Hitachi KS-2400R receiver. Where is the documentation?

[vferdman]

Just picked up this little beauty in good cosmetic shape. Looks like it's intact, all original, no damage and only one lamp is out. What I am wondering is where can I find any documentation on it? I found a schematic for KS-2400H on Hi-Fi Engine, but nothing on KS-2400K anywhere. In any case, it's a real entry level machine with NO phono preamp. Yes, it has a Phono input and a selector position for Phono, but alas, it does the absolute same thing as the tape input, which it also has (no aux). I opened it up and confirmed that indeed, there is no electronics indicating the presence of a phono preamp. Oh, well, it's ok for me as I like the way it looks and do not need a phono input for how I want to use it. I measured barely 3 watts output before clipping a 1kHz tone. So I began by recapping the preamp (tone control) board. It had a lot of 3.3 uF caps that were way out (measuring closer to 6 uF) and some were just measuring like a resistor. I replaced all caps in there. Only the bigger 220 uF one measured ok (i replaced it anyway). Now I am measuring closer to 9 watts and I think that may be its limit as the back pannel states 30W AC consumption. Those lamps probably take 10W and the amp is likely on the order of 10W per channel. But again, no literature at all I can find. Anyone played with these? It's really well made despite being oblviously a lower end model. Also, what's up with no phone preamp? I was under impression that was standard equipment for those days, especially if it has an input with "Phono" marked on it. In any case, I like this little unit and will continue to bring it up to good working order. It sounds really nice, actually. I saw a big drop off in high frequency response before the re-capping. Haven't looked at that after yet. Also plan to recap the power amps. They look very simple and heatsinks are smallish with some Hitachi outputs. I just wanted to get my hands on a service manual for this guy. The build quality is outstanding. The front pannel is extruded aluminum, the case is steel and plywood. My copy is in excellent condition. I believe these are from early 1970's, so 50 years or so and pretty much everything works on it and looks really good. I'll post pictures once I put it back togther. It's a really nice looking unit. Black on black with nice green dial. Please chime in if you ever encountered something like it.

 

[eiraved]

Have you compared the schematic for KS-2400H with your KS-2400R? They may be very similar.
Chances are you won’t find much more than that schematic as the model is basically entry-level.

 

[vferdman]

Yes, I downloaded the KS-2400H document and yes, there is a nice detailed schematic in there as well as AM and FM alignment procedures. To be honest, there are no other adjustments anywhere on the amp section and (oh, no!) there is NO phono preamp even though there is an input marked phono. It goes to the same place as the tape input. No Aux input. I think the KS-2400H is very similar, at least the amp section. Not sure about radio. The power supply on the "H" schematic looks to have a lot more than mine, but I may be misreading things. I have not spent much time on it yet. I have replaced all the old 2SC458 transistors with blackened legs. It had a lot of characteristic crackling that was fixed by replacing those with modern replacements. But I am still struggling with very low power level. It seems to have a 12V swing on each side of the signal, so I expect something like 15 Watts per channel into 8 ohms, but I am getting under 3 WPC. I am still troubleshooting. Have not found too many faulty components save for some 3.3uF caps that were gone. I replaced all electrolytics on preamp and amp. It is very clean, but clips around 2.7 Watts (6V peak or so). This little unit is very well built and is a pleasure to work on. It's got way more sturdy construction than it needs to. It's basically built like a tank, but electronics are super simple. The power supply is unregulated as far as I can see. There is a 12VAC secondary for the lamps and the 23VAC secondary with half wave rectifier for everything else. No regulation I can see whatsoever. The FM receiver seems very good and is still pulling in stations that even my Marantz and Pioneer struggle with. So it's a solid little unit that should be about 10-15 WPC with no phono preamp. There are many applications for such a machine. Like a very nice shop unit. No need for turntable in there. And the phono input functions like an Aux, so you can have another source selectable. It is also a very nice looking receiver. It's got a very nice plywood case, which on my copy is in great shape as is the rest of the receiver. One lamp was out, but that's it. Meter works, stereo indicator works. Just need to figure out the amplification.