ChrisP2
Member
Lots of time to spare so just tackled a shorted out SA-6500 II that was collecting dust and thought I would share some notes:
On BIAS, original reading was ~100 mV across the test points, I lowered R65/R66 from 39 Ohms to 15 Ohms to get the bias voltage back into a reasonable range ~35 mV on each side.
Did not tackle a full re-cap, only so much time/$$ to spare. Did end up pulling and replacing all of the in-path tantalum's and the orange electrolytic caps while I was in there and replaced all with Nichicon KW. Interestingly, everything I pulled measured just fine.
Face place on this one is minty, very nice sounding amp!!
Mouser # Customer # Description
863-MJE15033G Q17,Q18 Bipolar Transistors - BJT 8A 250V 50W PNP
863-MJE15032G Q19,Q20 Bipolar Transistors - BJT 8A 250V 50W NPN
567-175-6-210P Q17-Q20 Thermal Interface Products INSULATOR
647-UVZ1H682MRD C57/C58 Aluminum Electrolytic Capacitors - Radial Leaded 50volts 6800uF 22x50 20% 10LS
512-KSA1013YTA Q13,Q14 Bipolar Transistors - BJT PNP Epitaxial Transistor
512-KSC2383YTA Q15,Q16 Bipolar Transistors - BJT NPN Epitaxial Transistor
512-KSA992FBU Q7-Q10 Bipolar Transistors - BJT PNP Epitaxial Transistor
- One of the original bat-wing 2SB616's was shorted, took out the driver as well, both dead shorts.
- Replaced all 4 outputs, drivers, and differential pairs, parts list below.
- MJ's mounted to heat-seat on Sil Pads in new holes, not too difficult to pull heat sink and drill. Line up the bottom of the MJs with the bottom of where the bat-wings sat and you will the right lead length.
- Note the insulators and mounting screws are from the old bat-wings. Not having any TO-220 insulted bushings around, I ended up cutting off the tabs from the plastic bat-wing mounts (which have bushings) and used those, worked fine.
- New Filter Cap Leads bent to get the lead spacing right, couple of spots of hot glue, worked out fine. No need for all of the old filter cap mounting hardware, so pulled it all.
- New Indicator LED as well 8V 4mm Warm White w/leads from Dave Wojo.
On BIAS, original reading was ~100 mV across the test points, I lowered R65/R66 from 39 Ohms to 15 Ohms to get the bias voltage back into a reasonable range ~35 mV on each side.
Did not tackle a full re-cap, only so much time/$$ to spare. Did end up pulling and replacing all of the in-path tantalum's and the orange electrolytic caps while I was in there and replaced all with Nichicon KW. Interestingly, everything I pulled measured just fine.
Face place on this one is minty, very nice sounding amp!!
Mouser # Customer # Description
863-MJE15033G Q17,Q18 Bipolar Transistors - BJT 8A 250V 50W PNP
863-MJE15032G Q19,Q20 Bipolar Transistors - BJT 8A 250V 50W NPN
567-175-6-210P Q17-Q20 Thermal Interface Products INSULATOR
647-UVZ1H682MRD C57/C58 Aluminum Electrolytic Capacitors - Radial Leaded 50volts 6800uF 22x50 20% 10LS
512-KSA1013YTA Q13,Q14 Bipolar Transistors - BJT PNP Epitaxial Transistor
512-KSC2383YTA Q15,Q16 Bipolar Transistors - BJT NPN Epitaxial Transistor
512-KSA992FBU Q7-Q10 Bipolar Transistors - BJT PNP Epitaxial Transistor