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On Fri, Mar 26, 2021 at 06:33 AM, Jim Shorney wrote:
<I'm not going to waste time debating trivia with you. I just don't want the audience to get the impression that the L-4B is some pathetic POS that doesn't even deserve to be on 11 Meters based <on your rantings. The fact is that a countless number of these amps have been in service for decades and they do the job they were intended to do as-is.
<73
<-Jim
<NU0C
##? I never said the? L4B is a POS. (I own? 4 of them).? But it's not? 1963 anymore either.? ?With a bunch of? simple upgrades, the? L4B can be made much more? reliable.? ?My? yaesu's put out? 50%? power after just? 10 msecs.? ?That tells me the slow? 15 msec? oem? drake? 3PDT? TR relay hot switches? every time you trip the vox.? ?Running the tubes with zero bias,? insufficient cooling,? goofy cut off bias scheme, un-needed? bleeders? in the? HV? supply, substandard and dangerous? HV connector, deficient TR relay setup, poor excuse for a hv? fuse,? no? fault current limiting, no meter protection, insufficient? HV? filtering (ripple is way too high),? wrong value? bypass caps....... it's all easily? fixed and upgraded.?
?
On? CW,? I can? insert a 0-30 msec delay, so the L4B? relay's at least get a head start, so no hotswitching, and nothing gets? truncated.? ?On? SSB,? I added an external hb delay to the yaesu's TX? inhibit lead, so? ?again,? the? L4B? TR relay? gets a head start.
Ever seen a L4B? that has been run on 11 M? AM ?? Nothing left of the bandswitch contacts, they get so hot they lose their spring tension ( just like any ameritron? al-1500/al-1200/al-82? that has been used on any band, on? RTTY).? ?Ever measured the heat on the oem? ?L4B? tank coil on? 15m and also 10m ?? ?It gets fn hot.? No, the L4B? does not fare too well after a? 11m op gets his hands on it..and? runs it? with a 900 watt un-modulated? cxr.?
Art? Bell,? W6OBB? was telling me one night, he had to make a trip to Las Vegas,? 75 miles? away.? ?When he got back, his? ALPHA? 87? was on fire, smoke everywhere,? tank assy? completely melted, a real mess.? ?Art had been using the amp on 10m? FM.? ?His cat came along? and? fell asleep on the? footswitch.? Amp had been running 1.5 kw? FM on 10m? for almost? 4? 1/2? hrs.? ?Art had also installed the optional? rear fan assy for? extra? cooling, per? alpha manual.? ?Art phones? alpha, and? asks about the...'no time limit'? and the tech told him.....? 'don't believe the advertising? hype'.??
It's? 58 years? since the L4 came out, and? 60 years since it was engineered.? They did a pretty good job, all things considered.? ?It's an easy upgradeable amp, with simple mods.
Jim? ?VE7RF
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Just an update.... finished upgrading my L75.
Used the L75 for the first time the last night.
As reported by an old Heathkit HM-102 meter, I was able to obtain 500 watts output with 50 watts input on CW on 40 meters to a Heathkit Cantenna Dummy Load.?
Compared that read out against a Collins 312B-5 console and there it shows 600 watts. But the Relative Output function of the L75 shows way less.
Tried to adjust the Relative Output with the pot on the back of the L75, reaching the end of adjustment, but was only able to reach 300 watts. So something is still wrong there.
?
Apart from that, was able to use the amp to make a few contacts on SSB, CW without problems.
I kept an eye on the meter and adjusted accordingly to the manual (dip the plate and loading) thus not exceeding the plate nor grid mA stated there.
?
Also made a lot of contacts on 40 and 20 meters FT8 not exceeding 200 mA on the plate of the L75 (20 watts on the exciter) and performed very well. Got new countries into my log. I know this amp is not designed for digital 80% duty cycle modes but can be used with great care with very low input limiting thus the output.
?
Tested other bands and did well too. Only bands that I heard small arching was on 160 and 80 against a dummy load. Don't have an antenna for those two bands any way. From 40 and up was OK no arching.
?
So that concludes my report. Have to check on the Relative Output circuitry to find out why is not reading well.
i did adjust the meter for Plate and Grid according to the manual with a 1.5 VDC battery...
73 Rob
YS1RS
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When needed I run around 700 Watts on digital modes from a pair of 3-500s. The plates show a nice red color after an FT8 TX cycle, but that is good for them. They need to be run with some color in the plates to de-gas. Don't baby that tube! :) 73 -Jim NU0C On Wed, 31 Mar 2021 17:38:50 -0700 "Roberto - YS1RS via groups.io" <ys1rs@...> wrote: Also made a lot of contacts on 40 and 20 meters FT8 not exceeding 200 mA on the plate of the L75 (20 watts on the exciter) and performed very well. Got new countries into my log. I know this amp is not designed for digital 80% duty cycle modes but can be used with great care with very low input limiting thus the output.
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Yes, I will be careful not to switch bands while tuning.
Also forgot to mention:
- I protected the meter with two diodes back to back the same way ?I did with the old Collins 30L-1.?
- Added soft keying circuit to protect my radio. Before I had 28 VDC on the relay input. Now I see 1.2 VDC.
- I run the Amp from an Ameritron ICP-240. This saves the Amp from the in-rush current, saves its power switch and protects it from surges.
?
The photo shows it produces 3.0KV?
?
?
Was using only 200W on FT-8 and behaved well. Worked new Asian countries with a dipole on 20 meters.
?
?
The problem with the Relative Output problem has now been fixed too.
?
Now I am in need of a tuner like the Drake MN2700 to lower SWR on a couple of bands.
?
Can this amp be used on WARC bands? That another reason I need the MN2700.
?
73
Rob
YS1RS
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Was doing a quick recap after restoring this Drake L75 Amp.:
1- the two RCA connectors on the back of the unit (Vox Relay and Transmitter AGC) are too close together for comfort! ?I made the cable to connect to my Yaesu but both cables do not fit together. So I am using only the Relay. All the RCA connectors, locally sold, are intended for audio and those are the thick fancy type. Need to find old vintage RCAs to use here or build an “adapter” to connect my modern set of cables.
2- Had a lot of head scratching at the time of turning on the amp, after finishing the restoration. Had nothing on the meter. No activity at all. Though had failed with colors but at same time had relay activity and the humming inside sounded like all was ok, the fan was working and the power consumption measured was also OK. But still nothing on the meter... took the meter out and tested it outside and, to my surprise, the meter was not working but seemed mechanically ok. Well, found a cold solder on the connection of a small wire inside the meter! Had to take it apart completely and it was like working on an old clock mechanism. Slow and meticulous with magnifier glasses.?
Clearly this was a manufacturer’s failure.
Does anybody here has the warranty phone number from?Drake? LOL to claim warranty LOL?
Do you know (just curiosity) who made the Drake L75 panel meter? Simpson or maybe Weston??
Anyway was a great adventure to upgrade this.?
Now I know what I have inside and feel safer knowing that the components are new. Before was no guarantee I wouldn’t get a cloud of white smoke in the Shack if a big electrolytic failed anytime (today? Next month?) being so old, burning out the Main transformer with it, etc.
Enjoy the weekend guys!
73 de Rob
YS1RS
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Maybe Modutec made the meter.
73, Jim VE1RB
Was doing a quick recap after restoring this Drake L75 Amp.:
1- the two RCA connectors on the back of the unit (Vox Relay and Transmitter AGC) are too close together for comfort!? I made the cable to connect to my Yaesu but both cables do not fit together. So I am using only the Relay. All the RCA connectors, locally sold, are intended for audio and those are the thick fancy type. Need to find old vintage RCAs to use here or build an “adapter” to connect my modern set of cables.
2- Had a lot of head scratching at the time of turning on the amp, after finishing the restoration. Had nothing on the meter. No activity at all. Though had failed with colors but at same time had relay activity and the humming inside sounded like all was ok, the fan was working and the power consumption measured was also OK. But still nothing on the meter... took the meter out and tested it outside and, to my surprise, the meter was not working but seemed mechanically ok. Well, found a cold solder on the connection of a small wire inside the meter! Had to take it apart completely and it was like working on an old clock mechanism. Slow and meticulous with magnifier glasses.?
Clearly this was a manufacturer’s failure.
Does anybody here has the warranty phone number from?Drake? LOL to claim warranty LOL?
Do you know (just curiosity) who made the Drake L75 panel meter? Simpson or maybe Weston??
Anyway was a great adventure to upgrade this.?
Now I know what I have inside and feel safer knowing that the components are new. Before was no guarantee I wouldn’t get a cloud of white smoke in the Shack if a big electrolytic failed anytime (today? Next month?) being so old, burning out the Main transformer with it, etc.
Enjoy the weekend guys!
73 de Rob
YS1RS
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Yes, probably a Jewell (a.k.a. Modutech) MS3T series. The pedigree can often be seen printed at the bottom of the scale plate behind the bezel where you don't normally see it. Jewell data sheets are in the group file section. 73 -Jim NU0C On Fri, 2 Apr 2021 20:36:43 -0300 "Jim Harris" <radiove1rb@...> wrote: Maybe Modutec made the meter.
73, Jim VE1RB
On Fri, Apr 2, 2021 at 7:24 PM Roberto - YS1RS via groups.io <ys1rs=
[email protected]> wrote:
Was doing a quick recap after restoring this Drake L75 Amp.:
1- the two RCA connectors on the back of the unit (Vox Relay and
Transmitter AGC) are too close together for comfort! I made the cable to
connect to my Yaesu but both cables do not fit together. So I am using only
the Relay. All the RCA connectors, locally sold, are intended for audio and
those are the thick fancy type. Need to find old vintage RCAs to use here
or build an “adapter” to connect my modern set of cables.
2- Had a lot of head scratching at the time of turning on the amp, after
finishing the restoration. Had nothing on the meter. No activity at all.
Though had failed with colors but at same time had relay activity and the
humming inside sounded like all was ok, the fan was working and the power
consumption measured was also OK. But still nothing on the meter... took
the meter out and tested it outside and, to my surprise, the meter was not
working but seemed mechanically ok. Well, found a cold solder on the
connection of a small wire inside the meter! Had to take it apart
completely and it was like working on an old clock mechanism. Slow and
meticulous with magnifier glasses.
Clearly this was a manufacturer’s failure.
Does anybody here has the warranty phone number from Drake? LOL to claim
warranty LOL
Do you know (just curiosity) who made the Drake L75 panel meter? Simpson
or maybe Weston?
Anyway was a great adventure to upgrade this.
Now I know what I have inside and feel safer knowing that the components
are new. Before was no guarantee I wouldn’t get a cloud of white smoke in
the Shack if a big electrolytic failed anytime (today? Next month?) being
so old, burning out the Main transformer with it, etc.
Enjoy the weekend guys!
73 de Rob
YS1RS
|
Rob, I, too have found cold solder joints on older rigs — as well as point-to-point wiring that wasn’t soldered at all and worked for over 45 years before finally failing!
I worked at Digital in the 1970’s and remember that QC was 100% visual inspection and then to test. If the unit passed, it went out the door. Sometimes, things get missed and they stay hidden for years!
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent from ProtonMail for iOS
On Fri, Apr 2, 2021 at 18:24, Roberto - YS1RS via groups.io < ys1rs@...> wrote: Was doing a quick recap after restoring this Drake L75 Amp.:
1- the two RCA connectors on the back of the unit (Vox Relay and Transmitter AGC) are too close together for comfort! ?I made the cable to connect to my Yaesu but both cables do not fit together. So I am using only the Relay. All the RCA connectors, locally sold, are intended for audio and those are the thick fancy type. Need to find old vintage RCAs to use here or build an “adapter” to connect my modern set of cables.
2- Had a lot of head scratching at the time of turning on the amp, after finishing the restoration. Had nothing on the meter. No activity at all. Though had failed with colors but at same time had relay activity and the humming inside sounded like all was ok, the fan was working and the power consumption measured was also OK. But still nothing on the meter... took the meter out and tested it outside and, to my surprise, the meter was not working but seemed mechanically ok. Well, found a cold solder on the connection of a small wire inside the meter! Had to take it apart completely and it was like working on an old clock mechanism. Slow and meticulous with magnifier glasses.?
Clearly this was a manufacturer’s failure.
Does anybody here has the warranty phone number from?Drake? LOL to claim warranty LOL?
Do you know (just curiosity) who made the Drake L75 panel meter? Simpson or maybe Weston??
Anyway was a great adventure to upgrade this.?
Now I know what I have inside and feel safer knowing that the components are new. Before was no guarantee I wouldn’t get a cloud of white smoke in the Shack if a big electrolytic failed anytime (today? Next month?) being so old, burning out the Main transformer with it, etc.
Enjoy the weekend guys!
73 de Rob
YS1RS
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Wow Steve! I bet this is really common... to find this kind of failures on old equipment as you said. Now I won't be surprised again. Never happened to me before with Collins but sure that doesn't mean anything. I am sure they were also plagued with problems too. Just take a look at all the Service Bulletins they published fixing lots of problems.
With Heathkit you expect surprises (like completely missing solder wiring up to wrong wiring) but never have had that experience because from day one I remove all components and start assembling again, using the manual and modern resistors/caps, etc. and I have had terrible failures of my own but was able to discover them on time. But this is the second time it happens to me with Drake.
Had another cold solder in my restored Drake TR-4C... a very small cap was not soldered at all in the center of one multiple connection points and was behaving erratic. One of those kind of failures that by giving a thump on the chassis will fix it. Any way, spent one hour just to finally find where the fault was and fixed it. This radio was in use here in YS for many many years. Too bad the SK YS colleague who once owned it was no longer available, to ask him if he had any troubles with it.
There is so much wisdom in this list guys!
Thanks for all what you share with us here.
73
Rob YS1RS
On Friday, April 2, 2021, 7:52:02 PM CST, Steve Wedge, W1ES/4 via groups.io <w1es@...> wrote:
Rob, I, too have found cold solder joints on older rigs — as well as point-to-point wiring that wasn’t soldered at all and worked for over 45 years before finally failing!
I worked at Digital in the 1970’s and remember that QC was 100% visual inspection and then to test. If the unit passed, it went out the door. Sometimes, things get missed and they stay hidden for years!
73,
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent from ProtonMail for iOS
On Fri, Apr 2, 2021 at 18:24, Roberto - YS1RS via groups.io < ys1rs@...> wrote: Was doing a quick recap after restoring this Drake L75 Amp.:
1- the two RCA connectors on the back of the unit (Vox Relay and Transmitter AGC) are too close together for comfort! ?I made the cable to connect to my Yaesu but both cables do not fit together. So I am using only the Relay. All the RCA connectors, locally sold, are intended for audio and those are the thick fancy type. Need to find old vintage RCAs to use here or build an “adapter” to connect my modern set of cables.
2- Had a lot of head scratching at the time of turning on the amp, after finishing the restoration. Had nothing on the meter. No activity at all. Though had failed with colors but at same time had relay activity and the humming inside sounded like all was ok, the fan was working and the power consumption measured was also OK. But still nothing on the meter... took the meter out and tested it outside and, to my surprise, the meter was not working but seemed mechanically ok. Well, found a cold solder on the connection of a small wire inside the meter! Had to take it apart completely and it was like working on an old clock mechanism. Slow and meticulous with magnifier glasses.?
Clearly this was a manufacturer’s failure.
Does anybody here has the warranty phone number from?Drake? LOL to claim warranty LOL?
Do you know (just curiosity) who made the Drake L75 panel meter? Simpson or maybe Weston??
Anyway was a great adventure to upgrade this.?
Now I know what I have inside and feel safer knowing that the components are new. Before was no guarantee I wouldn’t get a cloud of white smoke in the Shack if a big electrolytic failed anytime (today? Next month?) being so old, burning out the Main transformer with it, etc.
Enjoy the weekend guys!
73 de Rob
YS1RS
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Roberto - YS1RS
Jim Shorney