I recently picked up a Harmon Kardon CA-35 PA amp. This is a 30watt mono 6L6GC PP amp with 2 5814-A (12AU7) driver/tone control tubes. It also has 2 12AX7 mic drivers. A missing 5AR4 rectifier.
I added a 5U4 and brought it up slowly on a varaic. B+ 440v.
It doesn't work. It has been worked on and some noticable things wrong include a 47uF on the output of the 5AR4 rectifier tube (which might explain why the tube is missing), various "upgraded" coupling caps, and other tweaks.
My plan is to strip this down to a simple mono amp with a volume control.
I'd like to use the power (Stancor #138410E) and output (Woodward-Schumacher #606305) transformers, 6L6s, and one (two?) 5814A for a driver. I have a 5U4GB and a 5R4GYB I could use for the rectifier. PS will be either CLC or CRCRC where first cap is around 10-20uF.
Questions:
Anyone have a schematic of the HK CA-35?
How about a simple 6L6 PP with 12AU7 drivers?
I've search the archives and googled but nothing jumps out to me. What about a Heathkit w-5m? I was thinking of only one 12au7 is needed to drive the 6L6s yet the Heathkit uses two. A simple Williamson design?
Any specs on the Schumacher output transformer?
Go back to my SE84 amp?
Thanks for any help. I've been sitting on this post for weeks searching archives and the Net. How hard can this be?
rick
I added a 5U4 and brought it up slowly on a varaic. B+ 440v.
It doesn't work. It has been worked on and some noticable things wrong include a 47uF on the output of the 5AR4 rectifier tube (which might explain why the tube is missing), various "upgraded" coupling caps, and other tweaks.
My plan is to strip this down to a simple mono amp with a volume control.
I'd like to use the power (Stancor #138410E) and output (Woodward-Schumacher #606305) transformers, 6L6s, and one (two?) 5814A for a driver. I have a 5U4GB and a 5R4GYB I could use for the rectifier. PS will be either CLC or CRCRC where first cap is around 10-20uF.
Questions:
Anyone have a schematic of the HK CA-35?
How about a simple 6L6 PP with 12AU7 drivers?
I've search the archives and googled but nothing jumps out to me. What about a Heathkit w-5m? I was thinking of only one 12au7 is needed to drive the 6L6s yet the Heathkit uses two. A simple Williamson design?
Any specs on the Schumacher output transformer?
Go back to my SE84 amp?
Thanks for any help. I've been sitting on this post for weeks searching archives and the Net. How hard can this be?
rick