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 Post subject: Collins R-390 solid state regulator (problem)
PostPosted: Oct Tue 03, 2017 2:16 pm 
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I found a circuit on the internet that replaces the regulator tubes in a R-390 with a solid state circuit.

Attachment:
Regulator.jpg
Regulator.jpg [ 76.91 KiB | Viewed 770 times ]


I plan on making this mod permanent which will make it easier to mount a heatsink.

What modern transistors would be suitable subs with the power transistor in the T0-3 package?

Also is there a darlington transistor in the TO-3 package that will work?

The 500 ohm resistor will be one of those chassis mount ones.

I will remove the regulator tube sockets, the 47 ohm resistors and whatever else related to the original regulator circuit I can remove.

The original circuit showed a .22uF cap across the 2.2uF cap on the output, but I eliminated that cap since I can get 2.2uF film caps in a small enough physical size and will be using those for all the caps. I may increase the one 2.2uF cap to a 10uF cap if I find that to be necessary.

Also I had replaced the 10uF can cap in the receiver with a higher value one while trying to troubleshoot a case of a slight bit of audio being present at the local audio output with the level control at 0, but I may reinstall that cap since I found the issue is the control itself.



EDIT:

Instead of the 500 ohm resistor why couldn't I just increase the value of the 47 ohm resistors in the power supply chassis to drop B+ some? Because there's more resistance between the first filter cap and rectifiers the B+ voltage will be lower and less resistance will be required versus dropping the B+ voltage after it's been rectified and filtered.

I will have four extra 47 ohm resistors so I may try two in series with each of the two solid state diodes in addition to the existing 47 ohm resistors and see if that reduces the unregulated B+ enough.

Here's the modified circuit.

Attachment:
Regulator 2.jpg
Regulator 2.jpg [ 80.86 KiB | Viewed 766 times ]


Last edited by Tube Radio on Nov Tue 21, 2017 7:36 pm, edited 1 time in total.

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Sun 08, 2017 4:36 pm 
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Would this transistor work?

http://www.goldmine-elec-products.com/p ... ber=G22524

Here's the datasheet.

http://pdf.datasheetcatalog.com/datashe ... U2508A.pdf

http://pdf.datasheetcatalog.com/datashe ... ic/884.pdf


Last edited by Tube Radio on Nov Fri 03, 2017 11:48 am, edited 1 time in total.

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Wed 18, 2017 12:04 pm 
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Any ideas on any suitable transistors or a darlington transistor that will work?

Really want to get this done as the receiver as is makes for a nice space heater.


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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Wed 18, 2017 12:52 pm 
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I don't think there is any advantage to a darlington. Just pick the pass transistor and then add another GP transistor to get the gain.
The pass transistor simply has to have adequate specs for voltage, current and power. Ft is not critical since the is no feedback loop.
Here is one possibility from a Q and D Mouser search:
http://www.mouser.com/ds/2/308/2N5655-D-40289.pdf

Obviously, the power rating depends on your dropping resistor. I'm wondering if a zener might be better there. With the resistor, could there be a transient at turn on where the voltage is too high?

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Wed 18, 2017 1:59 pm 
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The advantage to the darlington is that I will need only one transistor instead of the two shown on the schematic and the 50 ohm resistor won't be needed.

A zener may work for the voltage dropping, but I'll have four unneeded 47 ohm resistors once I remove the regulator tubes so I may try two in series in addition to the 47 ohm resistor already present after each rectifier and see if that drops B+ enough.


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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Wed 18, 2017 5:26 pm 
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You can get the three terminal regulators used in 1980s tv sets that come in values from 115 up. You can change their voltage just like you do an lm317 by raising the ground terminal. They had id numbers like str135 a 135 volg regulator. Look in an ecg/nte manual or sk manual for them.


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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Wed 18, 2017 6:40 pm 
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Cool. Did not know that.

Only thing is the unloaded B+ is around 300Vdc. Once the tubes start drawing current that voltage drops some.

Will that be ok for the regulator you mentioned?


Last edited by Tube Radio on Oct Wed 18, 2017 7:27 pm, edited 1 time in total.

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Wed 18, 2017 6:43 pm 
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Tube Radio wrote:
The advantage to the darlington is that I will need only one transistor instead of the two shown on the schematic and the 50 ohm resistor won't be needed.

A zener may work for the voltage dropping, but I'll have four unneeded 47 ohm resistors once I remove the regulator tubes so I may try two in series in addition to the 47 ohm resistor already present after each rectifier and see if that drops B+ enough.

For a given set of parameters, the darlington might be harder to find.---IOW, you have more design flexibility with discrete parts.

With the dropping resistor in series with the regulator, the pass transistor might see the full B+ until the load kicks in. The zener avoids this.

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Wed 18, 2017 7:35 pm 
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pixellany wrote:
The zener avoids this.


I see. Did not think of that.


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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Mon 23, 2017 3:15 pm 
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What voltage would the Zener need to be rated at and also how much will the B+ at the output of the rectifiers drop once the tubes warm up?

Would this darlington work?

https://www.mouser.com/ProductDetail/ON ... FkHJCIs%3d

http://www.mouser.com/ds/2/308/BU323Z-D-105939.pdf

The only thing that concerns me is the base to emitter resistor of the first transistor.

The circuit I have doesn't use a resistor there and I don't know how that will affect the regulator.


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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Mon 23, 2017 4:57 pm 
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That one is massive overkill. You need 200mA out, and that one is good for 10 amps. While one might say "so what?", the first potential issue is the DC beta at the lower current. The data sheet specs it for 5 amps. While it may very well work adequately at 1/10 of that, you won't know without testing.
It is normally better to buy parts that are speced for the parameters you plan to use.

Base-emitter resistor internal to the darlington: So what?---they give you the "black box" specs, so you never need to know that it is there. In fact---from out side the box---you would never know it wasn't an ordinary transistor, except for the higher Vbe.

The series zener: The only reason to use anything is to spread out the work between the main supply and the final load. If the regulator can handle the numbers, then nothing in series is **required**.
Voltage is not a rating of a zener---it is a parameter. The ratings to be concerned about are current and power dissipation.

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Mon 23, 2017 6:29 pm 
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Oh ok.

True there's no telling how it would work at the lower current.

Yes I meant to say parameter for the zener voltage.

For now I'll give the resistors a try and see how they work at dropping the voltage.


Last edited by Tube Radio on Oct Mon 23, 2017 6:56 pm, edited 2 times in total.

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Mon 23, 2017 6:45 pm 
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Tube Radio wrote:
For now I'll give the resistors a try and see how they work at dropping the voltage.

One of the comforting things about certain components is that they are almost completely deterministic......get a reasonable quality resistor, avoid overheating it or mechanically abusing it, and it will give a predictable voltage drop every time you put current through it------every time.....:)

Seriously.........some design steps to consider:

First, pick the component that will be the major determinant of performance---in this case, it's the pass transistor. Start with the required performance---here it is the DC beta at the operating current. Next, figure out the required ratings. This brings you to the question of whether you want to offload some of the voltage and power stress to the "dropping element"---in this case a resistor or zener. What some designers will do is pick the pass transistor based on cost and availability, and then add the other components as needed (resistors and zeners are cheap)

So---get the right pass transistor first. The one you linked ain't it..... <<EDIT: just saw your latest--I'll look at it>>

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Mon 23, 2017 6:57 pm 
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The resistors I figured since I already have them I'd use them.

Thinking this one for the power transistor.

https://www.mouser.com/ProductDetail/ON ... PY9WezQ%3d

http://www.mouser.com/ds/2/308/BD159-1121883.pdf

And perhaps this one for the driver transistor.

https://www.mouser.com/ProductDetail/ON ... QPv7zio%3d

http://www.mouser.com/ds/2/308/KSP45-1120811.pdf


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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Mon 23, 2017 7:03 pm 
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http://www.mouser.com/ds/2/308/BD159-1121883.pdf

that one looks promising. At Ic = 200mA, if you drop all the way from 300 to 180, the power is 24 watts, so you definitely need your dropper element. Be careful of power ratings....this one is 20 watts at 25C case temp---look at the derating curve

With a minimum beta of 30, you might not need the other transistor.

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Mon 23, 2017 7:10 pm 
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I have a heatsink from a Sansui 4000 receiver that had a TO-3 output transistor on it so I had figured on using that heatsink for whichever transistor I used provided it fits in the area where the regulator tubes are.


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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Mon 23, 2017 7:13 pm 
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Some more design notes:
Assume a beta of 30. the transistor then needs 200/30 = ~7mA of base current. Make at least twice that available---call it 15.

Next, how much current for the zener? For that, you'd need a spec on the quality of regulation, and then review the zener specs to see how much the current matters.

Add the two currents and you are just about done.

Note: one way to get better regulation with a zener is to drive it with a current source.


Footnote: I doubt that this thing needs to regulate to better than maybe 5%---ie 180 +/- 9 volts

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Mon 23, 2017 7:32 pm 
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The zener I'm looking at for the 180 volt one has a 5% tolerance.

I'll b glad to get this done as at the moment the receiver makes a nice space heater with the fan on the side by the regulator tubes drawing out the heat :mrgreen:


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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Tue 24, 2017 12:37 am 
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Tube Radio wrote:
The zener I'm looking at for the 180 volt one has a 5% tolerance.

That is not relevant to how well the supply regulates.....I assume the major reason to have any regulation is to keep oscillator frequencies from drifting. In terms of absolute value, you can probably be off by 10%.

also, that's a 5% spread among multiple samples---all measured at the same current. Look at the curves and you'll see you can fine tune the zener voltage by varying the current.

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 Post subject: Re: Collins R-390 solid state regulator
PostPosted: Oct Tue 24, 2017 3:32 am 
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Oh ok.

Does the transistor I selected as the first one in the Darlington configuration look like it will work?

If so I'll order the parts.

Will first try it with the one power transistor and see if that's enough. If I use the one power transistor do I need to ditch the 50 ohm resistor?

Before installing it in my R-390 I will breadboard the circuit and test it to see how well it works.

Now I have a question.

Would it be possible to just substitute that power transistor for the regulator tubes?


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