NEI 11akf series notes - General Description

NEI 11akf series notes

General Description

There are 3 chassis each has been been designed to operate with specific CRT sizes from 14' to 28', with minor modifications to the circuit.

The 110 degree version has an East/West modulator panel fitted, and is usually configured for Nicam Stereo (UK) or Zweiton stereo in Europe.

The 90 degree versions can be Mono or Nicam sound.

Teletext is optionally fitted, with 1page for 14' and 20', 8page text is fitted to 28'sets.

The PCB on the 14' is physically smaller than the other sets, however electrically they are virtually identical. Transformer styles will change, but the operating conditions are the same.

Audio Stages

See also Nicam/Zweiton (section 10)

In all cases this is a balanced bridge output stage. If external equipment such as active loudspeakers are connected, they must be isolated from chassis ground with an audio isolation transformer. The output IC's in which ever version are a bit fragile to miss-use, and can easily fail if lines or pins are accidentally shorted.

NO SOUND.

Check supply if 30v with ref to chassis, ground track broken adjacent to cut-out in pcb. Probably kills IC305 (TDA1521A) also.

INTERMITTENT SOUND (Both channels)

C364 (100n) shorting to link connecting pins 2/8 on IC305 (TDA1521A).

APPARENT ARKING NOISE FROM SPEAKER (No internal visible sparking)

Internal problem with TDA8361A

CRT BASE

Auto greyscale

In all cases a discreet component system is used with minor CRT dependant component changes. The 90 degree versions can employs a 22.5MM Mini neck CRT or a 29MM standard neck CRT. The physical layout is different but they are electrically compatible.

LOW BRIGHTNESS (or varying brightness).

C907 (1nf 1Kv) leaky.  R925 O/c, or track O/c

BRIGHT COLORED RASTER. (One colour)

Short circuit between collector and base of drive transistor

TOO MUCH OF ONE COLOUR ( Drive control makes Crt saturate in that colour).

High value res of that colour BCI control transistor (680K) O/C or BCI control transistor O/C

ONE COLOUR MISSING.

Emitter resistor of BCI control transistor of that colour O/C.(about 60v on emmitter when 190 v on crt cathode).

If collector voltage 170V then relavent drive transistor O/C.

ONE COLOUR MISSING (After CRT Flash-over or internal short).

Check drive in input pin, if there but low level ie 30% of others check relavent isolation diode to osd output on micro. If low resistance then change,This may also kill relavent OSD output pin on micro.

LOW GENERAL SATURATION LEVEL.

Check resistance of 680k's they should all read 680k one way. If one does not replace associated transistor.

E/W MODULATOR

(Fitted to 110 degree versions only)

HORIZONTAL OUTPUT

A conventional output stage with component variations dependent on CRT types.

NO RASTER. (Power supply tripping, maybe motorboating in speaker.)

Horiz D/Y Shorted turn. Dc resistance will still probably read 2R2. Collector pulse approx 400vpp and wide rather than 1200v and narrow.

JUNGLE

(Video/Audio I.F)

The relevant circuits in the IC are contained in the pins 1 to 9 and 44 to 52 end. There is very little de-coupling and only one variable inductor L401. The mono audio I.F circuit is contained from pins 1,5,50,51 & 52.

LOW GAIN NOISY PICTURE (AGC preset works but does not set correctly).

C428 (1U0) O/c.

JUNGLE

(Chroma/Luma path)

NO COLOUR. 

IC401 (TDA8361A) pin26 pulling Sat control voltage down.  X401 (4.43Mhz) crystal, C420 (12Pf)., R437 (100K), C418 (100n), C419 (4N7).

NO VIDEO (OSD OK).( Stuck in Av mode).

If Tv/Av software switches but not pin16 in IC401, check Q404 collector, if stuck at 7v measure resistance of pin 12 on micro, if 0R, a short on TV/AV line adjacent to right earth tag on base screening can.

If pin 16 stuck at 2v then Q404 (BC548) leaky.

NO VIDEO (NO OSD)

Check Sandcastle if low or missing, disconnect pin 5 IC402 (TDA4662) or pcb path from R612 (24K)

ONE COLOUR MISSING( After crt flash-over)

Check drive to Crt base if input 30% lower than other inputs see CRT BASE Page 3.

POOR OR NO SYNC (If line locks,no frame sync.)

C408 (47N) leaky, this shifts dc level and thus sync slicing level.

JUNGLE

(Vertical/Horizontal Timebases,Sync)

VERTICAL JITTER.

R441 (10M) O/C or intermittent

POOR OR NO SYNC (If line locks, no frame sync).

C408 (47N) leaky,(pin 15 IC401) this shifts dc level and thus sync slicing level. MICROCONTROLLER

There are three versions of software, one is a full menu operated system, the others are a normal OSD system. 11AK08 and early 11AK10 use the OSD system with software versions CTV351S and CTV422M. The menu system is used on 11AK10 ( Ser no's from A600001 and 6600001) and is software version CTV551SV2.

Version CTV551SV2 requires a service pass word and this is 734.

In the event of the Install function not working, go to Features and clear all locks to OFF.

GOES TO STANDBY AFTER A SHORT PERIOD.(removing Nicam pcb stops effect but no text). 11AK10/12

S=5V supply missing to Nicam and text circuits

GOES BACK TO STANDBY (After approx 5 seconds, Led will turn green then go out slowly).

Eht comes up then decays, if Line stage consumes over 450 M/a then Horiz D/.Y is faulty.

DISPLAY SHOWS LOCKED. (When unlocking strange effects can occur such as lock can change when addressing, not toggling).

IC501 (CTV351S) intenal fault.

DISPLAY SHOWS ALL CHANNELS LOCKED.   (Unplugging Nicam pcb cures problem).

Nicam pcb cracked in usual place, however break extends through supply to IC304 (TDA8425) thus upsetting I2C bus.

WILL NOT COME OUT OF STANDBY ( Comes out but immediately goes back to Stdby, also led flashes and sound may motorboat)

TR602 DST internal short.

WILL NOT COME OUT OF STAND-BY (Led stays in standby mode).

If pin 41 of micro changing state and Q804 switching but Q802 not turning on, Q805 not turning on ( Poss low gain).D840/D841 (1N4148) leaky.

If base of Q803 goes high but collector stays high (13V) check output lines of 8V regulator IC802 for s/c.

NO MENU FUNCTIONS (Comes out of standby but will not select any menu functions. When Install button selected XXX is displayed)(Vol +/-makes tv go back to Stand-by.)(Gobbledegook may be displayed on menu functions).

IC502 (240C4) ram faulty.

Microcontrollers cont

NO REMOTE FUNCTIONS. (Set goes back to stand-by when Vol+/- are used.

IC502 (24C04) ram faulty.

GOES TO STANDBY WHEN TUNING (Goes to stdby immediately a signal is located). 11AK08

IC502 (240C2) faulty.

GOES TO STANDBY WHILE OPERATING NORMALLY (no real time scale) 11AK08

IC401 (CTV422 .VE1) faulty

SHOWS TIME-OUT CLOCK AND WILL NOT STOP SEARCH TUNING.

No ident to pin 34 IC401 (poss track broken by Square hole for sound heatsink).

NOT STORING CHANNELS OR ANALOG LEVELS (will store on channel one but all data is in other locations also). (no text or nicam also)..

I2C line SDA not at TTL level on pin 50 (IC501 Micro). Pull-up resistor R539 (3K3) is adjacent to Vert lin pot, and pcb will be cracked under frame Ic heatsink.

NOT STOPPING ON SWEEP TUNE.

If not slowing down, look for Ident in pin 34. If slowing down, look at AFC pin 9, if it does not swing between 0 and +8V then suspect IC 501 (TDA8561A). But also check C509 (2N2) for leakage.

NOT STOPPING ON SWEEP TUNE. (Ident not switching)

Check pullup res R534 (33K) and C454(2N2 not shown on schematic.)

NOT COMMING OUT OF AV. (Software switches but line to IC401 stays high).

Check for S/c on pin 12 of Micro, if 0 Ohms then track s/c to ground adjacent to right earth tag on ground plate.

ONE OSD COLOUR MISSING (After crt flash-over).

See Section 3 CRT.

Power Supply

11AK08 R809 (0R47 fusible) O/C (possibly TR801 S/c).

TR802 Primary windings shorted together internally.

Q801 (BUZ77) S/C (Change D808 BA159 to BYT52M also).

R805 (330K) O/C (this will damage IC801 (TDA4605)

LOW OUTPUT(Ht 83v)

R813 (4K7) high, 

NO OUTPUT  (No start-up voltage on pin 6)

IC801 S/c pin 6. D806 (1N4148) S/C

NO OUTPUT (Start- up voltage pulsing, low drive to Buz90)

D808 (BA159) measures ok???? (reported from Ireland)

R804 (820K) O/C Causes TDA4605 to fail also

TRIPPING SLOWLY (Ht output but tripping)

VR801 (4K7) O/C May cause D809 (6V2) zener to fail.

TRIPPING SLOWLY (No Ht out).

D809 (6V2) O/C

IC801 (TDA4605) damaged by R804 (820K) or R805 (330K) going O/c

STEREO

(Nicam/Zweiton)

Nicam is processed by a single chip IC303 (SAA7283), however signal conditioning is carried out by IC304 (TDA8425). and Quasi parrallel and Mono signal chip IC301 (TDA2546).

NO AUDIO BUT NASTY AUDIO PULSES IN SPEAKER

IC301 (TDA2546) No output from pin 14 (Intercarrier)

NO AUDIO OUTPUT (R314 (3R3) ok.

If audio on input pins then IC304(TDA1521A)  faulty.

NO AUDIO OUTPUT (R314 (3R3) O/C).

IC304 (TDA1521A) int S/C.

DISTORTED AUDIO.

If input to IC304 (TDA1521A) is ok then IC faulty.

TUNER & BANDSWITCHING

NOT TUNING. (TU Voltage oK)

Check bandswitching voltages if missing check R825 (680R).

TELETEXT

NO TEXT (Page number only 'not floating')

IC1001 (SAA5254PE) faulty.

VERTICAL OUTPUT

FULL FRAME COLLAPSE

Check pcb for cracks around IC701 pins, if cracked they can be repaired but IC701 will most certainly have failed.

Check supply via R711 (4R7) fusible.

C701/702 (4n7) leaky (below 2K0),

R707/R702 O/c, C426 O/c C453 O/C (no ramp osc on pin 43 IC101 2vpp).

C705 (2U2) leaky or S/C.

D701 (BYD33J) O/C

R706 (value CRT Dep) O/C.

Dry joint Heatsink/pcb connection or copper broken

C703 (470P) leaky causes Pin 5 to drop to approx 5V ( Line central)

NEARLY FULL FRAME COLLAPSE (Approx 1' severely distorted if A1 increased).

C707 O/C. (May kill IC301).

FULL FRAME COLLAPSE (Pin 5 IC701 Mid voltage ie 15V).

Check supply to 33V Ref ie R818(15K), Ramp gen cap C426 and R441.

NEARLY FULL FRAME COLLAPSE (Picture could be bouncing).

R442 (330K) O/C.

NEARLY FULL FRAME COLLAPSE. (Approx 1' scan but shifted upwards above centre line).

R702 (10K) O/C

VARYING HEIGHT .

Height control VR702 faulty connections of pin to carbon track.

Heatsink earth tab/pcb cracked or dry joint

TOP FOLD-OVER

D701 (BYD33J) leaky, R717 (1K0) O/c. C703 (470P) leaky

TOP FOLDOVER AND BOTTOM CRAMPED.

C704 (100N) leaky.

LINE PAIRING TOP LINEARITY PULLED OUT.

R709 (Crt dep) high or O/C.

FRAME SEVERELY CRAMPED. (Bright foldover in centre, also curving in from edges 'horizontal').

One segment of D/Y O/c. Check resistance (13R5 14' & 20', 5R5 28').

TOP SEVERELY CRAMPED. (bottom reasonably ok).

IC401 (TDA8362A) Output pin 44 faulty.

BOTTOM CRAMPING. (Lower linearity varying).

C701/702 leaking .

BOTTOM SEVERELY CRAMPED. (Lin control no effect).

C705 (2U2) O/c.

PICTURE SHIFTED UPWARDS ( No real change in linearity).

C706 (value crt dep) leaky.

VISIBLE HORIZONTAL LINES ON STILL PICTURE. (Line frequency pulses on output waveform).

C704 (220N) O/C.

PICTURE BLANKING AFTER SEVERAL HOURS

C707 100u leaky or fitted wrong polarity.

BLACK LINES ON FRAME (Very noisy frame drive)

R461/463 (560R) noisy. Value ok)

VERTICAL JITTER.

R441 (10M) O/C or intermittent