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Old 19th Apr 2018, 2:06 pm   #1
peter_scott
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Default Sony 9-90 Width Control?

Can anyone tell me if this set has a width control and if so where is it?

Thanks,

Peter
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Old 20th Apr 2018, 8:29 am   #2
Panrock
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Default Re: Sony 9-90 Width Control?

Hi Peter,

There's no width control. I attach the relevant part of the circuit, in case others would like to muse on how one could be added.

I wanted to reduce the width on mine about 40 years ago and I seem to remember I resorted to reducing the 12v power voltage by a volt or so... not ideal. Presumably Sony set the width so it would still be reasonably sufficient even on a partly discharged battery pack.

Steve
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Old 20th Apr 2018, 8:39 am   #3
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Default Re: Sony 9-90 Width Control?

Hi Steve,

I rather suspected that. I might have a go at reducing the 12 volts. I did wonder about L804 but I couldn't locate it.

Thanks,

Peter
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Old 20th Apr 2018, 9:15 am   #4
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Default Re: Sony 9-90 Width Control?

I can't find L804 in the manual either! I'd be inclined to carefully examine the deflection yoke to see if it's hidden there.

Steve
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Old 20th Apr 2018, 9:19 am   #5
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Default Re: Sony 9-90 Width Control?

The yoke just appears to have the wire terminals on it. The 9-90 really is a hideous thing to work on.

Peter
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Old 20th Apr 2018, 9:40 am   #6
Panrock
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Default Re: Sony 9-90 Width Control?

On that we are agreed!

Have you tried following the connections to the line scan coils, to see where they lead?

Trouble is, if you try to wind a 'width coil' in series with the scan, it will likely give different results and linearity on 405 and 625.

Any other bright ideas out there?

Steve
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Old 20th Apr 2018, 10:49 am   #7
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Default Re: Sony 9-90 Width Control?

I think your adjustment of the 12 volts is the best bet. I've just tried this and 11 volts gives pretty near perfect width and it also reduces the height in proportion so if you had previously set the height for correct circles then they remain correct at 11 volts without further adjustment.

Thanks,

Peter
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Old 20th Apr 2018, 4:24 pm   #8
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Default Re: Sony 9-90 Width Control?

Two silicon diodes after the bridge gives a pretty decent width,

Peter
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Old 20th Apr 2018, 4:29 pm   #9
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Default Re: Sony 9-90 Width Control?

Elegant solution! Well done. I forget how much current this set takes.... up to 4 amps?

Steve
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Old 20th Apr 2018, 4:58 pm   #10
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Default Re: Sony 9-90 Width Control?

Before and after.

The current at 12 volts is only 0.8 amps.
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Old 20th Apr 2018, 5:01 pm   #11
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Default Re: Sony 9-90 Width Control?

(Being excessively critical!) slight loss of focus due to EHT reduction perhaps?

Steve
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Old 20th Apr 2018, 5:06 pm   #12
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Default Re: Sony 9-90 Width Control?

I know it looks like that but it was just my slip shawed camera work. The focus is actually unchanged.
Second thoughts, you may be right.
Or is it just slightly better interlacing?

Peter
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Old 20th Apr 2018, 6:07 pm   #13
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Default Re: Sony 9-90 Width Control?

You shouldn't have established a reputation in the past for fielding such impressive Test Card pictures from your various sets (often on exotic line standards). These invite extra-critical attention. Yepp, my jealousy is now showing through!

Steve
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Old 20th Apr 2018, 6:41 pm   #14
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Default Re: Sony 9-90 Width Control?

Well I ain't so clever. I think there is some blooming and loss of focus at higher brightness settings. So I thought I would recheck that using the 12 volt input. Unfortunately I don't know my left from my right! Yes, I've just killed it.

There is a little 2 amp fuse in the 12 volt line so I might be lucky. Now would the fuse blow faster than the semiconductors? Hmmm??

Peter
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Old 20th Apr 2018, 6:50 pm   #15
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Default Re: Sony 9-90 Width Control?

This is what you get with pesky transistors. None of this nonsense with valves, which always come back for more punishment...

Steve
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Old 20th Apr 2018, 8:44 pm   #16
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Default Re: Sony 9-90 Width Control?

Well, I don't understand what happened there. When I powered it from 12 volts all I got was what looked like a switch off dot and I assumed I had connected it with the wrong polarity. I then connected the AC power and it too gave a switch off dot.

I had hoped to find that 2 amp fuse that the schematic shows in the 12 volt rail but it doesn't seem to exist. I did a few ohms checks and it looked reasonable so I carefully connected the 12 volts and to my surprise got a raster. At this point I figured I'd got off lightly and decided to package it up again although I couldn't resist straightening the scan coils as there had always been a slight tilt.

It's all back together now with a straight picture and looks sharp at moderate brightness levels so I think I'll call it a day.
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Old 21st Apr 2018, 11:49 am   #17
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Default Re: Sony 9-90 Width Control?

I think what must have happened was that I had accidentally moved the charging switch to the charge position and had the AC mains also connected. The apparent "switch-off" dot presumably appeared because the mains was still powering the CRT heater and there was still some residual charge in the EHT circuit.

I checked again the effect of reducing the 12 volts on the EHT regulation/focus and running with the reduced width does have a very marginal effect but even running with full voltage an increase in brightness does swell the picture size and give slight defocussing.

Peter
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Old 21st Apr 2018, 1:41 pm   #18
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Default Re: Sony 9-90 Width Control?

A similar thing happened to me once. I returned to the set after a long absence and it appeared dead. I was about to strip it for parts when fortunately I remembered the existence of this little switch, hidden round the back. Flicking it on restored full operation.

Steve
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Old 23rd Apr 2018, 9:48 am   #19
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Default Re: Sony 9-90 Width Control?

The correct way to adjust the width on one of these is to add or remove capacitance across the C-E terminals of the line output transistor. It's mentioned in the full manual (which you can download from Mikey's site) and is a bit of an encumbrance, but that's the method the factory in Japan uses. The same thing applies to all the Sony monochrome sets that I've seen, right up to the end of production.

Note that all Sony sets of this era seem to be rather over-scanned, its just how they are. The TV9-90UB has no power supply regulator, it relies on a delicate balance of power supply output impedance and receiver load. It is therefore unwise to make any alterations to anything in the power supply or damage to things like the line output transistor and the tube heater can result.
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Old 23rd Apr 2018, 10:28 am   #20
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Default Re: Sony 9-90 Width Control?

That's excellent thanks. Having the full manual is a big help and the Sony method of width control is very interesting. I doubt that my running the 12 volt rail at 11 volts would cause any problem. It would represent dreadful design if a battery supply was not anticipated to fall below the nominal 12 volts without causing harm but I may revisit this and use the approved caps on the line output transistor.
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