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 on: Today at 02:06:53 AM 
Started by W9ZSL - Last post by WZ1M
Is the filament transformer a "REAL" 120 vac primary? If its a 110, 115 or a 117 vac primary, your going to be running closer to 7 vac on the filaments. Not to worry on the filament side but if the transformer is not heavy enough, it will saturate and cause high current draw on the primary. If your house line voltage is running near 124 vac, which many now do, your looking at close to 7.5 vac filament.
Just my confusing two cents.

 on: Yesterday at 11:23:11 PM 
Started by k7mdo - Last post by k7mdo
Well, yes, the tube was checkable  as other similar based tubes but without a figure of merit the only thing I could say was that of about the ten on hand, none checked significantly better or worse than any other...  Thus I think we can assume all are good, but that is it... 

That was good enough for the fellow that asked me to check them...

In my history of collecting tubes and filament transformers i can't recall a 20 volt filament before and I wonder if in the TV7 checker the 20 volt setting has ever been used?  It did seem like the meter reflection came closer to the acceptable by turning up the filament setting to a little higher voltage!  Next time I have the cover off i will check it's accuracy...  Should have done it first but got lazy.  Too many projects.

Thanks for the ideas, 73,Tom

 on: Yesterday at 11:04:36 PM 
Started by W8ACR - Last post by KB2WIG

Rockwell now has the patents and the development.

Rockwell Retro Encabulator .



 on: Yesterday at 08:03:24 PM 
Started by W8ACR - Last post by WD4DMZ
Turbo Encabulator

Hahah. As an aside, the turboencabulator was in the General Electric Company Master Handbook back in the 50s and 60s. It was created as a joke to see if it would be published by Schenectady in the handbook. Have not heard that term in decades. Somewhere around the piles of old manuals in the shed I have a copy of the specs. As I recall the picture was some sort of amplidyne or small MG set.


 on: Yesterday at 07:38:49 PM 
Started by W9ZSL - Last post by DMOD
The Filament supply schematic below should suffice for a grid-driven 807 Linear Amplifier.

No need to complicate things.

Phil - AC0OB

 on: Yesterday at 06:46:52 PM 
Started by KU8L - Last post by DMOD
The 2K-Classic was a free-standing Pedestal unit.

The 2KD-Classic was a Desktop unit that had a different metering setup.

On the 2KD-Classic because there was no need for wiring to enter from the bottom part of a pedestal, since everything was contained in the same level of the KD desktop, similar to an Ameritron AL-82.

As the metering schematic states, there is no TB101 on the 2KD-Classic because all wiring runs are on the same level from the metering to the PS. In addition, protection diodes are across the IP and Ig/Vs meters.

For the KD version, the B- rail still connects to the cathode of D107.

I think what happened was the guy drawing the KD metering circuit had not consulted the other power supply schematics because R121, for example, is a 20k 100W bleeder resistor and I don't see that it would make sense here. Other resistor values aren't recorded or listed.

I wish I had captured/drawn the KD Metering circuit the last time I had one in for upgrades, but the first schematic is what I think they meant, and the second schematic is what I think it "should be, " with the caveat the Ip meters had the same meter specs.

I would urge you to draw the metering circuit and record component values and post them here for future reference.

Phil - AC0OB

 on: Yesterday at 02:39:32 PM 
Started by WZ1M - Last post by WZ1M
Up for sale are some real nice, working, Collins gear.
KWM-2 with manual, nice shape and works well...$700.00
PM-2 power supply, goes on the back of the KWM-2, with manual, nice shape...$170.00
30L-1, RF amplifier, with manual, also nice shape...$700.00
These units were running just a few days ago with excellent reports.
Sorry, will not ship. Pick up only, Orono, Maine.
Sorry for the blurry picture.

 on: Yesterday at 12:57:13 PM 
Started by W9ZSL - Last post by KA2DZT
You can use your filament xfmr with the CT, just don't use the CT.  Leave the CT taped off and follow the schematic you posted.  Filament wiring is usually the easiest part of any tube project and normally doesn't require 20 questions.  Wake us back up when you get to the harder parts of this amplifier project Grin


 on: Yesterday at 12:12:22 PM 
Started by N2GC - Last post by N2GC
Collins 550A-1 AM broadcast transmitter for sale $1000.00 obo pickup only in Long Island, NY. The unit was aquired partially taken apart probably for transport purposes. It seems to be intact except that it is missing all of the heavy HV transformers that go in the bottom bay of the rack. The 4-250s were replaced by 4-400As. The cabinet is in good shape though it does have scratches and paint chipping in spots. Many pictures available upon request.

Mike N2GC

 on: Yesterday at 11:30:02 AM 
Started by W9ZSL - Last post by DMOD
My xfmr is 6.3 VCT and I'd like to ground the center tap and then run each side of the secondary to the tubes.

It won't work. A 6.3VAC center tapped secondary has 3.15VAC on either side of center tap. Your filaments would be running at 3.15VAC each.

Get a 12.6VAC CT transformer and wire according to my schematic #1.

Phil - AC0OB

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