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Drake L4B linear Amplifier how to install Harbauch Soft start and soft key module and some ranting

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Turns out my Soft start did not work as R9 on the Harbauch board was missing and this
bnew out the UJT Q1 transistor.
So waiting on a new Q1 and a 10K R9 resistor from Harbauch.
I should have NOTICED the empty R9 resistor was not soldered in.
I simply plodded along.
I did get ONE soft start OUT of the board haha the first and only soft start before Q1 blew up.

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16 дек 2023

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Комментарии : 6

@MontyGore-dt8vx 6 месяцев назад

I have several of the big power supply resistors if you need one.

@moviestudioland 6 месяцев назад

Thank you. Got a few from mouser. Amp got sold on eBay. All my big power is gone. Sb200 toy amp now

@hunt555fish 7 месяцев назад

I just installed a soft start soft key from Harbach but have not been able to get it to close the relay on the L4B.Checked the relay with my bench supply.Applied 24 volts DC to the coil and it works fine and contacts close.I get almost 10 volts showing on the vox relay connector on the back of the L4B.My Icom 7300 was not keying the amp relay.I took the vox relay connector to ground on the back of the L4B and relay still would not close.I am showing about 22 volts DC on the soft start soft key board going to the standby switch on the L4B.Not sure yet if the problem is in the Harbach board.

@moviestudioland 7 месяцев назад

Hey buddy. Check that R9 is not missing. R9 is a 10K resistor. This many have blown up either Q1 or Q2. Make sure you have a 24 ohm large resistor for 240 volts AC. Make sure you have a 12 ohm resistor if you are running on 120 volts A/C. See my next video on how it works. See the video after that for how the board should look.

@moviestudioland 7 месяцев назад

First check all the wiring. Link on schematic here: harbachelectronics.com/wp-content/uploads/2020/11/ES4L-4B-v1.0.pdf Note the schematic is missing R9. Also make sure R9 is in there - it is a 10K resistor.

@hunt555fish 7 месяцев назад

@@moviestudioland Thanks for the reply.I talked to Harbach and told them all the tests I ran and the problem must be in the board.He said they have gotten some bad Q1 on the board and are sending me a replacement board.The soft start was not working either.When the on switch was thrown the plate meter went to 1500 volts fast and and did not pause and go up anymore.After I saw how your voltage acted after throwing on switch I new there was also a problem with the soft start protection.Everything led to a problem on the board.