looking for a new switch for a Drake L4B. The one in it now is arcing when turned on. Need a replacement or a suggestion for a new switch.
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Drake L4B
- Thread starter Crusher
- Start date
Wish you luck on finding a replacement, none made in many years.
What some are doing is installing a DPST 30 amp relay for the main power and using a simple spst switch to control the relay.
The whole current surge goes through the switch on those old Drake's. Eventually the switch breaks down or arcs like you are describing.
What some are doing is installing a DPST 30 amp relay for the main power and using a simple spst switch to control the relay.
The whole current surge goes through the switch on those old Drake's. Eventually the switch breaks down or arcs like you are describing.
Yeah I might have to go the DPST switch. This Drake has the big oversized transformer. So can only imagine the inrush current. Already replaced bad electrolytic in bottom. Found a bunch of oil so replaced it. It was a 100uf @ 50V. Pulled and checked, only reading 1.9uF. The hint was the bottom was full of oil. The amp is in mint condition. Hate to have to modify it in anyway.
If you can get into the switch and clean the contacts you might be able to save it if you also install a soft-start system from harbach
These switches worked very well
Prepare to pay $100+ for a new switch...IF you can find someone willing to part with a new one...There are no suitable replacements...
WB4HFN Home Page*** Drake Techni
Only mod I did not do...Wish I had and but I will, if I have to do any additional work on her later...Other owners say it can increase tube life 20% or more
Harbach Electronics - Soft Keys
These are a must have kits for a retro build on the L4B...Jeff's are the best I have seen...
http://www.worldwidedx.com/amplifiers/64758-i-finaly-got-done.html
My retro build...
The oil on the bottom most likely came from the RF Filter feed-through Caps...Check the large: 1mf/ 250 VAC at 20 amps...The orange seal rings: Bulges/tears? Cracks or Bulges in cases? They will need replaced...Again hard to find...
No standard electrolitics can handle the filament current the 3-500's require and I would give you odds that's where the oil came from!
GL
All the Best
BJ
Prepare to pay $100+ for a new switch...IF you can find someone willing to part with a new one...There are no suitable replacements...
WB4HFN Home Page*** Drake Techni
Only mod I did not do...Wish I had and but I will, if I have to do any additional work on her later...Other owners say it can increase tube life 20% or more
Harbach Electronics - Soft Keys
These are a must have kits for a retro build on the L4B...Jeff's are the best I have seen...
http://www.worldwidedx.com/amplifiers/64758-i-finaly-got-done.html
My retro build...
The oil on the bottom most likely came from the RF Filter feed-through Caps...Check the large: 1mf/ 250 VAC at 20 amps...The orange seal rings: Bulges/tears? Cracks or Bulges in cases? They will need replaced...Again hard to find...
No standard electrolitics can handle the filament current the 3-500's require and I would give you odds that's where the oil came from!
GL
All the Best
BJ
Well I took switch apart, the side that had the cw/ssb wasn't too bad. Cleaned up. Basically as shown in previous post. The main on/off switch, well I cleaned it up best I could, but I don't have my hopes up. Used brass brush on dremel and polished the 2 bars up nicely. The tab on the inside, used a 7/32" polishing stone and just barely hit the tops to get a clean surface. But the power switch had to hit pretty good before I even saw surface. Put it all back together and gonna order soft start before I go any further. Also you were correct. Small residual oil on feedthru caps. I am sure these are shot. Probably have to run a set of leads thru. Tubes did light up, so I have filament voltage, but think I can leave then or run new wire to be safe?
if you get the soft start then just leave the main switch on and use an outboard terminal strip with its on-off switch or wire it to allways on and use the terminal strip
I traced the black wire back to the terminal strip. Should be able to install a heavy duty 30A switch on power supply. Should take care of my problems. Between switch and soft start, should be good to go. Hopefully after cleaning up cw/ssb switch, it should be fine. I hope.