference in performance, and not just one single major thing.
@@Jerrythenerdful I have here 2 of mine and the club's one. I'll check in the three of them. I agree that, unless a big design flaw stands out, improvement is the sum of small issues, sometimes related to cost of production at the time.
I have this amplifier with the same modification, but I get the same power output as you are getting with the four valves and you said that your only using two, can you please explain?
The 572 and the 811 both have a good bit of reserve emission, the 572 which has always been oxide coated (by Cetron and from China) and the modern 811 even more than the early 811 tubes.
The real limit in 811 tubes is the anode dissipation of 65 watts, not the emission current or peak power. You need four tubes to get around 260W of dissipation so the anodes do not melt down, not because of emission or peak power limits.
Collins beats the death out of 811 tubes by high voltage. They are up near the 2000-volt area. The Collins is also not neutralized and that makes it unstable on 10M and 15M with four tubes.
Everything gets better by dropping back to two 572B. The amp is more stable, and the dissipation becomes 320 watts with two 572 tubes instead of 260W with four 811s, plus 572s like the nearly 2kV anode a whole lot better than 811 tubes do. Plus everything can be converted back to make it a museum amp instead of a workhorse.
I just got one of these that have the 572s installed. Why don't they put 4 of the 572s in since theres room? Sorry, I'm clueless about this amp.
Read the replies above yours and all will be clear.
Comment connecter un transceiver moderne relais tampon etc? Merci 73
Great video, but need help finding 100 ohm non-inductive resistors, as none available from stackpole?
I have thousands of new RF components. Either email me at my ctrengineeringinc.com email or I think I have them listed on eBay if that listing is still up.
@@Jerrythenerdful hi jerry good day. can i have ebay link of 100ohm resistors and the 16guage wire for parasitic?
My question is do you perhaps have a written upgrade procedure for this mod and a parts list? or better yet can you provide the needed parts.
Thanks
73 de K2AES
There are some papers here
www.ctrengineeringinc.com/download-files-page/