Polk PSW-505 BASH Repair
Thought I'd share this...I know a lot of common failures with BASH (DIAC, thermistor, IRF540 HEXFETS shorting, etc..great engineering these things LOL)! Anyways bought a used Polk PSW-505 off CraigsList this weekend with the expess purpose of learning to troubleshoot BASH symptoms-sold to me as LED powers on does not blow fuses but no output. This was indeed the case hoping to get lucky like a loose speaker lead or so...but no really little to no output. Tested using PA Tone app on my phone via minijack to RCA into sub as a signal gen.
Further investigation led me to examine the common semiconductors-nothing seemed out of place, no burnt resistors, no shorted MOSFETS, all diodes OK, so what's the deal? Next check out the radial lead caps on amp sub-board with my ESR meter (if you don't have one of these and you repair electronics I strongly urge you to buy one they're cheap)! Anyways, (4) dead or dying caps with high ESR or open altogether. Replaced 'em all, (8) in total 4.7uF, 47uF, 22uF, 100uF all 35/50V whatever I could come up with (suggest using 105C caps, can buy 'em cheap thru MCM or Jameco)..All working great! PS remove the brown goobered glue or whatever that stuff is becomes conductive over time!
Thought I'd share this...I know a lot of common failures with BASH (DIAC, thermistor, IRF540 HEXFETS shorting, etc..great engineering these things LOL)! Anyways bought a used Polk PSW-505 off CraigsList this weekend with the expess purpose of learning to troubleshoot BASH symptoms-sold to me as LED powers on does not blow fuses but no output. This was indeed the case hoping to get lucky like a loose speaker lead or so...but no really little to no output. Tested using PA Tone app on my phone via minijack to RCA into sub as a signal gen.
Further investigation led me to examine the common semiconductors-nothing seemed out of place, no burnt resistors, no shorted MOSFETS, all diodes OK, so what's the deal? Next check out the radial lead caps on amp sub-board with my ESR meter (if you don't have one of these and you repair electronics I strongly urge you to buy one they're cheap)! Anyways, (4) dead or dying caps with high ESR or open altogether. Replaced 'em all, (8) in total 4.7uF, 47uF, 22uF, 100uF all 35/50V whatever I could come up with (suggest using 105C caps, can buy 'em cheap thru MCM or Jameco)..All working great! PS remove the brown goobered glue or whatever that stuff is becomes conductive over time!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.