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Old 8th Oct 2009, 9:38 am   #61
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Default Re: Solid State Vibrator.

Posts concerning a Philips NX393V moved to a new thread here:-

https://www.vintage-radio.net/forum/...ad.php?t=46166
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Old 9th Oct 2009, 10:20 pm   #62
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Default Re: Solid State Vibrator.

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Note that there is no "OFF" time between one MOSFET switching off and the other switching on.
Yep, I wondered about this. My Mentor who designed lots of switching PSU's told me to make sure there was delay so that both drivers were not switched on at the same time. As far as I can remember, he just used some logic gates to do it but sadly I cannot remember the circuit, it was way too far back in time for the grey matter here. I know that some of the gates were used just as delays by wiring them in series, perhaps one of the members on here has devised a similar set up?
Les
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Old 27th Jun 2010, 9:04 pm   #63
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Default Re: Solid State Vibrator.

This afternoon I Finally got round to trying the SS Vibrator in the set. Up until now I've been using a bench power supply for both LT and HT, as I didn't want too many unknowns in the equation whilst repairng the set.

I used a fully charged car battery with 50A fuses in each lead to guard against shorting the supply leads. There is of course a much lower rated fuse in the set.

On receive HT was good at 250V. There was no hash in the headphones so long as the can was in place on the SS Vibrator. Without the can hash, which was obviously RF borne, could be heard in the headphones. The receiver performed well on AM. I was able to listen to 49 meter band broadcast stations and the 3.615 MHz amateur AM net. I tried out the flick tuning facility and was surprised at how good resetability was.

There are couple of problems with the set which should be easily fixable.

The fixed BFO will suddenly leap in frequency. This is probably mechanical, so I'll have the can off for inspection. While I'm in there I'll change the capacitor in the tuned circuit just in case.

The volume cannot be reduced to zero. The volume control is a 500K log which is electrically quiet in operation. Measurements show that when in the min position there's about 16K resistance to chassis. I'll check how a modern pot compares.

The real test will come with the transmitter. Will there be hash on the transmitted carrier or audio? I have a bit more work to do before I find out.
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Old 1st Jul 2010, 1:14 am   #64
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Default Re: Solid State Vibrator.

Have a look at this.

http://www.vmarsmanuals.co.uk/newsle...s/vibrator.pdf

Al
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Old 1st Jul 2010, 6:55 am   #65
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Default Re: Solid State Vibrator.

Well, it looks simple enough, but (as the author of the article says himself) it is curious it has no timings caps (or even power rail decoupling !)

Consequently, there is a danger (IMHO), that the whole thing relies on capacitance inherent in that particular construction to work, and that it might be very difficult to replicate successfully for other applications.
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Old 1st Jul 2010, 8:19 am   #66
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Default Re: Solid State Vibrator.

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Have a look at this.
If you read the first few posts of this thread you'll see that that's what I started with. It doesn't work, at least not in this radio.
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Old 1st Jul 2010, 10:09 pm   #67
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Default Re: Solid State Vibrator.

Hi

Go on, make it. they work fine. I've now built three and they all work. It is worth saying though, They are a little temperamental, but if it did not start then just unclip the battery and reconnect. Mostly they start first time though.

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Old 1st Jul 2010, 10:45 pm   #68
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Default Re: Solid State Vibrator.

I have made one. There's a picture of it in post #1 for goodness sake. I still have it. It doesn't work. I explained all that in the first few posts of this thread. I can't reconnect the battery every time I want to transmit. I have a design which works well.

END OF STORY.
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Old 2nd Jul 2010, 1:30 pm   #69
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Default Re: Solid State Vibrator.

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I have made one. There's a picture of it in post #1 for goodness sake. I still have it. It doesn't work.
I wonder if you could add a piezo transducer to kick it into action when the can is whacked with a screwdriver handle as well as power-cycling it...

You'd then have an accurate solid-state replacement for a knackered mechanical vibrator...

Sorry...
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Old 2nd Jul 2010, 10:30 pm   #70
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Default Re: Solid State Vibrator.

Funny that!. They work for me. ALL OF THEM. Iff they do not start first time just Take clip off then put it back on. Once started they will run all day.

Pete

(Check you have made it right) No need to be proud about it, we all make the odd mistake.
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Old 2nd Jul 2010, 10:46 pm   #71
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Default Re: Solid State Vibrator.

Hi Peter,
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Iff they do not start first time just Take clip off then put it back on.
Sorry, but "not starting first time" equates to "faulty" for me, also it would appear for Graham.

A working mechanical vibrator starts first time, every time. A working solid-state replacement should be the functional equivalent of a brand-new, working mechanical vibrator but without the wear/age issues.

If any of the commercial products I've designed sometimes didn't work, I'd have been fired!

Regards, Kat
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Old 2nd Jul 2010, 11:29 pm   #72
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Default Re: Solid State Vibrator.

I'm inclined to agree - although, it has to be said, a lot of products these days seem to get onto the market with "undesirable features", a well known radio telephone maker seems to be in the news at the moment on that front
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Old 3rd Jul 2010, 12:43 am   #73
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Default Re: Solid State Vibrator.

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(Check you have made it right) No need to be proud about it, we all make the odd mistake.
The one I made is shown in the pictures in post #1. If you can find anything wrong with the construction I'd be delighted to hear what it is.

I don't doubt that the design may work in other radios, but it doesn't work in the New Zealand ZC1.
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Old 6th Jul 2010, 12:29 pm   #74
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Default Re: Solid State Vibrator.

Yes I must agree.. BUT something is not right. It maybe good just to strip down, take another look the rebuild.

They do work, simple yes, but they work (most of the time) hi

Pete G4MRU
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Old 7th Jul 2010, 10:22 am   #75
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Default Re: Solid State Vibrator.

Peter.

I do make mistakes in building stuff, it comes with advancing age, but there is nothing wrong with the construction of my original vibrator as described commencing in post #1 and subsequent posts. The components all test good too.

You yourself admit that the circuit doesn't always start up straight away. That's not good enough for me. I need a reliable start first time every time.

One inherent problem with the simple two transistor circuit is that it needs external circuitry, ie the step up transformer, to start it oscillating and maintain the correct frequency. This isn't a requirement for a mechanical vibrator, which will oscillate without the need to be connected to the step up transformer. It isn't a requirement of the SSV I finally built either.

A further problem I have is that the NZ ZC1 set I'm using has a HI/LOW transmit power option which switches turns into the secondary winding to give a higher HT voltage. Operating the HI/LOW switch can "stall" the two transistor SSV and that isn't good enough for me either.

My final comments. I have no doubt that the two transistor SSV works in such equipment as the WS 19. It doesn't work in the NZ ZC1 though. I have a good working reliable design and see no need to change it.
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Old 7th Jul 2010, 6:27 pm   #76
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Default Re: Solid State Vibrator.

The problem seems to be that this device is using the transformer primary as the main timing element.

There's nothing wrong with using inductance as a timing element (the current through an inductor builds up in a sort of 1 - e ** x way just like the voltage across a capacitor does) per se but the problem here is, the apparent inductance of a transformer primary depends on what is connected to the secondary.

Now, with a classic push-pull valve rectifier (e.g. EZ80) which is cold to begin with, the primary is effectively not connected to anything and so will behave more or less like a pure self-inductance at first. But I'd expect this design to have trouble starting with semiconductor rectifiers, because the secondary circuit will be taking stored energy from the core as soon as the primary circuit tries to supply any; and it may not work well with a half-wave valve rectifier, because of the effects of the asymmetrical loading.
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Old 7th Jul 2010, 9:21 pm   #77
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Default Re: Solid State Vibrator.

The set does use a pair of rectifier valves. I agree that at switch on there is little load on the secondary of the step up transformer. However when switching from receive to transmit, CW to AM, or high to low power the conditions on the secondary are changed suddenly and this sometimes stops the simple SSV dead in its tracks, which is unacceptable. I didn't check what happens when morse is sent, but it's possible the SSV and therefore the RF output could die intermittently as the transmitter is keyed.
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Old 6th Mar 2011, 5:27 pm   #78
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Default Re: Solid State Vibrator.

I've read this thread on the CMOS solid state vibrator with great interest! A couple of us here in Ontario Canada restore vintage car radios and have been going down the same road, starting with the 2N3055 transistors. We have also experienced starting difficulties on certain radios using the transistor design. I read that Colin produced a custom printed circuit board. Are these available at all? Also, has any further work been done on the concept of having a dwell between the on and off cycles? This is my first post... john
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Old 6th Mar 2011, 8:05 pm   #79
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Default Re: Solid State Vibrator.

I have done no further work on incorporating dwell, as the circuit works perfectly OK as it is. I have one spare PCB, but I'm hanging on to it.

You could try a PM to Colin to see what he says. Obviously I can't speak on his behalf.
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Old 24th Mar 2011, 2:26 pm   #80
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Default Re: Solid State Vibrator.

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I'm hoping to carry out some more detailed testing today. If the present device is unsatisfactory I'll try the 555 timer and MOSFET approach. I'm a great believer in the KISS (Keep It Simple Stupid) principle.
To drive a Mosfet its better to use a 4011 as an oscillator buffer driver.
I have just used such for a 6v vib replacement in a German set and a 12v replacement in a ZC1.

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