auto radio solid state vibrator for vintage tube radio

[sphinx]

i found this on YT and it is a replacement for a mechanical vibrator for creating high voltage on vintage car tube radios

i found this interesting and a fun small project

for some reason he made this private but i succeded to download before he did that

please check schematic for errors it is video please watch the pin on mosfet seems to be right for the irf3205
some info in schematic sheet

adjust for your own preferences this can easily be made with smd as well if wanted.

url file is for the video 

[sadman]

please upload schematic in pdf format
 

[sphinx]

here you go, please be advised to check with what is shown in video/

/sphinx

p.s. i forgot to say that the users name is shango066 that made this on his channel
next time i will try to remember to create a pdf file for shematics for those that might want it not much extra work for that thanks at @sadman

[sphinx]

i found a missing trace on pcb between pin 6 and 7 on IC yoou can correct it or download a corrected

i checked schematics no errors

the schematics is still same no edits i just made it a bit more readable there just the ocb that got a missing trace.

pdf is included as well

sorry for the mess

/sphinx

p.s. from now on i will not make the schematic designs compact it alot better to have easy readability

I MADE A NONO ON THIS ONE DELETING FILE WILL REUPLOAD WHEN I SORT THINGS OUT

THERE SHOULD NOT BE A CONNECTIONS BETWEEN PIN 6 AND 7 THAT WILL CREATE A SHORT BETWEEN 12+ AND GROUND
THERE WAS MADE AN ERROR WHEN MOVING COMPOENTS

THIS A NEW REUPLOAD AND THIS ERROR FIXED

I ADDED ALLREADY MADE GERBER FILES NO OTHER CHANGES MADE TO DESIGN

[PM3295]

I watched some of shango's videos in the past. Interesting guy.  The proposed circuit works ok, but there is no duty cycle control, if you need to reduce the final output voltage. I have done a design in the past (also single chip) that serves the same purpose, but has some duty cycle control as well. If someone is interested, I can dig out the diagram and post it here.

[sphinx]

it is mentioend in the video that voltage can lowered with diodes on the common source line from both transistor, he had some problems with that he talked about it

why not share it i could make a pcb and gerbers for it it seems llike a nice idea this could be use for other purposes as well.

[PM3295]

It was designed for driving a push-pull stage in open loop, with duty cycle control. I will look for it and post the schematic.

[PM3295]

I couldn't find my original design, so I had to make one up from memory, breadboard and test on the bench to be sure. You can experiment with the adjustable legs if you want more variation for duty or frequency. Out A/B is the drive to the MOSFETS.

With the actual circuit, the duty adjusts between zero and 49%, but in the Proteus model, the same values only adjust down to about 30%.

[sphinx]

could you please share the proteuss projest so i wont need to redraw that design

[PM3295]

Sure!

Posted on: January 31, 2023, 11:00:12 23:00 - Automerged
There is something wrong with the UC3525 model. With the real circuit, adjusting the pot to min is also min duty, as the chip should function. In Proteus, it is reversed. So, something is up with the model. It looks like the compensation pin function is not modeled correctly.

[sphinx]

is this same design for a transformator with middle tap and can i use 2 n type mosfets as with my old design ?

i tested it in proteus and it works just fine only thing i can see is thatso called "duty cycle" doesnt go up to edge to edge on the pulses
i guess it will work just fine as it is, now output voltage can be adjusted to the liking.

[PM3295]

Yes, it is meant for push-pull with center tapped transformer. In the real circuit, the duty cycle adjust over full range. It is the model messing around in Proteus. I checked the chip operation in Cadence Orcad, and their model works correctly as far as the compensation pin.

[sphinx]

i am almost finished with the schematic so i will soon create a pcb

[PM3295]

If you want to add some dead-time, you can put a 100 ohm or so in series with pin 7.

[sphinx]

i need to look up what that means for the chip and signals. thnx for that extra input

[PM3295]

In my original design, I also used pin 10 for current sensing and protection. If you want to implement that as well, let me know.

[sphinx]

man when i just completed the you just had to come up with something new so i need to re route the design, just kidding

that could be a good idea to have some protection of the circuit

i attach the new design a work in progress with pdf if you want to have a peek

just wondering if i really need to concerned about component placement that much since this will be 80-200Hz ?

[PM3295]

Maybe, you can design for two variants? One simple without the added features, and one with the current sensing protection. The last one we need to add another low-value power resistor. I will make the changes on the schematic for you.

Such low frequency should not be critical for layout.

[sphinx]

well if only a resistor is to be added for shutdown then it is ok it can be added to this design like the resistor on pin 7 it could be bridged if that function is not used

i checked the data sheet not much info on the shutdown from what i saw

ok roger that on placement that was what i was thinking.

[PM3295]

The value of the power resistor (0.1 in diagram) must be such; that peak current (under normal conditions) through the FETs generates a peak voltage < 0.7 V. The RC filter value will depend on the transformer, leakage inductance, etc. The time constant should be just long enough to remove any initial short spike, that may trigger the current limit prematurely. So you can play around with the R while scoping the waveform on pin 10 for sort of a saw-tooth signal, without any starting spikes...

[sphinx]

thanx for this addon i will add these to the design, these can be left out as well if one doesnt want this function

[PM3295]

You also want to minimize any voltage drop caused by switching current between the points marked, when using the current sense. Try and group those points together. Otherwise the bounce in the ground line will interfere with the current sensing.

[sphinx]

this is the design with the latest modifications with current sensing have a look at it.

[PM3295]

I will try and route it like this to have equal lengths of track on each source connection. Best to keep it sort of balanced for push-pull.

BTW, you have an error on the gate connection T2.Recheck against my diagram.

I see more errors Vref. Diagram should look like my attachment.

[sphinx]

roger that, will fix it and add documentation/info for those extra components i will also widen the power traces as well

now this works for both the first versio and with the extra additions.


Posted on: 2023-02-01, 05:04:02 - Automerged
this is with the fixed traces

will now sort out the component labels and documentation/info

will now take a cup of tea and watch some crime tvshows before bedtime.

will fix the stuff la

Posted on: 2023-02-01, 05:20:29 - Automerged
i fixed the t2 error with the gate and vref error those were easy to fix on pcb as well

sometimes altium does funny things if not careful when moving lines or components

now i just going to add info on schematic if someone wants those extra features or not but that will happen after i sleep.

brain is getting a bit woozy so better to stop now and do the rest with a fresh brain.

here is the latest fix for those errors i made.

[PM3295]

I believe that the old tube radio transformers required the drive to have some dead-time for maximum efficiency. It was related to the time needed for the vibrator contacts to switch over. Maybe we can limit the max duty as to have some minimum dead-time.

I found some servicing notes (attachment), about the shape of the switching waveforms.

[sphinx]

sounds good to me, tubes are not exactly my area. logic stuff is what ilike

[sphinx]

this is now in last stages of designing not much wil be changed after this documantation/info is added to schematic

there might be a resistor added to limit the duty cycle. the circuit can be used as is if one knows that 100% might not work properly

i also modified the ground trace to be on bottom for better current handling

i dont know what more i could add

if you have followd this thread you know what this is supposed to work as there could be other ways to use this but i guess the imagination is the limit

pdf's and gerbers are included

latest changes are that now it is a sngle layer boards since it was only one trace that was on top layer now it is possible to make this even at home.

this is also a 12 volt only design since ic 8volts and up

/sphinx

[sphinx]

this is sort the last big edit on the schematics and pcb

nothing i can really think of to modify or any other suggestions to the design

on the schematic i added a resistor (R12) that could be used to set limit of duty sycle if wanted other wise shorted
info is in the schematic sheet

on the pcb i moved around compoents to make the ground trace more compact short efficient, i figured out the word it is optimize
previously it was long and all over the board

thanx PM3295 for for this new design and additive suggestions for extra features

 i made this a single layer board, pdf included and so are gerber files

do as you wish with it

/sphinx

[Sideshow Bob]

Would it be an idea to enable the internal soft-start. To do this you only need a 5uF cap connected to pin 8

[sphinx]

i will have a look at it i havent got a cap with a smallish footprint with that value i guess a 4.7 would work too.

i will have to do some searching for one

hopefully wont be much trouble since it is only connected ground

[Sideshow Bob]

i will have a look at it i havent got a cap with a smallish footprint with that value i guess a 4.7 would work too.

i will have to do some searching for one

hopefully wont be much trouble since it is only connected ground

I would think any 5uF ish cap value will do. A larger value like 6.8 or 10 uF will most probably create a slightly longer soft-start period but nothing more. The track to ground can also be quite long. Or if it is more easy use a low ohm resistor(like one ohm) as a jumper

[sphinx]

a 4.7uf cap has been now been added for soft-start support which can be omitted as well is this function is not wanted

info is in the schematics sheet as well and so are pdf and gerbers files

do as you wish with it and modify it to your likings

i was sorta lucky and it could be placed with a short track to ground not that it was necessary but the space was sorta easy to make for it

all the extra features can be disable/(not used) info is provided in the schamtics sheet and pdf make it as simple/advanced as you want it to be.

/sphinx

[PM3295]

It appears that the switching frequencies used are 100 Hz or 115 Hz. The optimum drive needs about 1ms of dead time. There is also a resonating capacitor over the primary winding to improve efficiency. This YT video gives a good indication what drive waveform is needed.
https://www.youtube.com/watch?v=7EWTa1jQmng&t=1s

[sphinx]

interesting video i saw all of it from start to end

this guy is using a MCU for the control and his design is made for 2 6 12 24 and 48 volts

quite nice design

[PM3295]

The MCU is an easy and cheap solution, as long as you don't need to make the duty cycle adjustable. It also serves to protect their product design from being blatantly copied, cloned and sold on ebay etc. This may be a problem if it breaks down, and you can't replace the processor if blown, and need to buy another complete unit. At least with the switching-regulator type designs, most people will be able to repair it.

I think the 3525 circuit can be modified to work down to 6 V (overriding the UV cutout) without much trouble. You will need about 9 V at 14 mA on the Vin pin, which can be generated by a charge pump circuit, synchronized to the main clock (200 - 230 Hz). The Vc pin can be tied to the 6 V supply rail. This will reduce  inter-mods  you may have when running the pump asynchronous at higher frequencies, with harmonics showing up on the longer wave bands.  The main internal clock still runs happily at 6 V (see scope pic), and only the internal output drive is locked out. You most probably have to use logic-level gate threshold MOSFETs for proper switching.

Included, the schematic and prj file in Proteus. The circuit does not simulate correctly since the 3525 model shuts down completely under 8 V supply on Vin. Also the OSCOUT pulse is much wider than with the actual hardware, preventing the 555 from working correctly. I added a 20 uS wide pulse to represent the expected pulse input. At least you can get it running and play with it. The free running 555 should be set slightly slower than the sync frequency.  

[sphinx]

i was wondering about adding the 555 circuit to the design

i got 555's but not 3525's so i can't buid it on breadboard and try it, i will try to order some in near future and add some modfets as well to have try with

youre right about the mcu solution it is all about not making it simple to copy design but i wouldn't think it is that hard to write software for it.

[PM3295]

The SW would be easy, but not every user will be capable of doing their own code. Some older hobbyists avoid coding or learning to do so.

[PM3295]

The 555 part seems to work well. I made one modification by returning the discharge resistor to the discharge pin, and not the output. Switching seems more stable this way. I only had 1N914 diodes at hand, so the output voltage (8.6 Vavg) with appropriate diodes should increase at least another 500 mV. I loaded the output with 14 mA. First pic shows the operation with sync off, and then with 20 us wide pulse.

[sphinx]

this a version of the "vibrator" with a charge pump added to board

this is still a work in progress trying to make board a bit smaller if possible

sadly not single layer at this moment

p.s. perhaps time to go smd what you guys/gals say size of the board is getting bigger ?

[PM3295]

It looks good! As long as it can  fit into the old vibrator standard enclosures, it should be ok. I have seen some-odd  ones that are smaller, but that is not common. I will try and breadboard one fully to verify all works as it should.

Maybe we should limit the frequency of operation to around 100 -115 Hz (200 - 230 Hz) for the clock, as the charge pump will not sync correctly over a very wide frequency range. As it is intended for tube radios, it should only be required to work near the two (200 and 230 Hz) standard frequencies. It may be an idea to have a selection jumper/pads.

[sphinx]

thru  hole size is 1400x3100 mils, i thought it was getting a bit biggish

the whole design is sort of modular if a function is not wanted compoents can be deleted or jumpers placed
info is in the text

[PM3295]

I was thinking about three selection pads to pick operation between the two frequencies. The MCU board design may have something similar.

[sphinx]

ah ok thats understandable

i am on the way of tryng to shrink the board with smd's

my thought was to leave the mosfets as thru-hole since they a bit easier to replace than smd and most common to break is my guess

i was wonder if using tantalum caps would be ok to use on this board, since i am not sure about temps inside a radio or in the place where this board would be ?

[PM3295]

Ok, I managed to string together the two circuit blocks. It appears to be working as expected, with good startup and sync. I have to experiment with the values to determine the set limits for guaranteed sync action.
From the pics, you can see that the main clock starts running at around 5.2 V, and the output enables when the charge voltage reaches the 8 V threshold.

Tantalum's may be necessary to shrink the design.  

[sphinx]

ok sounds good i will put pcb'ing on ice so i can work with a complete circuit instead of modifying for every change

i will make this version smd since pcb is getting a bit big for my taste and i think it wouldnt fit in a vibrator can
i will have the mosfets thru-hole for easier reapir

[PM3295]

Here is the updated diagram with values that worked well for me.

1) I changed R14 so that the charge pump will only start once the sync pulse comes from the 3525 (see pic).
2) I found out that the OSCOUT pin has very limited current drive capability and caused strange pulse doubling of the output when loaded too much. The solution was to use a small darlington to prevent excessive loading of this pin. (MMBTA13,MMBTA14)
3) Adding D3 helps the charge pump to come up more quickly, and if the pump circuit is not needed, all the pump components can be left out.
4) R1(15k) now gives good sync over the stated frequency range.

It will be good if you can perhaps get one going as well so we can see if you get similar results.  

[sphinx]

this is a prerelease of the smd board with the latest changes

i feel like the routing and placement is a bit of mess not really satisfied with it.

i am trying to make the board small so it could be easy to fit (2000x1200 mil)

i need to have a look at it for a bit to "see" what changes i can make to make it cleaner
some traces need to be thicker as well but that will come later when i figure out a better placement and routing

[PM3295]

Maybe move C8 on the diagram, so it will stay in for filtering on Vin if the pump is not needed or populated. You already have it close on the pcb layout.

[sphinx]

i moved the cap on schematic as you can see i also did shuffling around with some compoents and moved C8 a tiny bit closer to IC
not much work with that

i moved some other compoents and modified some traces as well.

i take a day off to clear my head and come back with a freshish mind.

the top layer looks prety ok but the bottom layer not so much i will see if i can clear some of it up.

some power traces needs to get wider  but that comes after the other stuff is beautyid up.

[PM3295]

Fresh mind always works. No rush.

[sphinx]

i think this is as clean i am going to get it i think

because of having that ground compoents close to each other  to not cause issues or behaving weird

i also placed a couple of compoents on the bottom side to make it cleaner routingwise

i use thru hole transistors for easier repair design can be modified to have SMD's as well

info about the circuit is all in text please be aware of pinout on mosfet and change schematics and pcb if nescessary

i modified the R11 for better power handling (10w) smaller size can be used if wanted or can be shorted as well

board is now 2000x1200 mils

have fun with the design

[PM3295]

It looks good. On my design, I would maybe do a different placement for R11 as shown (*) in the pic. It shortens the trace between R11 and FETS, which I prefer. The increased length of the R10 trace is not a problem.

[PM3295]

After thinking more about the intended use in a car system, I think we should rather tie the top end of R8 back to the Vref pin. This way, we will not have duty cycle variations as the charging system varies the Vbat voltage. We only need about 3.6 V back to the Comp pin for full duty cycle, so using the 5.1 V ref output should work. R8 will change to about 2.7k for this. I will check it out and confirm.

Doing this mod on the pcb should not be difficult.

[sphinx]

i modified R11 on the board will wait with upload until you come back with confirmation

[PM3295]

Ok, we can leave as is. Since the variation is picked up by the feedback pin as well, the duty cycle adjusts in the right direction. With increased Vbat, the duty cycle is reduced, so that we have some correction on the final output of the transformer. The duty cycle increase with Vbat going lower.

Scope pic shows Vbat varied between 6 - 7.5 V and the responding duty cycle.

[sphinx]

ok here are the files with latest edits

r11 moved

have fun

[PM3295]

Looks even better in 3D!

[sphinx]

lets hope it fits in a can since i am not sure how big thos are

[PM3295]

Here are the dimensions on the most popular one out there. https://www.pekorf.com/RVB2_Assembly.html

They don't have such a large main capacitor. I don't think it needs to be 2200 uF. We can make it 220uF or so. The FETS can always be soldered from the opposite side and be bend over to save on the overall board height.

[sphinx]

i will make the big cap thru hole as well and mount it on the back side so that the fet's can be bent

Posted on: 2023-02-16, 01:46:16 - Automerged
nothing else has changed beside the cap has been made thruu-hole and placed on the backside so now both cap and
mosfets can be bent alongside the pcb and o also lef a bit of area where glue can be applied

now the pcb is even smaller than before and extremly close to his size

i used a 1000uf 25v cap wich can be changed to other size if wanted just bending the legs of bigger or smaller one

have fun with it

sadly i cant make it gorgeous with bent cap and fets so it would awesome in 3D

p.s. one can add mounting holes at the bottom of the card to make it easier to mount i wont upload with thiis because it can be very simple to add
i also realized i made pcb to mm just change back by presing "q"

p.p.s i just couldnt help myself i made the pcb as smaller to be easier to place in raios the size is now 1000x1900 mils a bit smaller than mcu version of the pcb

[PM3295]

At the moment, this design can only replace the asynchronous vibrators. If we want it to be used on synchronous types as well, we need to place two additional HV diodes with their cathodes connected to ground. The anodes go to each side of HV windings of the transformer.  The diodes should be rated at about 400 V/0.5A minimum.
Basically the diodes replace the extra set of contacts used for synchronous rectification.  

[sphinx]

man you are a good friend, just when i shrunk the pcb you just had to come up with something new. LOL

is it a schottky or normal diode ?

is your name perhaps Murphy ? you you bugger

[PM3295]

 Well, the first YT guy only worked with the simple type  . Just if we want it to be multi-purpose, we will need these diodes unfortunately. I think you can get sk diodes up to 600V last time I checked.

[sphinx]

now those 2 diodes are added on board as well, getting crowded/full on pcb, there is still some space to shoehorn something in.

i also added info about them in schematics as well.

tell me if if it looks ok.

[PM3295]

I think it is good for now.
One other thing; There is a sweet spot to set the P2 (duty), to get about 40% for the nominal operating voltage (no charging). Because the feedback and compensation action counter each other, you want to set it at the break-point where the duty adjusts in the correct sense. If you get it at the wrong side, you get the duty increasing with more voltage (comp dominates). Do you think we should have a note on the diagram for setting this adjustment? It may be a good idea to put a pad on the wiper trace of P2 to act as a test point. I will do more testing on 12 V and higher to see how this reacts. On a 6 V system, I can get a good response from 6 V up to 8 V, with the comp resistor increased to 2.2k and the wiper set at the 2.55V point. I will verify if this is good for the higher voltage systems also.

What do you think?

[sphinx]

i added a pad/hole for a testpoint for measuring on the wiper trace for easier measuring.

never hurts with information to make a circuit work better is my opinion

i also mean we have made a modular design of the circuit with lots of other info on how to use it so of course it is good to have that info as well

just tell me what tmessage i should put there on the schematics.

[PM3295]

Since the value of R2/3 will have some tolerance, and not always divide down exactly 50%, it is better to measure for a voltage difference between this point and P2 slider. It should be adjusted for +150 mV, and with R7 at 3k3 it tracks well for 6 V or 12 V once set at the nominal voltage of operation.

[sphinx]

i did the modifiations of schematics and added info as well

during the time i did some cleanup (beautying) it up.

[PM3295]

Hey man, it looks like our design work is done on this! Now we just need someone who plays with these radios to actually try it out. I don't have many valve type equipment, except for a few VTVMs, and they operate without this.

[sphinx]

i was wondering about adding some info on how it is connected to the transformers for both types on the schematic sheet

i just haave a couple of tubes somewhere in the bins but that is as far as own and valve related gadgets.

[PM3295]

If one could get hold of a 6 V vibrator type transformer, then it will be easy to make up test to see how well it generates the required HV supply. I suppose you could add a diagram to show how it needs to be connected, but I guess the people restoring these radios already know how to connect it. There are many online forums dealing with vintage radio restorations.

[sphinx]

i added info on how to connect it, better to be clear than not

this is only change to schematic sheet nothing else changes just added connection info thats all

even if people know never hurts with this info so no need to ask a ? when info is provided.

[PM3295]

And of course, if you want something simple and don't care about all the extra features of the 3525, you can modify the 4047 circuit to give you limited duty cycle control as shown.

[sphinx]

shall we create a schematic/pcb for variant ?

[PM3295]

If you want you can do it. I think a lot of people will prefer the simple design, to be honest. Something they can also quickly knock up on strip-board if they don't want to get a pcb. It will be more doable with standard TH parts. We will need a small 12V regulator (78L12) to supply the two chips if it is going to be used over 12 V. We don't need the zener then.

[sphinx]

ok i will use a 78L12 , was just starting with schematics and thought i'd make it smd going to change it to TH then. might be better when fiddling at home

i agree with you, if a simpler solution works good i would use it preferably.

[PM3295]

Maybe make it a 78L09, then it will still regulate with 12 V systems, as it requires 10.7 V input to maintain regulation. With the jumper you can select if you want the low 6 V operation.

[sphinx]

there are LDO types a 10v might work i will add a note about it

[PM3295]

I like the 78 series because they are really easy and cheap to get hold of. Nothing special. Old school. 

[PM3295]

I had to change the 4093 to 4011 since my breadboard test gave very limited adjustment due to the 4093's hysteresis band. I did not work as well like in Proteus.

[sphinx]

this is a simpler version 12v only with thru-hole components for making simply at home with a alsmost single layer boards

where there is only one trace that is on the top layer this trace is made si it can easliy be made with a wire

if there is no errors found this would be a final edit

have fun with it

if you want some extra info on the schematic sheet let me know.

have fun with it

[PM3295]

Don't you think having a jumper when 6 V operation is wanted will be a good option? Like I have it in my diagram.

[sphinx]

and i thought that was for sonething else, i will fix that, now i get it it was both 6v and 12v operation i thought it was 12v only thats why.

UPDATED !! with a jumper for 6v and 12v operation

Posted on: 2023-02-18, 07:07:23 - Automerged
i found an error in schematic now fixed

it will complain over missing gerber x2 files you disregardds this and delete those in "Generated Gergber X2"

i know this is a low voltage circuit, one can alllways make bigger spacing on IC1 voltage regulator. it coule make it easier to solder as well

do as you wish with it

[PM3295]

Here is an interesting book (+100 pages pdf) on the theory and design of vibrator-type-power supplies. Lots of info on the transformer design, etc. Link in txt doc.

[sphinx]

a simple vibrator may look simple but it is a lot of things to think of when making it and adjusting it, i starting to read document
and many interesting things one might not really think about

i recommend others to read it as well its a good book and i am even starting to read it