Building 3BP1 tube NBTV Anderson monitor II

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Building 3BP1 tube NBTV Anderson monitor II

Postby aussie_bloke » Sat Sep 17, 2016 9:45 pm

G'day all.

I am reading Harry Dalek's thread on his 3BP1 Anderson monitor as I so happen to have a 3BP1 tube myself and I intend to follow suit and build my own 3BP1. The difference with mine is I intend it to display not just 32 line NBTV but also standard 625 line video and possibly SSTV as well, I want it to be multistandard. Anyhow I have already made a start on my project and have been communicating with Harry who has been helping me plus I have been reading over his thread which Steve Anderson has been helping him extensively with his monitor.

So far for my project I have done the following:
Built the AC power supply unit which is also multipurpose for other projects
Built the Dual +/-12V power supply
Built the high voltage circuit that supplies about +340V and -1340V
Got an ex monitor amp enclosure for the tube which I cut a hole in the back for the tube to fit in.

I will elaborate on the above in the next few posts along with pics.
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Re: Building 3BP1 multi-standard monitor

Postby aussie_bloke » Sat Sep 17, 2016 9:52 pm

Firstly I had to find a suitable enclosure for the tube. I was recently given some ex ABC radio monitor amps, I decide to strip one of them for this project as the tube fits it nicely with some clearance space at the back. As the rear of the case has 2 gaping holes, I thought make that the front and enlarge one to fit the tube in. Harry suggested for mounting the tube to use a PC fan housing as and so I found a PC fan just the right size, cut the fan out and the housing fits nicely over the front of the tube. Also found a smaller fan housing that fits the rear of the tube too. I widened the gaping hole on the right side of the enclosure to fit the tube, screwed the fan housing to it and the tube sits in nicely.
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Re: Building 3BP1 multi-standard monitor

Postby aussie_bloke » Sat Sep 17, 2016 10:29 pm

Next thing to work on was building the AC power supply. Earlier this year I got the company I work for to build a transformer that outputs 250-0-250V, 6.3V and 5V for a DG7/32 tube video monitor I tried to build earlier in the year which I was not successful, so for this project I am using the same transformer but the 5V won't be used. I also needed power for the dual +/-12V power supply so had to get another transformer for it and found one with outputs of 10-0-10V, 4.5V and 44V so the centretapped 10V was good enough for the dual 12V supply. So having those transformers at hand I worked on building the AC power supply, and seeing I had those other outputs thought I'd make this AC supply multipurpose and use those other outputs as well.
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Here is the circuit layout wiring those 2 transformers up to mains. On the primary side I added a switch and fuse holder with a 4A fuse and connected the earth screen of one of the transformers to chassis. On the secondary side I grounded the 0V of the centretap 10V to chassis and reading that for the HV power supply one of the 250V windings is grounded and not the centretap I grounded one of the 250V windings to chassis. Here below is the circuit layout. I forgot to add in the diagram the mains earth is connected to chassis as well.
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For the enclosure I used two scrapped aluminium power supply enclosure bottoms given to me from my workplace and I fitted the transformers in the bottom half and the switch and fuse holder in the top half and riveted the two halves together.
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Working on the front I got another piece of aluminium for the front plate which fits nicely over the two enclosure halves and I drilled 6 holes to fit 6 ouput sockets for the windings.
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My choice of sockets for the windings are 5 pin DIN sockets for the centretapped 10V and 250V outputs and 2 pin sockets for all the other windings. For the DIN sockets I removed pins 2 and 4 so there's gap between the 3 pins used so there won't be arcing, particularly on the centretap 250V outputs. I understand when Harry used a DIN socket for his power supply Steve was very concerned about it due to risk of arcing on the 250V windings, Harry told me about it and I read his posts and Steve's replies, before deciding on changing the socket I brought my power supply into my workplace and talked to my boss about using the socket (he's an electronics wizz and designs power supplies we build at the company) to get his opinion, he gave me the okay with it seeing I removed 2 of the pins from the 5 pin DIN sockets. I also fired up the AC power supply and no arcing occurred with the 250V centretap outputs. Here below are pics of the final stages of my AC power supply:
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Re: Building 3BP1 multi-standard monitor

Postby aussie_bloke » Sat Sep 17, 2016 10:52 pm

Next phase was to build the dual +/-12V power supply and the high voltage power supply.

For the dual 12V supply I was fortunate enough to have an old premade PC board for it so with only some modification I used it for my power supply. Here below is the schematic I went by and the +/-12V power supply:
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Next the high voltage power supply. I made it according to the specs of the schematic Steve posted near the bottom of this page viewtopic.php?f=10&t=2059&start=90 of Harry's 3BP1 project. I recycled an old PCB and modified it for use in building the HV power supply.
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I also had to build a high voltage probe so I built one with 20x 10 megohm resistors and a switch to switch between 10x and 20x 10 megohm for dividing the voltage by 100 or 200. I was told initially to use 9x 10 megohm resistors but for my own multimeter I found I got more accurate readings with 10x 10 megohm so stuck with it. Anyhow testing the voltages of the HV power supply I got about +334V and -1346V:
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Now I found I was getting fluctuations on the +334V output so Harry suggested I used a capacitor with higher capacitance and so I dug out a 470uF 450V cap and used that in place of the 47uF 450V cap and that improved things.
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So the HV power supply is pretty much done, only need to add connectors. Here below is the final schematic of the HV power supply connected to the AC power supply:
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Re: Building 3BP1 multi-standard monitor

Postby Harry Dalek » Sat Sep 17, 2016 11:10 pm

Hi Troy
Might be a while till Steve A returns from the China work trip using the 3BP1 Anderson design as a basis for your Tube i would say is wise .
I mentioned to Troy all the trouble i have had with circuits with mistakes from magazine schematics and such it would be good to just use a design we know works .
Really looks Good Troy did a good job on the AC and DC supply.....i notice theres a mistake in the 18A jpg the caps should be connected to both sides of the 1meg resistors just a drawing mistake i should think ,Love the monitor case size lots of room to fit every thing .

Troys made a High voltage probe for he's multimeter looks just about set to start on the CRT schematic .

Wanting it to be multi system is a great idea perhaps just a matter of a multi position switch and some different caps of the sawtooth oscillators i think ,perhaps keep that in mind when you get up to that part .

And excellent use of old circuit boards a second life in this !

Watching with interest ! :wink:
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Building 3BP1 multi-standard monitor

Postby aussie_bloke » Sat Oct 01, 2016 2:48 pm

After completing the AC power supply and the +/-12V power supply and high voltage supply I was instructed to build the CRT driver board next and so have now built the CRT driver board according to the below schematic:
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Now was told each individual board made has to be tested to see if working properly or not and skimming over Harry's 3BP1 monitor thread and couldn't find any part about testing the driver board on its own so I was wondering how shall I test this board, do I just fire it up and test the output voltages or do I need to connect loads or do I need to actually connect the CRT? I also vaguely recall reading somewhere in Harry's 3BP1 monitor thread that the CRT needs to first be tested without the heater connected, am I correct?
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Re: Building 3BP1 multi-standard monitor

Postby Harry Dalek » Sat Oct 01, 2016 5:44 pm

aussie_bloke wrote:After completing the AC power supply and the +/-12V power supply and high voltage supply I was instructed to build the CRT driver board next and so have now built the CRT driver board according to the below schematic:


Yes Sir that is correct ...i explained to Troy what is and what isn't grounded a mistake i made and didn't want Troy to repeat ...had to make sure it was built as to Steve's Schematic ..High voltages not good to make mistakes .

Now was told each individual board made has to be tested to see if working properly


I only made it on each little board as to room and how i could mount them ..it could be all on one big PCB if you have room ,When i get back to my SSTV it will be built on one or 2 large PCB's/
But yes a section at a time and test it .i will help best i can,i am no Steve Anderson but i tend to recall what to do and not to do its still fresh in my mind.

or not and skimming over Harry's 3BP1 monitor thread and couldn't find any part about testing the driver board on its own so I was wondering how shall I test this board, do I just fire it up and test the output voltages or do I need to connect loads or do I need to actually connect the CRT? I also vaguely recall reading somewhere in Harry's 3BP1 monitor thread that the CRT needs to first be tested without the heater connected, am I correct?


I have a had a chat on face book with Troy and mentioned every thing i can recall what should be done testing the CRT board ...
Yes test circuit voltages without the heater on for now till every thing looks correct voltage wise then we will do the opto coupler test with the CRT fired up very carefully increase the brightness control ...so just in case one hand on the off switch don''t want a CRT dot burnt onto the phosphor screen that would be depressing :oops:
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Building 3BP1 multi-standard monitor

Postby Harry Dalek » Sun Oct 02, 2016 7:29 pm

Hi Troy
For others Troy has sent me a video of the first opto coupler test just to view the coupler works to adjust the 3bp1 CRT brightness .

Now we are getting results but some thing is a touch off so checking what is different to my voltages

Troys voltages Top mine below BTW my 75 v zener a in4761A ended up being 74.7 across it ...

Your up to where i was on page 10 of The 3bp1 Anderson monitor
viewtopic.php?f=10&t=2059&start=135


Seeing the results Troy have a read of Steves advice to me on this page when i was having problems around here with the zener theres some test advice in he's posts to me you could copy .
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Re: Building 3BP1 multi-standard monitor

Postby Harry Dalek » Tue Oct 04, 2016 5:08 pm

Hi Troy as asked here are my HV power supply voltages ,i had the board still in the monitor and took the voltages ...best i can make out without taking the board out seems logical to my readings.

The Ac supply is much higher than yours Troy can you post up your readings to see the difference ..perhaps as is -1300 is best we will get without some changes .
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Re: Building 3BP1 multi-standard monitor

Postby Steve Anderson » Tue Oct 04, 2016 11:00 pm

Gents, I'm now freed from China's blockade of this site, I'm currently in Southbank, Melbourne, where I expect to be until the end of the year, though I'll have to move to Ripponlee in due course.

Now, there is no real reason why this generic design cannot be adapted for a wide range of CRTs from around the same era. The 3BP1 requires quite a high final voltage across the tube. With a some adjustments to the voltages from the power supplies this basic arrangement should cater quite well for both NBTV (as per Harry's build) and SSTV - though you'd need a long-persistance CRT i.e. a P7 CRT - e.g. 3BP7 - if ever such was made. Of courese a P7 CRT isn't such a good idea for NBTV and useless for 25fps.

For 625 there would need to be quite a few changes required. SSTV has a video bandwidth of around 1kHz, NBTV around 10-20kHz, but 625 - 5MHz - if you omit the upper frequencies (including the colour information) you're still looking at perhaps 2MHz. Plus the horizontal timebase would require some changes.

None of the the above is impossible, just more complexity in the mix.

Actually I have the perfect answer...use a standard 625 TV with a baseband (AV) input for 625 and add my upcoming SSTV and NBTV up-converter to it. The up-converter does the job of the P7 phosphor for SSTV and eliminates the NBTV 12.5Hz flicker - though of course the frame rate is still 12.5Hz.

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Re: Building 3BP1 multi-standard monitor

Postby Harry Dalek » Thu Oct 06, 2016 11:06 am

Hi Steve
I have Tried to help troy up to this stage of he's build ,he has a 240 0 240 v transformer he got made at hes work its giving -1300 via your multiplier ...tried another stage and it was the same but .
He's finding as you turn down the test control on the opto coupler the beam moves up and out of sight as the dimming happens .
I can only think hes not got enough voltage for he's tube
I think he wants to try another transformer but would it be possible to add another stage to the multiplier ? we added one to the ground side but he got the same voltage little gain
On he's multi system plans i missed the bit on SSTV that would be a no no ...i think he would be happy seeing it as a 32 line and any thing else possible.
Yes of cause your converter is a way out of a lot of troys wants but i think he would like to use the tube as i did .
I will let Troy know you now back on the forum.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Re: Building 3BP1 multi-standard monitor

Postby Steve Anderson » Thu Oct 06, 2016 7:55 pm

Well, if it's a 240-0-240V transformer there should be few problems with getting the voltages a 3BP1 requires...unless it's really way to small, but that's unlikely with a 240-0-240V output. Even the smallest of transformers pulled from an old valve radio should be more than adequate. Though I'm saddened by the loss of another piece of history by doing so.

Troy (if you're following this) simply check out your wiring and in theory each capacitor in the voltage multiplier should have similar voltages across them. Depending on where you got the caps from they may be leaky, virtually open-circuit or have other ailments if they're old. Best to use new and batch-matched caps. i.e. all the same from the same manufacturer and made and bought at the same time. If you need eight, buy ten.

Steve A.

Even so, if you have a Variac it's best to slowly wind up the mains voltage from zero to the nominal 220-240V. If you don't have a Variac try a 110-120V auto-transformer first. Virtually all voltages should half those at 'full steam' and it gives the capacitors a while to re-form the dialectric and a chance for you to check things are as they should be with less risk of failure, funny smells, smoke and sparks.

We could start an entire new thread on reforming old (and new) high-voltage electrolytic capacitors, but there's plenty 'out there' on the 'net for that.
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Re: Building 3BP1 multi-standard monitor

Postby aussie_bloke » Thu Oct 06, 2016 9:24 pm

G'day Steve. Thanks for the info on the HV power supply. Firstly The transformer output is actually 250-0-250V, I initially thought it was 240 but on testing found it was more. Secondly the capacitors I used for the -1300V are brand new bought from Jaycar, however when I added an extra cap in hope to boost the voltage it was an older one pulled from my scrap box, how old I don't know. I do have a variac so I can vary the AC to reform the caps if it must be done.

In regards of making it multi-standard, I'm open to all suggestions and possibilities, will take in account your idea of using your upconverter.

Since my last post to the thread I have made progress to getting the CRT to display a spot which Harry has told about here in his posts, I will get the pics together and post my progress sometime tonight for all to see.
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Re: Building 3BP1 multi-standard monitor

Postby aussie_bloke » Thu Oct 06, 2016 10:43 pm

Here's my latest updates since building the CRT driver circuitry.

Firstly I rigged up the CRT driver board to the HV power supply and connected to the 250-0-250VAC output of my AC power supply. I used power cord wires for the AC lead as the insulation is nice and thick and after soldering the ends to the 3 pin DIN plug I double insulated each pin for further protection.
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I mounted the pots temporarily onto bakelite and whacked some well insulated knobs which are temporary for testing.
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Harry then told me to fire the CRT driver circuit up without the tube connected and test the output voltages and then connect the tube to the circuit but leave the heaters unplugged and test to see if the voltages are the same. The voltages test the same with and without the tube. Harry has posted the voltages I got in the previous post which are below par in comparison to Harry's circuits as seen. How I connected the tube pins to the circuit involved making my own female connectors which I cut some strips of thin copper sheeting, folded in half and soldered the wires to the strips and sleeved 2 layers of heatsthrink over them and shaping them to tightly fit the pins. I wire connected heater pin 1 to cathode pin 2.
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After rigging the tube to the CRT circuit and testing the output voltages I was ready to connect the heaters and test to see if I get a spot on the screen. Firstly I had to then make the heater lead and plug for the AC 6.3V output. Below is the pic of the whole setup minus the heater cord (forgot to photograph it).
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Now comes the fun part, firing the tube up with heaters and seeing if it displays a green spot. I set the test brilliance pot to the opto input to 1/2 way and turned it on and sure enough I got a green spot, so the tube is working!!! :) I focused it and quickly took a photo and here it is below:
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So that is a very good start so far! I played around with the brilliance, focus and astig and they all work but as Harry has mentioned when I had the brilliance down low the spot moves to the top of the tube and disappears which Harry said shouldn't happen so that's where the trouble shooting now starts and the first problem as mentioned is the fact I'm getting only -1320V to the HV input of the CRT driver and am getting lower focus voltages so the HV power supply needs trouble shooting. I have received a few suggestions from Harry, Steve and my boss at the electronics company I work for, so I will see what's most feasible for my HV power supply and go from there.

So that's my latest progress with my 3BP1.
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Re: Building 3BP1 multi-standard monitor

Postby Steve Anderson » Fri Oct 07, 2016 6:20 pm

If the deflection plates are not connected to anything - all sorts of things can happen. The best bet is to connect all four to the final anode for the time being. i.e. pins 7, 8, 10 and 11 connected to pin 9. (For a 3BP1). This should give you a nice focused spot in approximately the centre of the screen. (+/- a few mm).

The deflection plates do not (should not) intercept any electron flow so they are effectively one half of a small capacitor each - they can easily pick up all sorts of garbage - leakage currents, 50Hz hum, you name it. This temporary arrangement should stop the spot wandering around as you adjust the focus, astig and brightness.

Be very careful not to burn the screen phosphor - it's so easy to do!

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