Hantarex Polo 2/28 Maximum Width Issue High B+

[TobiasRieper]

Hi folks wondered if you could help. I have 4 Hantarex Polo 2 / 28 Chassis with various problems. The first one I'm trying to repair worked fine until I needed to adjust cushion then suddenly the picture increased its width to the absolute max.

I checked  B+ and it was super high at 197v!
I have changed the HOT and a few electrolitics. What steps can I take to remedy this? Everything I have done so far hasn't made a slight bit of difference. I saw a similiar post but it did not help me.
The coil does not change anything or make a difference as well as the adjustment pots.

Thanks you in advance.

[grantspain]

check the poly caps in the horizontal circuit - they need to be read with a cap meter
c99 7n5
c101 1n5

[TobiasRieper]

Thank you, would that affect the high b+ reading?

[grantspain]

hmmm, thats more affected by the caps in psu section, c18 22uf 50v c25 22uf 50v and c17 220uf 25v
where are you reading the b+, it should one of the two centre pins of the deflection yoke connector and should be about 145v - of course if this a standard polo2 15k 28" chassis european version

i was wrong about poly cap values in previous reply, for some reason i thought you had a polostar
These are correct cap values
c101 3n9
c99 5n6

to test b+ and psu voltage i always dummy load pin 3 of the flyback after isolating flyback pin from pad, you can monitor b+ and 17vdc and 27vdc - i then do same again with collector of the HOT (pin 3 resoldered)

[TobiasRieper]

Maybe I'm taking the b+ from the wrong parr? Positive probe Is the furthest pin of the 4ohm 10watt resistor (corner of flyback) and the negative probe on the metal chassis.
Thanks

[grantspain]

so its a polo 2 auto 15k/25k chassis, thats makes alot of difference
B+ should be about 110vdc, read at one of the centre 2 pins (of the deflection yoke connector - black probe to metal frame and red probe place into top of the one the two pins

[TobiasRieper]

Thank you. I will test tomorrow  and update you.

[TobiasRieper]

Hiya its super high at 192v. C18, C25, C17 have been replaced.

so its a polo 2 auto 15k/25k chassis, thats makes alot of difference
B+ should be about 110vdc, read at one of the centre 2 pins (of the deflection yoke connector - black probe to metal frame and red probe place into top of the one the two pins

[grantspain]

ok now desolder pin 3 of flyback and add a 50w mains lamp to the track of pin 3 and ground, then see what b+ is doing if good and adjustable on the b+ pot then resolder pin 3 and desolder pin 1 keeping the lamp in place

[TobiasRieper]

Hiya is this the correct pin? I am measuring DC voltage right? Also do I keep the tube connected via anode cap  neckband and yoke? Where do I change the b+ voltage ? Thank you for your help and patience.

[grantspain]

you just need the centre 2 pins on the yoke connector linked as thats the b+ passthrough, so either make a link or just plug yoke in
RV1 near ic1 in psu section for b+ adjust

What you can do here is prove all the power supply voltages are correct, you are basically removing the flyback from the circuit and using a lamp as a dummy load. You should check the b+, 25v and 16v - all dc of course
Every polo range chassis this is very first thing i do, i then move onto isolating the collector of the HOT and do the dummy load on the track of the collector

would be good if you could put up better photos of the solder side with the option to enlarge as it looks a bit of a mess

I am not sure how skilled you are on chassis repair, you must be dead careful when working on the secondary circuit and never touch the primary whilst doing so - if you have doubt then send for repair, if you are in the uk i can help

[grantspain]

what is very odd about this chassis is the fact its not shut down with the b+ running so high, maybe someone disabled the protection circuit

[TobiasRieper]

Hiya just read the voltage it's 100.4 volts. Changing the pot RV4 does not alter the voltage reading. How do I check the other voltages thank you

[grantspain]

RV1 i said, its in the power supply section cage
test point for 25v is R32, expect around 27v
test point for 16v is L6

100V is a bit low for b+ but not seriously

I expect your problem will be either one of poly caps in the horizontal section or east/west correction diode or could even be just a bad h.size pot

[grantspain]

no one replaced flyback recently have they?

[TobiasRieper]

Hiya sorry, its very hot in my workshop. I increased b+ to 110 v via RV1.
L6 is 14.8v
R32 is 23.7.
No, I don't believe anyone has. I did tidy up those solder joints mind. I will change these poly caps over.

[grantspain]

you could really do with a cap meter, normally when c101 goes bad it takes out other components. C99 is 5n6 and can cause odd problems - both are 1600v polypropylene caps
i think you should replace D47 and D48, should be either BY298 or BY399 but check on diode body and think about replacing T19 bdx53c and just make sure the h.size pot is good

flyback should be a HR7375 or f24n.0005

there is some kind of horrible looking solder bridge on your chassis but your photo is not good enough for me to work out why its there, some better photos and i can check on that

[TobiasRieper]

5n6 = 5356pf
4n7 was in place of the 3n9 cap 101 that is reading 2879pf

The h size both on chassis? I don't have one I have rv4 and rv1

[TobiasRieper]

I noticed the bad traces will check those diodes

[grantspain]

there is some shite soldering on there, i do hope thats not you
replace the 4n7 cap as thats way out, this means you are running on a sambers tube?

horizontal size is on remote board marked h.amp, pincushion is also on remote marked cushion

[TobiasRieper]

Hiya, no this came with some pretty bad joints and a hole I noticed. Well low and behold I cam change h width now, keystone as well as pincushion now works. I replaced those polys with ones i tested from another chassis. I also changed D47 over . I do have 3 others too repair. Going to do all the voltage tests on those first. Thanks so much , I've learnt alot from you. I'd like to get at least one more working

[grantspain]

you can get the poly caps from rs components, just check the leg pitch and physical size when ordering

5n6 the correct size are very difficult to source though but they rarely fail