Re: L-4PS Plate transformer primary color coding
On Wed, Apr 24, 2024 at 07:20 AM, Jim VE7RF wrote:
Still can't find it.? ?And I have 4 x manuals for the 4 x l4b's.? its not on the L4PS? schematic.
Jim; The second circuit breaker is between the bottom leg of the center-tapped input winding and the screw-terminal... it's drawn at a 45 degree angle. In this copy of the schematic, it's just below the 'BRN/BLK' marking:  It's a bit more apparent in my re-drawn copy of the L-4B PS:  Mark - AD7EF
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Re: L-4PS Plate transformer primary color coding
The two circuit breakers are circled in the attached schematic.?
Ken
WA2LBI
???
On Tue, Apr 23, 2024 at 05:56 PM, Jim Shorney wrote:
Look again. It's there, just easy to miss.
Still can't find it.? ?And I have 4 x manuals for the 4 x l4b's.? its not on the L4PS? schematic.??
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I just noticed that my L7 after for possible parasitic oscillations,, I note that the Load adjustment is only good when setting is about 0. I don't remember but that does not seem correct. I have tuned amp on several 40 meter freqs just doesn't seem right.? Any suggestions?? Thanks in advance.
73? Bob
This is all related to the replacement of the Parasitic Chokes and the Plate coupling capacitors.
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I was thinking the other day "I
wonder what was actually happening"?
This was in the late 70's, a common among DXers and Contesters was
a dirt cheap thing to do to make your signal just jump and stand
out in pile-ups.
My particular setup.
Plain TR-4
AC-4 power supply
Shure 444 Mic.
Like the D-104 the Shure 444"s frequency response was incredible
with all Drakes.
Now this is my question of what is actually happening. I'll say
what the Modification was at the end.
But doing this "Mod" you can immediately see the plate amp meter
being MUCH more aggressive,
jumping far higher than usual, so power is either higher or more
"Full".
Listening on the air It had the exact sound of a processed signal
made by a external speech processor
like the "Vomax" unit. but at a FAR cheaper cost. Adjusted for
Inflation the Vomax today would cost $412.00!!!!
Looking at a scope it also seems to look just like the vomax
signal. Still "Peaky" but fuller.
It did not sound distorted at all. Or the sound of a bad
flat-topped signal.
But the "Punch" it had was incredible! To a S meter and to the
"Ear"
it seemed pretty equal to like a modern rig running maybe up to 10
db of compression.
But it seemed "Clean" Never got a complaint about splatter or
distorted signal,
?if anything you got compliments on how great the audio was.
I never even thought to try to figure out what this "MOD" was
actually doing,
all I knew was it worked, and worked GREAT with never a hint of
anything negative from anyone.
What was this "MOD"?? On the AC-4 Power Supply is a Jack for the
ALC for when running with an amp.
This Jack is connected to the amp,,, well you all know what it is
for.
But this "MOD" was simply inserting a shorted out RCA plug into
that jack on the AC-4 shorting it out.
That's it!
The Drake Is now retired, But I got to wondering, has anyone else
done this "MOD" from the 70's
and even maybe still does it today?
And even more what was actually happening?
Joe WB9SBD
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Re: L-4PS Plate transformer primary color coding
On Tue, Apr 23, 2024 at 05:56 PM, Jim Shorney wrote:
Look again. It's there, just easy to miss.
Still can't find it.? ?And I have 4 x manuals for the 4 x l4b's.? its not on the L4PS? schematic.??
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Re: L7 makes alot of smoke
Running in the low tap position, that is the tune up position is OK as the operator on the other end will not be able to tell the difference, I used my L7 for years like that, I'm still doing it most of the time in fact.
Now when doing so, running in the low tap tune position the grid current will be a little higher so watch it but I have never had an issue, 500 watts would be OK for output, why do you need much more you will only get 4.5 db more on the receive end at 1500 watts.
You switched tubes you noted and have not had a problem. The internal wiring of the 3-500Z happens to be very close together, on an ohm meter everything can check out OK but as you use the tube of course the wiring expands as it heats up and can short. This is another reason to never store these tubes on their side as they are not meant to support the weight, only store standing up.
Good luck
Tim
WB8UHZ
On Wednesday, April 24, 2024 at 02:00:10 AM EDT, Rick W4XA <myr748@...> wrote:
FT8 is pretty hard any any amplifier running at or near maximum ratings.? It would be like running RTTY.
I have heard that the failure rate for imported 3-500's? is somewhat higher than the originals.....
--
73/Rick
W4XA
*Every post is created using Linux
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Re: FS: MN-2000 ANTENNA MATCHING UNIT
INTERESTED...
Give me a a lil time to do some research...how does this compare to the MN2700?
same freq range, balun compensation, power capacity, etc.
?
TOM? NU2W
On 04/24/2024 8:29 AM EDT Randy <wrmoore47@...> wrote:
?
?
Works fine, a 9/10 cosmetically, built like a tank. Asking $250 plus shipping. Photos and video here:
Please contact off=line if interested.
73,
Randy, KS4L
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FS: MN-2000 ANTENNA MATCHING UNIT
Works fine, a 9/10 cosmetically, built like a tank. Asking $250 plus shipping. Photos and video here:
Please contact off=line if interested.
73,
Randy, KS4L
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Re: L7 makes alot of smoke
FT8 is pretty hard any any amplifier running at or near maximum ratings.? It would be like running RTTY.
I have heard that the failure rate for imported 3-500's? is somewhat higher than the originals.....
--
73/Rick
W4XA
*Every post is created using Linux
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Re: L7 makes alot of smoke
From what I hear, not necessarily. I was just a little while ago running the same amp with a replacement tube of the same type on 80m FT8 with close to a kilowatt out and it held. However it is not unheard of to get one that is "out of spec". Others here probably have more experience with them than I do. Or you could check the Amps reflector for opinions. On Tue, 23 Apr 2024 21:53:49 -0700 "Rick W4XA via groups.io" <myr748@...> wrote: And even then Eimac had typical operation data up to 3500v.....? Are the imported tubes so bad that they can't be run at the original Eimac ratings? -- 73 -Jim NU0C
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Re: Drake TR7 transmit limit on digital modes
A.K.A. Rotron SU2C1 part number 028270. Available on eBay new $28.00 each plus shipping. Mouser has some equivalent NMB fans that are ball bearing for a few dollars less. The Rotron is sleeve bearing but to be fair they seem to last a long time. Generally speaking ball bearing is better suited to vertical mounting. Or you could use PC fans run off 12V. Some of the boutique fans targeted at gamers are very quiet. Insist on ball bearings. Avoid Sunon fans at all costs. 73 -Jim NU0C On Tue, 23 Apr 2024 19:27:47 -0700 "Lyndon VE7TFX via groups.io" <lyndon@...> wrote: FYI, while the FA7 tends to be a bit pricy when you can find a good one, th=
e
Rotron SUC21 is readily available brand new for less than half the cost. Can anyone provide a link to one of these sellers? The web searches
I did led to an endless maze of very dodgy looking websites.
I also see the Rotron website doesn't recognize that part number, so
I'm not sure about "new" ones being available. I haven't dug into
their catalog yet to see if there's an obvious replacement.
--lyndon
-- 73 -Jim NU0C
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Re: L7 makes alot of smoke
On Tue, Apr 23, 2024 at 07:15 PM, Jim Shorney wrote:
Well, the manual does say 2600 volts unloaded. So that's pretty close.
73
-Jim
NU0C
Isn't 2700V really "middle of the road" anyway? And even then Eimac had typical operation data up to 3500v.....? Are the imported tubes so bad that they can't be run at the original Eimac ratings? I know 1 guy with an L-4B and another with an L-7 that replaced the plate transformer with the higher voltage "upgraded" PW Dahl? (Hammond Engr) transformer and are now running 3500 v with no problems (the low "CW" setting is now around 2700v)  If the parasitic resistors (inside the coils) are burning up, sure seems like it points to oscillation. --
73/Rick
W4XA
*Every post is created using Linux
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Re: Drake TR7 transmit limit on digital modes
I use 80mm 12 volt DC fans, which are common case cooling fans used in
PC's, on my TR7 and PS7.? The ones I use are rated at 24 cfm and 22 Db
noise level.
I have a NMB 3115FS-12T-B30, 120 Volt AC fan on my DL-1000.? It produces
a lot more noise.
73
Stan
KM4HQE
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On 4/23/24 21:27, Lyndon VE7TFX wrote: FYI, while the FA7 tends to be a bit pricy when you can find a good one, th=
e
Rotron SUC21 is readily available brand new for less than half the cost. Can anyone provide a link to one of these sellers? The web searches
I did led to an endless maze of very dodgy looking websites.
I also see the Rotron website doesn't recognize that part number, so
I'm not sure about "new" ones being available. I haven't dug into
their catalog yet to see if there's an obvious replacement.
--lyndon
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Re: L7 makes alot of smoke
I did try my 7610 running about 50 watts into the L7 with a standard keying interface for Icom. It seems to work ok. I get about 500 watts out SSB with the CW position selected. Will try and run it that way for awhile and see if it is ok. Also I swapped out the newer 500zg tubes for my original 500z Penta tubes and they seem to be ok also.? I am happy with 500 watts if that is what I can get.
73? Bob
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Re: Drake TR7 transmit limit on digital modes
FYI, while the FA7 tends to be a bit pricy when you can find a good one, th=
e
Rotron SUC21 is readily available brand new for less than half the cost. Can anyone provide a link to one of these sellers? The web searches I did led to an endless maze of very dodgy looking websites. I also see the Rotron website doesn't recognize that part number, so I'm not sure about "new" ones being available. I haven't dug into their catalog yet to see if there's an obvious replacement. --lyndon
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Re: L7 makes alot of smoke
Well, the manual does say 2600 volts unloaded. So that's pretty close. However, idling the amp for four hours doesn't really tell you much beyond the fact that the tubes don't break down at 2645. The anode voltage will swing much higher under full power operation and can go crazy high if you have a load fault. Which is another good reason to have that low voltage switch that some like to consider an anachronism to be disposed of. If you suspect that the tubes might be gassy you can run them hard at lower voltage for a while to getter them. Of course that won't help you if there is a mechanical fault inside the tube or internal damage from a flash-over. W8JI has a nice article on tubes here: 73 -Jim NU0C On Tue, 23 Apr 2024 18:26:30 -0700 "K6OXN Bob via groups.io" <bobk6oxn@...> wrote: 2645 with my HV meter.
-- 73 -Jim NU0C
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Re: L7 makes alot of smoke
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Re: L7 makes alot of smoke
Bob,
That 2700 volts is a tad bit on the high side, perhaps.
73,
Evan, K9SQG
On Tuesday, April 23, 2024 at 05:54:31 PM EDT, K6OXN Bob <bobk6oxn@...> wrote:
The power supply has the Harbach mod done and has been working great. Of course when this happens only the .82 fuse resistor blows. I do notice some possible arc points on the cover of the L7 and will place some Fish paper in that area.? After the first repair, I left the amp on in idle with HV at 2700+ and had no problems for over 4 hours in that state. Now it seems that the arcing is taking out the 47 ohm parasitic resistors when I am modulating in SSB.? Only tested on 40 meters at this time and cannot see any parasitic oscillations on the scope. Replacing the parasitic resistors now along with the .82 in the PS.? Will bring it up slowly and may try SSB with the amp in CW mode unless that is not recommended. Otherwise, I will reduce the TR7 to about 50 watts and see how it is doing.
73? Bob
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Re: Drake TR7 transmit limit on digital modes
I have original fan installed and a Astron power supply. Seems like i will be able to run full power! I love how quiet the FA7 is.
Tim Gordish
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On Apr 23, 2024, at 19:04, Omni via groups.io <selcor@...> wrote: ?I have two TR7's with their companion PS7 supplies and concur that having fans on both the power supply and the TR7 is the best way to go. Use of the FA7 greatly improves the frequency stability of the TR7 and prolongs the life of the PA transistors. However, I disagree with any fan that fits is OK. The FA7 is a Rotron Sprite SU2C1 (19 CFM) fan that was private labeled for Drake. Power transistors are sensitive to temperature changes and engineers design circuits to run in within a specific temperature band for optimal performance. Too cool, while not as bad as too hot, is still not a desired result. The heatsink in the TR7 is a patented design that relies on the amount of air movement delivered by the FA7 to keep things within the desired temperature band. Except on rare occasions, I let my TR7's come up to ambient temperature before I get on the air with them. FYI, while the FA7 tends to be a bit pricy when you can find a good one, the Rotron SUC21 is readily available brand new for less than half the cost. All you have to do to a stock Rotron fan is put a two prong AC plug on it. You can easily adapt a polarized plug to fit the receptacle on the TR7 and PS7. The only thing you might want to add to is a finger guard, which is also not too hard to find. -----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of Jim Shorney Sent: Tuesday, April 23, 2024 6:32 PM To: [email protected]Subject: Re: [DRAKE-RADIO] Drake TR7 transmit limit on digital modes I would say that you want both fans even if you don't run digital modes. The fan on the PS cools the main filter caps which will extend their life. The fan on the radio keeps the internal temperature more stable across T/R cycles which reduces drift, as well as extending component life in the PA. Any off the shelf 20CFM fan of the proper form factor, oriented to pull air OUT, will work. You don't need a gen-yoo-wine FA7. 73 -Jim NU0C On Tue, 23 Apr 2024 18:20:37 -0400 "Omni via groups.io" <selcor@...> wrote: The PA in the TR7 is very conservatively rated and has plenty of headroom.
The radio is rated for 100% duty cycle in SSB and CW without a fan. If you have a genuine FA7 you can run 100% duty cycle in SSTV and RTTY, which place similar demands on the PA as digital modes. if you have any concerns you
can always run the radio at reduced power such as 100 Watts. Nobody will
notice any difference on the receive end compared to the full output of a
TR7, which is typically 140-150 Watts. If you are running the radio with a PS7 you should also have a FA7 on the supply for digital modes. --- This email has been checked for viruses by AVG.
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Re: Drake TR7 transmit limit on digital modes
I have a box full of a 32 CFM version. These are great for a DL1000 but way too loud for anything else. The FA7 is a 20CFM fan (or 19, depending on who you ask) as you say, easy to find. IMO it does not need to be a Rotron specifically. What I am not keen on is fan controllers. They mess with the temperature stabilization idea for the rest of the radio. What definitely DOES NOT work very well at all is the bad advice out there to reverse the direction of the fan so it forces air into the radio. I have proven experimentally that this impairs cooling. 73 -Jim NU0C On Tue, 23 Apr 2024 20:04:05 -0400 "Omni via groups.io" <selcor@...> wrote: I have two TR7's with their companion PS7 supplies and concur that having
fans on both the power supply and the TR7 is the best way to go. Use of the
FA7 greatly improves the frequency stability of the TR7 and prolongs the
life of the PA transistors. However, I disagree with any fan that fits is
OK. The FA7 is a Rotron Sprite SU2C1 (19 CFM) fan that was private labeled
for Drake. Power transistors are sensitive to temperature changes and
engineers design circuits to run in within a specific temperature band for
optimal performance. Too cool, while not as bad as too hot, is still not a
desired result. The heatsink in the TR7 is a patented design that relies on
the amount of air movement delivered by the FA7 to keep things within the
desired temperature band. Except on rare occasions, I let my TR7's come up
to ambient temperature before I get on the air with them.
FYI, while the FA7 tends to be a bit pricy when you can find a good one, the
Rotron SUC21 is readily available brand new for less than half the cost.
All you have to do to a stock Rotron fan is put a two prong AC plug on it.
You can easily adapt a polarized plug to fit the receptacle on the TR7 and
PS7. The only thing you might want to add to is a finger guard, which is
also not too hard to find.
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Mark Davis
NU2W
Randy
Jim Shorney