Realistic Portavision-150 5" color tv
 

Hi guys
I am trying to source a schematic for this 5" colour set. Possibly a Tandy/Radio Shack variant??
The hor hold was off when I switched on after receiving in the mail. I adj it for a good lock and was fine all day with cover off. I replaced the cover and turned on again and within 10mins the hor hold had drifted again. So I assume its a heat related issue? Capacitor maybe?
Anyway I took it to bits and noticed a burned out resistor. R702. I am wandering if this has anything to do with the fault? It is burned badly and therefore colour code has gone. I need to try and get a circuit for this chassis.
I have included a few pics in case anyone recognises it as being used in other sets? I cannot find any info on this set at all sigh!! Many thanks for any help.
Terry

It's possibly made by Toshiba. It's made for the European or UK market.
Tandy and Radio Shack used to be great for sourcing parts and servicing information, but I don't think that holds true today.
Not having a schematic, it's hard to tell what circuit that burnt resistor it's in. Possibly, the voltage regular circuit for the stage that's unstable. :scratch2:

Many thanks Dieseljeep
update. I pulled out the burned resistor and there was enough colour code left on the underside. It looked like a 10ohm and indeed it measured 11ohm. I replaced it and the line hold has stopped drifting. So its been on soak test all day and now developed frame jitter at the very top of the pic,and low and behold an hour later the colour went...sigh! so I think its determined to give me a hard time. I may just give up on it if I cant source a diagram and use it for spare parts?, Which is a shame because its a very clean little set. BTW. The CRT is Panasonic.

Ta7698ap
 

I have been looking at the TA7698AP Video-Chroma-Deflection chip data and think I might just replace this as they are relatively cheap. It does all the chroma processing and H & V deflection. It may make sense since I had Hor lock fault and then vertical jitter. And then the chroma died. Now I have data sheet it might pay to check supply rail voltage.

Dont give up yet ! First see if its getting hot now. You can
also see if the jungle IC is too hot. 10 ohm is probably in the power supply
as none of the parts seen are marked in the 700 series.

Other thing you can do is draw out a small schematic to see where it
goes.

BTW's There is what looks like a large blue cap at the rear. It looks out of place
See if its been monkeed with. Also there is no FCC ID number on it so it may not have been sold in the US.

73 Zeno:smoke:
LFOD !

Hi Zeno
Well I decided to crack on. Thanks. Yes I thought the large blue cap looks out of place, so will look at that. I have the data sheet on the Jungle chip and yes can try working out what goes where. Interestingly I am edging on incorrect B+ volts because I stumbled across when I turned up the brightness, the colour came back. Turning it down and the colour drops out again. Tweaking the B+ vr ever so cautiously restored the colour at all brightness levels. The height looks like its a tad too low as well, and was wandering if this jitter right at top is something going on that you would not see at normal height adj? Similar to the dots and dashes from teletext we used to see during blanking period?? Love to know what the B+ should be? There is no markings or test point that I can see as a clue to setting it. V size in is on pin 25 of the jungle chip. I see no height adj pot tho. I will crack on with it. BTW by 700 series ?
Terry

Most but not all modern sets are broken into blocks.
In each block parts are numbered differently. An example would be:

800 power supply
100 IF
200 audio
300 video
400 vert
500 hoz / HV

So if you see IC401 & its the vert IC all other 400 parts are vert as well.
If you want to just recap the vert all caps will be C4##.
Going on Q501 may be hoz drive, T501 hoz drive transformer, Q502
hoz output transistor. And all other stage related parts will be 500 numbers.
Its all part of the art of repairing a set without a manual.

So I mentioned FCC ID numbers. Usually on the back. They are assigned
to sets that pass FCC tests & can be sold in the US. If a set has one
you can look it up on fcc.gov. This will give the actual builder & its
model number for the set.
BTW use the long catalogue number to search for data.

good luck Zeno:smoke:
LFOD !

BTW I think I hear an accent, where are you from ??

Wow many thanks Zeno
I learned something new here. That's great. I will check these caps now.
I am from UK. Originally from West London. Now living in Buckinghamshire. Left school in 75 and trained as a television engineer. Many yrs out of trade and now working as audio visual Technician looking after av needs in offices on campus of Oracle Corp UK HQ
Turned my small spare room into workshop and getting back into the old analogue repairs again. Bit rusty after all these yrs. worked on the tube and hybrid sets back then inc the old 405/625 sets.
Regards
Terry

I would start backtracking through the circuit and check any electrolytics that at in the area. And especially ones that are placed near power resistors where they get cooked from heat over time.

The horizontal instability and the cooked resistor is likely a electrolytic with high leakage.
If it's drawing enough current to burn the resistor you could probably feel the cap warm also

Love these little sets.Was the schematic in back of the instructions.

RS was great back in the day when they did that..