Experiences with Sony 9-90UB

[Alkarren]

I retired last year after spending fifty years in the TV & Radio service trade although, the last few years were spent most of my time installing aerial to caravans on one of the largest caravan parks in the UK. The Sony 9-90UB must be the most common Television with 405 that you can acquire. The good point is that they were and are reliable with a good chance of being found working which is good as they are not easy to work on. But you won’t get away completely without doing some work. Always I find the system switch and tuner contact require attention Two squirts of Servisol 10 contact cleaner into both sides of the system switch is normally all that is required and the side of the VHF tuner comes off easy (held on by one screw). Four bands of contacts can be seen I clean these with an old toothbrush spraying the contact cleaner on the toothbrush and carefully rotating the selector until all four are polished. You may also find the side controls and volume control will need some contact cleaner as well. A word of warning to those reading this with little knowledge, don’t use WD40.

I obtained seven of these Televisions. Four worked and only required the afore mentioned Three required attention as follows. The easy one. There was little if any effect when turning the brightness control, this turned out to be a leaky capacitor C508 from the collector of the video output transistor. Set two had frame linearity and cogging. To cut a long story short I replaced the common items C601 and C603 as for the linearity, I blanket changed all the electrolytic capacitors in the frame stage. Like the earlier Sony 9-306 the capacitors tend to go higher in value example 3uf was 6.8uf and 20uf was 38uF always replace with the correct value 3.3uf is fine for 3uF though you will probably find a 3.3uF even though it is shown as 3uF on the circuit diagram. Now to number three the more trying one. This had two faults, both on the IF panel. What a devil to work on. Voltage checks found that the vision AGC transistor Q304 had full voltage on all terminals this turned out to be an open circuit choke L309 470uH. Now I had 405 with little gain and 625 with a washed-out picture and no sound. This turned out to be the first vision IF transistor Q301 it had zero voltage on its base. Obtaining a new 2SC657 wasn’t easy. I did try a BF199 as it was stated as an equivalent, but there was too much noise in the background. After much searching on the internet I found a supplier in the UK who had two in stock I brought both and now have a spare.

Knobs for these sets are often missing and impossible to obtain. I have been experimenting with making replacement VHF fine tune knobs. I have got as far as making them functional but some improvement is still required as to appearance. I am not ready to sell any just yet so please don’t ask.

[HamishBoxer]

Welcome to the forum, I love these sets and having stood for years always seem to work.

[Freya]

Hello & welcome Alkarren, what a good post to start.
I also have a fair few of these sets and encountered some of the issues you have mentioned, its handy you mention the fault on the IF panel as my 990UM has a similar fault.
Please put my name on the list for when you do have finalised the tuner knob.

[Alkarren]

Hi Stephen
Noted your request. I also hope to do the VHF channel change knob if if works out okay.
Peter.

[mark pirate]

These are great little sets, I was lucky enough to get a nice working one a while ago at a reasonable price, it came with all accessories in it's original box, but missing one of the small side knobs.

Picture quality is really good on both standards, no wonder these were so popular with caravanners!


Mark

[Graham G3ZVT]

I bought one of these sets two years ago.
Unfortunately the seller was not acquainted with Newton's laws, and included next to no packing in the box, so it arrived damaged.

One CRT mounting boss severed.




Power transformer in the base cast adrift.



Various trim trim detached.



and of course the VHF fine tuning knob damaged in spite of the plastic screen protector being present, that had fallen off too!



Anyway, spoiler alert, it has a reasonably happy ending.
A longer self-tapper into the bezel secured the CRT as good as new



I can't remember what I had to do with the transformer, but I secured it satisfactorily.

Glue dealt with the trim, and without the metal circlip the VHF FT knob works well enough albeit a bit lose.

I have a vintage 405 line set from 1949, for use with my PC graphics card based 405 line signal source, and I wanted a "modern" 405 line receiver to compliment it.

I also have happy memories of a Perdio Portorama on the cabin curser we holidayed in a couple of times on the Norfolk Broads when I was a kid, I bet you dealt with a fair few of those.

I owned one for a while, when 405 was still being broadcast, I wish I had kept it.

I presume you are 3D printing those knobs rather than injection moulding or vacuum forming...
Rhetorical question really, it just shows how ubiquitous 3d printing has become.

[Alkarren]

Hi Graham
Some people just think you can pop a TV into a box without any packing, I don't understand their thinking. The knobs are resin castings. Nice and strong. I use a vacuum pot to remove most bubbles. Next step will be to use a pressure chamber to compress any remaining bubbles so the resin will appear crystal clear.
Peter

[Rich Woods]

Hi Peter, yeah brilliant post. Please add me to the unofficial replacement list too. I’ve got two of these wonderful little sets, one I bought on eBay which is tatty but works, and a rough one I bought at Retrotek for spares which I haven’t tried yet. They are the Toyota truck of dual standard portables, it really is usually a case of plug it in & it works and they do seem to survive less than ideal handling and storage. The plastic screen cover on my better set looks like it has been dragged across concrete by the mains cable!