Hello all,
I picked up this unit dead. It's the Sonata version with 5 pairs of the obsolete K405/J115 OPT's. I found a pair of them were shorted, found a couple NOS on line, replaced them & all seemed well......at first. I was able to set the bias & play some music through it but the volume seemed a bit low. Anyhow, the next day I tried it again but after a few seconds my DBT went bright & I got a nasty hum through the speakers. I found I now have 60+vdc on the speakers outputs. I then did what I should've done first......pulled every opt & tested them instead of just finding the shorted pair & calling it good. I found two of the J115's tested with high voltage & another tested as a BJT.
I'll cut to the chase. I've learned through my searches that these opt's are hard to find......I paid $30 for the ones I found.......& that their replacements are also obsolete. I found an old thread here that suggested IRFP9140's would work but would need some modification on the PB's. I'm a novice, & this is a hobby........I've repaired some old receivers but am working with just a Fluke DMM & a component tester. My question is whether it would be better to replace all 10 pairs of OPT's in this with newer "replacements" & mods? I've learned that matching transistors is key, & I'm not sure that continuing to find/pay through the nose for the older units is the best long term fix.
I picked up this unit dead. It's the Sonata version with 5 pairs of the obsolete K405/J115 OPT's. I found a pair of them were shorted, found a couple NOS on line, replaced them & all seemed well......at first. I was able to set the bias & play some music through it but the volume seemed a bit low. Anyhow, the next day I tried it again but after a few seconds my DBT went bright & I got a nasty hum through the speakers. I found I now have 60+vdc on the speakers outputs. I then did what I should've done first......pulled every opt & tested them instead of just finding the shorted pair & calling it good. I found two of the J115's tested with high voltage & another tested as a BJT.
I'll cut to the chase. I've learned through my searches that these opt's are hard to find......I paid $30 for the ones I found.......& that their replacements are also obsolete. I found an old thread here that suggested IRFP9140's would work but would need some modification on the PB's. I'm a novice, & this is a hobby........I've repaired some old receivers but am working with just a Fluke DMM & a component tester. My question is whether it would be better to replace all 10 pairs of OPT's in this with newer "replacements" & mods? I've learned that matching transistors is key, & I'm not sure that continuing to find/pay through the nose for the older units is the best long term fix.
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