A Quadraphonic 8-track player: National Panasonic RS-845us

The JVC, my first 8-track

jvc ed-1240     IMG_20141125_161052

I possess one JVC 8-track player, the JVC ED-1240, a very nice and featureful deck.

The main reason I am interested into the 8-track world is, of course, the fact that aside from 4 track reel to reel tape, this is the only format that has discrete quadraphonic. I realise that the quality of the sound is not up to par like the Studer, or even a normal tape deck, but it will have to do 🙂

The first time I heard this 8-track deck i was very disappointed with the sound. So I found myself a challenge at hand. I have cleaned it, repaired it, refurbished the motor, changed the belt, demagnetized it, changed all the caps on the power board etc. etc. and eventually it performs quite well.teaser

tapes

I cleaned and repadded the 8-track cassettes that I have. I even found it necessary to lube the inside axis a little bit to prevent squeaking and to lower the rumbling and the mechanical noises from the cassettes while playing. The end result is quite pleasing I must say.

But there are still some issues with the player, so if anyone has the schematics, or the service manual, please contact me!

Quadraphonic 8-track

But this post is not about this deck. The JVC is just stereo. This post is about a new one I just bought. A few weeks ago I ran, quite to my surprise, into a quadraphonic 8-track player from National Panasonic, the RS-845us.

Here it can be seen on top of my JVC. At the moment the picture was taken, it was playing a quad tape as you can see by the ‘4 channel’ indicator light. In this mode there are only 2 programs, not 4 as you would find with a stereo tape.

problems ahead

But, alas, this player also came with its problems. I tested it before I bought it, and it was ok as far as I could test it at the time. Coming home, when I could test it for a longer period, I found the same issues I had with the JVC, like irregular tape speed etc. Also the sound was not as good as I was used to from the JVC.

So I did my usual fixup things, like cleaning everything, oiling etc. No good. I quickly found out that the voltage over the motor was dropping several volts at times. I suspected the power circuit board. So i tested the diodes, they were ok. I tested the caps and replaced them all nevertheless, although they were not really out of spec. Unfortunately, that did not help much. New belt. There was some improvement, yes. But still the voltage drop at times, from 12-13V all the way down to 6-7V. The motor would almost stop turning then. And it would squeak a lot.

motor fix

The solution would be to open up the motor and fix it there. That is always a bit tricky but I did it before and I therefore have some experience with the procedure. It went surprisingly well. There was some dust (powder) from the magnets and from carbon brushes. I also scraped clear the spaces between the 3 parts of the rotor (I think it’s called) so there would not be any more shortage. I reassembled a clean motor and lubricated it. When I tested it it it ran very smooth and silent. Cool! The tape speed is also a lot more constant than before. Also the sound seems to have some more punch to it. Maybe it has to do with improved tape-head contact, or with a more stable power supply to the audio board due to the changed caps.

audio fix

But I also have the capacitors ready for a complete overhaul of the audio prints. So somewhere in the next few days I hope I will find time to replace them and see if that will fix the muffled sound. I don’t expect a lot from that action, but hey, that’s what this hobby is all about.

[Update:]

Yesterday I did the recapping of one of the 2 audioprints, i.e. the print for the front channels. This is the result:

When I tested the audio after the process, I found that there was very little, if any at all, change in sound quality. I had made a ‘before’ recording so I could compare the sound.

So I am a little disappointed about that, but I guess the 8-track format was never intended for good audio quality, At least I didn’t break it. 🙂

So while I have all the caps here to replace the rear print also, I will not do that; too much trouble for little or no result…..

Anyway the unit is reassembled now and it playing happily.

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3 thoughts on “A Quadraphonic 8-track player: National Panasonic RS-845us

  1. Eero

    Hi. I have a similar RS-845. However, some bugger has removed the playback head and the seesaw part of the head moving mechanism. The rotating white plastic part and the solenoid are still in their places and work. Otherwise the player also seems to work ok.

    I can somehow imagine what the seesaw lever must look like. There must be a shaft or a piston that goes down the hole in the chassis. Then the seesaw lever moves the head up and down, as the white stepped “disc” rotates. The head moves vertically. You have taken your picture exactly from the right direction, but unfortunately it is not possible to see this detail from it. Could you be so kind and take a closer shot of the head moving mechanism? I’d like to reconstruct the missing part.

    As you say, this player is possibly not so high class, that it would be worth buying another wreck from somewhere to get spare parts, but as the player is otherwise almost ok, I thought I’d give it a try. A new playback head is not a big problem.

    Reply
  2. Vinny S.

    Hi, just curious if you could tell me where you got your new caps and which to use and replace? Mine just starting making a noise in my front left channel that just goes away after awhile of use…….like a static/crackiling sound. I suspect a capacitor is to blame, but I don’t know how to check them, other than for leaks. Anyways, I’d like to just go ahead and replace them all and (hopefully) use this deck for a while! Thanks!!!

    Reply
    1. PhilipAdmin

      Hello Vinny,

      Sorry for the late reply.
      I got my caps online, can’t remember where. I use a lot of different suppliers. Any will do.
      I did not make a list unfortunately, so can’t give you that.
      Replace them all is the best option, it won’t cost much and the deck will probably be better after that and will last another >40 years 🙂

      Reply

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