Mobile Network Section Master Class | Antenna, DPDT Switch, 2GPA & FEM IC Explained — Transcript

Full transcript

1. 0:00Let's start that to this topic. Now,
2. 0:02this one is antenna connector.
3. 0:07You can call antenna pin, antenna
4. 0:08socket. It's in a metal body with the
5. 0:10four legs, 1 2 3 4. Internally,
6. 0:14when you look at this, it's look like
7. 0:15this.
8. 0:16The three pin connected.
9. 0:19And it's all connected with the ground.
10. 0:21The another pin is connected here.
11. 0:24And this is called a main antenna pin.
12. 0:26It's connected to the
13. 0:29network IC.
14. 0:34Now, this antenna connector is a
15. 0:35starting point for the signals. Means
16. 0:38our receiving and the transmitting
17. 0:40signals for the starting point.
18. 0:43If this connector damage, this pin
19. 0:45damage, right? There is a emergency
20. 0:47call.
21. 0:52Right? Call failed.
22. 0:56No service.
23. 0:58Low network.
24. 1:01There are multiple issues related to the
25. 1:03network.
26. 1:04So, whenever a phone come to you with
27. 1:05the network issues, you have to check
28. 1:07this, the physical condition.
29. 1:10Right? Also, the RF cable.
30. 1:12Sometimes due to water logging, the
31. 1:15connection disconnect. So, related these
32. 1:17problems. This one is a basic means this
33. 1:20is the basic testing, right?
34. 1:22In a modern phones, as I mentioned,
35. 1:24there are
36. 1:25two network antennas.
37. 1:29This one is a primary. We call a PRX.
38. 1:31The other one is called a DRX connected
39. 1:33with the diversity antenna.
40. 1:36Means our diversity antenna connected
41. 1:38with the DRX IC.
42. 1:40I'll explain you or I'll I will show you
43. 1:42also one by one each and everything,
44. 1:44right?
45. 1:45Now, look at this.
46. 1:47In a modern phones, right? This DPDT IC.
47. 1:52Double pole double throw. It's a small
48. 1:55IC with the 10 legs,
49. 1:56Right?
50. 1:58We call a RF switch.
51. 2:01This IC control the antennas.
52. 2:03Like this antenna connected to this IC
53. 2:05in a modern phones.
54. 2:08Which phone has specially the SDR IC SDR
55. 2:11transceiver? Which phone has a WTR? You
56. 2:13will see
57. 2:14the antenna pin directly connected to
58. 2:16the FEM. FEM means front end module or
59. 2:19you can call a 2G PA a 2G power
60. 2:21amplifier which has internally antenna
61. 2:24switch.
62. 2:26In previous video as I mentioned, right?
63. 2:28A 2G power IC
64. 2:30work as a power amplifier, also work as
65. 2:33a antenna switch. So, in a old models,
66. 2:37right? In a 4G old models, you will see
67. 2:39this pin directly connected to the FEM
68. 2:41and the secondary antenna directly
69. 2:43connected to the DRX IC.
70. 2:48In a modern phones which has this IC
71. 2:50placed specially with the SDR
72. 2:52transceiver IC,
73. 2:54the DRX IC, sorry, the DRX antenna and
74. 2:58the PRX antenna means the main both
75. 3:00antennas connected to the
76. 3:03this IC. This IC call a DPDT switch.
77. 3:07So, this is the main IC, one of the main
78. 3:09IC.
79. 3:10And many technician does not know about
80. 3:12this IC, right? So, they forget about
81. 3:15the testing
82. 3:16about this IC. So, let's say any problem
83. 3:19comes related to the network, no
84. 3:20service, emergency call, call failed,
85. 3:23right?
86. 3:24Any
87. 3:26the lack of knowledge,
88. 3:28they did not check this IC. And if this
89. 3:30IC had some kind of issue, the
90. 3:32requirement not fulfill, the IC damage,
91. 3:36anything, right? Due to this IC,
92. 3:39your phone
93. 3:41did not recover. Means if you reball the
94. 3:44CPU,
95. 3:45you replace the RF IC means a
96. 3:47transceiver IC multiple time, you work
97. 3:49on a
98. 3:51PS a 4G PA 2G PA, 5G PA multiple times.
99. 3:55You work everything, but still the fault
100. 3:58remains same because the fault in this.
101. 4:01How does I see work?
102. 4:03How to bypass this I see? I'll explain
103. 4:05you about all the I'll give you all the
104. 4:08details in this video.
105. 4:10Now, first of all, I'll show you a
106. 4:12schematics one by one a model. First of
107. 4:15all, like in an old model, where is this
108. 4:18I see is not
109. 4:19installed, but give the place, right,
110. 4:22with the manufacturers.
111. 4:24So, after this
112. 4:26with this I see some models and how this
113. 4:29I see work, I'll explain you through
114. 4:31animation, right? After that, after this
115. 4:34video you 100% whenever the phone come
116. 4:36to you will 100% check this I see if
117. 4:38this I see install in a motherboard. So,
118. 4:40let's go to the Borneo and I will show
119. 4:42you something informative new
120. 4:44information. And this is the Borneo. And
121. 4:48let me go you to the Redmi 7A. So, this
122. 4:51is a Redmi 7A, little old model, right?
123. 4:54Compared to the modern phones of 5G
124. 4:56phones, this is a 4G phone also.
125. 4:58Now, look at this. There are two
126. 5:00antennas.
127. 5:03One of this, this is a primary antenna
128. 5:05and this is a secondary antenna. Look at
129. 5:06this. There is a track connected to this
130. 5:08I see. This is a DRX I see. And this one
131. 5:10is a FEM.
132. 5:12A 2G PA, a front end module work as a
133. 5:14antenna switch. Now, look at this.
134. 5:16There is a track. This track goes to
135. 5:19this from this. This is internally a
136. 5:21short. This is a switch.
137. 5:23And this track internally.
138. 5:26Now, this track call antenna as I
139. 5:28mentioned.
140. 5:30Let me show you a schematic also. Now,
141. 5:32there is a place. There is a no I see.
142. 5:34Just a print,
143. 5:36right?
144. 5:38A DPDT DPDT
145. 5:41DPDT
146. 5:42I see on this place. But, in a 7A
147. 5:46this I see not used.
148. 5:48Just a place for the DPDT.
149. 5:51Right? I'll give you I'll show you a
150. 5:53schematic route. First of all, from our
151. 5:56main antenna to the FEM.
152. 5:58After we go to the another model another
153. 6:01models
154. 6:02for upgrade models. You can say the
155. 6:04latest models compared to this.
156. 6:06And I will show you about this.
157. 6:09As I mentioned already, there is a WTR.
158. 6:11So which phone has a WTR? You will see
159. 6:13really the DPDT switch. Really. Right?
160. 6:17But with the SDR, you will see most of
161. 6:20the phones with the DPDT switch. And
162. 6:24the location of the DPDT switch is the
163. 6:26most important.
164. 6:28Why I'm saying this? Why this is
165. 6:30important? Let me share you further.
166. 6:33Right? Give you information.
167. 6:36So first of all, we go to the schematics
168. 6:38of
169. 6:39this.
170. 6:41So
171. 6:44this is the layout. And
172. 6:46then we
173. 6:48on the other side.
174. 6:50Here.
175. 6:52Right? So this is the
176. 6:54connector. Just copy this and paste in a
177. 6:58schematics. Next, zoom.
178. 7:04Okay.
179. 7:05Now look at here.
180. 7:07This is a main antenna. As I mentioned,
181. 7:11on this antenna,
182. 7:14there are four legs.
183. 7:16Three legs connected with the ground.
184. 7:17The one leg called main antenna output.
185. 7:20Clear?
186. 7:21Now we follow this line. Right?
187. 7:25And
188. 7:27next,
189. 7:29after this, there is a line goes to the
190. 7:31DPDT switch.
191. 7:33But on this IC, means on this model,
192. 7:37there is a no DPDT switch in a main
193. 7:38motherboard. When you look at only a
194. 7:41place
195. 7:42where the DPDT switch installed.
196. 7:45But, this IC
197. 7:47will be bypass internally. Right? So,
198. 7:51there is a no IC. You have look at on
199. 7:54this resistance here.
200. 7:57Not connected. Not connected on the
201. 8:00output on the D. This is a main antenna.
202. 8:03And the this is a DI a diversity
203. 8:06antenna.
204. 8:07So, both
205. 8:09four inputs means are four connections.
206. 8:11There is a NC means this is not
207. 8:13connected here.
208. 8:15So, we forget about So, just we
209. 8:18one thing
210. 8:20the output to main antenna input. We
211. 8:22click here. Now, look at here.
212. 8:26Now, look at here. This is a main
213. 8:28antenna.
214. 8:29Right? From a RF main connector.
215. 8:33Now, look at this. This is a second one,
216. 8:34J2701. I will show you.
217. 8:38Like this is this is, right?
218. 8:41When you see in a bit map, it's directly
219. 8:43connected
220. 8:49like this. Okay? These pins are
221. 8:52connected with the ground. When you
222. 8:54connect RF cable, this pin is connected
223. 8:55to the ground. And this pin
224. 8:57goes to the 2 GPA. Let me show you. This
225. 9:00is a just a switch in out switch.
226. 9:05Clear?
227. 9:06Get it? Now, let me show you in a
228. 9:09schematic also. Right? These things.
229. 9:13So, we go to the This is a in out
230. 9:15switch, right? You can
231. 9:18It's a connected. Right? Look at here.
232. 9:20There is a zero ohm resistance. The
233. 9:21company says if there is a switch or
234. 9:23connected a zero ohm resistance, so
235. 9:25the both side you will get a beep. Now,
236. 9:28look at here one thing more important.
237. 9:31Right?
238. 9:33Now, there is
239. 9:34a coil connected to the ground. And one
240. 9:37side, let me clear this.
241. 9:43And look at this circuit. First of all,
242. 9:45follow this line. This line goes to that
243. 9:472G antenna.
244. 9:49But
245. 9:50there is something important. I will
246. 9:53explain you first this.
247. 9:55Right?
248. 9:57Something interesting. Right? Now, look
249. 9:59at this. This coil, L2701,
250. 10:03right? This is a coil symbol connected
251. 10:04with the ground.
252. 10:06Right? And there is a capacitor over
253. 10:08there. Now, this capacitor in a series.
254. 10:10This is in a parallel. Right? In a
255. 10:12parallel, in a series.
256. 10:14Now, this is a NC coil. That means this
257. 10:16coil is not connected, but there is a
258. 10:18resistance, a zero resistance in a
259. 10:20series.
260. 10:21And another coil in a parallel.
261. 10:24So, what happened here?
262. 10:26Right? And the mostly technician do the
263. 10:29mistake.
264. 10:30And whenever a phone come to you,
265. 10:32sometime a phone come to you for a
266. 10:34another technician. So, check properly
267. 10:37because sometime these mistakes
268. 10:40save your time.
269. 10:41So, what happened? This is a capacitor
270. 10:44in a series in a network section.
271. 10:47Mostly you have seen the capacitor in a
272. 10:49series because they passes the
273. 10:51frequency. Right? But block the DC
274. 10:54voltage because the DC voltage create
275. 10:57the noise. For the noise filtration, it
276. 11:01in a series. But when you check with the
277. 11:04diode mode, right? Because this side
278. 11:07will you give you a beep.
279. 11:10And on this a beep
280. 11:12means a ground reading.
281. 11:14On both side, you will get a beep, a
282. 11:16ground reading. Similar with the
283. 11:17resistor.
284. 11:19Both side, you will get a beep.
285. 11:21With the coil, you will get a beep with
286. 11:24right? So,
287. 11:26the
288. 11:26new technician, it means intermediate
289. 11:29technician or beginner, right? They does
290. 11:31not know about the component working.
291. 11:34The component knowledge, how the
292. 11:35components work.
293. 11:37Why what is a series? What is a
294. 11:39parallel? The basic knowledge,
295. 11:41basically.
296. 11:42So, when they look at a four or five
297. 11:44components in a
298. 11:46ground beeping with the ground, they
299. 11:48think there is a short. So, they remove
300. 11:51one by one. When they look at the
301. 11:52capacitor over there, they think this
302. 11:54capacitor is short. They remove the
303. 11:57capacitor. After that, they work on the
304. 11:59ICs, let's say.
305. 12:02They replace IC one by one.
306. 12:04They check the voltages.
307. 12:06They reball the CPU. They do everything.
308. 12:09Let's say they did not fix the phone
309. 12:10because when they remove this capacitor
310. 12:14or thinking it's a short,
311. 12:16right? Or any coil, this coil is
312. 12:19connected to ground with the
313. 12:22give the strength to the signals, right?
314. 12:24And as I mentioned, this capacitor for
315. 12:27the frequency passes, for the filtration
316. 12:29noise.
317. 12:30When they remove the capacitor or any
318. 12:32component in a series, especially,
319. 12:35the RF signal broke.
320. 12:38Due to this,
321. 12:39the phone
322. 12:41remain in the same state. Whatever the
323. 12:43you you reball the CPU, you replace the
324. 12:47transceiver IC SDR WTR multiple times,
325. 12:49you replace the 2G PA, check the whole
326. 12:52lines. Still, there is a no
327. 12:55nothing. The phone in a same situation.
328. 12:59So, when the phone give to the another
329. 13:01technician, if they had a knowledge,
330. 13:04they will check
331. 13:05these components first. Otherwise, they
332. 13:08will do same things. They reball the
333. 13:10CPU, they reball, replaces the IC, but
334. 13:14the phone remain same.
335. 13:16So, this is a one second job. That's why
336. 13:18I told you this is a basic work.
337. 13:22I'll give you a one golden rule for the
338. 13:24network section.
339. 13:26These type of the circuit multiple time
340. 13:28you have seen in a network section. So,
341. 13:30everyone every time you will get a beep,
342. 13:32that means there is a no short. You have
343. 13:35to first look at the schematics.
344. 13:37Why this line behaving like this, right?
345. 13:39Anything, right? So, this capacitor on
346. 13:41the both side short because the both
347. 13:43side had a coil connected to the ground.
348. 13:45A basic logic.
349. 13:47The golden rule is
350. 13:49whenever a phone come to you for the
351. 13:50network section, you have to first check
352. 13:54the network section.
353. 13:56Right? All network section under the
354. 13:58microscope.
355. 13:59Look it properly.
356. 14:01Right?
357. 14:02A visual inspection properly.
358. 14:05Any component
359. 14:07damage,
360. 14:09right? A small component damage,
361. 14:11missing,
362. 14:14burn,
363. 14:15not burn, it means due to
364. 14:19other or technician, right? Because
365. 14:21these are frequency lines, so component
366. 14:23does not burn. They just someone work on
367. 14:26the another IC due to this
368. 14:28component any burn, right? I hope you
369. 14:31get my point. Or due to water logging,
370. 14:34right? Due to rust, corrosion.
371. 14:37This component not connected.
372. 14:39Or weak, disconnected.
373. 14:42You have to first focus on this.
374. 14:45You have to cover all the components in
375. 14:48a proper. If there is a capacitor, you
376. 14:50have to replace the capacitor.
377. 14:52Some technician put the technique
378. 14:54resistor on this side.
379. 14:55Cuz they think they're same thing. Or if
380. 14:58you connect with a jumper, that will
381. 15:00also give the trouble on this line.
382. 15:04So, you have to This is a golden rule.
383. 15:07Whenever a phone come to you, you have
384. 15:08to check all components, small to small
385. 15:11components, their location. If any
386. 15:13component damage, missing, burn, water
387. 15:16logging, due to rust, not connected,
388. 15:19you have to
389. 15:21first repair this.
390. 15:24Focus on this. After move on to the ICs.
391. 15:28Due to this mistake
392. 15:31you did not repair the phone. This is a
393. 15:3310-minute job, max.
394. 15:36Or sometime a 5-minute job.
395. 15:38And it will save you.
396. 15:41Because due to this in a 5-minute you
397. 15:43repair the network.
398. 15:45Otherwise
399. 15:46you will change any IC if any component
400. 15:49break on this line. As I said, give you
401. 15:51example.
402. 15:52Right? And
403. 15:55if any component giving you a beep, that
404. 15:57doesn't mean
405. 15:59this is a short. You have to check
406. 16:01through the schematics, through the
407. 16:02logic. Think through the logic. I hope
408. 16:05you will
409. 16:06clear in this.
410. 16:09So, always this is a golden rule,
411. 16:11mention on your notebooks.
412. 16:13Right? In a network section you have to
413. 16:15check each and every component. A small
414. 16:17component is important. If there is a
415. 16:19missing
416. 16:22Maybe this is the reason for the network
417. 16:24section or network issue.
418. 16:27Clear?
419. 16:28Right? Now, let me
420. 16:31follow this line. Right? So, this line
421. 16:34goes to the antenna. This is a RF.
422. 16:37Sorry, this is a PA.
423. 16:40IFEM
424. 16:42or 2G PA. Right? Now, there are
425. 16:45TRX lines.
426. 16:47How this TRX line
427. 16:49work, where they connect, there are HB
428. 16:51higher band, lower band
429. 16:53route.
430. 16:54There is a VRAM, VCC, VBAT supplies.
431. 16:58RFFE line, SDSCL, VIO.
432. 17:01Right? Some ground, CPL line.
433. 17:04All these things about the 2G PA, I'll
434. 17:06explain you in the next video. This
435. 17:09video especially for the DPDT switch.
436. 17:11So, you have to focus on this.
437. 17:13Our main motive in a this phone
438. 17:17that network from a network switch this
439. 17:20line directly connected to the
440. 17:23FEM. Okay? Now, let's go to the
441. 17:26This is a Redmi Note 8.
442. 17:30Now, this model isn't Redmi Note 8.
443. 17:33Now, look at this.
444. 17:34This one is a network switch.
445. 17:39Right? There is a diversity antenna,
446. 17:41second.
447. 17:42Now, look at this. There is a IC.
448. 17:44Which
449. 17:45not used in a Redmi 7A, but this is a
450. 17:48Redmi K20.
451. 17:49The
452. 17:50upward model, right? Compared to the
453. 17:53Redmi 7A, there is a
454. 17:55DPDT switch. And this is a SDR IC.
455. 17:59As
456. 18:00Now, this is FEM.
457. 18:01Now, when we go to this schematics on
458. 18:04this model, let me show you
459. 18:07how this DPDT switch connected.
460. 18:09Because in a previous it's connected
461. 18:11directly to
462. 18:13FEM, but in a modern phones or you can
463. 18:16say the which has a SDR or latest phones
464. 18:19that
465. 18:20this pin it's connected here, both
466. 18:23antennas. Otherwise, what happened
467. 18:26previous
468. 18:29Like this is a diversity antenna.
469. 18:32And this is a main antenna. Right? Now,
470. 18:35this line connected to the 2G PA.
471. 18:39You can call a FEM.
472. 18:42Right?
473. 18:43And this pin is connected to the DRX.
474. 18:46After this, they goes to the WTR or
475. 18:50RFIC.
476. 18:51But in a modern phones
477. 18:53the both antennas
478. 18:56connected with the DPDT switch.
479. 18:59Right? This is a RF switch.
480. 19:03This is called a RF switch.
481. 19:06Right? A radio frequency switch because
482. 19:09it switches the frequencies from a
483. 19:11receiving or transmitting signal is a
484. 19:14frequency. So, it switches the
485. 19:16frequency. How this IC important? Let me
486. 19:19give you example. First of all, about
487. 19:22this location.
488. 19:23Why this location is too important?
489. 19:27Most of the time you have seen
490. 19:29this is in a corner. Sometime you will
491. 19:31see internally in the motherboard.
492. 19:34But most of the cases as like in a Redmi
493. 19:367A as like this K20.
494. 19:39This is in a
495. 19:41corner of the motherboard.
496. 19:43So, what happen when you open the frame?
497. 19:46Means the motherboard
498. 19:48remove the motherboard from the frame.
499. 19:50Right?
500. 19:52If you
501. 19:53connect let's say if you take a support
502. 19:56with the any
503. 19:57tweezers
504. 19:58right? Or any tool.
505. 19:59Sometimes
506. 20:01these layers are broken.
507. 20:03Or let's say a beginner technician do
508. 20:06this mistakes.
509. 20:08Right?
510. 20:09And nobody notice this.
511. 20:12Sometime
512. 20:13when you remove the shield because the
513. 20:15shield is closely
514. 20:17near about this IC. If you remove the
515. 20:19shield with the cutter, sometime any
516. 20:22component miss near about this.
517. 20:25As I told you, every component is
518. 20:27important
519. 20:28on a network section.
520. 20:31Sometime
521. 20:32due to
522. 20:33tool
523. 20:34this IC shift from the location. Means
524. 20:37it's displace.
525. 20:39Like the direction change or it
526. 20:42displace.
527. 20:44And
528. 20:45due to lack of knowledge, nobody work on
529. 20:48this IC.
530. 20:49They think this is a switch. Sometime
531. 20:51they just remove and throw it.
532. 20:55Due to this
533. 20:57what are the problems and what are the
534. 20:58consequence? I'll show you. First of
535. 21:01all, we go to the schematics.
536. 21:03Right?
537. 21:04To tell you about this IC.
538. 21:07Now, let me show you another model,
539. 21:10right? Before we go to the schematics,
540. 21:13this is a Redmi
541. 21:15K20.
542. 21:16This is a Redmi Note 8 and this is a
543. 21:18Redmi K20.
544. 21:19This is a main antenna where the RF
545. 21:21cable connect, right?
546. 21:23And when we go to the network section,
547. 21:27this is the network section of the Redmi
548. 21:28K20.
549. 21:29Now, look at it. This is the main
550. 21:31connector.
551. 21:32This is a antenna switch. You can say
552. 21:35input-output switch, right? Now, this is
553. 21:37a DPDT switch. This line goes to the
554. 21:39DPDT.
555. 21:41Follow this line on the other side of
556. 21:43the motherboard, right? There is a
557. 21:46network section where the 4G PA and the
558. 21:482G PA install. Now, look at this.
559. 21:51This is a DPDT switch, a 10-leg IC,
560. 21:55right? 1 2 3 4 5 6 7 8 9 10, okay?
561. 22:01Now,
562. 22:02the clock anticlockwise means you count
563. 22:05the balls through the anticlockwise.
564. 22:07But, in a Borneo, when we go to the
565. 22:09hardware solution, there is a two lines,
566. 22:11input and the output. There is nothing
567. 22:13There is a nothing mentioned related to
568. 22:15the DRX who control this IC, how this IC
569. 22:19work, these all things.
570. 22:22These all things are important
571. 22:24while we troubleshooting about this IC.
572. 22:27So, you have to know about this IC and
573. 22:29how to bypass this IC. So,
574. 22:32let me give you a another Redmi Note 8A,
575. 22:35right? And show you.
576. 22:37So, this is a Redmi Note 8A.
577. 22:40Look at this. There is a connector over
578. 22:42there, right? From a connector where the
579. 22:44RF cable connects. From here, this is
580. 22:46the IC. Similar, six and eight pins.
581. 22:49This is a 10-leg IC.
582. 22:51And there is a diversity
583. 22:54antenna over there.
584. 22:55Over there, diversity antenna,
585. 22:57right? Now, how this
586. 23:00DPDT switch work?
587. 23:02Let me explain you.
588. 23:04Right, that will be interesting. You
589. 23:06will get something new. If you do not if
590. 23:08you don't know about this.
591. 23:11Right, and we go to the schematic first,
592. 23:13right?
593. 23:14This is a layout
594. 23:16and in a layout
595. 23:17we just copy this.
596. 23:19Right, in a diagram.
597. 23:21Paste.
598. 23:23Next.
599. 23:24Zoom.
600. 23:26So, this is a main connector. You can
601. 23:30call RF connector. Uh means
602. 23:32right, I mean antenna connector, right?
603. 23:35Now
604. 23:36on this point, there are some mistakes
605. 23:38by the board near or you can get through
606. 23:40the schematics.
607. 23:42What are the mistakes?
608. 23:44Sometimes the schematics also
609. 23:47you have to read carefully because if
610. 23:49you had a good knowledge, then you can
611. 23:51read the schematics because in a
612. 23:53schematic sometime you will see
613. 23:54mistakes.
614. 23:55What are the mistakes?
615. 23:57The capacitor capacitor the C denote the
616. 23:59capacitor we already learned in a basic
617. 24:02section, but this symbol is the coil.
618. 24:06But this denote the capacitor. So, this
619. 24:07is the clearly mistake over there.
620. 24:10Right, and there is a Henry, right?
621. 24:13Mention as a Henry
622. 24:15digit a coil.
623. 24:17Right, uh means
624. 24:19capacitor. Now look at here.
625. 24:21When we go to the further, now this
626. 24:24Now this symbol for the resistance in a
627. 24:26schematic. Right, but there is a mention
628. 24:29a coil.
629. 24:30Now this is the capacitor symbol and
630. 24:32there is a coil mention. Look at this L.
631. 24:34L denote to the coil.
632. 24:36So, these are the mistakes.
633. 24:38So, that's why
634. 24:40the basic the concept clearance in your
635. 24:43mind is important when you do the
636. 24:46repair. Otherwise, you will
637. 24:49feel a struggle
638. 24:51while the repairing. Always stuck if
639. 24:53your concept are not clear.
640. 24:55I'll give you each and every detail bit
641. 24:57by bit. So, watch properly
642. 25:00and
643. 25:01make notes because I want to you be a
644. 25:04good technician, a better technician in
645. 25:07your area, in your city.
646. 25:10So, watch it properly. Now, this is the
647. 25:14DPDT switch.
648. 25:16Right? This is a DPDT switch.
649. 25:20Yeah. Now, there are multiple
650. 25:21connections from a DPDT DRX antenna.
651. 25:25Right?
652. 25:26So, how this connection work? There is a
653. 25:28voltage also called
654. 25:30V reg L21A 2.704.
655. 25:34Right?
656. 25:35And
657. 25:37this line when you follow the sixth
658. 25:39number pin, right? This line
659. 25:42connected to the
660. 25:44This is a 2G PA. There is antenna.
661. 25:47Antenna connected to the FEM, right?
662. 25:50Everybody know.
663. 25:51Right?
664. 25:52This is LBHB. So, this is a 2G PA,
665. 25:55right? U3003. Let me show you.
666. 25:59U3003. This is a 2G PA in a square
667. 26:01shape.
668. 26:04So, let me show you a diversity antenna
669. 26:06also means
670. 26:08So, look at here.
671. 26:12So,
672. 26:13this is
673. 26:15Right? When we go to the
674. 26:17Look at here.
675. 26:19DRX antenna from RF
676. 26:23pin number RF3 or two.
677. 26:26So, let me show you in a bitmap.
678. 26:28So, this is the bitmap and when we focus
679. 26:31this
680. 26:32This is
681. 26:33Right? So, when we copy this
682. 26:37Click here and
683. 26:39after this, this
684. 26:42This line goes to the
685. 26:45DRX IC. This is a DRX IC.
686. 26:47Means a DRX IC also connected to this.
687. 26:50Right?
688. 26:52Okay?
689. 26:54So, like this.
690. 26:56And one pin is connected to the DRX IC
691. 26:59and other pin is this is a DRX antenna.
692. 27:02Look at the DRX antenna.
693. 27:04And this is an DRX switch. A connector.
694. 27:07Like the PRX connector, this is a DRX
695. 27:09connector. And when you see here, this
696. 27:12line
697. 27:13is also connected to the DPDT switch.
698. 27:18Pin number two.
699. 27:20Right? The four number connected to the
700. 27:22DRX IC.
701. 27:23Now, how this IC work? I'll explain you
702. 27:26through the animation.
703. 27:28So, it will be easy for you. When you
704. 27:30look at the schematics,
705. 27:32right?
706. 27:34This will be uh complicated.
707. 27:38Now, let me give you uh
708. 27:41next. Now, look at this. This will be uh
709. 27:44easy for you.
710. 27:45Right? Now, this is a 10 leg IC.
711. 27:49Small IC.
712. 27:50As I mentioned, this is in a corner. So,
713. 27:53you have to be careful on this.