Hello, I found an HK570i at a second hand store that obviously had an issue but for $5.00 US I thought I'd give it a shot. Got it home and plugged it into the DBT (dim bulb tester) and "bright light!". So I started checking things out. I found two of the four output transistors were shot and many of the associated driver transistors were as well. I had suitable replacements on hand and now I've got good voltages (...w/ the dbt of course) all around but the thing that's got me stumped is this: C8, one of the power supply caps will not discharge when the unit is powered down. In fact it'll hold it's negative supply charge of (~ -36V) all day long. I've checked and rechecked, thought and thought some more and now it's time to ask for help. Even though I've got expected voltages from the supply through the preamp and amp circuits currently this cap issue is something I've not run into before and don't want to take it off of the dbt before asking for help. By the way all of the other caps discharge readily. And I've also replaced C8 and it's 3 other comrades just to rule them out.
Here is a link to the SM: https://www.hifiengine.com/manual_library/harman-kardon/hk570i.shtml
Whatever the recommendations my be I'm willing. If this isn't the best way to post a help request please let me know the correct way. It's not a mint unit but it does seem like it wants to live again. If anyone has a minute and could lend a hand I'd appreciate it.
Thanks much, Mark
Here is a link to the SM: https://www.hifiengine.com/manual_library/harman-kardon/hk570i.shtml
Whatever the recommendations my be I'm willing. If this isn't the best way to post a help request please let me know the correct way. It's not a mint unit but it does seem like it wants to live again. If anyone has a minute and could lend a hand I'd appreciate it.
Thanks much, Mark