Bush TV22 - No Signal
 

Happy Christmas to all.
Finally got to try my re-capped Bush TV22 on the Aurora, should I not be able to see a test pattern with no video input connected?

To complicate things I have a band 3 converter fitted, tried injecting the signal through this and the original aerial input, but to no avail.

Any help much appreciated.

Regards Graham

Re: Aurora from Santa
 

Hi Graham,
If you have a model SCRF405A then I do flash these with Test Card C before shipping. I also set the RF channel to Band I Channel 1 by default. The unit as shipped supports all 13 Band I channels but no Band III channels so there would be no way to use the Band III converter on your set. You would need to have the set back to it's original Band I specifications. I'm sure there are many people here on the forum that know these converters very well and could help with this.
I will mention that the converter is capable of up to 880MHz RF, so it could be programmed with Band III channels. This does require redoing the fpga firmware and reflashing the unit as this is stored as a table.

Darryl

Re: Aurora from Santa
 

Hi Darryl,
If it supports all 13 VHF channels, then that's Band I and III - 1 to 5 are Band I, 6 to 13 are Band III. Are you confusing Band III with UHF, aka Bands IV and V?

I wonder if it's the mention of a converter..? I recall the US had UHF converters; we had Band III converters. When ITV launched (on VHF Band III channels) there were many sets around whch covered VHF Band I only so there was a market for Band III converters for a brief period.

Cheers, Kat

Re: Aurora from Santa
 

I think that Darryl must be suffering from Xmas excess. Kat is indeed correct about the channels for Bands I and III.

Obviously the Band III converter is one further possible cause of trouble in the signal path. I would suggest injecting on the original Band I channel for initial trials.

Re: Aurora from Santa
 

Right you are Kat! I wrote that late last night, so I guess I had a little to much Christmas cheer! We did have UHF converters here and that's what I was thinking of. The converter does have the 5 Band I channels and 8 Band III channels.

Graham, you should just be able to adjust the converter to the channel of your set through the dip switch inside, but as Jeff mentioned, the Band III converter could be a source of your problem, so it might be good to start the trouble shooting farther down the chain.

Darryl

Re: Aurora from Santa
 

Brilliant, I've got it, the test card, strangely though via the band 3 converter only.

Dismantled the converter and found the tuning wheel lock nut loose. Retightened, retuned and got the test card. Still needs improving, but that's another thread.

Thanks for your help guys and thanks to Darryl for supplying a such brilliant device. Graham.

Re: Aurora from Santa
 

Hi,

Interesting... If memory serves, some converters were connected up by removing a valve from the tuner then plugging a flying lead into the vacated valve socket. Didn't the Bush TV22 have a converter made specifically for it?

If the Band III converter fitted is of this type, I suppose it's possible that a fault in either the tuner or the converter could leave the set working on Band III but not on Band I.

Cheers, Kat

Re: Aurora from Santa
 

Hi Kat,
I can't find any brand name on the converter; this type I have seen fitted to other TV22s. No valves have been removed, but the original inter-chassis flying lead is plugged into the side of the converter.

I guess I could return it to original spec by simply swapping over the flying leads? Then try the original aerial input again?

Graham

Re: Aurora from Santa
 

If you remove the converter, which I think may be the original Bush one, you need to refit a wire from the contrast pot to one of the tagstrips.

Andi

Re: Bush TV22 - No Signal
 

The switch fully out confirms that I am only getting a signal (very grainy) via band 3.
So would the original set up have had two different aerials for the the band 1 and 3 inputs?

Regards Graham.

Re: Bush TV22 - No Signal
 

I have now completely bypassed the band 3 converter and put the wiring back to the original route (thanks, Andi, for the photo) but still no test card signal via the original bi-pole input.

Dare I try adjusting the tuning coils?

This is my first TV restoration project so I am a bit nevous about that. Thanks for the info; perhaps someone else could answer the aerial query?

Regards Graham.

Re: Bush TV22 - No Signal
 

Success,test pattern C via Band 1 (thro' the original input).

I completely removed the Band 3 converter then found that I had left one cable still connected !
Also found the the nameplate "Bush Television Converter type 184". I will try to reinstate it, once I have fine-tuned everything.
One further question: on what end of the scale is the tuning knob?

Regards Graham.

Re: Bush TV22 - No Signal
 

In your shoes I would have left the converter connected exactly as it was. There are internal connections to it in addition to the multi-plug. Ensure the Band I/III switch is pushed fully in. You can find full details of the Bush ITA TV184 converter on sheet 1212 of the BVWS Trader sheets CD ROM (PM me if you need a copy emailed).

Ensure you are only feeding the Band I signal into the original aerial connector. It won't work if you feed it into the converter. What you might have been seeing before was a harmonic in Band III from the Aurora. I've heard it produces a fair few of these harmonics and this is normal. The fact you could see this is highly encouraging.

I assume your Aurora is set to give out Channel 1. Is your TV22 also set to Channel 1? If not, it's a pretty straightforward job to tune it in. All the below is to be carried out at your own risk.

First, ensure your chassis is at mains neutral, not mains live.
Set the vision interference limiter fully anti-clockwise.
Ensure the screw adjustments located between the aerial connector and the 'tuning' button are adjusted to sit level with the top of their screening cans. Now adjust the 'tuning' button for maximum sound. It should end up pointing somewhere near '1' on the channel indicator. Then tweak in the two other screw adjusters for maximum vision, reducing the contrast as appropriate as the tuning improves. Finally make a slight adjustment to the 'tuning' knob again. Done!

Steve

Re: Bush TV22 - No Signal
 

Thanks Steve, retuned following your instructions and now have a much sharper clearer picture, but being a bit pedantic the test card circle is a bit out of shape on one side, any tips?

Yes please; I will PM you for the Bush 184 operating manual. Once I am fully sorted, I will replace the band 3 converter and wire it back in.

Regards Graham.

Re: Bush TV22 - No Signal
 

ITA Tuner Service sheet sent.;)

Re: line linearity...

1: Adjust C25 (underneath). Set this for maximum width and brilliance without any vertical white lines becoming apparent.

2. Adjust the 'width' slider and the line linearity adjustment (through hole) together for best overall effect.

3. Adjust little capacitor C33 on top of scan yoke for minimum kink at extreme left of picture.

4. With the set switched off, check the core of the line output transformer isn't really hot (it's OK if it's 'warm'). These transformers suffer from rusted laminations - a hidden condition. If you're really unlucky, shorted turns are a possibility.

5. Check the condition of the PL38 line output valve and the ECL80 line oscillator.

6. Check the PZ30 is OK on both its sections.

7. Check other components in the line output stage, particularly C30 and C31 and C34.

HTH

Steve

Re: Bush TV22 - No Signal
 

Oh... and another thing. Check that the multipole plug going into the scan coils lead is clean and bright and making a good connection into its chassis socket. I've had past trouble with these...:-X

All the best,

Steve

Re: Bush TV22 - No Signal
 

Thanks for the 184 sheets, Steve. Further tweaking as per your suggestions has given me a more uniform test card circle.

The LOPT has shown past signs of overheating, but before I put my hand in, what's the best way to discharge the EHT?

Graham.
PS: I will also clean up the plug

Re: Bush TV22 - No Signal
 

Insulated handle screwdriver with blade touched to chassis and EHT terminal. If it won't reach, then a clip lead from chassis to screwdriver.

Remember the capacitor can recharge to some extent by itself so you may want to connect a clip lead from EHT to chassis. DOn't forget to remove it before switching on!

Purists say you should discharge via a resistor. In a valve set this is not necessary. Even in a solid state set it's not normally a problem provided you discharge to the earth strap on the CRT rather than a random point on the chassis.

Re: Bush TV22 - No Signal
 

You've put me on the spot there! When the set's switched off I have to admit with old sets I don't usually bother to discharge the eht (but should). I guess a croc clip terminated lead connected to chassis first would do the trick (although there are lots of volts there's little charge involved and no static-sensitive devices nearby, so a resistor isn't necessary IMO - others may disagree). The above does not apply to mains eht sets though.
Obviously, remember to remove this lead before switching the set on !8-o

Best check the transformer for temperature just after a run of half an hour or so. I always strip the pitch off these LOPTs and then spray with a modern anti-corona aerosol. I add a little matt black to the uppermost face of the laminations first too to increase heat radiation. No, this may not be 'original' but it allows proper inspection of the LOPT and should provide better cooling and reliability.

Steve

Re: Bush TV22 - No Signal
 

How? Is this an oven job? What do you recommend as the anti-corona spray?