Hello DYA:
I have 3 testers. B&K 747, B&K 707, and Eico 666.
All 3 have been extensively rebuilt and have no problems.
747 and 707 have the 55 line regulation bulbs soldered into the circuit (sockets are bypassed).
All 3 testers have had solder joints reheated, all components checked and replaced if necessary, and worn sockets replaced.
All meters work freely. All are set to factory specs.
The problem occurs when testing rectifiers. Test 1 always reads lower than Test 2. This occurs on all 3 testers. 5U4, 5Y3, 5Z3 all do this. I have at least 20 of each, old and new, they all do this, except for a very few.
The same circuit is used to test both sides of a FWR. Switches have been cleaned multiple times.
Can anyone explain this? Does it have something to do with asymmetric heating? Thanks, Mark
I have 3 testers. B&K 747, B&K 707, and Eico 666.
All 3 have been extensively rebuilt and have no problems.
747 and 707 have the 55 line regulation bulbs soldered into the circuit (sockets are bypassed).
All 3 testers have had solder joints reheated, all components checked and replaced if necessary, and worn sockets replaced.
All meters work freely. All are set to factory specs.
The problem occurs when testing rectifiers. Test 1 always reads lower than Test 2. This occurs on all 3 testers. 5U4, 5Y3, 5Z3 all do this. I have at least 20 of each, old and new, they all do this, except for a very few.
The same circuit is used to test both sides of a FWR. Switches have been cleaned multiple times.
Can anyone explain this? Does it have something to do with asymmetric heating? Thanks, Mark
Series heaters mean that one cathode has 2.5V more applied (Applied voltage is low, as DROP is what matters...). On the 666, you can use the other heater pin and see that the opposite side is higher. And indirectly heated 5Z4, 5V4, 5AR4 don't show this do they?
The Knight 600 shows different numbers for each half - but some ignored the small difference.
The Knight 600 shows different numbers for each half - but some ignored the small difference.
Thanks for the reply, Tom.
I found the following on Direct and Indirect Heating of Cathodes
I need to think on this temp differential. Also mentioned is the difference in potential with respect to anode.
5Y3 and 5U4 have a single directly heated cathode. 5Z3 has twin directly heated, and other such as 5V4 have indirectly heated cathode.
Tom, I looked at the Knight 600 setup chart and saw no difference in settings for 5Z3 and others. 5Y3 is not in the chart.
The directly heated single cathode in the 5Y3: does it emit electrons to the anode from a different location for each plate?
I am looking for any difference in the two tests. The Kimberly quote below mentions a temperature difference. Do you know why?
I was looking at the B&K 747 transformer winding in the schematic. More than I can deal with.
I guess the next step would be to see if the anode voltages for both tests are the same. I'm not sure how the whole circuit is grounded. The grounding may have something to do with it. The transformer has many secondaries.
I found the following on Direct and Indirect Heating of Cathodes
First, I have a 667 Eico, but there should be no difference here.
I need to think on this temp differential. Also mentioned is the difference in potential with respect to anode.
5Y3 and 5U4 have a single directly heated cathode. 5Z3 has twin directly heated, and other such as 5V4 have indirectly heated cathode.
Tom, I looked at the Knight 600 setup chart and saw no difference in settings for 5Z3 and others. 5Y3 is not in the chart.
The directly heated single cathode in the 5Y3: does it emit electrons to the anode from a different location for each plate?
I am looking for any difference in the two tests. The Kimberly quote below mentions a temperature difference. Do you know why?
This is an advanced question. Have you had experience with this difference in readings?
I was looking at the B&K 747 transformer winding in the schematic. More than I can deal with.
I guess the next step would be to see if the anode voltages for both tests are the same. I'm not sure how the whole circuit is grounded. The grounding may have something to do with it. The transformer has many secondaries.