tuttebenne
Active Member
Was gifted a Hitachi HMA 8500 Mk II preamp and amp by a friend who needed to downsize. Cool looking amp with those huge meters. I am preparing it to hand off to my brother. The preamp had some issues with the controls. Deoxit fixed most of them but there was an issue where the amp would trigger into safe mode. Previously I found that any noise in the controls would cause the amp to go into safe mode. A little fussing with the cartridge matching switch indicated it was the only control that was still noisy but no amount of cleaning would take care of it. This led to disassembly and the discovery of two cold solder joints on one of its many switch points. They are fixed and now, so on to the amp.
Oddly (at least to me) many of the high current and some low current connections are wire wrapped around pegs rather than soldered. Connections from the two transformers to the power supply section, to the four meter lamps and to the four banks of output transistors are all examples of where Hitachi chose to wire wrap rather than solder. This just is odd to me. I have seen wire wrapping in low current applications but not in an amp. Does this sound like something Hitachi just got wrong? The amp has been exhibiting a slight flutter when at medium and high volume but I couldn't really nail it down to one channel or the other. At first I thought that maybe after years of inactivity, the caps needed to fully stabilize. Well I have used it a few times now and the flutter was still there till last night. What I did was solder each of the wire wrapped connections (not fully, just at the tip of each wrapped coil. Now there is a soldered connection between each wire and its respective pin. Could this have actually been the problem?
Oddly (at least to me) many of the high current and some low current connections are wire wrapped around pegs rather than soldered. Connections from the two transformers to the power supply section, to the four meter lamps and to the four banks of output transistors are all examples of where Hitachi chose to wire wrap rather than solder. This just is odd to me. I have seen wire wrapping in low current applications but not in an amp. Does this sound like something Hitachi just got wrong? The amp has been exhibiting a slight flutter when at medium and high volume but I couldn't really nail it down to one channel or the other. At first I thought that maybe after years of inactivity, the caps needed to fully stabilize. Well I have used it a few times now and the flutter was still there till last night. What I did was solder each of the wire wrapped connections (not fully, just at the tip of each wrapped coil. Now there is a soldered connection between each wire and its respective pin. Could this have actually been the problem?
