1957 Tremolo Questions

[Stymie]

I built a Tremolo from a schematic first published in the December 1957 edition of Popular Electronics.  They mistakenly described it as a vibrato.  I call it my 1957 Tremolo.

Parts and Build

I found a Thorarson 26R37 PT that is an exact match for the specified Stancor.  I also found a 130-volt selenium rectifier, and initially installed it.  I wired it backwards, or it does not work.  I replaced it with a 1N4007 Diode.  The tube sockets are from my AO-47, all other components are new.

I used a conventional On/Off switch.  I wired the power input circuit from the power cord to the switch, fuse, primary side of transformer, and back to the power cord.

Both the Depth and Rate pots are Alpha pots.  Their rotational range, when viewed from the front, is 7 o’clock to 5 o’clock.

Testing

After completion, I tested the effect and had a loud thumping such that it was hard to tell if the tremolo actually worked.  I changed V1 from the 12AX7 to a 12DW7.  This reduced the thumping level significantly.  The article stated that one could reduce thumping by reducing the value of C7.  I removed the .022uF cap and tired a .015uF, which did almost nothing.  I then tried a .001uF cap and this reduced the thumping to a useable level; however, I would like to reduce the thumping further.  Does anyone have any suggestions?

Depth Pot Issues

The current low level thumping begins at 1 o’clock and increases to the max position of 5 o’clock,

The tremolo effect becomes audible at 1 o’clock, there is none below that pot position,

The pot has scratching when rotated from about 2 to 4 o’clock.

I would like to eliminate the thumping and increase the available depth range.  I have no idea how to accomplish this.

Rate Pot Issues

The tremolo speed is medium from 7 o’clock to 2 o’clock then increase to very fast at 5 o’clock max pot position,

The pot has scratching when rotated between 4 and 5 o’clock.

Would a higher value resistor for R9 work to reduce the speed significantly?  I tried jumping a 3.9M resistor in parallel with the existing 3.9M at R9 and the speed increased.

I also want to eliminate the scratching noise.  I have used electronic spray cleaner on the pots but there was no noticeable noise reduction.  I have not taken the pots apart to clean them though.

Other

Where should I connect the positive lead for the tremolo speed LED?

I also have a 60Hz low-level hum present.  I know it is in the effect and not my amp because I played the guitar straight into the amp and it is dead quiet.  How can I eliminate this hum?)

The specific voltages, with both Depth and Rate set to the minimum, are:

B+ is 193VDC
              V1                    V2
Pin1         120 to 130 VDC         185.4 VDC
Pin2         -300 to 220 mVDC      0.6 mVDC
Pin3         6.5 to 16.5 VDC         12.86 VDC
Pin4 or Pin 5 to Pin9   6.93 VAC         6.93 VAC
Pin6         113 to 128 VDC         193.8 VDC
Pin7         -28 to 31 mVDC      0.2 mVDC
Pin8         1.75 to 1.89 VDC      12.77 VDC

Te first attachment is the 1957 Popular Electronics article.  The second attachment is my turret board layout.