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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions. |
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22nd Dec 2012, 11:56 am | #1 |
Heptode
Join Date: Jan 2010
Location: Killamarsh, Sheffield, South Yorkshire, UK.
Posts: 746
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Building Darius converter - some parts NLA
Hello all
As I will be getting a 405 set very soon (today, in fact), I don't have a standards converter. For a long time I have been intending to build the Darius converter so i can learn more about the principles of standards conversion. However, looking at Darius' original design, it's now become clear that some parts are difficult to obtain or are NLA. https://www.vintage-radio.net/forum/...ead.php?t=1757 The list of ICs/transistors with which I've had difficulty in obtaining are the following: LS221 MFI 2n26k8 M7403 CCD CD74HCT4046 HCT40103 LS73 M7403A 1) What substitutes are available for the purposes of these chips? 2) There are several transistors in the schematic that do not have their type listed - are these ordinary PNP/NPN transistors? 3) Also, there are several diodes listed as "4148" - what types are these? 1N4148? Best regards, Aidan Lunn |
22nd Dec 2012, 1:54 pm | #2 | ||||||||
Nonode
Join Date: Oct 2008
Location: Warsaw, Poland and Cambridge, UK
Posts: 2,669
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Re: Building Darius converter - some parts NLA
That's a 74LS221, which should be readily available as a 74HCT221. It's a monostable multivibrator, so beware that you might have to adjust the R/C values to get the same time delay as the original design when changing from LS to HC or HCT logic.
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Disclaimer: I'm just an electronic engineer and have never had anything to do with Darius standards converters. Chris |
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22nd Dec 2012, 2:43 pm | #3 |
Pentode
Join Date: Oct 2012
Location: Dorset, UK.
Posts: 240
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Re: Building Darius converter - some parts NLA
The 7403 CCD 1H delay device is used in the dropout compensator of many VHS VCR's, scrap machines would be a source of this device or an equivalent. (although many vcrs are becoming vintage in their own right now!). A search for PAL 1H CCD delay will find some alternative devices with the same function, though probably not pin compatible. What I've been unable to find is a datasheet for the 7403 device.
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22nd Dec 2012, 5:16 pm | #4 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,820
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Re: Building Darius converter - some parts NLA
Darius' phone number is on his profile, so I suspect he wouldn't mind talking things through with you:
https://www.vintage-radio.net/forum/member.php?u=153 Nick. |
22nd Dec 2012, 11:16 pm | #5 |
Heptode
Join Date: Jan 2010
Location: Killamarsh, Sheffield, South Yorkshire, UK.
Posts: 746
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Re: Building Darius converter - some parts NLA
Does anyone know of any substitutes for/alternative sources of BF506 transistors
I could only find Donberg - and they quoted £19.80 for just two!! |
22nd Dec 2012, 11:40 pm | #6 |
Retired Dormant Member
Join Date: May 2009
Location: Norwich, Norfolk, UK.
Posts: 717
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Re: Building Darius converter - some parts NLA
I found 50 for less than a fiver on ebay. Uk stock are a couple of quid each.
Rob |
23rd Dec 2012, 12:11 am | #7 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Building Darius converter - some parts NLA
Hi
Aidan's request for suitable component equivalents for Darius's Standards Converter has prompted me to mention my great success in building Darius's later (MK4) Standards Converter. This may well be a better option to build the later version as PCBs were available. As it is a fairly complex circuit, PCBs at least give you a better chance of success. It has been a long project on and off for the last five years due to other more pressing committments. I also built his CH1 VHF modulator and found this to be really stable. Also within the enclosure, I decided to build Jon Evans's and Peter Brown's Test Card C generator. The MK4 version is built on two PCBs, one is the Clock board, the other is the CCD board containing the three delay line ics which are all Sony CXL5508s in my version. Looking at the first photo, the CCD board is at the front left. To it's right, is the Clock board. The CH1 modulator is at the left back and the large board front right is the Test Card C generator. Many thanks to Peter Brown who kindly supplied the EPROM and some other ics for this. Two voltage regulator boards are situated to the right side. I used a toroidal mains transformer to minimise mains fields. The whole project was built in a redundant Philips On Digital box with a small amount of surgery on the lower plastic tray. I made up a Paxolin rear panel to accomodate the BNC sockets, IEC filtered mains inlet and the RF output Coaxial socket etc. I used a made up wafer switch for the different modes of operation. The switch only controls the supply voltage to each section, no attempt was made to switch the video signals. Using a short 75 Ohm BNC to BNC jumper cable loops the video as required on the rear panel. Switching the video signals may be a further refinement if done properly! I hope this gives others encouragement to build this excellent design, the whole project has been a complete joy to build. More pics to follow. Seasons Greetings, Symon Last edited by Philips210; 23rd Dec 2012 at 12:15 am. Reason: text |
23rd Dec 2012, 12:47 am | #8 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Building Darius converter - some parts NLA
Hi more pictures of the combined Standards Converter and Test Card generator.
The first picture shows the rear panel layout. The second picture is a standards converted picture, note the low emission tube on my Philips TVette doesn't really show the converter at its best. I have a Sony 9 90UB that I will use for further pictures. Note also the lashed up log periodic aerial on top of the TVette. This connects to a Goodmans freeview box. The third pic is the Test Card C generator and pictures four and five are the Standards Converter CCD and Clock boards respectively. I took a great deal of photos of oscillograms at many test points in the standards converter in case of future faults. A good feature of Darius's MK4 design is that it will accept both a 405 and 625 line video signal and will automatically switch the conversion stage as necessary. Regards Symon |
23rd Dec 2012, 1:02 am | #9 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Building Darius converter - some parts NLA
Hi
A few more pictures, this time from the CH1 modulator and bandpass filter units. The bandpass filter has not been set up yet and I envisage it could be tricky to do so. I have a spectrum analyser that isn't working (another project to do) so hopefully I'll get somewhere setting up this bandpass filter in due course. Regards Symon. |
23rd Dec 2012, 11:03 am | #10 | |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,273
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Re: Building Darius converter - some parts NLA
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Peter |
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27th Dec 2012, 12:19 am | #11 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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Re: Building Darius converter - some parts NLA
This topic has motivated me to rebuild one of my standards converters.
This one dates back to 1990 and was my second attempt. It fell into disrepair ages ago. The first two pictures show the wreckage of the thing and the third and fourth are of the PCBs now grouped together in a much more tidy manner. The converter had three line store units, one is the the primary line store, the other two performed the function as interpolation stores. One as "line above" and the other as "line below". For the sake of simplicity, the rebuilt converter will have one interpolation line store unit, although a third line store could be added sometime. I should have enough parts to construct another similar converter. DFWB. |
27th Dec 2012, 11:30 pm | #12 | |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Building Darius converter - some parts NLA
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That was quite an achievement building a successful standards converter back in 1990 and the end result must have been very satisfying. Were there any difficult to obtain ics particularly in the line store circuits? I would like to have a go at building your design if that's ok with you. If so, do you have the full circuit diagram to hand. Regards Symon |
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28th Dec 2012, 9:51 pm | #13 | |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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Re: Building Darius converter - some parts NLA
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I believe just about all the chips I chose for the 1990 version are still available. Stocks must still exist for the CA3306 ADC, I do know that an SMD version was availble in 2004, in fact I might have some. All the TTL types are plentyful except for the 74ALS688 and the 74LS625 VCO which do seem be scarce. The line store SRAM is the CY7C128 and I think that type is still in the RS catalogue. The PCBs were designed using crepe tapes. That was the way we made PCBs in the late 1980s. I am redesigning many of the circuits so there will be some changes to the PCB artwork. After I've settled on the circuit changes it might be possible to submit the revised designs to one of those firms that make printed circuit boards. In May this year I modified the 405 clock pulse and timing board, It was found that there were some worthwhile changes to do to the original design which dated back to 1985. The 625 clock and timing PCB will be redesigned. The problem with present design is that the VCO drifts off frequency when there is no input signal. The divider circuits employ the excellent 74LS161/3 TTL counter, no changes in that department. I do know that another Forum member is interested in the construction of my converter after the new circuits have been sorted out. The present job is simply to tidy up the existing mess. I'm making progress. In 1992 I made a simple non interpolating converter which employed a FIFO in the line store. It did work but there was no further development on that idea. I believe that this converter is still in existence. I have the FIFO line store PCB artwork. The support circuits are the same as the SRAM version. DFWB. |
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28th Dec 2012, 10:25 pm | #14 | |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Building Darius converter - some parts NLA
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Hi David. I can second that. When I worked for a small marine electronics manufacturing firm in 1985, my first job was to design the complete IF board layout for their latest receiver using the crepe tapes in a 2:1 ratio I think. Red for component side, blue for solder side. Black was reserved for single sided PCBs. Time consuming and sometimes frustrating, though quite satisfying when it all works out. Your standards converter is progressing well and I certainly look forward to seeing it complete and having a go at building it. Regards Symon. |
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28th Dec 2012, 11:49 pm | #15 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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Re: Building Darius converter - some parts NLA
I've assembled another carrier for the PCB boards. This one carries the power supply unit and the the analogue signal processing boards.
The PSU is an RS components part and was bought in 1984 for the original converter. It has been utterly reliable, made in the USA by a firm called Powertec Inc. The original converter now has a Farnell SMPSU fitted instead. The metal angle strips and corner brackets were sourced from B & Q. The metal plate was salvaged from the old converter. For the PCB carriers I've settled on a standard size of 400 X 225mm which means they can be easily installed in a standard 19 inch rack assembly. I intend that the rebuilt converter will be an easy to service and repair unit, quite unlike the original shambolic wreck. One of the reasons why it fell into disrepair was that it was a horrible thing to work on. . DFWB. . |
1st Jan 2013, 8:26 pm | #16 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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Re: Building Darius converter - some parts NLA
Some output waveforms from an early Darius converter. The video amplitude is 2 volts unterminated. Should be 1 volt into 75 ohms.
The first pic shows the line sync pulse and picture content. The second and third pics show the frame pulse and frame blanking blanking period. The sync pulse height needs adjusting during the frame blanking. A good converter to build if you can find those CCD chips. DFWB. |
2nd Jan 2013, 10:49 pm | #17 |
Triode
Join Date: Sep 2005
Location: Hemel Hempstead, Hertfordshire, UK.
Posts: 27
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Re: Building Darius converter - some parts NLA
Hello all.
This thread has has re-kindled my interest in building Darius's "Normwandler" converter. I followed the original articles in this forum around 2005 but have to confess lost interest when the Auora appeared. (I bought two of them!) However still think there is a lot of appeal in building this discrete design with the opportunity to learn about the standards converter process. As I have lost track of where the design ended up, what was the final design version with PCB's, version III or iV? Are the boards or PCB layout artwork still available? As to problems of obtaining 1H delay lines, I think it was the MK-I which used the the CXL5508, with MK-II using the MSM7403. For the Sony CXL5508 I have a data sheet for but as noted by others, devices are not available. The MSM7403 is apparently available (littlediode.com) but no data sheet so I'm reluctant to purchase. I have been searching for other delay devices and have found that the Sanyo LC8992 looks like it might be suitable. The only possible problem might be its having 565.5 stages and not 565 as per the CXL5508. There is also a LC89925 having 566 stages available for PAL format. Both are clocked at 8.8672375MHz giving 63.77us & 63.83us respectivly for a PAL 1H delay. I'm not sure however if they are tolerant to the ~4.4MHz & ~2.95MHz clocks required by the other delay lines used in the convertion process. I attach the data sheets for both. I would be interested in any comments on these or any other delay devices. |
3rd Jan 2013, 1:31 am | #18 |
Nonode
Join Date: May 2007
Location: Redruth, Cornwall, UK.
Posts: 2,562
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Re: Building Darius converter - some parts NLA
Hi Mikey.
The Darius Standards Converter that I built was the Mk4 version and was built on two PCBs available from Darius himself. That was however over five years ago. The full circuit diagrams for the Clock and CCD boards are to be found in this thread: https://www.vintage-radio.net/forum/...?t=7795&page=3. I thought the MSM7403 delay lines were used in his earlier designs and the CXL5508 and CXL5506 (twice clock frequency version) in his later designs. I think Peter Scott will be able to confirm this as he built the earlier version. You'll see on the circuit diagrams in the above link, the option to use the CXL5506 instead of the CXL5508 for ics 3 and 5 on the CCD board with associated component value changes. The interpolator CCD (IC4) remains as a CXL5508 however. I had also considered the Sanyo LC8992 but seem to remember the supply voltage requirements were different to the CXL5508. I managed to obtain my CXL5508s from JH Components though I ended up buying 10 ics due to a special order requirement. He doesn't currently list this ic but has an eBay shop: http://www.ebay.co.uk/sch/jhcomp25/m...&_trksid=p3692 It may be worth contacting him. I reckon if enough people are interested in building this converter, then if say 20 or 30 pieces were ordered from him it would be fairly cost effective buying this quantity. I do have a few spare 74HCT4059 counter ics if required as these are a little difficult to find. These are in the standard 0.6" pitch rather than the slim 0.3" version. Regards Symon Last edited by Philips210; 3rd Jan 2013 at 1:41 am. Reason: context |
3rd Jan 2013, 8:06 am | #19 |
Triode
Join Date: Sep 2005
Location: Hemel Hempstead, Hertfordshire, UK.
Posts: 27
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Re: Building Darius converter - some parts NLA
Hi Symon,
Many thanks for the update to the Darius converter. I note the 9v requirement for the Sanyo LC8992 but if push came to shove this might not be a problem in a revised design. I also note the possible source of CXL5506/8 & will contact JH components. Regards. Mike |
4th Jan 2013, 8:02 am | #20 |
Triode
Join Date: Sep 2005
Location: Hemel Hempstead, Hertfordshire, UK.
Posts: 27
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Re: Building Darius converter - some parts NLA
Hi all
I have now managed to purchase four off CXL5508's from JH comps and have established the following component availbilities from Farnell:- LM1881 Farnell Nos: 1564700 74LS221N 1470898 CD74HCT4046 1740251 74LS92N 1470791 74LS73 1470822 74LS51N 1740034 BC547C 2101811 BC557B 1574384 1N4148 9843680 TL431 9593543 74HCT4059N are indeed difficult to find from the usual sources but looks as though are available although expensive from littlediode.com. I assume that if the 74HCT4095N is deemed too difficult / expensive then the divide by 283 could be achieved using alternative devices, i.e the HCT40103 / HCT83 as used in the MKII converter? Obviously a revised PCB would need to be considered. I don't anticipate any problems with other semiconductor devices. So it seems that the converter could be built without too many problems of obtaining components. |