The Mongrel

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Re: The Mongrel

Postby Steve Anderson » Wed Sep 15, 2021 4:04 pm

Not really 'off topic' as you're using tubes/valves anyway.

I agree with all the author puts forward. I have a valve/tube mic pre-amp I built for when I'm using Skype or similar...for no particular reason, I just fancied doing it!

Very simple, an EF86 in triode mode plus a 9002 tube as a cathode follower. The heater for the EF86 is fed from DC to reduce hum, but the EF86 is well screened internally, so one could say it's not really necessary, but again, it's a whim.

Originally the EF86 was in the conventional pentode mode, but it had too much gain, around 44db (x160-ish), now it's 28db (x25). That's one of the trade-offs with triodes, lower gain, but that's what I needed. Schematic below, the original pentode version, I haven't created the triode version (yet). I may have posted this before...

EF86 Mic Preamp III.gif


Steve A.

Here's the silicon version it replaced...the LM394 is a matched super-beta low noise transistor pair, now made of Unobtainium...I did also do a lower gain version..

LM394 Mic Preamp 1.gif


LM394.pdf
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Re: The Mongrel

Postby Harry Dalek » Wed Sep 15, 2021 5:25 pm

Steve Anderson wrote:Not really 'off topic' as you're using tubes/valves anyway.

I agree with all the author puts forward. I have a valve/tube mic pre-amp I built for when I'm using Skype or similar...for no particular reason, I just fancied doing it!

Very simple, an EF86 in triode mode plus a 9002 tube as a cathode follower. The heater for the EF86 is fed from DC to reduce hum, but the EF86 is well screened internally, so one could say it's not really necessary, but again, it's a whim.

Originally the EF86 was in the conventional pentode mode, but it had too much gain, around 44db (x160-ish), now it's 28db (x25). That's one of the trade-offs with triodes, lower gain, but that's what I needed. Schematic below, the original pentode version, I haven't created the triode version (yet). I may have posted this before...

The attachment EF86 Mic Preamp III.gif is no longer available


Steve A.


Here's the silicon version it replaced...the LM394 is a matched super-beta low noise transistor pair, now made of Unobtainium...I did also do a lower gain version..

The attachment EF86 Mic Preamp III.gif is no longer available


The attachment EF86 Mic Preamp III.gif is no longer available
[/quote]

Going off track Steve as in thinking about a future try with some small Russian valves i got on site below 6J1B-V to play with in the future but they are all pentodes and i was looking into if i needed a triode i could adjust these when needed .could buy a few dual triodes i suppose but they are a bit more pricy if you call 3 dollars pricy :lol:
86efcfbd6f1c.jpg
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https://tubes-store.com/product_info.ph ... ts_id=1235
Arrrr Unobtainium ! now thats hard to get :lol:
I like your preamp went from the transistor ,ic type to Valve evolved in a direction as every one seems to prefer the valves amplifiers ,i don't think you post this before new to me .
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Re: The Mongrel

Postby Steve Anderson » Wed Sep 15, 2021 6:04 pm

Harry Dalek wrote:I like your preamp went from the transistor ,ic type to Valve evolved in a direction as every one seems to prefer the valves amplifiers..

I don't want to open 'a can of worms' here, but there's no magic, no mystique, or anything objectively 'better' with valves/tubes. They obey the laws of physics as everyone and everything does. Sorry to any valve/tube audiophiles here. I like valves/tubes simply as they are a link to my past, and a link to our collective past. Nothing more. There are applications where tubes/valves are still better suited, but as time goes on they are becoming less and less.

So really, in the context we're dealing with here (not audio, despite my earlier posting) there are applications where vacuum-state electronics still are applicable. Here it's primarily interfacing with electrostatic CRTs, though there are now plenty of semi's capable of doing the same job.

As before, it's whim, a fancy, choose your own poison...

I concede that a bunch of glowing tubes is better looking than a batch of 2N3055s bolted to a heatsink...

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Re: The Mongrel

Postby Harry Dalek » Wed Sep 15, 2021 9:11 pm

Steve Anderson wrote:I don't want to open 'a can of worms' here, but there's no magic, no mystique, or anything objectively 'better' with valves/tubes. They obey the laws of physics as everyone and everything does. Sorry to any valve/tube audiophiles here. I like valves/tubes simply as they are a link to my past, and a link to our collective past. Nothing more. There are applications where tubes/valves are still better suited, but as time goes on they are becoming less and less.


I just look at it its how it was done with no other choice at the time but like every thing you to look back fondly to things that existed in your earlier life ....except school !

So really, in the context we're dealing with here (not audio, despite my earlier posting) there are applications where vacuum-state electronics still are applicable. Here it's primarily interfacing with electrostatic CRTs, though there are now plenty of semi's capable of doing the same job.

As before, it's whim, a fancy, choose your own poison...


True lot of different ways using electronics of different eras to get the same results ,its nice but to give it a go hands on ,i do favor earlier eras i know every thing gets bigger but perhaps not better ...

I concede that a bunch of glowing tubes is better looking than a batch of 2N3055s bolted to a heatsink...

Steve A.
[/quote]

Funny enough i came across a video where the subminiature vacuum tubes are horivontal and on a heat sink a amp again i think ..Yes teh glowing tubes any type are very pleasing to look at .
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Re: The Mongrel

Postby Harry Dalek » Sun Sep 19, 2021 9:48 pm

I was mistaken with the results with the current sync separator and its best after a few days of testing to start again here on the sync separator side of it .
After a lot of reading i think the way forward is to use a circuit called the transitron sync separator.
It uses a EF 91 which equivalent is a 6AM6 the EF91 was replaced in mid 1950 with The EF80 so i have many of those .
What i can see the timing capacitor C1 would need to be adjusted ,looks simple enough to build ,so work on this next see how it go's .
http://www.r-type.org/articles/art-135.htm
easier to read pdf below
bestPractical-Television-1954-07-best.pdf
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Re: The Mongrel

Postby Harry Dalek » Fri Sep 24, 2021 4:12 pm

A week of head scratching wondering why my line oscillator refuses to sync at all i worked out it was the scope probe causing the problem on the above sync separator output capacitor :roll:
It now syncs , video level control sensitive but sync it does .
My camera for some reason didn't record to the sd card so have to do that again show results .
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Re: The Mongrel

Postby Harry Dalek » Fri Sep 24, 2021 7:54 pm

I am syncing the line phantastron oscillator in video below ,i seem to have to set up the oscillator each time i power on for syncing well so far just managed to get it to do that from this afternoon ,i am thinking since the circuits don't have a regulated supply voltage this must be a problem or part of it tweaking part values i will have a look at next .
Any case i can get the line to sync so a step forward and interesting learning how to use Valves again

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Re: The Mongrel

Postby Harry Dalek » Thu Oct 14, 2021 3:31 pm

Haven't posted for a while but have been working on the monitor ,i hooked up the CRT today just to see how things would work with it .
So wired up another 3BP1 but looks like i still have to learn more about the deflection side ! i was expecting better this shameful !
I really only have one axis deflection plate working either axis at the moment still this is pretty small ~ ! only good thing so far nothing blew up ! and it seems to be behaving, not that i can see to much yet but linearity looks ok
This morning i had nothing even to power the CRT up so better than nothing another step .
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DSCN6678.JPG
DSCN6679.JPG
DSCN6672.JPG
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Re: The Mongrel

Postby Harry Dalek » Thu Oct 21, 2021 6:14 pm

Still learning as i go but slight improvement today ,i was blaming the deflection amplifier for my woes not taking into account what's feeding it and what i am seeing in some triode deflection amplifiers .
Some i have noticed have an amplification stage before the deflection amplifier makes sense now .
I swapped the triode deflection amplifier with a pentode version and getting much better results but this is without that triode amplification stage , seems fine for the line as i have reduced size here but frame is on maximum size a little weak and could do with more amplification before hand .
I have had better rasters in the past but first via vacuum tubes so baby steps for me !



Forget the silly dangerous power supply in this schematic below and don't use it but i used the position control part of the circuit changed the 2 plates that go to the last positive grid or Anode 2 that is now grounded instead gives you a good enough positioning controls for centering ,i used the pentode deflection amplifier's pretty much as is only the pot is a 1k which could be a matching problem but that's what i was using before hand circuit below as a size control so need to look into this .
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Re: The Mongrel

Postby Steve Anderson » Fri Oct 22, 2021 11:18 am

Hi Harry, the 'bunching up' of the lines (i.e. the raster is brighter on the left) to the left of the display is possibly caused by the capacitor feeding the horizontal plate(s) being too small. Increase the 0.1uF (100n) to whatever you have, 1uF being a good start. Watch the voltage rating though!...and NOT electrolytic!

That's assuming the input waveform is actually a 'straight' and proper sawtooth.

There are one or two other things I'll come back to later...

Two things that really p**s me off in circuit diagrams, 1) Components not being identified, e.g. C1, R2, TR25 etc. in this case I can't say "The 100n on the anode of the 6AU6" as there's two of them! 2) No 'typical', measured or design voltages/currents shown...here, what is 'B+'? Anyone wanna guess?, or work it out?, you can, but you shouldn't have to...simple laziness and no thought for those who may use the diagram...

I do my best in this regard, but I'm not infallible...

An example...supply voltage shown, and estimated current too (to be measured on prototype). Items in red my change, the circuit is still under development.

Example 1.gif
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Re: The Mongrel

Postby Harry Dalek » Fri Oct 22, 2021 8:54 pm

Steve Anderson wrote:Hi Harry, the 'bunching up' of the lines (i.e. the raster is brighter on the left) to the left of the display is possibly caused by the capacitor feeding the horizontal plate(s) being too small. Increase the 0.1uF (100n) to whatever you have, 1uF being a good start. Watch the voltage rating though!...and NOT electrolytic!


Hi Steve

I have been doing this one very slowly just seeing how sections go one at a time ,the deflection part of this i was interested to see how it went wanting it fully hollow state i am pretty much making a guess what i use and looks correct other wise i would just copy yours, Valve deflection amplifiers testing seeing the results .
I think the 2 things that confuse me are the push pull type and the position controls so went a bit simpler testing here

You are correct on the deflection plates being AC connected as in video shown ,i have made sure caps rated for the voltage ,i will look into getting the value correct mentioned .

I found i had to also Ac connect the line ramp oscillator to the deflection amplifier , the screen line jumped to nearly full screen doing that other wise it was about only what you see in the photo last post

Funny that did not work at all at 12.5 hz infact made it smaller ac connecting oscillator to deflection amp so far left it DC connected .

That's assuming the input waveform is actually a 'straight' and proper sawtooth.


Well that was on my mind ,i found when i connected the line oscillator to the deflection amp DC it distorted the ramp input made it a touch rounded AC its a nice ramp again .

There are one or two other things I'll come back to later...


This is all very experimental for me any hints welcome .


wo things that really p**s me off in circuit diagrams, 1) Components not being identified, e.g. C1, R2, TR25 etc. in this case I can't say "The 100n on the anode of the 6AU6" as there's two of them! 2) No 'typical', measured or design voltages/currents shown...here, what is 'B+'? Anyone wanna guess?, or work it out?, you can, but you shouldn't have to...simple laziness and no thought for those who may use the diagram...


HAHAHAH i do see the guessing game on The B+ a fair bit looking at these types of circuits and as you notice some times yes you have to guess well it must lower than A+, some times forgetful some times lazy .i do these days really look into using parts rated for the voltage's currents ,have had no problems in ages must be learning ; )

I do my best in this regard, but I'm not infallible...

An example...supply voltage shown, and estimated current too (to be measured on prototype). Items in red my change, the circuit is still under development.


Steve A.
[/quote]

Well with yours all i had to do is learn to take note you put in its a good estimate but might change and read your notes .
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: The Mongrel

Postby Klaas Robers » Fri Oct 22, 2021 11:22 pm

Harry, you should realize yourself that the deflection plates of a CRT should be steered both, and in opposite phase. For a constant focus it is needed that the induced 'mean' voltage at the position of the deflection plates is constant, not changing with the deflection voltage. That will say both plates should contribute to the deflection, one in positive way, the other in negative way. So the idea of feeding just one plate with a saw tooth signal, and the other with a fixed voltage that you can adjust for centering control, is not Ok.

If you feed just one plate, you will see that the spot may be focussed at beginning edge of the screen, but unsharp at the end side. Adjusting the focus control will not help you; if you make it sharp at the end side, then it will be unsharp at the beginning side. I re-realized myself these facts when yesterday I jumped into the circuit diagrams of one of my Heathkit waveform / spectrum displays, the SB-620. It shows horizontal deflection problems.......
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Re: The Mongrel

Postby Harry Dalek » Sat Oct 23, 2021 8:46 am

Klaas Robers wrote:Harry, you should realize yourself that the deflection plates of a CRT should be steered both, and in opposite phase. For a constant focus it is needed that the induced 'mean' voltage at the position of the deflection plates is constant, not changing with the deflection voltage. That will say both plates should contribute to the deflection, one in positive way, the other in negative way. So the idea of feeding just one plate with a saw tooth signal, and the other with a fixed voltage that you can adjust for centering control, is not Ok.


Hi Klass what you are mentioning is what i am confused about some example's i have been looking at one shown ,i was thinking what you are telling me about driving the deflection plates in a opposite phase to each other this is the push pull meaning to me ....i missed something in circuit below with out looking at it carefully at first i was thinking they were driven in the same phase direction but i see now the first 12At7 triode out put is sent to the second triode which i think inverts the sawtooth then feeding the second deflection amplifier
Screen 00000.jpg
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Not a good example of what i want to do here but doe's show what i would expect a push pull deflection amplifier waveforms out of phase to dive the plates to look like
Hdef (2).jpg
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If you feed just one plate, you will see that the spot may be focussed at beginning edge of the screen, but unsharp at the end side. Adjusting the focus control will not help you; if you make it sharp at the end side, then it will be unsharp at the beginning side. I re-realized myself these facts when yesterday I jumped into the circuit diagrams of one of my Heathkit waveform / spectrum displays, the SB-620. It shows horizontal deflection problems.......


This build is very experimental to me more a learning build than any thing with Valves so i do expect result mistakes and changes to be made , i am seeing what you are telling me so i need to look into a circuit change to drive both plates .

I was looking at trying this one only the deflection amplifiers since there dual triodes and better positioning controls and perhaps the cathode follower also, i should just adjust Steve's deflection amplifier to work all hollow state would this be possible Steve doing away with the 12v supply and 2n2222's?
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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: The Mongrel

Postby Steve Anderson » Sat Oct 23, 2021 12:39 pm

Harry Dalek wrote:...I was looking at trying this one only the deflection amplifiers since there dual triodes and better positioning controls and perhaps the cathode follower also, i should just adjust Steve's deflection amplifier to work all hollow state would this be possible Steve doing away with the 12v supply and 2n2222's?


Klaas is quite right, driving just one plate isn't such a good idea. It saves components (cost) size, weight, power consumption, and improves reliability. However, it produces defocusing, even on tubes designed for single-ended deflection. Here's the result on my 1CP1/DH3-91 1" CRT, it's designed for single-ended drive on the horizontal deflection. Note the defocusing to the left, whereas the centre portion is quite good....but what can you expect on a 1" (2.5cm) CRT?

Defocus 1.jpg
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This was the best I was able to obtain and followed the datasheet to the letter. It's not really meant for picture presentation, but AM modulation monitoring in transmitters. With a tube not designed for single-ended deflection it'll probably be worse.

As for the transistors, they could be replaced by a single resistor, BUT you'll also need a high voltage negative supply similar in voltage to the positive, but negative. Or replace the transistor with a pentode current source which will also need a high voltage negative supply and a separate insulated heater supply - take your pick!

There is a reason why 99% of CRTs use symmetrical deflection (as per above) and it doubles the sensitivity...and reduces the bandwidth requirements of the deflection amp(s), though that's not an issue here...

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Re: The Mongrel

Postby Harry Dalek » Sat Oct 23, 2021 8:03 pm

Steve Anderson wrote:
Klaas is quite right, driving just one plate isn't such a good idea. It saves components (cost) size, weight, power consumption, and improves reliability. However, it produces defocusing, even on tubes designed for single-ended deflection. Here's the result on my 1CP1/DH3-91 1" CRT, it's designed for single-ended drive on the horizontal deflection. Note the defocusing to the left, whereas the centre portion is quite good....but what can you expect on a 1" (2.5cm) CRT?


mmmmmmm.. yes i can see the results and know what i have made before and so far it is inferior to past go's, another thing to learn i see .

And yes also i see it in the image you posted also .

This was the best I was able to obtain and followed the datasheet to the letter. It's not really meant for picture presentation, but AM modulation monitoring in transmitters. With a tube not designed for single-ended deflection it'll probably be worse.


Not bad for indeed for some thing never designed for a Low def TV screen ..proof of concept i always like !

As for the transistors, they could be replaced by a single resistor, BUT you'll also need a high voltage negative supply similar in voltage to the positive, but negative. Or replace the transistor with a pentode current source which will also need a high voltage negative supply and a separate insulated heater supply - take your pick!


This time i think i will try the simpler resistor solution just to make sure i have the right idea i put it down in your circuit and run this change by you ,if i got your explanation correct ..forgive me if its a total mistake taking some thing that works well and butchering it is not some thing i want to do but just trying to see how to do this just with the tubes
The position control i use the tubes positive supply i know i would have to lower the voltage more with another high ohm resistor ,as you were doing position with only 12 volts .

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There is a reason why 99% of CRTs use symmetrical deflection (as per above) and it doubles the sensitivity...and reduces the bandwidth requirements of the deflection amp(s), though that's not an issue here...

Steve A.


OH well i will stick with the better idea from now on learning all the time .
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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