tel ray ad n echo

[turk 182]

this is my first encounter with a spinning disk/oilcan delay thankfully the "can" is ok and seems to be functioning normally but the unit hums like crazy!

i've subbed all the B+ filters with no change to the noise not sure where to look next...
anyone familiar "adineko" type delays?

 

[djgibson51]

Do you have a schematic?

 

[turk 182]

this is what i've found there are some additional .o1 ceramics in the unit i have not sure what their function is.
members of dedicated forum have commented that the 7199 tube is not noted for it's noise performance.

 

[JonSnell Electronic]

Make sure the playback head is properly grounded on the screen. We are high impedance here and a loose/broken wire will cause havoc.

 

[turk 182]

shielding in these is indeed questionable.
wish i had taken pic's of it while i had it on the bench.
best i could do to help reduce residual hum was to re-dress the heater leads by twisting them and shortening the run
the other thing i've noticed is the supply isn't like the schematic i linked to it had an independent 6.3 v winding not a main B+ derived supply

 

[turk 182]

doh! seems that someone in an attempt to "update to a three wire grounded ac cord" forgot to remove a line bypass (death cap!) capacitor which was putting some 40 odd volts to the chassis. better now but still very noisy...