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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 8th Mar 2019, 11:41 am   #121
FRANK.C
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Default Re: Hedghog standards converter

Hi Semir
Glad it is working well for you. Getting rid of the 5V reg and powering it from a phone charger should reduce the heat inside he case quite a bit as well as making use of a redundant charger.
Looking forward to seeing your completed Hedghog.

Frank
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Old 14th Mar 2019, 12:39 pm   #122
Lloyd 1985
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Default Re: Hedghog standards converter

This is frustrating!! I'm so close to finishing now, I've got both my FPGA's, programmed them, and finished just about everything on the main board, but the sockets to connect the 2 parts together still haven't arrived! I'm tempted to buy some more from a different seller. Never mind, I'll make a start on the front and back panels to pass the time.

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Old 14th Mar 2019, 12:47 pm   #123
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Default Re: Hedghog standards converter

I know what you mean about those connectors Lloyd, I was waiting for some from 27th Jan to be delivered, they turned up Friday last week.
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Old 14th Mar 2019, 3:34 pm   #124
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Quote:
Originally Posted by Lloyd 1985 View Post
This is frustrating!! I'm so close to finishing now, I've got both my FPGA's, programmed them, and finished just about everything on the main board, but the sockets to connect the 2 parts together still haven't arrived! I'm tempted to buy some more from a different seller. Never mind, I'll make a start on the front and back panels to pass the time.
Hi Lloyd,
That is, indeed, frustrating! I got mine from Farnell with all the other bits so they came next day. Mind you, I tried to be clever and ordered 50 way ones thinking I could cut them in half. Obviously enough, they are only 25 way when you take both rows into account!

I re- ordered 15 way ones and cut one way off in the end!

I still haven't tested mine on a TV yet. My 'scope failure put an end to that as it's now cluttering up the bench. Hopefully next week....

Cheers
Nick
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Old 14th Mar 2019, 5:48 pm   #125
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I should have got some from Farnell too really, would have been quicker! I bought some 7x2 pin ones, so 2 side by side should do it. I have got some 1x40 pin ones in a box, but I didn’t fancy chopping them up, especially as you loose a pin each time you cut it.

Made a bit of a mess of the front panels, managed to drill the holes for the switches just slightly off, it sort of fits, but sort of isn’t good enough! So I’ll start again..

Regards
Lloyd
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Old 14th Mar 2019, 6:00 pm   #126
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Lloyd,

The holes will be masked by the front text paper/plate, so don't worry.

I printed a front panel (as made made Frank) cut it along the lines and attached it with tape to the plastic front part, after which I punched where the holes should come, and drilled them carefully. You can always file them a bit larger if required, or in your case extend the holes to where they should be.

Check that your printed front-paper is size-accurate. A "better" printer was way off, so I used my normal printer for it.
For the back I made an alternative, since I added an RCA connector, switch, a 2-pin mains inlet and mains switch, and the shaft of a small volume control protrudes (to be able to adjust the volume - not all sources supply the same level). And a hole to be able to set VR2 when the case is closed.

Hope this helps a bit.

Jac
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Old 15th Mar 2019, 12:36 am   #127
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Hi Lloyd
Like Jac has said, I drill the holes for the switches and connectors in the panels larger than necessary and cut the printed legends out to fit tight around them. This hides any gaps. The hole for the hex switch is the only one that needs to be fairly accurate.

Frank
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Old 17th Mar 2019, 11:50 pm   #128
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Default Re: Hedghog standards converter

Tonight I cleared the bench of dead 'scopes and detritus, dug out a 405 TV, spent some time working out why that didn't work only to find I'd nicked the ECC82 ...

The Marconiphone VT161 displays stunning pictures, so I thought this would be a good test for the Hedghog.

Well it does work- sort of! It has issues!

The internal test card is quite juddery. It's like each field is starting a few lines vertically displaced from the next one.

Monitoring the video out, the internal greyscale pattern gives a nice stable stairstep waveform on the scope.

Switching to external input and feeding in a greyscale pattern from a 625 pattern generator, the 'steps' are twitching in amplitude.

Feeding in actual video from a DVD player and looking at it on the TV screen, it looks like there are sampling bits missing. The mid greys have a silvery look with no detail and there is noticeable background noise on the video.

I wonder if one of the data lines from the video decoder chip is missing?

My second HH is nearly finished, it just needs the IC's fitting. I can then compare the two and hopefully narrow down the fault. I've still only got one FPGA at the moment, but if the second HH displays the same fault, then it's probably the FPGA that's faulty.

By the way, there is no vertical judder when watching actual video, only when viewing the internal test card.

Cheers
Nick
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Old 18th Mar 2019, 12:09 am   #129
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Default Re: Hedghog standards converter

Might be worth getting the FPGA under a microscope if you have one, or a good magnifier, the soldering isn’t the greatest on them! Mine had solder balls left all over them, so I gave them both a good scrub with IPA and reworked any joints that looked iffy. Still don’t know if they work yet though!

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Lloyd
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Old 18th Mar 2019, 12:24 am   #130
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Default Re: Hedghog standards converter

Hi Lloyd,
As others had had problems with the soldering on the FPGA board, I scrutinised it under a lens when I first got it. I couldn't see anything wrong and the soldering actually looked pretty good.

Are you hoping to get the connectors for yours this week?

I've just taken some pictures to try and show the problem. You can see the effect if you look at the uniforms, especially picture No3. There should be lots of shades of grey rather then just one!

The same picture viewed on the Aurora looks as it should do.

You can also see the background noise in the second picture.

Cheers
Nick
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Old 18th Mar 2019, 12:49 am   #131
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Default Re: Hedghog standards converter

Hi Nick
It is difficult to tell for sure but looking at the photos it could be a faulty FPGA board.
For a pixelated output it would be worth checking the resistors that form the R2R DAC (R46 to R64)

Frank
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Old 18th Mar 2019, 1:10 am   #132
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Default Re: Hedghog standards converter

Hi Frank,
I've just this minute ordered another FPGA board for the second HH. Hopefully it will come as quickly as the first one which took less than 2 weeks.

I can get the chips soldered into the second board over the next few nights and see if that works.

Luckily I wasn't expecting building these things to be plain sailing and so far It hasn't been! It just makes it more fun when things don't work!

Playing with it earlier, I love all the front panel selectable options! Rotating the (very expensive) little knob to channel 2 and then clunking the knob on the TV to CH2 and there it is! Brilliant!

All the best
Nick
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Old 18th Mar 2019, 10:01 am   #133
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Default Re: Hedghog standards converter

Quote:
Originally Posted by 1100 man View Post
By the way, there is no vertical judder when watching actual video, only when viewing the internal test card.
Hi Nick,
Have you adjusted the audio carrier level pot yet? My test card was very wobbly until I adjusted mine.

Regards
David
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Old 18th Mar 2019, 10:12 am   #134
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Default Re: Hedghog standards converter

Perhaps a stupid remark, but do the divider resistors in the video input have the correct value? R1 and R2 at resp 39 and 36 Ohms.
The IC has a very low supply voltage, and thus needs a low video input.
Also check the soldering. I found this the most difficult component in the Hedghog.

Jac
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Old 20th Mar 2019, 12:29 am   #135
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Default Re: Hedghog standards converter

I've just spent the last couple of hours fault finding, and the result? Success!

Checking the 8 bit data lines Y0 - Y7 coming out of the video decoder chip showed activity on all of them. All 8 were still present when checked on the pins of the socket on the FPGA board.

I next checked the data lines coming out of the FPGA going to the 5k6/2k8 resistor network. There are 9 of these (I'm not sure why 9 not 8?).
With the internal test patterns selected, there was activity on all of these lines.

However, with the external input, the lowest one (shown as pin 41 on the circuit) was not doing anything.

My conclusion, therefore, was that the problem was with the input side of the FPGA, so I separated the development board and did some continuity checks between the 8 data pins on the socket and the actual pins of the FPGA. It transpired that there was a short between two of the data lines (119 & 120 on the circuit). There was a whisker of solder between the two pins of the chip!

The video now looks perfect, but strangely there is still no activity on the lowest 5k6 resistor. I would have expected there to be as there is with the internal test patterns. I'm guessing this would be the least significant bit so loss of this may not be that noticeable on the screen?

I would be interested if someone could explain the operation of this part of the circuit.

Dave, thanks for your suggestion, but there is no audio modulator chip fitted yet, so there is no audio carrier to adjust! I imagine the effect on yours would have been wobbly verticals if the audio carrier was too high.

Jac, I checked the video level getting to the decoder chip and it was about 0.8V. The resistors were the correct values.

Next step will be to fit the audio mod chip and get the latest software programmed into the FPGA.

All the best
Nick
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Old 20th Mar 2019, 12:39 am   #136
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Default Re: Hedghog standards converter

Well done finding that one! Useful one to keep a note of when testing mine.

Oh, in an earlier post you asked if I was hoping to get the connectors this week, the answer to that is yes! They are here at last! I’ll get them in tomorrow morning before work, and hopefully test them both too if I wasn’t so completely drained of energy right now I’d be in the shed getting on with it!

Regards
Lloyd
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Old 20th Mar 2019, 12:51 am   #137
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Default Re: Hedghog standards converter

Ooh that's exciting! It's handy building two as you can compare them if you get faults.
Hopefully by this time tomorrow, you will have two working ones!

Good luck
Nick
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Old 20th Mar 2019, 8:37 am   #138
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Well done Nick!

Jac
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Old 20th Mar 2019, 4:18 pm   #139
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Hi Nick
Well done for getting that sorted.
The TVP5150 must be pretty robust to withstand two video data pins being tied together.

The fact that you have activity on the least significant bit to the DAC on the test card and none when video in is selected is strange.
The output from the FPGA is obviously OK as it is working when test card is selected. All the video data pins from the video decoder must be connected OK to the FPGA as if even one was missing the FPGA would not be able to extract the syncs. As you found if two video data pins are shorted together (depending on which two) it can still be possible for the syncs to be extracted.
Considering all that, it looks as if the problem is internal in the FPGA,

To answer your question of why 9 bits and not 8.
Within the converter the video expands to much more than 8 bits in places. For example the output from the interpolater is 18 bits wide. The output of the interpolater is the result of adding fractions of 6 input lines together so there will be fractions in the result. After some processing the 18 bits gets truncated to 8 bits so it is able to fit into the time redistribution memory. After all the processing the video is 8 bits wide.

But this is just video no syncs. The sync value is added to the video before been sent to the DAC. The video takes up almost all of the available room in the 8 bits so an additional bit is needed to accommodate the syncs.

An explanation of the R2R DAC can be found here. It is explained there a lot better than I could explain it.

Frank
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Old 20th Mar 2019, 5:53 pm   #140
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Hi Frank,
Thanks for the explanation, that makes things clearer. So it is the LSB that is not doing anything on the video input. I must say there is no effect that I can see on the picture. If I hadn't seen the lack of activity on the scope, I wouldn't know there was a problem!

I will examine (yet again) and test continuity of all the data pins of the FPGA to the socket. They are difficult to see with a powerful lens as the socket gets in the way!

A more minor point is that the test card exhibits quite a bit of vertical judder. Each field looks like it starts a couple of mm vertically away from the last one.

The line timebase in this set is very loud. Unless the line hold is set to just before it goes out of lock, you can hear the LTB rattling away at 50Hz in time to the judder. I assume the line oscillator is being triggered when it doesn't expect it on alternate fields. This set uses direct sync rather then flywheel.

I need to investigate this further.

Thanks for your continued help!

Cheers
Nick
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