11-02-2011, 06:49 PM
Well, today brought some good news - the "Lowboy" just came to life.
I received the Mouser package with resistors, and changed all 5 of them, plus restoring the 1.4Kohm open section of the multi-tap voltage divider bu just soldering 3W 1.4K resistors in parallel.
Now, I started touching anodes (plates) and once I touched the plate of the 24 detector tube, I heard a loud 60Hz buzz from the speaker, so I knew my Audio amp works, and my speaker works.
Then I took off the screen (the one protecting the tubes in HF section) and was able to tune to some buzzes and whistles. Then I heard a faint signal.
Then I swapped couple of tubes places and the reception became very loud, and when i connected the GND wire to the actual Earth GND, it became even louder. I was able to achieve a nice low distortion sound by reducing the volume. At high volume it would go into excitation.
I think one of the three 24 tubes is subpar, but I lack the tester, and a Hickok in a working state is over 300 bucks, so I will start from buying one extra 24 and trying to see if it makes things better.
So far only one station is received clearly and is loud.
The last thing is (have to find out why - thoughts welcome) - when replacing the protection screen over the 24 tubes, I lose the reception almost completely - I can barely hear that station that comes in very well without the screen.
And another question (about the voltage chart you guys gave me the link for):
I am not sure, on the voltage chart, what those figures on top of the tubes mean. The plate voltages etc are in the table, which lists the tubes and their finctions vs. Plate/grid etc voltages. But in the sch on to of the tubes there are volt/curr. figures like "225V 3ma" / "130V 3ma"/"30V"/"115V 3mA".
Not sure. Are these the voltages measured at 3mA through each tube?
And in what mode then the table voltages are measured (the plate voltages are fairly close to what I have now; Grids - different).
PS> The reception is achieved without rebuilding the potted/canned caps. Do you think I should start looking at those?
I received the Mouser package with resistors, and changed all 5 of them, plus restoring the 1.4Kohm open section of the multi-tap voltage divider bu just soldering 3W 1.4K resistors in parallel.
Now, I started touching anodes (plates) and once I touched the plate of the 24 detector tube, I heard a loud 60Hz buzz from the speaker, so I knew my Audio amp works, and my speaker works.
Then I took off the screen (the one protecting the tubes in HF section) and was able to tune to some buzzes and whistles. Then I heard a faint signal.
Then I swapped couple of tubes places and the reception became very loud, and when i connected the GND wire to the actual Earth GND, it became even louder. I was able to achieve a nice low distortion sound by reducing the volume. At high volume it would go into excitation.
I think one of the three 24 tubes is subpar, but I lack the tester, and a Hickok in a working state is over 300 bucks, so I will start from buying one extra 24 and trying to see if it makes things better.
So far only one station is received clearly and is loud.
The last thing is (have to find out why - thoughts welcome) - when replacing the protection screen over the 24 tubes, I lose the reception almost completely - I can barely hear that station that comes in very well without the screen.
And another question (about the voltage chart you guys gave me the link for):
I am not sure, on the voltage chart, what those figures on top of the tubes mean. The plate voltages etc are in the table, which lists the tubes and their finctions vs. Plate/grid etc voltages. But in the sch on to of the tubes there are volt/curr. figures like "225V 3ma" / "130V 3ma"/"30V"/"115V 3mA".
Not sure. Are these the voltages measured at 3mA through each tube?
And in what mode then the table voltages are measured (the plate voltages are fairly close to what I have now; Grids - different).
PS> The reception is achieved without rebuilding the potted/canned caps. Do you think I should start looking at those?
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