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 Post subject: Making a Solid State 83 rectifier
PostPosted: Feb Sat 17, 2018 8:51 pm 
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We had started this on the wrong forum and had a decent discussion started up, let's continue on as 83 tubes are getting harder to find.
I had posted this schematic of a popular design. Mainly for the Hickok Tester line.
Using:
R1/2 - 10ohm 3 watt resistor, or 5 size permitting
D1/2 - 1N5341B
D3/4 - 1N4007


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Hickok-83SS-1.jpg
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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Sun 18, 2018 3:18 am 
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From here:

http://www.antiqueradios.com/forums/viewtopic.php?f=8&t=225280


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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Mon 19, 2018 3:48 am 
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Curious. Why the filament resistors? Don't these tubes have their own filament winding?

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Mon 19, 2018 4:00 am 
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The solid state replacement isn't a tube with a filament.


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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Mon 19, 2018 4:11 am 
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xwarp wrote:
The solid state replacement isn't a tube with a filament.

Neither does it need resistors connected to the filament pints.

Your 4-pin schematic works fine if you connect the center point to one of the filament pins.

- Leigh

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Mon 19, 2018 4:31 am 
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Leigh wrote:
xwarp wrote:
The solid state replacement isn't a tube with a filament.

Neither does it need resistors connected to the filament pints.

Your 4-pin schematic works fine if you connect the center point to one of the filament pins.

- Leigh


Maybe I misunderstood his statement.

He wrote: "Curious. Why the filament resistors? Don't these tubes have their own filament winding?"

To which my answer was because I interpreted his statement as if he thought the diagrams above were actually of tubes, but they are not.

I understand that the resistors are there to simulate the filament voltage drop of the 83/5y3 tubes so that the transformer is loaded approximately the same as the tubes. If you have something to counter, please post and then again in the multiple threads regarding these s/s replacements in the "test equipment" forum. Your expertise is appreciated.


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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Mon 19, 2018 4:54 am 
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xwarp wrote:
I understand that the resistors are there to simulate the filament voltage drop of the 83/5y3 tubes so that the transformer is loaded approximately the same as the tubes.

The 83 filament draws 3 amps at 5 volts. The resistance is R = E / I = 5 / 3 = 1.67 ohms.
That's a fur piece from 20 ohms.

Removing that 15-watt load from the transformer will make it run cooler.

Any decent tube tester has a line voltage adjustment to compensate for tube filament loading.

- Leigh

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Mon 19, 2018 5:00 am 
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Filament resistors also give a center tap to the supply. This will make each side of the high voltage winding equal. Without resistors one side would be seen as 5 volts higher than the other.

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Mon 19, 2018 4:24 pm 
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When replacing vaccum for solid state rectifiers IHMO it should not be ignored that the tube also acts as a current limiter (and ultimately as a fuse)...
In case of a short, the 4004 diodes will pass some amps before they blow with foreseeable consequences...

I suggest disconnecting the heater and taking two diodes directly from the HT lines to the test tube anode in series with a small lightbulb (some 24...30 V, 100...200 mA) and a resistor or zener to drop the excess voltage. The bulb or simply a fuse could also be incorporated into the tube adapter.

Lightbulbs make excellent soft current limiters/fuses in many applications - particulary with tubes which tend to thermal runaway. I have added them to the HT lines of all my vintage tube amps, and I am using a 60 V telephone bulb in the anode supply of my little guitar amp to make it "sing" at lower output levels.

regards


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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Mon 19, 2018 11:49 pm 
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Leigh wrote:
xwarp wrote:
I understand that the resistors are there to simulate the filament voltage drop of the 83/5y3 tubes so that the transformer is loaded approximately the same as the tubes.

The 83 filament draws 3 amps at 5 volts. The resistance is R = E / I = 5 / 3 = 1.67 ohms.
That's a fur piece from 20 ohms.

Removing that 15-watt load from the transformer will make it run cooler.

Any decent tube tester has a line voltage adjustment to compensate for tube filament loading.

- Leigh

Yep. That's what i was thinking.

Something along these lines.


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elm.png
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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Tue 20, 2018 3:27 am 
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The first diagram presented will give an output that is negative going, not positive going. Even accounting for the fact that the same symbol is used for both a rectifier diode and a zener diode, they're in backwards.

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Tue 20, 2018 5:07 am 
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I don't see where I'm backwards on the 1st drawing, here is pics and reference.


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20180219_230133.jpg
20180219_230133.jpg [ 104.16 KiB | Viewed 658 times ]

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Wed 21, 2018 2:35 am 
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glue_ru wrote:
I don't see where I'm backwards on the 1st drawing, here is pics and reference.

In your photo, I can't tell which diodes are the rectifiers and which are the zeners. Perhaps the rectifiers and zeners are just switched in the BOM.

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Wed 21, 2018 3:17 am 
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the larger ones on circuit board, 1N4007
smaller going into pins, 1N5341B

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Wed 21, 2018 9:06 am 
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On some of the Hickoks you will run into trouble calibrating as the voltages will be too high due to the lack of the 83 filament load on the transformer.

Dave


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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Wed 21, 2018 2:30 pm 
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it doesn't have to be perfect, or even close. why? There are many Hickok's out running with 83 tubes
in many states of operating efficiency, and they are working, reading and moving the meter to the right place.
so I can't image being off a bit in the SS 83 would make any more difference than changing the 83 tube.
Maybe design a circuit that does put less load on the transformer but still operates the circuit correctly.
Never hurts to try and preserve the parts in these old units, many hitting 60 years.

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Wed 21, 2018 4:00 pm 
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IMHO If one is going to develop a replacement for the 83, actually setting up a power source and a load in the range of current that represents the the tube testers greatest and least load plus a margin. Run the load up and measure the voltage drop through that range. That curve will represent what the solid-state replacement has to accomplish.

I do not think that the tube testers charts are so sophisticated to account for a droop in the voltage as the current increase through the 83. Therefore, a Solid-state replacement may prove to be more effective in regulation than the 83 when measured as above.

I do think that the load testing should be done with the tube tester, intact. Though there is some risk if one gets careless, using the tester will account for the gain/loss of the filament current.

This would be a better test platform rather than plugging in, say a "calibration" tube, of which represent only a small portion of the current range the 83 is put to or testing a 1U4 vs say a 6080 regulator.

Success is determined by how closely the circuit responds to current demands and how much it droops, If the device meets or exceeds, job done.

My other concern is how, long term, will the transformer react to the use of a solid-state rectifier that has an abrupt switching characteristic in respect to the 83. Will the solid-state diodes generate an electrical noise, like the 83 does and is of no consequence? Taking wave forms under the load conditions may give evidence to hidden issues.

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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Thu 22, 2018 5:13 pm 
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It took me a while to find this, and I know there are people that may disagree with Alan's statement in this post, but, the man, (may he rest in peace), was way smarter than I'll ever be, explained the 10 ohm resistors here:

http://www.antiqueradios.com/forums/viewtopic.php?f=8&t=926

Alan Douglas wrote:
The info is in my book on tube testers. The easiest mod is to wire a pair of 1N4007s right to the 83 socket, from each plate pin to the heater center tap on the transformer. If you use an old tube base as a plug-in adapter, the center tap does not appear at the 83 socket, so you need to create an artificial center tap with a pair of 10 ohm 1 watt resistors. Wire the adapter as follows: one end of a 10 ohm resistor to pin 1, one end of a second resistor to pin 4, a 1N4007 anode to pin 2, another 1N4007 anode to pin 3. The free ends of the resistors and diodes all tie together.


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 Post subject: Re: Making a Solid State 83 rectifier
PostPosted: Feb Sun 25, 2018 5:49 pm 
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interesting, thanks for tracking that down.

How about adding a #47 bulb into the circuit, 2, one for each side?
Add a bit of a load, give a buffer to abrupt starts, dim bulb protection...

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