Sony 9-90UB TV - VHF Tuner 'Null' Position

[Spot Wobble]

Greetings to all.

Have noticed that some (or all) of the Sony 9-90UB dual standard television receivers have a 'null' position (indicated with a dot) on the VHF tuner selector between channels '5' (end of band one) and '6' (start of band three). In this position, with the VHF/UHF selector buttons set to 'VHF', the receiver appears to give a blank (black) screen - no tuner static - but with a visible 405-line raster (well, 377 lines perhaps I should say).

Is this 'null' position on the VHF channel selector merely supposed to be an 'off' position for the tuner, to show the boundary between bands one and three?

Was hoping that it might be provision for viewing a video baseband signal, but when I tried feeding in a 405-line baseband video test signal (via the external aerial connector socket on the receiver) no picture appeared on the screen.

Interestingly, when I subsequently tried feeding in this video signal to what is normally the audio socket (with a little 'tape recorder' symbol on the 9-90UB) - again with the VHF selector in the 'null' position - I did get a little 'vision on sound' from the 9-90UB's loudspeaker, so wondered if the 'null' position might have been intended for audio monitoring for an audio tape deck or radio tuner? Although I imagine the signal that I was putting in may have just been finding its way to the receiver's audio amplifier inadvertently.

Best wishes,

Francis Niemczyk

[Reelman]

I hope someone comes back with an answer I too, have wanted to know about the function of the little dot.
Peter

[ppppenguin]

I have a couple of the receiver/monitor version of the TV9-90. They have an extra box on the side which has the AV connectors and switch. Very handy little sets when doing 405 experiments.

Since this genuine Sony monitor version exisits, I doubt that the standard TV has monitor capability built in. It should be possible to modify one easily enough - no live chassis problems

[Murphyv310]

No the TV9-90 is not a monitor as it stands. The gap is purely a mechanical addition to the tuner switching. Simply for a gap between band one and three. All the non monitor versions are the same.
The monitor versions like the ones Jeffery have are very rare, I only saw one in the time I worked for SES Glasgow (Sony service UK) although saw many TV9-90 UB models for repair, usually before the caravaning season.

[Spot Wobble]

Many thanks Jeffrey and Trevor for the information: very greatly appreciated. I suspected that the 9-90UB probably wouldn't include a video monitor function, although these sets are incredibly versatile (405 on UHF, 625 on VHF with the right button pushing).

I do have monitor version of the North American 525-line equivalent (110UA?) of the 9-90UB with the AV panel that you mention Jeffrey. I was wondering if it would be possible to 'transplant' this AV panel onto a standard 9-90UB receiver so it could serve as a 405-line video monitor and ALSO a video out for 405-lines: would be nice to have the capability to record some of the 405-line transmissions (for private, non-commercial use) that Heritage will hopefully do at some point in the future. (I have a VHS machine that records 405-lines pretty well.)

I don't have the technical capabilities to do the above 9-90UB conversion: is there anyone whose services I could employ for this? (They would probably need suitable tools to cut the 9-90UB casing to fit the AV panel.) I should have the circuit/wiring diagrams for the 9-90UB and the 525-line monitor version somewhere.

Best wishes,

Francis Niemczyk

[Murphyv310]

I'd like to see the diagram of the monitor. I've only got the 9-90 manual here to see the differences.

[ppppenguin]

I'd like the monitor manual too. I have a paper original for the 9-90 plus PDFs.

PS: Francis, I've just sent you an email via the forum.

[`FRANK.C]

Some information in here about converting to a monitor.

Frank

[Richard_FM]

I've wondered how VHS machines can record 405 lines, do they need a base band feed? as even early ones normally only had a UHF 625 line tuner.

[Spot Wobble]

Thank you for all your messages and for the helpful article Frank: much appreciated.

I have found the download of the Sony CVM-90UB monitor manual. I will attempt to attach the file to this post so that Trevor, Jeffrey and anyone else interested can view it. (This is the first time, as a new GVR member, that I have tried an attachment - so hope it works.)

In answer to your question Richard: as you say, 405 lines can only be recorded on the VHS machine as baseband via the video line input. Therefore, the only way of making a video recording of a 405-line transmission would be from a 405-line receiver with a baseband video (and audio) line output. (The 9-90UB does have an audio line out, intended for recording on an audio tape recorder via the latter's microphone input.) 

Some VHS machines from other countries do have a VHF tuner, but that would be for (625 or 525) negative vision modulation and FM sound, NOT the positive vision modulation and AM sound used for 405-line transmissions in the UK in the past (and to be replicated if Heritage get their 405 transmissions going, according to my understanding).

Best wishes,

Francis