Re: [Drakelist] R-4A PTO - transistors substituted?
Thanks, Garey - I've done loads of rework over the years, so hoping I won't mess up the basing (though I won't say that I've never messed it up). I'm ordering 3 each anyway. I used to have scores of 2N3904's but gave all my parts away when I moved five years ago. Not a big deal - Mouser has 'em for less than a quarter each. The shipping's going to cost me more than the parts :-) I was just figuring I can order some of the caps while I'm paying $7 for shipping anyway. I have no idea what these transistors are that are in there now. Someone must have had these around as generic NPN's and used them. Even though that 3000 pF cap is huge and funny-looking, am I right in assuming I could replace it with a standard SM one? Here's hoping replacing them takes care of the problem. 73, Steve Wedge, W1ES/4 "I can't complain, but sometimes I still do." - Joe Walsh If the above message appears, it came from Steve's Son of Laptop! - Original Message - From: "Garey Barrell" To: "Steve Wedge" Cc: Sent: Sunday, July 24, 2011 6:24 PM Subject: Re: [Drakelist] R-4A PTO - transistors substituted? Steve - No, typically they are smaller values. The TC caps are some of the ones with asterisks (*) beside them. Those are the selected caps, picked at final test. It's certainly possible that the 3000 or 90 pF ARE TC though. The small disc ceramics caps that are TC type have the top half 'dipped in paint', and the color indicates TC. The tubular _glass_ caps have a complex, colored dot pattern. The capacitance value is often "Body - End - Dot" for the capacitance value (first - second significant figures and third multiplier) and typically the rest of the dots specify either a third significant, or TC, or There is a set of tables in the back of the ARRL Handbooks that explain a lot of the codes, or I'm sure they're on the internet. So far though, all the PTOs that I've had to replace devices in have resulted in good linearity. I don't think the active device has much of an effect on TC, it's mostly the relationship between the coil's, form, core, capacitance. Don't overheat anything in there, and be sure to let it cool to room temp before becoming concerned about TC. WATCH the device basing 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs Steve Wedge wrote: Thanks, Garey - Yeah - I've seen that they're only about a buck-seventy-five on Mouser. I think that this is where I'm going next. Just in case this doesn't work out, which capacitors are the ones with the negative temp coefficients? I suspect the 3000 pF would be one of them. Steve Wedge, W1ES/4 "I can't complain, but sometimes I still do." - Joe Walsh If the above message appears, it came from Steve's Son of Laptop! - Original Message - From: "Garey Barrell" To: "Steve Wedge" Cc: Sent: Sunday, July 24, 2011 2:45 PM Subject: Re: [Drakelist] R-4A PTO - transistors substituted? Steve - I've looked in a LOT of PTOs, and I've never seen anything but a 2N3858 in the Buffer and either a 2N3858 (early) or 2N706 (late) in the oscillator. No other changes required with either oscillator transistor. The '3858 is just about extinct, but the 2N706 is still a common transistor. Defective transistors have definitely been known to cause the kind of frequency changes you're seeing. So while they may even be a 'later' modification than factory built, and may even be a suitable substitute, they can still fail just like the originals. By the way, if you look at the PTO schematic, the FSK 'shift' terminal is connected to the output of the oscillator stage. This allowed you to _SHIFT_ the PTO frequency by up to 850 Hz by adding a cap from this terminal to ground. So variations in the Buffer transistor CAN dither the frequency. And yes, it does. I think transistors were about the third thing down on the list once you get through the lubrication, mechanical and ground faults. I know you said you were short on components, but '706s are cheap from Mouser, or if you can find a couple of 2N3904 (everywhere!) transistors you could try them just to see. They may not work perfectly, but if the PTO becomes stable you'll know. Watch the basing on whatever transistors you use. Seems like they are all different these days! 73, Garey - K4OAH Glen Allen, VA Steve Wedge wrote: Looking at the transistors in this PTO, I'm 99.9% sure someone replaced them: they are both marked "NSRS / 2018", with the / being a line break. I'm sort of thinking that Drake used different parts for the oscillator and buffer for a good reason. Asid
Re: [Drakelist] R-4A PTO - transistors substituted?
Steve - No, typically they are smaller values. The TC caps are some of the ones with asterisks (*) beside them. Those are the selected caps, picked at final test. It's certainly possible that the 3000 or 90 pF ARE TC though. The small disc ceramics caps that are TC type have the top half 'dipped in paint', and the color indicates TC. The tubular _glass_ caps have a complex, colored dot pattern. The capacitance value is often "Body - End - Dot" for the capacitance value (first - second significant figures and third multiplier) and typically the rest of the dots specify either a third significant, or TC, or There is a set of tables in the back of the ARRL Handbooks that explain a lot of the codes, or I'm sure they're on the internet. So far though, all the PTOs that I've had to replace devices in have resulted in good linearity. I don't think the active device has much of an effect on TC, it's mostly the relationship between the coil's, form, core, capacitance. Don't overheat anything in there, and be sure to let it cool to room temp before becoming concerned about TC. WATCH the device basing 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs Steve Wedge wrote: Thanks, Garey - Yeah - I've seen that they're only about a buck-seventy-five on Mouser. I think that this is where I'm going next. Just in case this doesn't work out, which capacitors are the ones with the negative temp coefficients? I suspect the 3000 pF would be one of them. Steve Wedge, W1ES/4 "I can't complain, but sometimes I still do." - Joe Walsh If the above message appears, it came from Steve's Son of Laptop! - Original Message ----- From: "Garey Barrell" To: "Steve Wedge" Cc: Sent: Sunday, July 24, 2011 2:45 PM Subject: Re: [Drakelist] R-4A PTO - transistors substituted? Steve - I've looked in a LOT of PTOs, and I've never seen anything but a 2N3858 in the Buffer and either a 2N3858 (early) or 2N706 (late) in the oscillator. No other changes required with either oscillator transistor. The '3858 is just about extinct, but the 2N706 is still a common transistor. Defective transistors have definitely been known to cause the kind of frequency changes you're seeing. So while they may even be a 'later' modification than factory built, and may even be a suitable substitute, they can still fail just like the originals. By the way, if you look at the PTO schematic, the FSK 'shift' terminal is connected to the output of the oscillator stage. This allowed you to _SHIFT_ the PTO frequency by up to 850 Hz by adding a cap from this terminal to ground. So variations in the Buffer transistor CAN dither the frequency. And yes, it does. I think transistors were about the third thing down on the list once you get through the lubrication, mechanical and ground faults. I know you said you were short on components, but '706s are cheap from Mouser, or if you can find a couple of 2N3904 (everywhere!) transistors you could try them just to see. They may not work perfectly, but if the PTO becomes stable you'll know. Watch the basing on whatever transistors you use. Seems like they are all different these days! 73, Garey - K4OAH Glen Allen, VA Steve Wedge wrote: Looking at the transistors in this PTO, I'm 99.9% sure someone replaced them: they are both marked "NSRS / 2018", with the / being a line break. I'm sort of thinking that Drake used different parts for the oscillator and buffer for a good reason. Aside from this maddening frequency-shifting and crummy audio, the frequency calibration is still good. What are the chances that using the "wrong" transistors could be the source of all this grief? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO - transistors substituted?
Thanks, Garey - Yeah - I've seen that they're only about a buck-seventy-five on Mouser. I think that this is where I'm going next. Just in case this doesn't work out, which capacitors are the ones with the negative temp coefficients? I suspect the 3000 pF would be one of them. Steve Wedge, W1ES/4 "I can't complain, but sometimes I still do." - Joe Walsh If the above message appears, it came from Steve's Son of Laptop! - Original Message - From: "Garey Barrell" To: "Steve Wedge" Cc: Sent: Sunday, July 24, 2011 2:45 PM Subject: Re: [Drakelist] R-4A PTO - transistors substituted? Steve - I've looked in a LOT of PTOs, and I've never seen anything but a 2N3858 in the Buffer and either a 2N3858 (early) or 2N706 (late) in the oscillator. No other changes required with either oscillator transistor. The '3858 is just about extinct, but the 2N706 is still a common transistor. Defective transistors have definitely been known to cause the kind of frequency changes you're seeing. So while they may even be a 'later' modification than factory built, and may even be a suitable substitute, they can still fail just like the originals. By the way, if you look at the PTO schematic, the FSK 'shift' terminal is connected to the output of the oscillator stage. This allowed you to _SHIFT_ the PTO frequency by up to 850 Hz by adding a cap from this terminal to ground. So variations in the Buffer transistor CAN dither the frequency. And yes, it does. I think transistors were about the third thing down on the list once you get through the lubrication, mechanical and ground faults. I know you said you were short on components, but '706s are cheap from Mouser, or if you can find a couple of 2N3904 (everywhere!) transistors you could try them just to see. They may not work perfectly, but if the PTO becomes stable you'll know. Watch the basing on whatever transistors you use. Seems like they are all different these days! 73, Garey - K4OAH Glen Allen, VA Steve Wedge wrote: Looking at the transistors in this PTO, I'm 99.9% sure someone replaced them: they are both marked "NSRS / 2018", with the / being a line break. I'm sort of thinking that Drake used different parts for the oscillator and buffer for a good reason. Aside from this maddening frequency-shifting and crummy audio, the frequency calibration is still good. What are the chances that using the "wrong" transistors could be the source of all this grief? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO - transistors substituted?
Dennis -
And watch those reverse breakdowns too!! :-)
The 2N is the 6L6 of the transistor world. No matter how much you abuse them, they just keep
going
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
Dennis Monticelli wrote:
For the oscillating device in the LO I would add "noise" to the list of what to look for in a
transistor. This varies a lot from type to type and even from maker to maker. For example, the
2N is not exactly the world's quietest transistor. To just check to see if that osc
transistor is the root of the problem, then free subsitution is fine. Otherwise stick to a device
that was designed for RF service, which is different than a device designed for general saturated
switching. I know this from experience; my company was a transistor manufacturer in the past.
Dennis AE6C
On Sun, Jul 24, 2011 at 2:20 PM, Garey Barrell <mailto:k4...@mindspring.com>> wrote:
Funny, I don't recall you working for me during college :-)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
http://www.k4oah.com/>>
Paul Christensen wrote:
Or even a 2N. Between the 2N3858, 2N3904, and 2N, the fT /
GBP, hFE, and C in/out
parameters are reasonably identical. Probably the biggest variant will
be the hfe value
across samples, but I agree with Garey to give it a shot. The PTO is
only running at 5 MHz.
During college, I worked for an engineer who's philosophy was to replace with
"2NAnyThing"
that worked. He certainly knew the widely different transistor
parameters, but his point
was that in many general purpose switching, amplification and
oscillating circuits,
"2NAnyThing" is often an adequate substitute, taking into account the
need to watch for
NPN, PNP, FET, etc. configurations.
Paul, W9AC
- Original Message - From: "Garey Barrell" mailto:k4...@mindspring.com>>
To: "Steve Wedge" mailto:w1es1...@earthlink.net>>
Cc: mailto:drakelist@zerobeat.net>>
Sent: Sunday, July 24, 2011 2:45 PM
Subject: Re: [Drakelist] R-4A PTO - transistors substituted?
Steve -
I've looked in a LOT of PTOs, and I've never seen anything but a
2N3858 in the Buffer
and either a 2N3858 (early) or 2N706 (late) in the oscillator. No
other changes
required with either oscillator transistor. The '3858 is just
about extinct, but the
2N706 is still a common transistor.
Defective transistors have definitely been known to cause the kind
of frequency
changes you're seeing. So while they may even be a 'later'
modification than factory
built, and may even be a suitable substitute, they can still fail
just like the
originals. By the way, if you look at the PTO schematic, the FSK
'shift' terminal is
connected to the output of the oscillator stage. This allowed you
to _SHIFT_ the
PTO frequency by up to 850 Hz by adding a cap from this terminal to
ground. So
variations in the Buffer transistor CAN dither the frequency. And
yes, it does.
I think transistors were about the third thing down on the list
once you get through
the lubrication, mechanical and ground faults.
I know you said you were short on components, but '706s are cheap
from Mouser, or if
you can find a couple of 2N3904 (everywhere!) transistors you could
try them just to
see. They may not work perfectly, but if the PTO becomes stable
you'll know. Watch
the basing on whatever transistors you use. Seems like they are
all different these days!
73, Garey - K4OAH
Glen Allen, VA
Steve Wedge wrote:
Looking at the transistors in this PTO, I'm 99.9% sure someone
replaced them: they
are both marked "NSRS / 2018", with the / being a line break.
I'm sort of thinking that Drake used different parts for the
oscillator and buffer
for a good reason. Aside from this maddening
frequency-shifting and crummy audio,
the frequency calibration is still good. What are the chances
that using the
"wrong" transistors could be the source of all this grief?
___
Drakelist mailing list
Drakelist@zerobeat.net
http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO - transistors substituted?
For the oscillating device in the LO I would add "noise" to the list of what to look for in a transistor. This varies a lot from type to type and even from maker to maker. For example, the 2N is not exactly the world's quietest transistor. To just check to see if that osc transistor is the root of the problem, then free subsitution is fine. Otherwise stick to a device that was designed for RF service, which is different than a device designed for general saturated switching. I know this from experience; my company was a transistor manufacturer in the past. Dennis AE6C On Sun, Jul 24, 2011 at 2:20 PM, Garey Barrell wrote: > Funny, I don't recall you working for me during college :-) > > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line > and TR-4/C Service Supplement CDs > > > > > Paul Christensen wrote: > >> Or even a 2N. Between the 2N3858, 2N3904, and 2N, the fT / GBP, >> hFE, and C in/out parameters are reasonably identical. Probably the biggest >> variant will be the hfe value across samples, but I agree with Garey to give >> it a shot. The PTO is only running at 5 MHz. >> >> During college, I worked for an engineer who's philosophy was to replace >> with "2NAnyThing" that worked. He certainly knew the widely different >> transistor parameters, but his point was that in many general purpose >> switching, amplification and oscillating circuits, "2NAnyThing" is often an >> adequate substitute, taking into account the need to watch for NPN, PNP, >> FET, etc. configurations. >> >> Paul, W9AC >> >> - Original Message - From: "Garey Barrell" >> To: "Steve Wedge" >> Cc: >> Sent: Sunday, July 24, 2011 2:45 PM >> Subject: Re: [Drakelist] R-4A PTO - transistors substituted? >> >> >> Steve - >>> >>> I've looked in a LOT of PTOs, and I've never seen anything but a 2N3858 >>> in the Buffer and either a 2N3858 (early) or 2N706 (late) in the oscillator. >>> No other changes required with either oscillator transistor. The '3858 is >>> just about extinct, but the 2N706 is still a common transistor. >>> >>> Defective transistors have definitely been known to cause the kind of >>> frequency changes you're seeing. So while they may even be a 'later' >>> modification than factory built, and may even be a suitable substitute, they >>> can still fail just like the originals. By the way, if you look at the PTO >>> schematic, the FSK 'shift' terminal is connected to the output of the >>> oscillator stage. This allowed you to _SHIFT_ the PTO frequency by up to >>> 850 Hz by adding a cap from this terminal to ground. So variations in the >>> Buffer transistor CAN dither the frequency. And yes, it does. >>> >>> I think transistors were about the third thing down on the list once you >>> get through the lubrication, mechanical and ground faults. >>> >>> I know you said you were short on components, but '706s are cheap from >>> Mouser, or if you can find a couple of 2N3904 (everywhere!) transistors you >>> could try them just to see. They may not work perfectly, but if the PTO >>> becomes stable you'll know. Watch the basing on whatever transistors you >>> use. Seems like they are all different these days! >>> >>> 73, Garey - K4OAH >>> Glen Allen, VA >>> >>> >>> >>> >>> Steve Wedge wrote: >>> >>>> Looking at the transistors in this PTO, I'm 99.9% sure someone replaced >>>> them: they are both marked "NSRS / 2018", with the / being a line break. >>>> I'm sort of thinking that Drake used different parts for the oscillator >>>> and buffer for a good reason. Aside from this maddening frequency-shifting >>>> and crummy audio, the frequency calibration is still good. What are the >>>> chances that using the "wrong" transistors could be the source of all this >>>> grief? >>>> >>> >>> __**_ >>> Drakelist mailing list >>> Drakelist@zerobeat.net >>> http://mailman.zerobeat.net/**mailman/listinfo/drakelist<http://mailman.zerobeat.net/mailman/listinfo/drakelist> >>> >> >> >> __**_ >> Drakelist mailing list >> Drakelist@zerobeat.net >> http://mailman.zerobeat.net/**mailman/listinfo/drakelist<http://mailman.zerobeat.net/mailman/listinfo/drakelist> >> >> > __**_ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/**mailman/listinfo/drakelist<http://mailman.zerobeat.net/mailman/listinfo/drakelist> > ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO - transistors substituted?
Funny, I don't recall you working for me during college :-) 73, Garey - K4OAH Glen Allen, VA Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line and TR-4/C Service Supplement CDs Paul Christensen wrote: Or even a 2N. Between the 2N3858, 2N3904, and 2N, the fT / GBP, hFE, and C in/out parameters are reasonably identical. Probably the biggest variant will be the hfe value across samples, but I agree with Garey to give it a shot. The PTO is only running at 5 MHz. During college, I worked for an engineer who's philosophy was to replace with "2NAnyThing" that worked. He certainly knew the widely different transistor parameters, but his point was that in many general purpose switching, amplification and oscillating circuits, "2NAnyThing" is often an adequate substitute, taking into account the need to watch for NPN, PNP, FET, etc. configurations. Paul, W9AC - Original Message - From: "Garey Barrell" To: "Steve Wedge" Cc: Sent: Sunday, July 24, 2011 2:45 PM Subject: Re: [Drakelist] R-4A PTO - transistors substituted? Steve - I've looked in a LOT of PTOs, and I've never seen anything but a 2N3858 in the Buffer and either a 2N3858 (early) or 2N706 (late) in the oscillator. No other changes required with either oscillator transistor. The '3858 is just about extinct, but the 2N706 is still a common transistor. Defective transistors have definitely been known to cause the kind of frequency changes you're seeing. So while they may even be a 'later' modification than factory built, and may even be a suitable substitute, they can still fail just like the originals. By the way, if you look at the PTO schematic, the FSK 'shift' terminal is connected to the output of the oscillator stage. This allowed you to _SHIFT_ the PTO frequency by up to 850 Hz by adding a cap from this terminal to ground. So variations in the Buffer transistor CAN dither the frequency. And yes, it does. I think transistors were about the third thing down on the list once you get through the lubrication, mechanical and ground faults. I know you said you were short on components, but '706s are cheap from Mouser, or if you can find a couple of 2N3904 (everywhere!) transistors you could try them just to see. They may not work perfectly, but if the PTO becomes stable you'll know. Watch the basing on whatever transistors you use. Seems like they are all different these days! 73, Garey - K4OAH Glen Allen, VA Steve Wedge wrote: Looking at the transistors in this PTO, I'm 99.9% sure someone replaced them: they are both marked "NSRS / 2018", with the / being a line break. I'm sort of thinking that Drake used different parts for the oscillator and buffer for a good reason. Aside from this maddening frequency-shifting and crummy audio, the frequency calibration is still good. What are the chances that using the "wrong" transistors could be the source of all this grief? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO - transistors substituted?
Or even a 2N. Between the 2N3858, 2N3904, and 2N, the fT / GBP, hFE, and C in/out parameters are reasonably identical. Probably the biggest variant will be the hfe value across samples, but I agree with Garey to give it a shot. The PTO is only running at 5 MHz. During college, I worked for an engineer who's philosophy was to replace with "2NAnyThing" that worked. He certainly knew the widely different transistor parameters, but his point was that in many general purpose switching, amplification and oscillating circuits, "2NAnyThing" is often an adequate substitute, taking into account the need to watch for NPN, PNP, FET, etc. configurations. Paul, W9AC - Original Message - From: "Garey Barrell" To: "Steve Wedge" Cc: Sent: Sunday, July 24, 2011 2:45 PM Subject: Re: [Drakelist] R-4A PTO - transistors substituted? Steve - I've looked in a LOT of PTOs, and I've never seen anything but a 2N3858 in the Buffer and either a 2N3858 (early) or 2N706 (late) in the oscillator. No other changes required with either oscillator transistor. The '3858 is just about extinct, but the 2N706 is still a common transistor. Defective transistors have definitely been known to cause the kind of frequency changes you're seeing. So while they may even be a 'later' modification than factory built, and may even be a suitable substitute, they can still fail just like the originals. By the way, if you look at the PTO schematic, the FSK 'shift' terminal is connected to the output of the oscillator stage. This allowed you to _SHIFT_ the PTO frequency by up to 850 Hz by adding a cap from this terminal to ground. So variations in the Buffer transistor CAN dither the frequency. And yes, it does. I think transistors were about the third thing down on the list once you get through the lubrication, mechanical and ground faults. I know you said you were short on components, but '706s are cheap from Mouser, or if you can find a couple of 2N3904 (everywhere!) transistors you could try them just to see. They may not work perfectly, but if the PTO becomes stable you'll know. Watch the basing on whatever transistors you use. Seems like they are all different these days! 73, Garey - K4OAH Glen Allen, VA Steve Wedge wrote: Looking at the transistors in this PTO, I'm 99.9% sure someone replaced them: they are both marked "NSRS / 2018", with the / being a line break. I'm sort of thinking that Drake used different parts for the oscillator and buffer for a good reason. Aside from this maddening frequency-shifting and crummy audio, the frequency calibration is still good. What are the chances that using the "wrong" transistors could be the source of all this grief? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] R-4A PTO - transistors substituted?
Steve - I've looked in a LOT of PTOs, and I've never seen anything but a 2N3858 in the Buffer and either a 2N3858 (early) or 2N706 (late) in the oscillator. No other changes required with either oscillator transistor. The '3858 is just about extinct, but the 2N706 is still a common transistor. Defective transistors have definitely been known to cause the kind of frequency changes you're seeing. So while they may even be a 'later' modification than factory built, and may even be a suitable substitute, they can still fail just like the originals. By the way, if you look at the PTO schematic, the FSK 'shift' terminal is connected to the output of the oscillator stage. This allowed you to _SHIFT_ the PTO frequency by up to 850 Hz by adding a cap from this terminal to ground. So variations in the Buffer transistor CAN dither the frequency. And yes, it does. I think transistors were about the third thing down on the list once you get through the lubrication, mechanical and ground faults. I know you said you were short on components, but '706s are cheap from Mouser, or if you can find a couple of 2N3904 (everywhere!) transistors you could try them just to see. They may not work perfectly, but if the PTO becomes stable you'll know. Watch the basing on whatever transistors you use. Seems like they are all different these days! 73, Garey - K4OAH Glen Allen, VA Steve Wedge wrote: Looking at the transistors in this PTO, I'm 99.9% sure someone replaced them: they are both marked "NSRS / 2018", with the / being a line break. I'm sort of thinking that Drake used different parts for the oscillator and buffer for a good reason. Aside from this maddening frequency-shifting and crummy audio, the frequency calibration is still good. What are the chances that using the "wrong" transistors could be the source of all this grief? ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
[Drakelist] R-4A PTO - transistors substituted?
Looking at the transistors in this PTO, I'm 99.9% sure someone replaced them: they are both marked "NSRS / 2018", with the / being a line break. I'm sort of thinking that Drake used different parts for the oscillator and buffer for a good reason. Aside from this maddening frequency-shifting and crummy audio, the frequency calibration is still good. What are the chances that using the "wrong" transistors could be the source of all this grief? Steve Wedge, W1ES/4 "I can't complain, but sometimes I still do." - Joe Walsh If the above message appears, it came from Steve's Son of Laptop!___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
