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
?
?
|
Good on you, Craig.? Glad you got your honey back singing! David Assaf III W5XU, VP8RXU ?
On Mon, Dec 30, 2024 at 6:17?PM Craig W8CS via <craig_severson= [email protected]> wrote: Victory! I now have keyed CW output on all bands.?
?
- The main culprit was the switched +5V bias regulator U2301 on the final amp board. No + output from this 7805 and switched +13.6V going into it. This was relatively easy to find after I started checking voltages and seeing nothing on the bias circuitry.?
- After replacing this 7805, still no output. I could see that the regulator was producing switched +5V but not getting to the rest of the board. I had to get to the lower traces of the PA board which was a chore since I did not see that the final amp transistors had TWO small allen head screws attaching them. You have to bend some parts out of the way to get to them and release the board from the heat sink.?
- Once the board was liberated, I could see that I didn't have a "trace" issue, the output of the regulator was apparently not soldered down correctly so a heating of the joint from the bottom side cured that.?
Really cool to be able to put this dude back into service after a twenty year lay-off. That receiver is so sweet.?
?
Thanks for the hand, everyone.?
--
Craig/W8CS
Greenville, SC
|
Victory! I now have keyed CW output on all bands.?
?
- The main culprit was the switched +5V bias regulator U2301 on the final amp board. No + output from this 7805 and switched +13.6V going into it. This was relatively easy to find after I started checking voltages and seeing nothing on the bias circuitry.?
- After replacing this 7805, still no output. I could see that the regulator was producing switched +5V but not getting to the rest of the board. I had to get to the lower traces of the PA board which was a chore since I did not see that the final amp transistors had TWO small allen head screws attaching them. You have to bend some parts out of the way to get to them and release the board from the heat sink.?
- Once the board was liberated, I could see that I didn't have a "trace" issue, the output of the regulator was apparently not soldered down correctly so a heating of the joint from the bottom side cured that.?
Really cool to be able to put this dude back into service after a twenty year lay-off. That receiver is so sweet.?
?
Thanks for the hand, everyone.?
--
Craig/W8CS
Greenville, SC
|
Re: TR-5 BPF AMP Board Oddness
That is the cover I took off with the hole itn it near the back of the chassis. Sorry I will take the bottom cover off again and try to do better hi hi
Jim Ve1RB
Jim, you're looking at the wrong board.? The picture you sent is
of the pre-mixer board.? The board you want is accessed through the
bottom of the chassis.? Open the radio on its back, with the rear
panel facing you.? The BPF Amp board is on the left side, above the
compartment where the output filters live.
See the picture on page 5-9 of the manual.
--lyndon
|
Found your file and downloaded it to my Drake file.
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On 12/30/2024 3:24 PM, Gary WB6OGD via groups.io wrote: [Edited Message Follows]
Richard,
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
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.
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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
|
You are probably right but I was puzzled.
Both Lionel and ARH keys are good keys, easy to clean. J-38 keys were made by several manufacturers but these two, and Radio Specialties, which is evidently the same as ARH, are the most common.
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On 12/30/2024 3:18 PM, Steve Wedge, W1ES/4 via groups.io wrote: Low resistance when the contacts are open, is what I¡¯m assuming what is being described.
I have a T-4 that went stuck in transmit but I lucked out ¡ª it wasn¡¯t putting out full power. ?I¡¯m going to check my J-38 this evening. ?It¡¯s conceivable for this to have picked up some schmutz over 80 years¡
--
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
?
|
Low resistance when the contacts are open, is what I¡¯m assuming what is being described.
I have a T-4 that went stuck in transmit but I lucked out ¡ª it wasn¡¯t putting out full power. ?I¡¯m going to check my J-38 this evening. ?It¡¯s conceivable for this to have picked up some schmutz over 80 years¡
On Mon, Dec 30, 2024 at 5:49 PM, Richard Knoppow via groups.io < 1oldlens1@...> wrote: I don't understand this. Low resistance, ideally NO resistance, of
the key contacts is their normal condition. What am I missing here?
On 12/30/2024 12:19 PM, Jay W6CJ via groups.io wrote:
> Gary & Group,
>
> A straight key with intermittently low-R contacts was the cause of this
> meltdown.
> I discovered this when I plugged the key into another transmitter - so
> check those contacts.
>
> 73
> Jay
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
Thank you,that would certainly cause problems. I discovered that the key contact resistance could affect the frequency of my Bud code practice oscillator. I began to get chirp from a bug and found that the resistance varied between dots and dashes. A good cleaning fixed this. If it can affect a simple code practice oscillator it might also affect a transmitter keying circuit.
I am a collector of telegraph keys in a small way (there are people with hundreds of them). I try to keep them in good condition. Most straight keys are pretty simple but resistance can get high if the various joints through which the current must flow become a little corroded. I mean to include bugs here since they sometimes have more complex current paths. one can check this with any VOM.
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On 12/30/2024 2:53 PM, n4buq wrote: I think he meant that the key was closed, or at least at a very low resistance, when it was supposed to be fully open.
Barry - N4BUQ
I don't understand this. Low resistance, ideally NO resistance, of
the key contacts is their normal condition. What am I missing here?
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
I think he meant that the key was closed, or at least at a very low resistance, when it was supposed to be fully open.
Barry - N4BUQ
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I don't understand this. Low resistance, ideally NO resistance, of
the key contacts is their normal condition. What am I missing here?
On 12/30/2024 12:19 PM, Jay W6CJ via groups.io wrote:
Gary & Group,
A straight key with intermittently low-R contacts was the cause of this
meltdown.
I discovered this when I plugged the key into another transmitter - so
check those contacts.
73
Jay
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
I don't understand this. Low resistance, ideally NO resistance, of the key contacts is their normal condition. What am I missing here?
toggle quoted message
Show quoted text
On 12/30/2024 12:19 PM, Jay W6CJ via groups.io wrote: Gary & Group, A straight key with intermittently low-R contacts was the cause of this meltdown.
I discovered this when I plugged the key into another transmitter - so check those contacts.
73
Jay
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
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.
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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
|
Re: Want: List of Drake Repairers
Check out the last page of the following document on WB4HFN's web site.??
?
?
73's,
Mark, WB0IQK
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Re: TR-5 BPF AMP Board Oddness
Jim, you're looking at the wrong board. The picture you sent is
of the pre-mixer board. The board you want is accessed through the
bottom of the chassis. Open the radio on its back, with the rear
panel facing you. The BPF Amp board is on the left side, above the
compartment where the output filters live.
See the picture on page 5-9 of the manual.
--lyndon
|
Re: TR-5 BPF AMP Board Oddness
Lyndon my TR5 is serial 1159 and picture added.?
73, Jim VE1RB
Lyndon VE7TFX writes:
> Anybody know what's going on here?? I have another TR-5 (s/n 1024)
> that I got from Steve; I haven't opened it up yet to see if it's
> the same.
I popped the other one open, and it has the expected board (see
attached).? So it would appear that something changed between #1024
and #1051.? But in my rather limited searching I can't find any
documentation related to this.? If any of you have a TR-5 in the
s/n range 1025-1050 and are inclined towards doing a bit of detective
work, I'd appreciate it if you could pop off the bottom panel and
let me know which version of the board you have.
--lyndon
|
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
?
|
Re: TR-5 BPF AMP Board Oddness
Lyndon VE7TFX writes: Anybody know what's going on here? I have another TR-5 (s/n 1024)
that I got from Steve; I haven't opened it up yet to see if it's
the same. I popped the other one open, and it has the expected board (see attached). So it would appear that something changed between #1024 and #1051. But in my rather limited searching I can't find any documentation related to this. If any of you have a TR-5 in the s/n range 1025-1050 and are inclined towards doing a bit of detective work, I'd appreciate it if you could pop off the bottom panel and let me know which version of the board you have. --lyndon
|
Gary & Group, RGR - the solder blob could have fallen from where the parasitic chokes connect to the top of the larger choke. Looks like I'll be buying parasitic chokes, Sylvania (?) finals and maybe a driver.
A straight key with intermittently low-R contacts was the cause of this meltdown.?? I discovered this when I plugged the key into another transmitter - so check those contacts.
73 Jay
Are you saying that the parasitic choke got hot enough to melt solder? Safe bet the tube(s) are bad.
Gary
W0DVN
Gary & Group,
More info- Suspecting that I slagged my finals, I looked in the cage. Saw a fresh solder blob near the base of the choke and a lead popped out from one of the parasitic choke resistors.
Looks like I'll need parasitic chokes (my hands can't make my own) and a pair of finals to substitute?
Suggestions welcome
73 Jay W6CJ
Gary- About 50mA, keying in CW mode. In Tune mode, about 90-100mA.
Do you get idle plate current when you key the radio?
Gary
W0DVN
Gary- Using an AC4-R supply. PA plate, plate, filament, dial light and bias voltages are getting to the T4XC. Dead driver or finals?
There was a reason the power supply fuse popped. Check voltages there first.
Gary W0DVN
Group, I'd welcome any advice on where to start looking.??
The 5A fuse on the AC4 blew in my absence. Replaced the fuse, and cannot get a peak greater than 0.1A when switching from SSB to tune, regardless of the gain setting on 80 and 40.??
D'oh.....? ??
73 Jay
|
L4B replacement potentiometer
Fellow Drake Enthusiasts,
Happy New Year to all!!!
A while back somebody had mentioned that Mouser part number?313-1601F-100K was a direct replacement for the L4B pot, right resistance, with a push pull switch. ?However, that particular pot does not have a shaft that is long enough for the L4B. ?Might I have the part number wrong?
I already have some pots that are direct replacements after I machine the mounting collar to the right length. ?However, if there are direct replacements it would save me some time.
Can you help?
73,
Evan, K9SQG
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Gary WB6OGD
David
Craig W8CS
Jay W6CJ