Sony 9-90

[Sean Williams]

Ok, before I go wading into this set, which basically works, just has one or two niggling problems...

Are there any stock faults/"features" I should be aware of?

Mine has a bit of an issue with strange smearing when going from black to white, and the top of the screen is an order of magnitude brighter than the bottom...

It also has the knack of ending up a little trapezoid in the picture department when warm - not all the time though.......

Any immediate thoughts?

Cheers
Sean

[peter_scott]

Hi Sean,

Does it perform differently on VHF as against UHF?

See https://www.vintage-radio.net/forum/...ead.php?t=2464

Peter

[Steve_P]

With these Sony sets, do be careful taking them apart and putting them together. One thing wrong and... bang! So take it carefully.

Anyway, the first thing to do with these sets is to resolder everything in sight, on the panels and on the tube base. You'll find it gets better then. Most intermittent faults on these sets (and others) will be cured in this way.

Then see what happens. The various mods for these are in the thread above.

Good luck, from somebody who hates these small Sony sets.

Cheers,

Steve P

[Sean Williams]

Hi Peter,

Ok, performance is the same on both 405 and 625 - so I guess it has more to do with the video side of things than anything else.

Steve, Ok, will get out with the old iron soonish - not looking forward to playing with this one - sounds like it is well packed inside!

Cheers
Sean

[Mr Hoover]

Hi

From my experience with this and other old Sony Black and White sets change
as many electrolytic capacitors as you can.

Access is horrible possibly the worst of all the Sony BW sets.I had to change
an IF transistor below the system switch recently

Look around the video amplifier transistor Q503 which is near the top end of the board level with the vert linearity control but on the far side.(two transistors immediately by the preset are vert output )

In particular change C509 (10uF 100 volts) beside the brightness preset which decouples the supply to the video amplifier transistor.Had a lot of problems with
The equivalent one in the earlier 9-306UB

Have fun!

[peter_scott]

Hi Sean,

You say performance is the same 405 and 625 but try comparing the performance of UHF relative to VHF. If I remember correctly, the images in the thread I quoted are all 405 but the second in the group of 3 is UHF and the third VHF. Perhaps what you are seeing is similar to the third image.

(It gives 405 UHF if you push both the UHF and VHF buttons in together.)

Peter

[Panrock]

These sets can often exhibit cogging on test card can't they? I think Kat once posted a fix here involving replacing an electrolytic in the sync separator.

Steve

[Sean Williams]

Ok, more to report - I tried the 405 uhf route, and guess what - the picture is much improved on uhf (using the modulator in the VCR).

So, I guess this narrows the fault down further - the picture on 405 uhf is nothing short of perfect.

Cheers
Sean

[Steve_P]

It does indeed. Anyway, looking at and tracing round the circuit, (which is as bad as the set...)

C504, D501, C505, C509, C323.

Cheers,

Steve P

[peter_scott]

Originally Posted by Sean Williams

the picture on 405 uhf is nothing short of perfect.

Cheers
Sean

Hi Sean,

I suspect they all perform like yours and mine on VHF with the same lack of black level control. It would be interesting to hear from other 9-90 owners.

Peter

[Mr Hoover]

I know the previous 9-306UB is pretty awful regarding black level
on Vhf.
From memory the 990UB wasn't as bad,when I have a moment
will power one up(have several) and have a look.

Can also feed 405 video direct into one from the aurora standards
converter via the earphone jack,gives slightly better HF response
on testcard C.
Despite all comments I actually rather like the set

Cheers

[Mr Hoover]

I've just looked at this DVD caption on 2 different 990UB's and they both
produce the same effect,hopefully you can see the black/grey level varying with the caption lines and also before it starts, it's pretty awful really.
Attached is an off-air channel 3 testcard shot, via the Aurora converter
and a comparison of the same caption with a Bush TV 22a which came out
a little dark unfortunately.
One thing I haven't done yet is to try looking at the same caption
via video input which, I'll try to do before long, it should be better, though;
couldn't be much worse??!!

[Sean Williams]

Yep, the middle piccy is the exact problem I have!