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comparison: content/TeK2445_3.rst

content/TeK2445_3.rst

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8 :series: Tek2445 PSU repair 8 :series: Tek2445 PSU repair
9 :series_index: 3 9 :series_index: 3
10 10
11 11
12 After having mostly `destroyed the PSU of my Tek 2445 12 After having mostly `destroyed the PSU of my Tek 2445
13 <{filename}/TeK2445_2.rst>`_, I've decided to be a bit less foolhardy 13 <{static}/TeK2445_2.rst>`_, I've decided to be a bit less foolhardy
14 and I've subscribed to the `yahoo Tek group`_. I discovered that such 14 and I've subscribed to the `yahoo Tek group`_. I discovered that such
15 a failure has already been reported there, also after a full recap of 15 a failure has already been reported there, also after a full recap of
16 the preregulator and regulator of the power supply. 16 the preregulator and regulator of the power supply.
17 17
18 I also found that I was not completely wrong when I built my 18 I also found that I was not completely wrong when I built my
21 It seems to be built on a 75Ω resistor. Mine was not so far, but I 21 It seems to be built on a 75Ω resistor. Mine was not so far, but I
22 decided to rebuild one with closer specifications, so I took a new 68Ω 22 decided to rebuild one with closer specifications, so I took a new 68Ω
23 resistor and I wrapped some 34 gauge wire around. The result is a bit 23 resistor and I wrapped some 34 gauge wire around. The result is a bit
24 cleaner, from: 24 cleaner, from:
25 25
26 .. image:: {filename}/images/tek2445/lr1060.jpg 26 .. image:: {static}/images/tek2445/lr1060.jpg
27 :alt: first attempt of a hand made LR1060 chocke. 27 :alt: first attempt of a hand made LR1060 chocke.
28 28
29 to: 29 to:
30 30
31 .. image:: {filename}/images/tek2445/lr1060_v2.jpg 31 .. image:: {static}/images/tek2445/lr1060_v2.jpg
32 :alt: a better hand made LR1060 chocke. 32 :alt: a better hand made LR1060 chocke.
33 33
34 34
35 However, I was stuck because of my dead T1050. Due to the lack of 35 However, I was stuck because of my dead T1050. Due to the lack of
36 success getting the main oscillator starts, I end up suspecting that 36 success getting the main oscillator starts, I end up suspecting that
48 ===================== 48 =====================
49 49
50 This transformer is a small input transformer with 4 coils around a 50 This transformer is a small input transformer with 4 coils around a
51 common ferrite core: 51 common ferrite core:
52 52
53 .. image:: {filename}/images/tek2445/tr1050.jpg 53 .. image:: {static}/images/tek2445/tr1050.jpg
54 :alt: The T1050 input transformer. 54 :alt: The T1050 input transformer.
55 55
56 I was not sure of the specifications of each coil, since mine as (at 56 I was not sure of the specifications of each coil, since mine as (at
57 least on one coil) defective. From the schematic, it looked natural 57 least on one coil) defective. From the schematic, it looked natural
58 that both the primary windings should have the same charactritics. So 58 that both the primary windings should have the same charactritics. So
80 - 0Ω8 80 - 0Ω8
81 - ~ 10µH 81 - ~ 10µH
82 82
83 I've also quickly checked the voltage ratios using a 42kHz signal: 83 I've also quickly checked the voltage ratios using a 42kHz signal:
84 84
85 .. image:: {filename}/images/tek2445/tr1050_ratio_measurement.jpg 85 .. image:: {static}/images/tek2445/tr1050_ratio_measurement.jpg
86 :alt: Measuring the turn-ratios of the T1050 transformer. 86 :alt: Measuring the turn-ratios of the T1050 transformer.
87 87
88 I use CH2 of my scope to probe the signal produced by the `HP890A4 88 I use CH2 of my scope to probe the signal produced by the `HP890A4
89 <{filename}/hp8904a.rst>`_ linked to pins 1 and 2 (thus a primary 89 <{static}/hp8904a.rst>`_ linked to pins 1 and 2 (thus a primary
90 winding), and CH1 on a secondary winding (pins 6-7), which resulted 90 winding), and CH1 on a secondary winding (pins 6-7), which resulted
91 in: 91 in:
92 92
93 .. image:: {filename}/images/tek2445/DS1Z_QuickPrint17.png 93 .. image:: {static}/images/tek2445/DS1Z_QuickPrint17.png
94 :alt: Measuring the turn-ratios of the T1050 transformer. 94 :alt: Measuring the turn-ratios of the T1050 transformer.
95 95
96 .. image:: {filename}/images/tek2445/DS1Z_QuickPrint18.png 96 .. image:: {static}/images/tek2445/DS1Z_QuickPrint18.png
97 :alt: Measuring the turn-ratios of the T1050 transformer. 97 :alt: Measuring the turn-ratios of the T1050 transformer.
98 98
99 As one can see, the turn ratio seems to be 10. Both the 2 secondary 99 As one can see, the turn ratio seems to be 10. Both the 2 secondary
100 windings (6-7 and 8-9) which provide power for the preregulator 100 windings (6-7 and 8-9) which provide power for the preregulator
101 control (U1030) and the inverter drive (U1062, U1064 and U1066), are 101 control (U1030) and the inverter drive (U1062, U1064 and U1066), are
116 - Power up and check for 120V accross load (plus a 1Vpp triangle 116 - Power up and check for 120V accross load (plus a 1Vpp triangle
117 wave). 117 wave).
118 118
119 The test load consist in: 119 The test load consist in:
120 120
121 .. image:: {filename}/images/tek2445/psu_test_load.png 121 .. image:: {static}/images/tek2445/psu_test_load.png
122 :alt: Primary Test Load. 122 :alt: Primary Test Load.
123 123
124 So I built one and connected it: 124 So I built one and connected it:
125 125
126 .. image:: {filename}/images/tek2445/psu_with_test_load.jpg 126 .. image:: {static}/images/tek2445/psu_with_test_load.jpg
127 :alt: The PSU with the test load in place of T1060. 127 :alt: The PSU with the test load in place of T1060.
128 128
129 Was a little anxious when I switch the PSU on, but it did not 129 Was a little anxious when I switch the PSU on, but it did not
130 exploded. And the voltage across the dummy load was just fine! 130 exploded. And the voltage across the dummy load was just fine!
131 131
134 PSU was starting... it was not completely stable though, but I was 134 PSU was starting... it was not completely stable though, but I was
135 pretty sure this was due to the fact the load was not correct. So I 135 pretty sure this was due to the fact the load was not correct. So I
136 reinstalled the PSU in the scope, and gave it a try: 136 reinstalled the PSU in the scope, and gave it a try:
137 137
138 138
139 .. image:: {filename}/images/tek2445/back_from_the_death.jpg 139 .. image:: {static}/images/tek2445/back_from_the_death.jpg
140 :alt: It's alive! 140 :alt: It's alive!
141 141
142 At last! 142 At last!
143 143
144 144
182 Post Scriptum 182 Post Scriptum
183 ============= 183 =============
184 184
185 For the fun: 185 For the fun:
186 186
187 .. image:: {filename}/images/tek2445/side_by_side.jpg 187 .. image:: {static}/images/tek2445/side_by_side.jpg
188 :alt: Side-by-side: DS1054Z vs. Tek2445 188 :alt: Side-by-side: DS1054Z vs. Tek2445
189 189
190 Despite the fact the Rigol DS1054Z has an incredible number of 190 Despite the fact the Rigol DS1054Z has an incredible number of
191 features for which the Tek cannot compete, I still like this 191 features for which the Tek cannot compete, I still like this
192 old puppy a lot. Its front panel is much easier to use: every control is 192 old puppy a lot. Its front panel is much easier to use: every control is
193 directly accessible. And yet, I don't think the Rigol can measure both 193 directly accessible. And yet, I don't think the Rigol can measure both
194 the rise and fall time (with a decent precision) of a square wave: 194 the rise and fall time (with a decent precision) of a square wave:
195 195
196 .. image:: {filename}/images/tek2445/rise_and_fall.jpg 196 .. image:: {static}/images/tek2445/rise_and_fall.jpg
197 :alt: Side-by-side: DS1054Z vs. Tek2445 197 :alt: Side-by-side: DS1054Z vs. Tek2445
198 198
199 Beautiful double time-base! 199 Beautiful double time-base!
200 200
201 201

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