In this video we take a quick look at the Drake L4B with solid state relay failure. Support us on Patreon; / theradioshop Contact Information; gokarters.com/smf/index.php?to... Discuss this on my website; www.gokarters.com/smf
Good to see no major damage was done. Had to laugh when you said the owner turned it off and retreated to the other side of the room. Reminds me of the first time I accidentally installed a high voltage electrolytic cap backwards. Surprising how much steam and noise a 100uF 500V cap can make. I swear to this day I still cringe a little when I first turn on something tube type after recapping it.
LOL. I do the same thing every time I rebuild a unit like this. You are right about those caps exploding. Remember the old Sprague 500 volt caps with the paper cover?, Man those would let a lot of smoke out.
Hi Buddy Another great repair and so informative. It is wonderful to watch you work and thank you for explaining everything so carefully for us. So many know so much more than me but it is nice how you make it relevant to experienced and non experienced. My best to you today. Mel
Had a resistor smoke when working on my Military signal Corp R336 receiver. Apparently it had been used as a test radio for techs a total of 9 wires were found cut. The worst being inside a big IF can all the screws were unscrewed from the cover and 5 wires cut then it was was screwed back down. That relay sure did make a nice fireworks show and a bit scarey for sure. Glad you were able to fix it and get it up and running again.
Good job on that L4B, Buddy. It is always a pleasure to watch someone like yourself that knows what they are doing. Mt amp is the old Heathkit SB-200. She has a few issues that I haven't figured out how to fix yet, both mechanical. One problem is the TUNE knob is stuck on the shaft and the set scew is broken down inside the knob. I think I am going to have to butcher the existing knob to get it off, then replace it LOL. Thanks for the video. 73 DE K7RMJ Frank
Another good one Buddy. My current amp is a TENTEC Centurion. I have an Alpha 76A and a 30L-1 as backup, to bad the Collins don't do 160. Thanks for the look under the L-4B.
Yes high voltage is dangerous. Nice amp to go along with the Drake collection. Wait a while for the cap's to discharge. I have worked on SB-200 and FL-2100B always remember about discharging the high voltage after the power is turned off. Thanks Buddy for a very good video
Good job Buddy.I wanted an L4B for the shack,but sense I use a LDG pro 1000 auto tuner,I settled for a SB1000.Added a soft start ,a wafer on the selector switch and a little solder work and it been a good amp.73 from Ronnie
Great video Buddy, it is so strange that you would do this video since last week about this time I turned on my L4B with the solid state relay in it and the same failure happened. It took me a bit more testing and checking to fix it and make sure I had solved the problem than it did for a pro like you. Keep the quality videos coming I enjoy them more than any other videos on RU-vid.
Kevin, personally I think you are better off NOT doing this electronic relay mod. You can obtain the exact results this mod deals with by making no mods to the amp itself. You would be much better off simply making a cheap external on switch for the amp by switching the line voltage to the amp cord and leaving the switch in the ON position on the amp. It accomplishes the same thing and you will probably NEVER have a fault like this. Better yet a TRUE step start circuit is still better yet. I would not recommend this mod with other better options available.
Great video Buddy. I would also like to see exactly how you discharge all of the caps before you start. I have an Ameritron AL-811H that is fine but if I ever take toe cover off to clean dust and such I would like to know the high voltage is gone. Thanks for sharing. Enjoy all of your videos alot.
Hi Buddy, Talk about high voltages, was working on my SB221 about 20 years ago and thought I had bled off all the high voltage. Well, there was still several hundred volts and when my hand came in contact the jerk back caused my hand to hit the chassis and slice open the side of my hand. Needed a dozen stitches to close the wound. At least I had survived and it was an unexpected learning experience. 73 WB3BJU
Wow Donald. Horrible experience for sure. That is mostly the problem with getting hit by something like that. If the current don't get you the obstacles in the way will. Never liked working on the SB221 series.
Ha! Reminded me of turning the HV on my HB pair of 3-500z s once and a big bang. Instead of smoke though, dirt went flying everywhere. A dirtdobber had built across the diode connections. Vaporized that poor fellow. I just recently did the Harbauch mods to my 4-LB. Love that amp, but wish it had 160 meters. Again, nice video Buddy.
Nice fix Buddy...usually the 0.82 ohm "safety resistor" in the HV supply is what pops. I've been maintaining and fixing my L-4B since I bought it new in 1979. The Harbach soft start kit is what I have installed in my two L-4Bs. Just about everything that can go wrong has done so at one time or another but that amp just keeps on purring and the only microprocessor installed in it that can burp is the one between my two ears! ;-) 73 - Dino KL0S
Thanks Dino. I will say they are one of my favorite amplifiers to work on. Had plenty of those 0.82 ohm resistors blow. I think I still have 50 or so of them in stock. One thing about it, these amps can erase that micro between the ears.....
That's for sure, if you're not comfortable around VERY high voltage leave it to someone who is - it WILL KILL YOU. I've rebuilt several L-4BPS power supplies for folks and even replaced one of my supply's transformers with a higher voltage unit (Hammond makes them now; a couple of KL0S Shack Notes describing that fix is on the WB4HFN website along with another about a fix for the 3-500Z socket to fix the tube pin problem you described).
Thanks Buddy for the upload, can tell me how you can check the vswr through the input tuned circuit with the power off, I have an sb220 and need to adjust the input side for 80m as it's a little high but am a little nervous to do it while the full 3k volts are on. My best regards,hope your keeping well, Carl.73.
I have a Drake l4b unkeyed I have 80-something V DC bottom of the tube when keyed it goes to zero not getting my 3 V zener good yellow word seems to be dead out of the Transformer is this the problem or not
Buddy, It looked like the diode that you checked after the 1N4007 was shorted. The meter read zero ohms (or close to it) from the digits that were visible on the video (8:49). That would explain the blown resistor. Have a look and see if you agree. 73 de Randy wb0smx.
Just me, I hate the design of the SSR DC control voltages. The DC control components are connected directly to the 220 mains and are unisolated and unfused. This also seems to be the case in the original one that blew up and is what will happen when one goes south when it is hooked directly to the mains. I would think a redesign using a 12v transformer to drop the voltage and isolate it from direct 220 contact would be in order instead of a resistive / zener dropping circuit connected to the mains. This transformer would provide isolation if something where to go south, plus I would add a fuse to the hot side of the transformer for more protection too. I also think if that's too much, one could use an AC controlled SSR instead of DC. An AC controlled SSR is designed and legal to hook to the mains. IMHO this DC configuration being used is dangerous and illegal. IMHO
Easy jobs are good. You are correct. The normal house hold voltage is 120 volts here. But all the higher amp stuff uses 220. Like the clothes dryer, water heater, heating unit. And in the shop the AC welder, Air Compressor.
That delay relay is still too fast. If you can hear the transformer clank you are damaging th ac power switch. You cant even find the rebuild kits for the switches. I had at least 5 kits and 10 switches. I wish I knew you sooner. 73 W5DN
