Transistor Conversion of Tube Amplifier

On Wednesday, 3 August 2016 07:02:41 UTC+1, Robert Baer  wrote:
> tabbypurr wrote:
> > On Tuesday, 2 August 2016 00:01:51 UTC+1, Kevin Foster  wrote:

> >> The circuit linked below appears to be a conversion of a three stage
> >> inverting tube amp tube to a transistor circuit, powered by 3VDC.
> >>
> >> https://app.box.com/s/dwflbolnqe58ra9c1kssqjuq14dulxo0
> >>
> >> It appears to be intended to capture high frequency ambient signals and
> >> re-broadcast them. It may also be designed to self-oscillate to add a
> >> carrier wave.
> >>
> >> In any case, I would like to build it out of curiosity to see what it does.
> >>
> >> Can anyone please explain the function of the inductors, and what might
> >> be a suitable value for same?
> >
> > raises collector load reactance at rf to increase stage gain.
> >
> >> What would be a modern equivalent of the CK722 PNP Germanium transistor?
> >
> > any modern jellybean tr capable of the frequency being used.
>  > The base bias Rs seem high at 220k on 3v.
> * Really? crude i=e/r gives 3V/0.22Meg or 14uA which is decent for the 
> CK722. Remember that their leakage current can be in that region.

Low current doesn't help the tr's hf response - which presumably is lousy at the best of times.

From 1952 CK722 datasheet - which is rather brief:
Abs max: Vce 20v, Ic 5mA. Pdiss 30mW @ 30C amb. Tamb max 50C. 
Average gain characteristics: Vc 1.5v, Ic 0.5mA, Ib 20uA, beta 12, power gain 30bD, NF 22dB@1kHz. With 1k source, 20k load.


NT

On 8/3/2016 1:06 AM, Robert Baer wrote:
> John S wrote:
>> On 8/1/2016 6:01 PM, Kevin Foster wrote:
>>> The circuit linked below appears to be a conversion of a three stage
>>> inverting tube amp tube to a transistor circuit, powered by 3VDC.
>>>
>>> https://app.box.com/s/dwflbolnqe58ra9c1kssqjuq14dulxo0
>>>
>>> It appears to be intended to capture high frequency ambient signals and
>>> re-broadcast them. It may also be designed to self-oscillate to add a
>>> carrier wave.
>>
>> Perhaps. Or maybe the output coil and input coil are lightly coupled by
>> distance and maybe it is a metal detector?
>>
>>> In any case, I would like to build it out of curiosity to see what it
>>> does.
>>
>> That is admirable.
>>
>>> Can anyone please explain the function of the inductors, and what might
>>> be a suitable value for same?
>>
>> I think Tabbypurr explained the function.
>>
>> Values. Hmmm. Well, the dia is .25" and the length is .75". No magnetic
>> core is indicated so that's pretty much all we have to go on. Maybe it
>> is air-core? What wire size shall we use for an estimate? Let's start
>> with #30 AWG.
>>
>> I calculate the inductance could be 10uH with 75 turns on, say a wooden
>> dowel.
>>
>>> What would be a modern equivalent of the CK722 PNP Germanium transistor?
>>
>> That's difficult. My bet is that the 722 did not have much HF gain so
>> using some other device may have its consequences.
>>
>> You can buy (for collector's prices, link below) the original
>> transistor. Otherwise, I suggest you search for germanium PNP
>> transistors. If it were me, I'd just try it with a jellybean PNP,
>> (whatever you have on hand) just to see what happens. That's your aim
>> anyway, yes?
>>
>> You have a larger problem facing you. There is nothing to indicate the
>> "Well" and "Plate" coil characteristics. Also, there seems to be no
>> indication of value for the "Rate" cap variable capacitors nor the pot
>> below them.
>>
>> Good luck. Please report back with your success.
>>
>>>
>>> Thank you for any advice.
>>>
>>> Kevin Foster
>>
>> Maybe go for the original transistor?...
>> <http://www.ebay.com/itm/VINTAGE-GERMANIUM-NOS-RAYTHEON-TRANSISTORS-CK722-CK718-CK721-2N63-/291834924222>
>>
>>
>   OK, i give up; where in the heck did you get those dimensions?
>

On the drawing he linked to.

On 08/02/2016 12:59 PM, John S wrote:

> You can buy (for collector's prices, link below) the original
> transistor. Otherwise, I suggest you search for germanium PNP
> transistors. If it were me, I'd just try it with a jellybean PNP,
> (whatever you have on hand) just to see what happens. That's your aim
> anyway, yes?
> Maybe go for the original transistor?...
> <http://www.ebay.com/itm/VINTAGE-GERMANIUM-NOS-RAYTHEON-TRANSISTORS-CK722-CK718-CK721-2N63-/291834924222>
>

There are tons of ex-Soviet germanium PNPs on eBay for cheap, and it 
should be possible to find a cross-reference. Many Soviet active 
components were spec-copies of US devices anyway..

On 03/08/16 19:04, piglet wrote:
> On 02/08/2016 00:01, Kevin Foster wrote:
>> Can anyone please explain the function of the inductors, and what might
>> be a suitable value for same?
>>
>
> My guess is those were section wound ferrite* chokes of 5-10mH. Since
> they are in series with 10k resistors that puts a slight gain peak at
> 100-150kHz just where the CK722 could start to roll-off. Judging by the
> interstage capacitors 50-70pF that implies operation frequency might be
> in the 100kHz region. Alternatively the chokes were intended to couple
> to each other as a poor mans transformer?
>
> Was the app underground potholing/mines communications repeater?
>
> piglet
>
>
> * Like ebay item "Vintage J.W. Miller CO. #6302 Ferrite Choke 2.5 MH 200
> MA New Old Stock"
>

Judging by the layout below, it seems the chokes are individual, and 
probably air core.

https://app.box.com/s/gjr4rrba3cmsbak5o5zfsemz7h9rcjpk

The final cap value chosen appears to be 70pF.

Any further assessment of the circuit based upon this would be most 
appreciated.

Keven Foster

On Thursday, 4 August 2016 02:59:42 UTC+1, Kevin Foster  wrote:

> Judging by the layout below, it seems the chokes are individual, and 
> probably air core.
> 
> https://app.box.com/s/gjr4rrba3cmsbak5o5zfsemz7h9rcjpk
> 
> The final cap value chosen appears to be 70pF.
> 
> Any further assessment of the circuit based upon this would be most 
> appreciated.
> 
> Keven Foster

In 1955 one paid a heavy premium for transistors, so the finished device must need portability & low power consumption.

All the chokes oriented the same means some coupling is inevitable. I don't know if it's worth looking at which paths create nfb & which pfb. Low frequency might make this minor, I don't know.


NT

On Monday, August 1, 2016 at 4:01:51 PM UTC-7, Kevin Foster wrote:
> The circuit linked below appears to be a conversion of a three stage 
> inverting tube amp tube to a transistor circuit, powered by 3VDC.
> 
> https://app.box.com/s/dwflbolnqe58ra9c1kssqjuq14dulxo0

  Reminds me of this with different transistors:

http://www.wdjensen123.com/hieronymus/Plans_files/image004.jpg

  from here:

http://www.wdjensen123.com/hieronymus/Plans.htm

  I don't think it does anything. Please report back if you find out otherwise.


  Mark L. Fergerson