UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Television Standards Converters, Modulators etc

Notices

Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

Closed Thread
 
Thread Tools
Old 15th Mar 2015, 5:42 pm   #41
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: An ITV converter.

The problem of patterning on Band 3 renders the converter unusable. Even with the Band 1 signal attenuated the patterning is still present. So what can be done about it? For starters we know that the problem is not caused by direct injection of the Band 1 signal from a transmitter and the reason for the B1 breakthough on a Band 3 channel is the result of leakage inside the converter.
Pull out the Band 1 input and the patterning disappears.
Examining the circuit diagram reveals that on Band three channels the Band I input is terminated by a 68 ohm resistor and the link between the Band 1 input to the output socket is broken.
Shorting out the 68ohm termination resistor solves the problem, no breakthough whatsoever. In fact EMI did this in their converter. The Band 1 aerial was simply shorted out.
In practise that was OK but nowadays we often connect more than one 405 line receiver to our aerial systems and the Band 1 signal supplying other sets will be degraded when the converter is switched to Band 3.
Actually, I'd imagine in the old days viewers simply pulled out the Band 1 aerial plug when they watched ITV. That action would get rid of the patterning.

Something to discuss perhaps?

DFWB.
FERNSEH is offline  
Old 15th Mar 2015, 8:46 pm   #42
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: An ITV converter.

Follow up to my last post. R13 the Band 1 termination resistor has been shorted out and the patterning problem on Band 3 has been solved.

DFWB.
FERNSEH is offline  
Old 3rd Jan 2016, 3:23 pm   #43
line sync
Heptode
 
Join Date: Sep 2009
Location: Kinver, Staffordshire, UK.
Posts: 628
Default Re: An ITV converter.

I acquired this band 3 converter recently so after cleaning it up I thought I would post a picture because I`v never seen one this colour before.
There also should be two smaller knobs on the metal shafts but these were missing off the unit when I got it , I`ll never find 2 knobs that colour but its a converter worth keeping.
Its made by Wolsey.

Robin
Attached Thumbnails
Click image for larger version

Name:	DCP05119.jpg
Views:	308
Size:	54.5 KB
ID:	117748  
line sync is offline  
Old 12th Jan 2016, 10:49 pm   #44
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: An ITV converter.

Hi Robin,
Is it a switch tuner like the Invicta 245 converter which started this thread?
Or is the tuner continuously variable.

What type of valves are employed in the converter?

DFWB.
FERNSEH is offline  
Old 13th Jan 2016, 12:34 am   #45
line sync
Heptode
 
Join Date: Sep 2009
Location: Kinver, Staffordshire, UK.
Posts: 628
Default Re: An ITV converter.

Hi David
This is a switched tuner with a fine tuning control.
The valves are 30C1 and 30L1.

Robin
line sync is offline  
Old 5th Feb 2016, 1:02 am   #46
beery
Heptode
 
beery's Avatar
 
Join Date: Jun 2006
Location: Ware, Hertfordshire, UK.
Posts: 988
Default Re: An ITV converter.

Hi all,

Does anyone know who made this converter?

It has no maker's markings and has a Spencer-West kind of look to it.

The valves are both type 6BW7. The front panel looks like paxolin, but is actually brown painted steel. The casing is light straw painted tin plate with louvers at the sides.

I tested it and found the transformer prone to primary-to-chassis breakdown

I tried it connected to an isolation transformer and it worked. I've taken the plug fuse out now though. It is hardly worth re-winding the transformer...

Cheers
Andy
Attached Thumbnails
Click image for larger version

Name:	P1030326.JPG
Views:	213
Size:	76.0 KB
ID:	119559   Click image for larger version

Name:	P1030324.JPG
Views:	201
Size:	84.4 KB
ID:	119560   Click image for larger version

Name:	P1030323.JPG
Views:	197
Size:	97.0 KB
ID:	119561  
beery is offline  
Old 5th Feb 2016, 12:37 pm   #47
FERNSEH
Dekatron
 
FERNSEH's Avatar
 
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
Default Re: An ITV converter.

Hi Andy,
I'm sure a similar looking band 3 converter was advertised in the Practical Television magazine offered fully built or as a kit. Used two EF80s instead of the 6BW7. You'd think they'd use a better pair of valves though.
100Mhz was considered the limit for those RF pentodes.
EF95/6AK5 is good for 400Mhz.

DFWB.
FERNSEH is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 8:09 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.