bigdano123
New Member
Hi everybody.
I'm new to this forum, but have been following many posts for a while now. Let me start out by saying that I am not a technician as, it appears, most folks posting on this forum are. I have a basic understanding of electronics and am pretty good with a soldering iron and have a DMM and a fairly good soldering station. I'm not blessed with the many technical tools that a technician would have, nor do I have an understanding of how to use them.
I have a Phase Linear 300 series 2 that has been giving me fits. It sat in a closet for many years. I finally decided to pull it out and see if it still worked. I powered it up and was greeted by a lot of smoke and sparks. Of course, I immediately unplugged it and took off the bottom cover to see what the damage was. The 0.33 resistors on one of the channel boards were fried and the 220 ohm resistor under the power transistors was also toast. I checked the power transistors first, per the service manual, and found that all of the power transistors on that channel were shorted. I disconnected the toasted board and powered the unit up again. Thankfully, I was no longer greeted with any smoke or sparks. I checked for no DC at the outputs and found none. I hooked up a source and plugged in a (disposable) speaker. The remaining channel worked with no problem and the sound was good.
At this point I decided it was best to try and completely rebuild the amp. Rebuilding only one side seemed like a stupid thing to do, so I ordered a cap kit, a semiconductor kit and also 5% metal film rsistors to replace all components on the boards. I was also able to find 746A's and 706A's to replace the shorted power transistors. After carefully replacing all the components per instructions that came with the kits, and carefully replacing all the resistors, I installed the replacement power transistors. I reassembled the unit.
With great apprehension, I powered up the amp. No sparks or fire (thank goodness), but the relays would not latch up. Without the relays latching up, I knew it was useless to try and plug in a source or speakers. I have been racking my brain to try and figure out what went wrong, but have no idea. I decided to check the power transistors again, per the service manual, and found that all of them, on both channels, were now open. The manual states that between the collector buss and the emitters, I should be showing between 400 and 700 ohms. On all power transistors, both channels, I am showing hundreds of Kohms of resistance.
I know the first response I will get is to take this to a shop. I'm in central Texas and I know of no place anywhere near me that works on Phase Linear equipment. Plus, I'm retired and live on a fixed income so there is not a lot of disposable income to work with. I would like to get this amp working before I try and tackle a bigger project, a PL Dual 500 that has one good channel and one that has very low volume and major distortion in the other (thinking it is probably bad caps).
I have rebuilt my JBL L220's due to massive water damage, my Infinity RS III's and my JBL 4312's and hope I can get something going to power them. Any assistance I can get here would be great. Thanks for taking the time to read this rather long post.
As my high school chemistry teacher used to say: "There are no stupid questions, only stupid answers."
I'm new to this forum, but have been following many posts for a while now. Let me start out by saying that I am not a technician as, it appears, most folks posting on this forum are. I have a basic understanding of electronics and am pretty good with a soldering iron and have a DMM and a fairly good soldering station. I'm not blessed with the many technical tools that a technician would have, nor do I have an understanding of how to use them.
I have a Phase Linear 300 series 2 that has been giving me fits. It sat in a closet for many years. I finally decided to pull it out and see if it still worked. I powered it up and was greeted by a lot of smoke and sparks. Of course, I immediately unplugged it and took off the bottom cover to see what the damage was. The 0.33 resistors on one of the channel boards were fried and the 220 ohm resistor under the power transistors was also toast. I checked the power transistors first, per the service manual, and found that all of the power transistors on that channel were shorted. I disconnected the toasted board and powered the unit up again. Thankfully, I was no longer greeted with any smoke or sparks. I checked for no DC at the outputs and found none. I hooked up a source and plugged in a (disposable) speaker. The remaining channel worked with no problem and the sound was good.
At this point I decided it was best to try and completely rebuild the amp. Rebuilding only one side seemed like a stupid thing to do, so I ordered a cap kit, a semiconductor kit and also 5% metal film rsistors to replace all components on the boards. I was also able to find 746A's and 706A's to replace the shorted power transistors. After carefully replacing all the components per instructions that came with the kits, and carefully replacing all the resistors, I installed the replacement power transistors. I reassembled the unit.
With great apprehension, I powered up the amp. No sparks or fire (thank goodness), but the relays would not latch up. Without the relays latching up, I knew it was useless to try and plug in a source or speakers. I have been racking my brain to try and figure out what went wrong, but have no idea. I decided to check the power transistors again, per the service manual, and found that all of them, on both channels, were now open. The manual states that between the collector buss and the emitters, I should be showing between 400 and 700 ohms. On all power transistors, both channels, I am showing hundreds of Kohms of resistance.
I know the first response I will get is to take this to a shop. I'm in central Texas and I know of no place anywhere near me that works on Phase Linear equipment. Plus, I'm retired and live on a fixed income so there is not a lot of disposable income to work with. I would like to get this amp working before I try and tackle a bigger project, a PL Dual 500 that has one good channel and one that has very low volume and major distortion in the other (thinking it is probably bad caps).
I have rebuilt my JBL L220's due to massive water damage, my Infinity RS III's and my JBL 4312's and hope I can get something going to power them. Any assistance I can get here would be great. Thanks for taking the time to read this rather long post.
As my high school chemistry teacher used to say: "There are no stupid questions, only stupid answers."