hammomd 370HX issues

[Enzo]

One bit of advice: If you are not sure what a wire does, don;t ground it. In fact, don;t make any connections unless you know what they do. You had yo0ur B+ grounded off, and that was arcing your rectifier tube.

I reread the thread, but... did you ever figure out the primary was dual, and the two "halves" of it were to be wired in parallel, not series, for 120v operation?

[Ken Moon]

There is usually slight imbalance in the HV CT winding of most transformers because it takes a longer piece of wire (more resistance) to wind an equal number of turns on the second half of the winding. This results in a every other ripple pulse being a couple of volts higher than the others. You could fix this by imbalancing what Merlin calls RLim1 and RLim2. You can simply measure the resistance to the CT to get the required resistance and figure out which red wire needs more resistance.

The 5V CT is really intended for directly heated rectifier tubes like the 5Y3 and 5U4. The GZ34 has a cathode so the B+ should be taken from pin 8 and the CT not used.

In most guitar amps the imbalance is not considered significant.

Interesting!

So, is there any harm in using the 5Vct for the HT, as I did above?

On the Hammond 276X I used, one secondary was 57.7 ohms, and the other was 49.9 ohms.

If I use the formula on Merlin's web site, I could balance the windings by using a 67R limiting resistor on one leg and a 75R on the other leg - I went with slightly lower 47R limiting resistors because some GZ34 datasheets show curves to get a more accurate Rt at a specific B+ and current load, vs. using the min Rt value from the table at the front of the datasheet, as Merlin shows.

It will take about 2 minutes to switch the HT from the 5V ct to pin 8 of the GZ34 - I'll try it this weekend and report back if I hear anything

Thanks, Mr. Thud

[loudthud]

Interesting!
So, is there any harm in using the 5Vct for the HT, as I did above?

No, you'll probably never notice.