Teeco 610D conversion

[angelodp]

Yes the secondary is grounded at the IEC ground. Could that be an issue?

A

[martin manning]

I doubt it. I just wanted to be sure that the NFB loop wasn't the only path to ground. Maybe your NFB defeat should switch a very large resistor in instead of disconnecting it.

[angelodp]

Ok I paralleled a 200r and now have new readings. I am going to put in that large R as you suggest. I have a feeling that my foot switch arrangement for the NFB is screwing up the ground reference. I think I will remove that. I might be a tad hot now on PD.

[angelodp]

Hum possible answer. It seems that this wire that was capped and left out of the circuit may be the center tap for the heaters. I get continuity between the two green heater wires and this wire. I do believe that the green and yellow color indicates center tap. I suppose I should ground this. There is no other wire that grounds the heaters.

A

[TUBEDUDE]

On second thought, that looks more like the a 5V ct. More yellow with green stripe than green wire with yellow stripe.

[sluckey]

On second thought, that looks more like the a 5V ct. More yellow with green stripe than green wire with yellow stripe.

Did you miss this statement? "I get continuity between the two green heater wires and this wire."

[angelodp]

Ok so Its grounded and the hum has diminished quite a bit. Still have some low level stuff, likely due to the horrible layout and lead dress.

How about the 14w PD - ok for now?

A

[thetragichero]

Yes the secondary is grounded at the IEC ground. Could that be an issue?

A

well yes it could be an issue but more of a safety issue. the iec safety ground lug should go to its own dedicated bolt to chassis. any other ground should be attached to something else

[angelodp]

Copy. switching out now.

[TUBEDUDE]

On second thought, that looks more like the a 5V ct. More yellow with green stripe than green wire with yellow stripe.

Did you miss this statement? "I get continuity between the two green heater wires and this wire."

Oops, sure did.

[martin manning]

How about the 14w PD - ok for now?

No, I’d want that down around 11.

[angelodp]

Ok, just in case any are still interested in this. Since I discovered the unused heater center tap and now am employing it, I suddenly noticed that the original design had elevated the heaters at the 6V6 cathode and it was still in place. Snipped that out...... dead quiet no hum.... at last. I need to be much more careful when doing these conversions.... lesson learned. Thanks for the input along the way.

A