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

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Old 20th Mar 2019, 7:06 pm   #141
FRANK.C
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Default Re: Hedghog standards converter

Hi Nick
Can you post a photo of the test card?


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Old 20th Mar 2019, 9:08 pm   #142
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Well, Iíve done it! Completed the fitting of the sockets this morning just before noon. I wasnít impressed by the sockets, firstly putting them side by side they wouldnít fit on the board together, so I had to file them down a bit, second problem was solder refused to stick to the pins on some of the sockets, so I had to give the pins a scrub with the fibreglass pencil too. Once all that was done I got the FPGAís fitted, pulled a suitable telly off the shelves (Ekco TMB272, thought itíd make a change from all the Sony TV9-90ísí), and got ready to plug in the first one, I also set up a camera to record the event

In went the plug, nothing went bang, but then not a lot of anything else happened either, after a fiddle with the switches up popped the Hedghog test card! Complete with ĎHedghog standards converterí scrolling in the box at the bottom, neat touch, I like that! Connected a Sumvision SD card video player to the input and switched over, and up came the menu screen for that, played back some videos and had a play with some of the options, it all seems to be working!

I disconnected it and repeated the above with the second one, which also works too, Iíve got V2 firmware on this one. This one did some funny things with the test tone when I plugged in the video player, it sort of went up in volume, then faded back down, but other than that itís working fine.

I did notice the vertical jittering on the test card on the first Hedghog, the one with the latest FW, which was not present on normal video, didnít notice it on the second one, but Iíll have to check again to be sure. The TMB272 didnít like the equalising pulses, they make the picture drop down about an inch.

Iím not quite at the end of the road with these yet, both boards could do with a wash, as they are a bit sticky with flux, and Iíve still got the front and rear panels to finish. This has certainly been one of the best projects Iíve built, so many thanks to Frank for making it possible. Iím sure there will be many more years of enjoyment to come from these yet!

Regards
Lloyd
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Old 20th Mar 2019, 9:29 pm   #143
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Default Re: Hedghog standards converter

Well done LLoyd, it is great when they initialise for the first time.
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Old 20th Mar 2019, 9:36 pm   #144
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Well done Lloyd on your two successes.

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Old 21st Mar 2019, 12:26 am   #145
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Default Re: Hedghog standards converter

Quote:
Originally Posted by Lloyd 1985 View Post
I did notice the vertical jittering on the test card on the first Hedghog, the one with the latest FW, which was not present on normal video, didnít notice it on the second one, but Iíll have to check again to be sure. The TMB272 didnít like the equalising pulses, they make the picture drop down about an inch.
Congratulations, Lloyd!! I'm glad they worked after all that waiting!

It would be interesting to compare the jitter on the test card between the two firmware versions.

I've just had a further look at mine with regards to the jitter. As Lloyd said, it's either not there or not noticeable on actual video, but is very noticeable on the test card.

If I turn off the equalising pulses, I can carefully adjust the frame hold so that it goes completely out of interlace. At this point there is no vertical jitter and the picture is rock steady. As soon as the picture interlaces, that's when the jitter starts.

Also, as I mentioned before, the setting of the line hold is critical or the LOPT clatters away at 50Hz!

The same set fed with test card C from the Aurora gives a rock steady picture with no jitter at any setting of the frame hold. You can wind the line hold nearly end to end before it goes out of lock and at no point do you get the 50Hz chatter from the LOPT.

I tried a different TV with flywheel sync. There was (understandably due to the flywheel action) no clatter from the LOPT but the vertical jitter was just as bad. In fact, with the equalising pulses on, at some settings of the frame hold, I could get a good 1/2" of jitter!

I took a picture of the test card, but obviously this won't show the jitter!

All the best
Nick
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Old 21st Mar 2019, 11:37 am   #146
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Default Re: Hedghog standards converter

Cheers it is a great sense of achievement when you power something up for the first time and it comes to life!

Just done a quick comparison of the two, both have the jitter. I’m going to try some different sets at some point, if I can find a long enough cable to plug into my RF distribution boxes behind the telly shelves. I’ve certainly not heard any complaints from the LOPT in the Ekco, line hold hasn’t been touched since it was last set up with the Aurora, but I’ll give it a twiddle and see what happens.

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Old 21st Mar 2019, 12:40 pm   #147
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Default Re: Hedghog standards converter

My line hold has also become difficult to adjust, exactly as Nick describes, when using the Hedghog.

I'm also having trouble setting up the audio carrier pot. Can it be done without an oscilloscope? I hoped that by turning it very slowly that somewhere along the line the sound would stop interfering with the picture, but it doesn't seem to happen.

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Old 21st Mar 2019, 12:59 pm   #148
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Default Re: Hedghog standards converter

The second modulator IC is only used for the sound, and the input used is the video input, because we need AM modulation.
There is a video clamp on the input (inside the IC), and for this reason the audio circuit (just before the modulator) is made like this, providing an adjustable DC level. The level pot on the sound modulator biases the input to disable the video clamp on the IC.
So far my setting of the carrier pot (in fact the pot to get around the video clamp) about half-way seems to be good.

The audio level control should be set to give sufficient audio, but not more than that. I put in a (very) small pot with a shaft, so that I can adjust this from the outside of the case. Not all sources have the same audio level.
As a kind of reference level, you can use one of the internal test tones Frank has provided.

I still have to compare the hor sync of the Hedghog with other standard converters on various sets.

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Old 21st Mar 2019, 1:25 pm   #149
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Default Re: Hedghog standards converter

I’ve tried another 3 sets with one of mine, line hold is rock solid for a good range of the control, the vertical jitter is present on all of the sets I’ve tried so far, an Ekco TU211, T161, and a Sony Tv 9-90. Maybe we’re just being too critical about the jitter? I get the same jitter on 625 line sets when using the Raspberry Pi, or the menu from some freeview boxes, I just thought it was tvs having a bit of a dislike to displaying thin horizontal lines!

I’m happy with both of mine, I was actually surprised they both worked first time! Picture quality with them is excellent.

One slight thing I’ve noticed with the one with V05 firmware is the LED isn’t doing much, it glows very faintly, on the other one with V02 on it the LED flashes, is it supposed to do a bit more than glow?

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Lloyd
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Old 21st Mar 2019, 1:36 pm   #150
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Ignore my question about the LED, just worked out that it depends on the DIP switch settings! And also, the LED’s I’ve used are a bit crappy, swapping to a high brightness red one makes it glow brighter!

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Lloyd
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Old 21st Mar 2019, 4:03 pm   #151
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Default Re: Hedghog standards converter

Quote:
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I was actually surprised they both worked first time!
So was I!! I'm not casting aspersions on your constructional skills, but when you consider all the possible issues like dodgy modulator chips from China and FPGA boards with poor soldering, SMD assembly issues (those components are very small) and programming difficulties, I think we all deserve a pat on the back when the thing actually works!!

I did wonder if we were being too critical about the jitter, but the test card from the Aurora doesn't jitter, so it is possible!

Dave,
I assume you are using the Murphy V310? This doesn't have a fine tune control (I don't think). I've always found all my sets need careful fine tuning to get minimal sound on vision or vision buzz. I guess the Murphy relied on all the IF's being spot on. The fine tune control allows for a bit more leeway!

Have you ever used the Murphy with a different standards converter? It may be an alignment issue with the set rather than a HH problem.

Jac,
Thanks for the explanation. I read somewhere the correct set up procedure from Frank for the carrier level, but can't find it now.

I plan to built mine in the larger case as I will probably also incorporate a level control.

I'll be interested to know how the HH compares sync wise to your other converters on different sets.

I plan to fit the audio mod chip tonight so I can have a play with carrier levels etc.

Thanks for all the input, it's great to know what other issues people are finding.

All the best
Nick
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Old 21st Mar 2019, 4:22 pm   #152
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Default Re: Hedghog standards converter

Nick,

It is very well possible to mount a volume control pot directly onto the pcb or at an angle to the pcb.
Just see what you have lying around in your component boxes.
Any value between 20k and 100k would do. When you use 20k, you could reduce the input resistors to 2k2, and if you use 100k, you could put a resistor of 100k parallel to the pot, to reduce noise (if required).
Frank can advise better of course.

I tried to buy miniature pots, but did not manage to find small enough ones, so this is just what I had in my boxes.
A (vertical) preset pot with a kind of thin shaft would do nicely as well.
I mounted the pot at an angle to the pcb, so that the shaft lines up with the audio RCA connectors, but that is just for esthetics.

Jac
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Old 21st Mar 2019, 8:21 pm   #153
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Default Re: Hedghog standards converter

Quote:
Originally Posted by Jac View Post
So far my setting of the carrier pot (in fact the pot to get around the video clamp) about half-way seems to be good.
That's interesting because at around half way the picture is good but the sound is distorted. I'm sure it was ok until I removed the FPGA board to flash a newer firmware so I check and see if I've damaged something.

Quote:
Originally Posted by 1100 man View Post
Have you ever used the Murphy with a different standards converter? It may be an alignment issue with the set rather than a HH problem.Nick
Yes the vertical hold on my V310 is fine when using an aurora. With the hedghog I only have a few degrees of adjustment between loss of lock and nasty spluttering/buzzing sound.

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David
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Old 21st Mar 2019, 9:25 pm   #154
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Default Re: Hedghog standards converter

The test card on the Hedghog is generated in a different way to the one on the Aurora.

In the Aurora the test card is stored in memory external to the FPGA as an image and can be changed at any time to any image.

In the Hedghog it is generated within the FPGA by an algorithm and cannot be changed.
The Hedghog test card is harsher. Much of the test card is the same on both odd and even fields which gives rise to a degree of 25 Hz flicker.
The test card and grey scale are freebies as they use the logic that was left over in the FPGA after building the converter and no extra memory is required.

Jac has done a good job of explaining the audio carrier level. Setting the pot at half way is a good starting point.

It is easy to damage the surface mounted components removing the FPGA board.
Removing the board shouldn't be attempted until the Hedghog PCB is removed from the case as a lot of strain can be put on the components close to the mounting holes if left in the case.

Frank
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Old 22nd Mar 2019, 1:01 am   #155
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Default Re: Hedghog standards converter

I've now fitted the audio modulator chip to the first HH and it works perfectly. The audio quality sounds excellent with no distortion or vision buzz.

The audio carrier pot doesn't seem very critical: midway works fine and it's only towards each end of the pot that the sound gets distorted. With the DVD player I'm using, the audio level pot needs to be up full.

I've fitted the remaining bits to HH No2, and using the FPGA board from No1, that all works fine too. There is still no activity on the LSB on either board, so I guess the fault is on the FPGA board. I'll see what happens when I get the second FPGA board in a couple of weeks.

Notwithstanding the lack of the LSB in the video, the quality is excellent. I've just sat and watched 'Dad's Army' for half an hour and I can't fault it- picture and sound are superb!!

Frank, please don't think I was being critical of the test card- I just like to understand why things are the way they are! After all, I'm not going to sit and watch the TC and it's perfectly useable for setting up raster geometry etc. The greyscale pattern is really useful and something I will use a lot for signal tracing.

The thing that really appealed to me about the HH was the front panel selectable options:- this turns it into a useful piece of test gear.

This has been a hugely enjoyable project and a steep learning curve with the SMD and the computer aspects. Initially I was going to take the easy route and buy a complete unit from 'Freya', but I'm glad I didn't as I've learnt a lot and have two units into the bargain!

Many thanks to everyone that's helped with suggestions and advice, but especially Frank for designing the HH and making that design freely available.

Cheers
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Old 22nd Mar 2019, 12:02 pm   #156
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Default Re: Hedghog standards converter

I found two legs on the ic7 (MIC5504) had not been soldered! Soldering them down has fixed the line hold problem. I now behaves exactly the same as when using my aurora.

I'm still having problems with the sound upsetting the picture but with the gain set low it's not too bad (as long as nobody screams!). I need to get on with my second HH so I can compare the two.

While I had the opportunity I flashed the firmware to V05 but I notice that two test tones are back on the front switch and the 16:9 input has gone. Was this intentional?

Regards
David
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Old 22nd Mar 2019, 12:15 pm   #157
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Default Re: Hedghog standards converter

Sounds like another FPGA issue.I have just programmed another five FPGA boards with v5 and they all have the single tone and 16:9.
The sound affecting the vision is not usual, I have to turn the input device to quite an extreme to get it to do this,.
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Old 22nd Mar 2019, 12:36 pm   #158
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Default Re: Hedghog standards converter

Did you put the DIP switches in the correct position?
Notably SW8-C.

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Old 22nd Mar 2019, 2:10 pm   #159
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Default Re: Hedghog standards converter

Dave, SW8-C selects the function of the Tone/Input Aspect Ratio switch.

Frank
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Old 24th Mar 2019, 8:09 pm   #160
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Default Re: Hedghog standards converter

Hello everyone,

I have now completed my first Hedghog converter. It is residing in an aluminium case designated "AKG105-30" made by Fischer. Since the PCB board has components mounted very close to the edges the board could not be slid into the grooves on both sides of this case, instead I had to mount the board turned by 90į this meant all the switches had to be mounted on a separate helper PCB. Here is a view of the insides:

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This is the front with the helper PCB for the switches. I chose some very small micro switches available from mouser.

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All connections were mounted on the back panel and I used BNC jacks for the video I/O. The F connector was also mounted at an angle of 90į i.e. "sideways" on the PCB with respect to the original design. Here is a view from the back:

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It also has CE mark now

The text captions of both front and back were done with adhesive foils that were printed on my laser printer. I made some small changes to some of the text and used a software called "FrontDesigner" to make the labels. This is a tool that is precise to about 0.05mm and has some useful features for making all sorts of front panels.

Here is the final product in action. I have used the "o" of the Hedghog caption as a power on indicator so it lights up in blue when the converter is on.

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The unit is powered by a USB Jack using a regular mobile phone charger.


It was quite a bit of work to get everything to work that way but I wanted to use this case since I have a few of them lying around and it is really small and neat.

Semir
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