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? What would be a modern equivalent of the CK722 PNP Germanium transistor? Thank you for any advice. Kevin Foster
Transistor Conversion of Tube Amplifier
Started by ●August 1, 2016
Reply by ●August 2, 20162016-08-02
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. I do suspect it's self oscillating. I don't see the point in building it.> Thank you for any advice. > > Kevin FosterNT
Reply by ●August 2, 20162016-08-02
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 FosterMaybe go for the original transistor?... <http://www.ebay.com/itm/VINTAGE-GERMANIUM-NOS-RAYTHEON-TRANSISTORS-CK722-CK718-CK721-2N63-/291834924222>
Reply by ●August 2, 20162016-08-02
On Tuesday, 2 August 2016 17:58:47 UTC+1, 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.If it's a converted valve circuit they'll almost certainly be coils wound on varnished card with air core.> > 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.nor what the connection to the 'radiator' is> 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>Maybe my haul's worth a bob or 2 then. You could probably sub the 3 stage amp with an LM386. Whatever you do just ensure any oscillation occurs out of licensed rf bands. NT
Reply by ●August 3, 20162016-08-03
On 03/08/16 04:46, tabbypurr@gmail.com wrote:> On Tuesday, 2 August 2016 17:58:47 UTC+1, 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. > > If it's a converted valve circuit they'll almost certainly be coils wound on varnished card with air core. > >>> 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. > > nor what the connection to the 'radiator' is > >> 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> > > Maybe my haul's worth a bob or 2 then. > > You could probably sub the 3 stage amp with an LM386. Whatever you do just ensure any oscillation occurs out of licensed rf bands. > > > NT >Thanks for the pointers. My suspicion is that it functions as both an amplifier and transformer in the RF range. I will build it using air coils and substitution PNP's as suggested. The loose coupling idea makes sense. The tuning caps were probably the old half plate variety. Kevin Foster
Reply by ●August 3, 20162016-08-03
On 8/3/2016 12:47 AM, Kevin Foster wrote:> On 03/08/16 04:46, tabbypurr@gmail.com wrote: >> On Tuesday, 2 August 2016 17:58:47 UTC+1, 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. >> >> If it's a converted valve circuit they'll almost certainly be coils >> wound on varnished card with air core. >> >>>> 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. >> >> nor what the connection to the 'radiator' is >> >>> 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> >>> >> >> Maybe my haul's worth a bob or 2 then. >> >> You could probably sub the 3 stage amp with an LM386. Whatever you do >> just ensure any oscillation occurs out of licensed rf bands. >> >> >> NT >> > > Thanks for the pointers. My suspicion is that it functions as both an > amplifier and transformer in the RF range. > > I will build it using air coils and substitution PNP's as suggested. > > The loose coupling idea makes sense. The tuning caps were probably the > old half plate variety. > > Kevin FosterPut some flexible leads on them so you can move them around. Seems like a fun experiment to me.
Reply by ●August 3, 20162016-08-03
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? > > What would be a modern equivalent of the CK722 PNP Germanium transistor? > > Thank you for any advice. > > Kevin FosterUse any small-signal transistor you want; if NPN reverse the polarity of supply an electrolytics. Helpful if ft is not excessive (well under 1 gHz). No clue as to frequency; try 100uH first; their impedance should be high WRTR2 to maximize signal coupling. .
Reply by ●August 3, 20162016-08-03
tabbypurr@gmail.com 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.> > I do suspect it's self oscillating. I don't see the point in building it. > > >> Thank you for any advice. >> >> Kevin Foster > > > NT
Reply by ●August 3, 20162016-08-03
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?
Reply by ●August 3, 20162016-08-03
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"
