The Medium band Television Monitor

[Steve Anderson]

...I can't find where you mean by 'D4'...

"deflection amplifier above D4"

Steve A.

[Harry Dalek]

...I can't find where you mean by 'D4'...

"deflection amplifier above D4"

Steve A.

I am pretty sure at that point Steve

Screen 00040.bmp (161.21 KiB) Viewed 3812 times

Yes the rounding is Strange but must be a reason i was thinking because i used the different transistors

[Steve Anderson]

"deflection amplifier above D4"

Ah, my fault, not having completed the drawing before I posted it. Instead, if completed, the red XX would have said something like 9C in black...you then find the same '9C' on another drawing or sometimes within the same one if it's large and complex. It simply means the two '9Cs' are one feeding the other... The 'D4' in this case is the deflection plate number (D4) within the CRT datasheet, similar to (say) 'G1' (grid 1). In future maybe I should, 1) Complete drawings before posting, but this may cause delays until I verify everything, 2) Be more explicit in the descriptions and designations. In my drawings anything in red is likely to change sometime soon, it's not set in stone. It signals to myself that some work needs to be done here, it's in a state of flux or uncertainty.

Occasionally AOT appears (Adjust On Test), where a component needs 'tailoring' to each individual unit built due to variations in component tolerances (e.g. transistor gain). If a value appears, it's a starting point, a suggestion. In a way all circuit diagrams are a suggestion, others may see another way to achieve the same, simpler and/or better result.

Circuit diagrams are a form of language, many have tried to standardise them over the years, but still very few fully adhere to one standard, including myself. A mix-up and confusion are the likely results. The above is an example...another is slang nouns for common everyday items between US, British and Australian English... Some electronic component names have changed over time or location, condenser has become capacitor, vacuum tube verses valve, thyristor verses SCR (Silicon Controlled Rectifier)....and so on.

Steve A.

I've never heard of a GCR...(Germanium Controlled Rectifier)....probably with good reason!

[Harry Dalek]

[quote="Steve Anderson"
Ah, my fault, not having completed the drawing before I posted it. Instead, if completed, the red XX would have said something like 9C in black...you then find the same '9C' on another drawing or sometimes within the same one if it's large and complex. It simply means the two '9Cs' are one feeding the other... The 'D4' in this case is the deflection plate number (D4) within the CRT datasheet, similar to (say) 'G1' (grid 1). In future maybe I should, 1) Complete drawings before posting, but this may cause delays until I verify everything, 2) Be more explicit in the descriptions and designations. In my drawings anything in red is likely to change sometime soon, it's not set in stone. It signals to myself that some work needs to be done here, it's in a state of flux or uncertainty.

No problems Steve don't worry easy to point it out ,i am just happy i can use the well designed ramp oscillators and deflection amplifiers

Occasionally AOT appears (Adjust On Test), where a component needs 'tailoring' to each individual unit built due to variations in component tolerances (e.g. transistor gain). If a value appears, it's a starting point, a suggestion. In a way all circuit diagrams are a suggestion, others may see another way to achieve the same, simpler and/or better result.

The slight curving of the ramp out of the line deflection amplifier i seem to have the best resistor Value to the deflection amps input too high or to low can cause distortion in the ramp at D4 ,i noticed frequency does not effect shape really just amplitude of it .
I will have a look how it looks of the other 3 deflection amplifiers perhaps it is the transistors type's hope its just the low voltage 2n's they are easy to replace Still it will be interesting to see if it effects it or not .

Circuit diagrams are a form of language, many have tried to standardise them over the years, but still very few fully adhere to one standard, including myself. A mix-up and confusion are the likely results. The above is an example...another is slang nouns for common everyday items between US, British and Australian English... Some electronic component names have changed over time or location, condenser has become capacitor, vacuum tube verses valve, thyristor verses SCR (Silicon Controlled Rectifier)....and so on.

Steve A.

Well i did change the The High voltage and low voltage transistors so must effect results to what your original design was designed ,any case no problems i knew what was expected but experimented here works but perhaps it effected the results now ..again have to look whats happening at the other deflection amplifiers for a full picture

I've never heard of a GCR...(Germanium Controlled Rectifier)....probably with good reason! [/quote]

[Steve Anderson]

I've never heard of a GCR...(Germanium Controlled Rectifier)

....and you probably never will, AFAIK they don't (and didn't) exist, which is probably a good thing! Germanium devices were first introduced to consumers in transistor radios in the late 50s, 60s and into the 70s, after that Silicon took over. The only advantage over Silicon is their lower forward junction voltage. Maybe 0.3V as opposed to 0.6V. Otherwise simply terrible, forget them today. The GCR thing was a bit of a joke...

Steve A.

[Harry Dalek]

Bit of bad news today start off good ended as i suppose i knew it would .
First up i scope tested the rest of the deflection amplifiers here's the reading at D3

The NBTV side same as before yellow to Deflection amplifier inputs Blue output one side H And V

only photo i took to day of the line should of adjected the scope better on the deflection amp out

Any case i can see now looking at the much lower NBTV frequencies results are better on lower ramp frequencies for ramp shape .

My goal today was swap the CRTs deflection plates for Horizontal scanning very easy if needed for the 3BP1 don't even have to do that just twist the tube a problem for the square CRT only choice here swap the deflection plates connection to the amplifiers ...heres were it all went down hill today !
I expected just a horizontal version what i was doing Nope ! my fine focus went ,i had to first adjust the input ramp to be a touch higher amplitude to fill the screen with the raster but i
had very bad focus try as i might lowering raising resistor values around the focus pot area could not get right .
I had another chiose i knew could result in circuit failure Increasing the High Negative so i did this slowly each time creeping up to 1.6Kv ,i had the insight to disconnect the NBTV side High negative just in case .
Even so i still could not get the focus correct i was getting an increase in Brightness but shrinking of the raster size as i have noticed with other CRT's was not enough here on this CRT it made little difference .
Very different results to vertical scanning CRT settings
At I.6 Kv about the 5th try there was a circuit failure under the opto coupler and around the 60 v zener area ,i was sort of expecting it but i wanted to see either way if The HV negative being low causing poor focus pretty much a poor excuse to rebuild this area .
After this happened i disconnected the HV negative to the CRTS damaged circuits and testing the Voltage its now jumped to 2 Kv Testing again to see if there was any power supply damage no load but a bit of sparking now and again with close connections ...I can't say i noticed 2KV before this happened but is in my CRT readings may be no load memory loss !.
So off it went today and looks like i have some work on the HV negative power supply side ...!
To repair is easy enough but i need to improve the results i as getting also .

addtext_com_MDM1ODAyMzU3ODE (1) (1).jpg (67.19 KiB) Viewed 3760 times

[Harry Dalek]

Well the 2 opto diode's i ordered a while back turned up to day they are dark face so very much IR peaking i would think as in the data

To use will have to wait for a Steve A circuit update before i start building the modulation circuit .

I will not to reuse the Anderson Monitors CRT modulation circuit for the large tube it was there for testing the CRT only in the first and would not have the bandwidth in any case ,so that will be scrapped ..its pretty much scrap after the sparking the other day good excuse to move on .

Thinking of using the CRT powering circuit below the Below ,Screen 00005 CRT connection are correct

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The scope circuit below with my CRT pin connections are all wrong so don't use it for data ! but shows the Resistor chain powering focusing and brightness control a little clearer both circuits look to be same apart from minor change in focus area .

[Steve Anderson]

You could use the IR version of the BPW34 (all black encapsulation) but with IR LEDs. I would expect them to perform similarly to the visible versions. The downside is we can't see the emission, so positioning of them becomes a bit of hit-and-miss. Although most cameras have an IR filter in front of the sensor, at these levels of intensity enough may seep through for alignment. Try aiming a TV remote at the camera in your phone...the result is often a blue/purple flashing light, the modulation. It may well be possible to align the IR LEDs onto the IR BPW34 using this, though I've not tried it myself...or use the BPW34 signal output to maximise the coupling...

It appears that if there's a 'S' in the part number it's IR only, the datasheets are a bit vague, I think the BPW34 is the visible version, the BPW34S is the IR version. Better still, find a supplier that has a picture of the device, the one you want is in a clear package, not black.

Steve A.

I may have a couple of spares, not sure, if I do have I'll send you a couple.

[Harry Dalek]

You could use the IR version of the BPW34 (all black encapsulation) but with IR LEDs. I would expect them to perform similarly to the visible versions.
The downside is we can't see the emission, so positioning of them becomes a bit of hit-and-miss. Although most cameras have an IR filter in front of the sensor, at these levels of intensity enough may seep through for alignment. Try aiming a TV remote at the camera in your phone...the result is often a blue/purple flashing light, the modulation. It may well be possible to align the IR LEDs onto the IR BPW34 using this, though I've not tried it myself...or use the BPW34 signal output to maximise the coupling...

It appears that if there's a 'S' in the part number it's IR only, the datasheets are a bit vague, I think the BPW34 is the visible version, the BPW34S is the IR version. Better still, find a supplier that has a picture of the device, the one you want is in a clear package, not black.

Steve A.

I may have a couple of spares, not sure, if I do have I'll send you a couple.

Thanks Steve i would like to see if these can work knowing yours was a different version i did buy them under BPW34 they look dark to me in this room light yours looked light blue in your photos so i am thinking its IR red to it to IR much muchness slight loss ?

Either case i have IR and Red Leds is it very critical the aiming of the LEDs to the opto diode ?
Yes i find my cameras also see IR light also i could try red slightly less peaking but again does that matter using it for what it will be used for ?
I haven't tried it so from what you mentioned do you remember if it was critical at aiming at it ...Sounds like fun times building this later on.
Noticing they call it a solar cell ? not a diode it reminds be of the dome sensor we used in NBTV a while back i have one of those as well looks like these but with the dome lens

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[Steve Anderson]

I think the alignment isn't that critical, if arranged as per my visible version photos posted previously it should work fine.

If you have DigiKey in Australia (it seems you do) their stock number for the visible BPW34 is 475-BPW34-ND, the item listing is here...

https://www.digikey.com.au/en/products/ ... w34/607274

The picture in the listing is of the clear version. Attached is the datasheet from that very page...that datasheet doesn't even mention the IR version....page 4 it shows "Relative Spectral Sensitivity", in the red region it's at 80%, a slight loss compared to IR, the fix? Throw more red light at it! I found that two high-intensity red LEDs worked fine. Even just one worked OK. The actual silicon chip inside the transparent plastic isn't clear, don't worry about that. Be careful with the polarity, the cathode is identified by a small 'tab' on the lead/pin. See the mechanical drawing on page 7...the 'tab' is very small...about 0.6mm square...

Steve A.

BPW 34_EN.pdf

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[Harry Dalek]

I think the alignment isn't that critical, if arranged as per my visible version photos posted previously it should work fine.

OK that's good to know ,i see how yours was mounted and seems easy enough

If you have DigiKey in Australia (it seems you do) their stock number for the visible BPW34 is 475-BPW34-ND, the item listing is here...

Yes i did try them but it was the postal costs that put me off 24 dollars for a 2 dollar part

The picture in the listing is of the clear version. Attached is the datasheet from that very page...that datasheet doesn't even mention the IR version....page 4 it shows "Relative Spectral Sensitivity", in the red region it's at 80%, a slight loss compared to IR, the fix? Throw more red light at it! I found that two high-intensity red LEDs worked fine. Even just one worked OK. The actual silicon chip inside the transparent plastic isn't clear, don't worry about that. Be careful with the polarity, the cathode is identified by a small 'tab' on the lead/pin. See the mechanical drawing on page 7...the 'tab' is very small...about 0.6mm square...

Steve A.

Mine says it peaks at 900Nm but i do have the 900Nm leds i might try just red off peak freq for testing any case i may as well use it i have 2 and the leds but thats still a ways off a rebuild on the large CRTs power supply is on my mine for this week .

[Steve Anderson]

If you have DigiKey in Australia (it seems you do) their stock number for the visible BPW34 is 475-BPW34-ND, the item listing is here...

Yes i did try them but it was the postal costs that put me off 24 dollars for a 2 dollar part...

What? That's ridiculous! How to stifle a business! Extortionate postal costs (it's the government after all)....How do companies in China often ship their stuff for free? OK, Chinese shipping might be included in the item price, but even then it's not ridiculous...Unless DigiKey are taking the p*ss...

I often order stuff that comes from Singapore (RS, Farnell/Element 14), the shipping cost is insignificant. Granted, Australia is a long distance away from almost anywhere, but A$24.00 even from Singapore to Melbourne for an item that weighs less than 20 grams including packaging is obscene...I'll find out what it would cost me to send 20 grams Bangkok to Melbourne...

I just checked on-line, that figure seems 'about right', so how do these Chinese companies do it? I have to visit our local post-office soon, I'll check with them, if it's anywhere near the same figure I'll be shocked. I very rarely send stuff overseas except ordinary letters which are about A$0.60 airmail Bangkok to the UK...

Steve A.

The device in the photo above looks the exact thing...clear package so the photo-diode is visible...but it is NOT a solar cell as said in the attachment above, it will generate some open circuit voltage upon illumination, but a useless non-linear amount. Get the terminology right guys...it's a PIN photodiode...P-doped Silicon, Intrinsic Silicon, N-doped Silicon...shame they never read the datasheet...PIN diodes are often used in GHz frequency switching applications...e.g. receivers...a hint as to why I got almost 5MHz with little loss, and that includes the LEDs in the chain too...

The reason I had these BPW34 photodiodes was I wanted to develop a mechanical SSTV camera using them, it didn't get anywhere...I might come back to it one day...

I could try the IR version for completeness, it may help in situations where there's some ambient (visible) light. The visible version worked OK in normal 'office' type ambient light, no light-shielding was employed. The LEDs I used are VERY bright even at a peak current of only 25mA. They do drop a greater voltage than the usual red LED, around 3.5V instead of about 1.7V. Maybe two LED chips internally in series to get more light?

Added later... Harry, I recall sending you several high voltage capacitors (100nF or 1uF? 1750V?) years ago, certainly heavier than photo-diodes, I don't recall the postage being excessive....they looked something like below...though I think they were a bit larger...20-25mm pitch?

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[Harry Dalek]

What? That's ridiculous! How to stifle a business! Extortionate postal costs (it's the government after all)....How do companies in China often ship their stuff for free? OK, Chinese shipping might be included in the item price, but even then it's not ridiculous...Unless DigiKey are taking the p*ss...

Yes pretty much the place i got it from was the cheapest postage wise normal costs ,then you have Digikey you can still buy 1 part but the postal cost doesn't make it worth it for one or 2 parts . The other places like Mouser want you to buy hundreds at once not interested in the one or two part buyer at all .

I often order stuff that comes from Singapore (RS, Farnell/Element 14), the shipping cost is insignificant. Granted, Australia is a long distance away from almost anywhere, but A$24.00 even from Singapore to Melbourne for an item that weighs less than 20 grams including packaging is obscene...I'll find out what it would cost me to send 20 grams Bangkok to Melbourne...

Here's 3 of those parts via Digikey order i was going to make till i saw the total costs !

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I just checked on-line, that figure seems 'about right', so how do these Chinese companies do it? I have to visit our local post-office soon, I'll check with them, if it's anywhere near the same figure I'll be shocked. I very rarely send stuff overseas except ordinary letters which are about A$0.60 airmail Bangkok to the UK...

Steve A.

Postal costs are silly theses days any thing with a bit of size of weight used to sell old books old transistor radios to collectors over seas and its just not worth it any more .

The device in the photo above looks the exact thing...clear package so the photo-diode is visible...but it is NOT a solar cell as said in the attachment above, it will generate some open circuit voltage upon illumination, but a useless non-linear amount. Get the terminology right guys...it's a PIN photodiode...P-doped Silicon, Intrinsic Silicon, N-doped Silicon...shame they never read the datasheet...PIN diodes are often used in GHz frequency switching applications...e.g. receivers...a hint as to why I got almost 5MHz with little loss, and that includes the LEDs in the chain too...

That's why i mentioned the old dome sensor i got from Gary some years back ,that was discussed on the forum as a solar cell as well have to get it out and test it again i bet its one of these ,Yes very strange not knowing what they are selling .

The reason I had these BPW34 photodiodes was I wanted to develop a mechanical SSTV camera using them, it didn't get anywhere...I might come back to it one day...

It has a bit of surface area ,played around with the idea my self ended up a bit like fax a rotating drum with a image and scanning it with a photo diode or transistor i tried to make a SSTV camera but once again i didn't take into account the thing should be in a light proof box that would of Helped ! Just before the camera try tried this idea a reflective image that was my scanning idea ! i think i was just using room light as well so results varied .

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I could try the IR version for completeness, it may help in situations where there's some ambient (visible) light. The visible version worked OK in normal 'office' type ambient light, no light-shielding was employed. The LEDs I used are VERY bright even at a peak current of only 25mA. They do drop a greater voltage than the usual red LED, around 3.5V instead of about 1.7V. Maybe two LED chips internally in series to get more light?

I have 2 IR 900 Nm they say they 940Nm in the data below

IR333_A_datasheet_190618853bf (1).pdf

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Added later... Harry, I recall sending you several high voltage capacitors (100nF or 1uF? 1750V?) years ago, certainly heavier than photo-diodes, I don't recall the postage being excessive....they looked something like below...though I think they were a bit larger...20-25mm pitch?

100Nf 630V ............... about the size of the dots They came in handy for sure i think i still have a few others soldered into projects Yes looked like that capacitor but 630V

[Steve Anderson]

Actually, you could well be right, maybe they were 630V caps, not 1750V, I was working from my memory....which is nowhere near as reliable as an EPROM!! An elephant supposedly has a better memory than me!....Later on...found those caps via the order I placed, yep, 630V. The 1750V versions I bought at around the same time from a street vendor in the Bangkok electronics souk/bazaar/market...always worth a wander around, you never know what you'll find! If anyone comes to Bangkok it's right behind the Grand Palace on the river in a place called Ban Mo. I'll show you around maybe, and translate as virtually no-one speaks English there...not a place tourists go (but it is safe), it's also much easier to get to now, a short walk from the new-ish underground train system...

I would suspect that the 'Dome Sensor' has a limited bandwidth, and without a datasheet, what colour/wavelength is it most sensitive to? But if it's Silicon it'll probably be in the red/IR region. What it was made for seems to be unknown.

Steve A.

[Harry Dalek]

Actually, you could well be right, maybe they were 630V caps, not 1750V, I was working from my memory....nowhere near as reliable as an EPROM!! An elephant supposedly has a better memory than me!....Later on...found those caps via the order I placed, yep, 630V. The 1750V versions I bought at around the same time from a street vendor in the Bangkok electronics souk/bazaar/market...always worth a wander around, you never know what you'll find!

I would suspect that the 'Dome Sensor' has a limited bandwidth, and without a datasheet, what colour/wavelength is it most sensitive to? But if it's Silicon it'll probably be in the red/IR region. What it was made for seems to be unknown.

Steve A.

I found i still had a untouched 104 630v sitting here next to the CRT and HV negative board i have been working on today . Yes memory is a bugger what do you call a memory that fades (useless) !
I am not sure about using the blanking circuit yet as the modulation circuit has to be added as well here just enough to power the CRT again but hopefully this time no sparking at the over 1.6 KV range .
i had a data sheet for the dome sensor once i am sure its on the forum some where if i can find it i will post it up again out of interest.