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Collins 30L1 problem




 
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Author Topic: Collins 30L1 problem  (Read 24642 times)
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WA1GFZ
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« Reply #25 on: February 07, 2005, 12:40:36 PM »

the tubes light up so the choke is probably good.
It sounds like RF does not pass to the tubes.  
How about the relays. I never saw and tube resting currents?
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xe1yzy
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« Reply #26 on: February 07, 2005, 01:41:47 PM »

Quote from: WA1GFZ
the tubes light up so the choke is probably good.
It sounds like RF does not pass to the tubes.  
How about the relays. I never saw and tube resting currents?


Ok...

Well, I made an RF test of the filament choke (out of the amp.) and they let pass trough the RF, maybe the core is broke , overheated or something, I made a new ferrite core choke with a FT-200 and 15 turns of bifiliar wire, they works great  @7.5mH.

Im test again the amplifier and nothing happens, well not more high SWR between the exiter and the amplifier...but still dosent works

I found and article about the 30L1 in Svetlana homepage, the article talks about a filament fuse, made with a number 30 wire in the central tap ground return of the filament winding of T1!!. and that "fuse" its not show in the schematics dammit!  with that fuse broke the tubes light up, but they dont have any ground return.

I going to check that " f@#!%#" fuse this afternoon and see what happens!

Thanks a lot for your support Francis 73's
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WA1GFZ
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« Reply #27 on: February 07, 2005, 01:44:06 PM »

open center tap or fuse would do it.
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xe1yzy
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« Reply #28 on: February 07, 2005, 05:58:36 PM »

It's Fixed!!

Finally the problem was fixed, the problem was the filament choke, and a burned kind of " fuse" made with #30 wire, conected to the central tap ground return of filament winding in T1 not showed in the schematics!!! :-x

Collins 30L1 ownwers be aware!, this amp is designed to work on 110V, not 125V! that make the plate voltage increase 1990 to 2000V, that makes the power disipation go to high 278W or so, the maximun disipation is 180W per tube

Many thanks to all, you are great folks!
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K1JJ
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« Reply #29 on: February 07, 2005, 06:17:18 PM »

Excellent!

Your detective clue was that there was no resting current when keyed.  Over the years I've built many linears and if keyed and there is no idle, it was the PTT internal relay or whatever connection takes the fil CT to gnd.

ie, there's nothing else to prevent a good triode from idling once the fils are running and there is HV.  A continuity check from fil to ground when the unit was keyed wud have shown this.

Of course, hindsight is 20-20 and they hid that "fuse" real well on you...  :lol:

73,
T
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w3jn
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« Reply #30 on: February 07, 2005, 06:36:03 PM »

Outstanding, Pedro!  There's nothing like the feeling of kicking a tough dog's ass (ano de perro fuerte?).  

Good info on the CT "fuse".  I never would have guessed.  That bears posting to the CCA group if you're a member!

73 John
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WA1GFZ
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« Reply #31 on: February 07, 2005, 07:55:57 PM »

VERY GOOD.  hey Tom do you still use the fusable link with a strand of RG8 shield like the old PDM rig.  (a cat story here)

I use a center tap fuse in my linear with Bypass caps on it to keep RF
from blowing it.  A resistor across it will also limit the cathode voltage to cut off. I use 50 Kohms 10 watts.
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K1JJ
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« Reply #32 on: February 07, 2005, 08:04:18 PM »

Quote from: WA1GFZ
VERY GOOD.  hey Tom do you still use the fusable link with a strand of RG8 shield like the old PDM rig.  (a cat story here)



Yes, Franz, I use a single tiny strand from RG/8U coax stretched between insulators on the output of the big HV supply here.

It has burned many times before the breaker, possibly saving the solid state rectifiers.  Most of the time it's when I forget to take the shorting cable off of the transmitter when done working...

Yes, I agree that fil CT keying is the best way to key ANY amplifier, linear, class C, modulator or RF.

T
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WA1GFZ
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« Reply #33 on: February 07, 2005, 08:09:25 PM »

Tom Vu had a section of shield on the sill above the power supply and he would pull out a strand when he needed to replace the fusable link.
Then a cat walked along the sill and shoved in down on to the supply.
I think old Yaz left claw marks overhead from the bang.
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xe1yzy
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« Reply #34 on: February 07, 2005, 08:12:07 PM »

Quote from: w3jn
Outstanding, Pedro!  There's nothing like the feeling of kicking a tough dog's ass (ano de perro fuerte?).  

Good info on the CT "fuse".  I never would have guessed.  That bears posting to the CCA group if you're a member!

73 John


Dear Mr. Johny Novice Esquire, the correct translation is " Como patearle el culo a un perro bravo"  but I like the way you are thinking  :mrgreen:
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af1z
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« Reply #35 on: May 20, 2020, 08:08:06 AM »

After I spent a week of spare time trying to fix a 30l-1, Came across this thread. Its 15 years old-- that little s o b #30 fuse , not shown on the schematic, was vaporized. Even looking directly at the terminal strip, its hard to see. 60 years, still learning! Mark. AF1Z
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« Reply #36 on: May 21, 2020, 09:59:34 AM »

good going and sleuthing ...now just one more thing .....  your line voltage sounds high since the B+ is so high ... you will need to reduce the filament voltage to 6.3 Vac (I'll bet its at 7 volts or more) or your fil life will be greatly reduced.  I used a couple of  .15 ohm 20W power resistors ... these are usually anodized finned things that bolt down to the chassis in series before the choke ... worked fb
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