Testing Amplifone HV Transformers

Sorry it took a while, here is the info I gathered while testing various
Amplifone high voltage transformers while searching for one that may be
ok, in a pile of supposed dead ones...

Marc

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Amplifone Red ( dead :) ) transformer 'ring' testing using an Audio signal generator.

Audio signal generator output 10V AC sine wave ( 10V peak-peak ) @ 20KHz.

Audio signal generator output ground pin to HVTFR pin 4
                              positive pin to HVTFR pin 8
 ...this is the B+ winding, I fed a signal in here as the audio
    sig gen did not have the output current ability to feed directly
    into the primary.

TEST:1 2 3 4 5 6
CRO: pins4&8 1-9primary 1-2unknown 7-anode/hv 7-focus heater RESULT
1. 3.9Vpp 1.2Vpp 2.3Vpp 1.05V 1.3V 100mV 150mVpp semi-ok, low hv
2. 4.0Vpp 1.2Vpp 2.3Vpp 1.3V 1.7V --- 150mVpp dead, no focus V
3. 3.6Vpp 1.0Vpp 2.0Vpp --- 50mV 150mVpp dead, no hv
4. 4.0Vpp 1.1Vpp 2.3Vpp 1.15V 1.5V 110mV 150mVpp ok
5. 3.1Vpp 0.9Vpp 1.8Vpp --- 50mV 150mVpp dead, no hv
6. 3.9Vpp 1.1Vpp 2.2Vpp 0.8V 1.1V 100mV 150mVpp dead, low hv
7. 3.9Vpp 1.1Vpp 2.2Vpp --- --- 150mVpp dead, no hv or focus

I also performed a test on the focus block, by putting the 10Vpp sine wave in the
top pin(4) of the block and seeing if the main focus output on the next pin down
(3), and the grid voltage on (2) changed when adjusting the block. There was
about 50mV on the focus out, and 10mV on the grid out.

Using the various tests, I could see the transformer load with test 1,
as the sig gen output would drop when connected. Test 4 has two
voltage readings as is mostly a DC signal because of the internal diode,
but with a little bump in it matching the input frequency. the second,
higher voltage reading is the level of the top of the bump.

These tests were much better than wiring it all up and plugging it into the rest
of the monitor. I found out the hard way when one of the units blew the deflection
board! :( At that point I thought I would stop plugging them in, and just test the
transformers individually.

The deflection boards, where present, were invariably stuffed, with the main TO220
regulators commonly being dead, or worse; short circuit, allowing a much higher
voltage rail out...

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Received on Mon Jan 1 20:33:21 2001