|
Thanks, Gary, for the explanation. I replaced my 1K pull-down resistor with a 0.1uf and it seems to work fine. Obviously that point of the oscillator wants to be at RF ground. I feel much better about the capacitor solution than the 1K solution that matched my knob fiddling. I'll confirm it tonight when the radio is truly cold. The flux around the .47 is from my swapping it out to see if it was bad. Dave
?
?
?
|
I'll have to go and look.? I can remember that it was built in 1967 because it has the QC tag with it.? Since I reported it to Ron, the s/n is between 6136 and 6968.? Mint condition.? I bought it from a friend who was collecting as much Drake stuff as he could but never got around to putting the station together.? He has a good eye and my A Line is a great proof of that.
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Monday, December 30th, 2024 at 10:18 AM, Dave W7GZ via groups.io <w7gz@...> wrote:
Many tnx reply, Steve. Mine is an 11-tube with S/N 6717B. How does it compare in age to yours? It works fine with the pull-down resistor now, before I had to wait many minutes, sometimes forever for the BFO to start.
?
This one is an interesting specimen. It was sold to me for dirt cheap as a parts radio because it had been left in humidity and has quite a bit of rust on the top surface, but underneath it is pristine. After replacing 5 tubes that had vented through their pins, I discovered it was actually a working set. Not as nice looking as my R-4C, but it is completely usable and sensitive.
?
Thanks for posting your issue, it helped me realize it has been seen before. Dave
|
Welp, I guess I need to put my receiver back on the bench and take a butcher's...
Steve Wedge, W1ES
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Monday, December 30th, 2024 at 10:49 AM, Gary WB6OGD via groups.io <winbladgary@...> wrote:
> I have no idea what the added capacitor started the oscillator, but it has worked ever since.
?
Drake had an error for a short while (like one month) and fixed the schematic with a missing capacitor.
From message #65666
?
"C188 seems to be added to the same BFO circuit in the R-4B.
It decouples the exact node you propose to put a 1K to ground!!
Might be something Drake discovered in later models??
Also, schematic 919664054 seems to have a big error in the BFO, my downloaded from somewhere
copy has the correction marked in, that makes it like the R-4B schematic (the emitter connects to C163)."
Steve somehow found that a resistor (to lower the supply voltage?) fixed the problem, but the real fix is
probably a capacitor like you and Drake used.
73,
Gary
WB6OGD
|
Yeah, I think the cap is the correct fix.? But Steve, you did fix it, can't argue with success.
?
Your receivers must have worked in the past, without cap nor resistor!? Aging must explain it.
This year it might take a 1K, next year a 2K?
?
If you are lowering the supply voltage, you are probably also lowering the output amplitude too.
Might not be any problem but might lead to signal degradation?
?
Interesting, you both seem to have 1967 radios, the "bad" schematic without the cap is from 1966.
?
BTW, the real fix for the 11 tube R-4A and the R-4B is Rob Sherwood's product detector mod.
This makes a real difference, mostly in the Slow AVC.? Highly recommended, my R-4B has never
sounded better.
?
73,
Gary
WB6OGD
?
|
Where can I find details of Sherwood's product detector fix for the 4B? I have one, which I need to work on for other reasons. If its not an extensive mod, and it really makes a difference, I would like to do it.
toggle quoted message
Show quoted text
On 12/30/2024 1:11 PM, Gary WB6OGD via groups.io wrote: without the cap is from 1966.
BTW, the real fix for the 11 tube R-4A and the R-4B is Rob Sherwood's product detector mod.
This makes a real difference, mostly in the Slow AVC.? Highly recommended, my R-4B has never
sounded better.
73,
Gary
WB6OGD
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Richard,
Look in the Files section for my file:
?
"Product Detector board instructions.doc"
(I should have put a better title on it!)
?
This was for my version of Rob's board and how I installed it in my R-4B.? I think its a little easier
than Rob's method, I left all Drake parts in place and just cut one small Drake trace.
My pcb is slightly smaller than Rob's too, so it fit in really nicely.? I sent out my extra boards, maybe
you got one?
?
NOTE: there is another file "MouserParts.xls"? that has the parts list for my board.
I am not sure why these files are not in their own folder..?
?
73,
Gary
WB6OGD
?
|
No, I never got a board. I am familiar with Rob's upgrades for the R4C but didn't know about the B. The B is really a very good receiver and doesn't seem to need much help but I am always interested in improvements.
toggle quoted message
Show quoted text
On 12/30/2024 3:19 PM, Gary WB6OGD via groups.io wrote: Richard,
Look in the Files section for my file:
"Product Detector board instructions.doc"
(I should have put a better title on it!)
This was for my version of Rob's board and how I installed it in my R-4B.? I think its a little easier
than Rob's method, I left all Drake parts in place and just cut one small Drake trace.
My pcb is slightly smaller than Rob's too, so it fit in really nicely. I sent out my extra boards, maybe
you got one?
73,
Gary
WB6OGD
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Found your file and downloaded it to my Drake file.
toggle quoted message
Show quoted text
On 12/30/2024 3:24 PM, Gary WB6OGD via groups.io wrote: [Edited Message Follows]
Richard,
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Richard,
I think the Product Detector mod is quite worthwhile.
?
If you've ever used an R-4 or R-4A(13 tube) you will notice its? VERY nice and slow AVC on ssb.
You can see the s-meter virtually hang on the highest audio peaks.
?
Drake eliminated the tube product detector and went to two diodes in the 11 tube R-4A and kept it to the last R-4C (I believe).
It was simpler, solid state but it caused detected audio to get back into the AVC, making it into a Fast (or medium) AVC.
You can watch the s-meter dance around on sylables and hear the harsher audio as noise is allowed in between sylables.
?
Rob also found problems like the signal exceeding the BFO on AVC attack (if I recall correctly) and that may be.. but that's
above my pay grade, I never noticed that.? But now my R-4B sounds like my old 13 tube R-4A with its slow AVC.
?
I gave away a lot of boards, someone may be able to give you one.? I might have a few more if I can find them after my move.
My board is SMD.? The NE-602/SA-612(?) is now obsolete, you might have to get some from china?
?
73,
Gary
WB6OGD
?
?
|
You have my sympathy with your move. My least favorite thing is moving. Done it too often in the past. Right up there with surgery but at least with surgery someone else does it for you.
I found the AVC on my 4B is sensitive to gassy tubes. If gassy the AVC acts as you describe rather than hanging.
toggle quoted message
Show quoted text
On 12/30/2024 4:29 PM, Gary WB6OGD via groups.io wrote: Richard,
I think the Product Detector mod is quite worthwhile.
If you've ever used an R-4 or R-4A(13 tube) you will notice its? VERY nice and slow AVC on ssb.
You can see the s-meter virtually hang on the highest audio peaks.
Drake eliminated the tube product detector and went to two diodes in the 11 tube R-4A and kept it to the last R-4C (I believe).
It was simpler, solid state but it caused detected audio to get back into the AVC, making it into a Fast (or medium) AVC.
You can watch the s-meter dance around on sylables and hear the harsher audio as noise is allowed in between sylables.
Rob also found problems like the signal exceeding the BFO on AVC attack (if I recall correctly) and that may be.. but that's
above my pay grade, I never noticed that.? But now my R-4B sounds like my old 13 tube R-4A with its slow AVC.
I gave away a lot of boards, someone may be able to give you one.? I might have a few more if I can find them after my move.
My board is SMD.? The NE-602/SA-612(?) is now obsolete, you might have to get some from china?
73,
Gary
WB6OGD
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
YES, even my 13 tube R-4A had fast AVC with a gassey tube! (only until Garey told me I had a gassey tube!).
But, the best tubes in an R-4B will still give the too fast AVC.? You can tell if an R-4B is stock by watching the s-meter on YouTube videos. 73, Gary
WB6OGD
On Mon, Dec 30, 2024 at 4:49?PM Richard Knoppow via <1oldlens1= [email protected]> wrote: ? ? ?You have my sympathy with your move. My least favorite thing is
moving. Done it too often in the past. Right up there with surgery but
at least with surgery someone else does it for you.
? ? ?I found the AVC on my 4B is sensitive to gassy tubes. If gassy the
AVC acts as you describe rather than hanging.
On 12/30/2024 4:29 PM, Gary WB6OGD via wrote:
> Richard,
> I think the Product Detector mod is quite worthwhile.
> If you've ever used an R-4 or R-4A(13 tube) you will notice its? VERY
> nice and slow AVC on ssb.
> You can see the s-meter virtually hang on the highest audio peaks.
> Drake eliminated the tube product detector and went to two diodes in the
> 11 tube R-4A and kept it to the last R-4C (I believe).
> It was simpler, solid state but it caused detected audio to get back
> into the AVC, making it into a Fast (or medium) AVC.
> You can watch the s-meter dance around on sylables and hear the harsher
> audio as noise is allowed in between sylables.
> Rob also found problems like the signal exceeding the BFO on AVC attack
> (if I recall correctly) and that may be.. but that's
> above my pay grade, I never noticed that.? But now my R-4B sounds like
> my old 13 tube R-4A with its slow AVC.
> I gave away a lot of boards, someone may be able to give you one.? I
> might have a few more if I can find them after my move.
> My board is SMD.? The NE-602/SA-612(?) is now obsolete, you might have
> to get some from china?
> 73,
> Gary
> WB6OGD
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Same here. Garry said it was gassy tubes, I didn't believe him but tried new tubes anyway. Fixed it. The amount of gas is so slight it doesn't show up on most tube tester gas tests. My TV-7 instructions explain that the gas test is really not a valid test and show up only the most extreme tubes.
Garry has been gone a long time now but I still miss him. We had some private correspondence, he was not only extremely knowledgeable but also a refined gentleman, an all around good guy.
toggle quoted message
Show quoted text
On 12/30/2024 4:56 PM, Gary WB6OGD via groups.io wrote: YES, even my 13 tube R-4A had fast AVC with a gassey tube! (only until Garey told me I had a
gassey tube!).
But, the best tubes in an R-4B will still give the too fast AVC.? You can tell if an R-4B is stock by
watching the s-meter on YouTube videos.
73,
Gary
WB6OGD
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
I have probably seen maybe 3 tubes that have failed the gas test on a tube tester.?
The remainder have taken me on various journeys through some really interesting territory. The one that really opened my eyes was one that Ronnie had sent me. I chased that AGC problem over hill and Dale. Even swapped the whole board. I then replaced all the tubes at once with ones from my known good desk R-4B. I believe there were at least two gassy tubes ¡ª which is why I was chasing my tail by replacing one at a time.?
Because of how this radio taught me that the problem can easily be more than one tube, I now do a full replacement and then put the old tubes back in, one at a time.?
Since then, I¡¯ve found that many failures of R-4C¡¯s To pass the S meter calibration have been due to gassy tubes.?
73,
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Mon, Dec 30, 2024 at 20:03, Richard Knoppow via groups.io < 1oldlens1@...> wrote: Same here. Garry said it was gassy tubes, I didn't believe him but
tried new tubes anyway. Fixed it. The amount of gas is so slight it
doesn't show up on most tube tester gas tests. My TV-7 instructions
explain that the gas test is really not a valid test and show up only
the most extreme tubes.
Garry has been gone a long time now but I still miss him. We had
some private correspondence, he was not only extremely knowledgeable but
also a refined gentleman, an all around good guy.
On 12/30/2024 4:56 PM, Gary WB6OGD via groups.io wrote:
> YES, even my 13 tube R-4A had fast AVC with a gassey tube! (only until
> Garey told me I had a
> gassey tube!).
>
> But, the best tubes in an R-4B will still give the too fast AVC.? You
> can tell if an R-4B is stock by
> watching the s-meter on YouTube videos.
> 73,
> Gary
> WB6OGD
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Gary WB6OGD