Hey all,

I was trying to record a radio program yesterday on my JVC RC-M70, and I noticed when I press down the record button, the tape just plays - no recording. Is there a common cause for this problem?

Thanks!

Did it ever record and did someone replace the belts? Cause it almost sounds like the record/playback switch is not being activated. That switch is also commonly referred to as the record bar and is a long ginormous multi-pole switch mounted on the PCB, and which is lever activated when the record button is depressed. If the record bar is not being thrown, that could explain it.

Whew, its hard to tell. The tape deck is really buried inside there, and partially beneath a circuit board. When looking closely, I can see that there is one mechanism activated when pushing the play button, and then another different mechanism activated when pushing the record button. There are parts and levers moving when record is pressed, but still no sound ends up on a blank tape, from either radio or line-in.

OK. Maybe I got confused. You mentioned that when you press record, the tape just plays - no recording. Are you saying that the tape spins or actually plays? Because the play/record bar switches the modes. So if you can actually playback a tape in the record mode, then something is wrong there. On the other hand, if it doesn't actually play anything during record but also doesn't record anything, then either the record bar is seriously dirty and requires serious cleaning, or my guess is probably a defective bias oscillator.

Here are the possible causes:

Defective record/play head
Defective bias oscillator
Record/play head dirty
Defective cassette tape
Defective record slide switch

I tried recording over a Memorex tape that already had music on it, but it just played the music already on it. I've tried a few different cassette tapes, so unfortunately, the problem isn't that easy. I'll try cleaning the record head, but I have a feeling the issue is larger than that.

quote:

Originally posted by Salavatin'Army:
I tried recording over a Memorex tape that already had music on it, but it just played the music already on it.

That's what makes me think the record bar is not being switched. The reason is that the same heads perform both record and playback functions. During record, the current is reversed and the source becomes the mics in tape mode. No way should it be playing the program currently on the tape if it was in record mode. So that's what I'd check. Perhaps whoever did the belts did not put the mechanism back properly and so the lever that operates the record bar (the long horizontal bar mounted on the PCB) is not being thrown into the proper position.

I had another look, and I think I see a board way below the cassette mechanism inside. But quite frankly, I think if I attempt the daunting task of disassembling everything, I'm just going to break the m70 worse. Or I wont be able to get it back together.

I believe you were the last person to work on my m70. I wish I would have checked the record function before I sent it off to you, ha ha! Heh, I also wish I would have gotten you to do one of those paint jobs on it. I'd love a royal blue coat on my m70.

quote:

Originally posted by Salavatin'Army:
.........I think if I attempt the daunting task of disassembling everything, I'm just going to break the m70 worse. Or I wont be able to get it back together......

I believe you were the last person to work on my m70. I wish I would have checked the record function before I sent it off to you, ha ha!.

Yep. That has happened to more than one collector before. You are either mechanically inclined or not and if you're not or don't feel comfortable, go with your gut because it's probably right.

As for your M70, yes, that's correct. I fixed the items you indicated you wanted fixed. If I recall, I asked about the cassette but you said it was working fine so I didn't even bother to look at that area other than to confirm that it works after the voltage regulator was repaired. The diodes and other toasted components didn't require disassembly of the cassette area. Well, if you want a minty fully restored/upgrade painted M70 -- you might get that opportunity someday. Ya never know.

Yep, no blame - you did a great job. I just wish I would have thought of those 2 small details before I sent it off to you.

Actually, I think last week is the first time in all these years that I've tried to make a tape on my m70. I dug out my service manual from storage. I dunno... maybe I'll flip through and see if I can muster up the confidence to find the record bar. The m70 does have a great tuner on it that picks up the semi-local college station (none of my other radios do) that I'd like to record some shows from.

Ok, I braved it and opened up my m70. Here's some pics of the cassette mechanism. Let me know if you see anything that doesn't look right. I can't see anything that looks obviously loose or out of place

I think what stormin normin is trying to say that there is a bar that comes off the record switch/button on deck and has to slide into a long silver switch bar (on pc board) with an attachment so when you hit the record button the record bar switch moves to switch record on Also looking at your pics the large wheel is missing for the flat belt Norm I believe is on vacation...Good luck

Bill is right. The record bar I'm talking about is nothing to do with the cassette mechanism. In fact, the mechansim has to be mounted in order to see if it's linkage is meshed correctly with the record bar on the PCB. Look at the following image. It is of an M70 without the back. The arrow is pointing to a double row of solder pads. Those are the leads to the record bar switch. It has multiple poles that are all flipped simultaneously when the tape switches from play to record function. It is hard to see because with the mechanism installed, it's sandwiched but you can see it on the other side of that board if you look carefully from the underside. It has a spring loaded slide that is pushed sideways when the tape is put into record mode. You will somehow need to observe with the mechanism installed to verify that the switch is actually "thrown" when in record mode. When in record mode, the boombox should only playback the source being recorded whether it is radio or aux. If set to tape in the record mode, the source becomes the built in microphone and the boombox should be silent while recording.

Hey there Stormin,

I finally got around to checking out the record bar switch - and, you were right! I saw the spring loaded slide and lined it up with the lever, and presto! The tape is now recording from radio & mics. Excellent.

One final question: in your photo above, in the upper left corner there are two little metal "tabs" pointing to the left. I have two loose wires in my M70, and I'm trying to find out which wire goes to which tab. One wire is black, and the other is green, I believe (might be orange - not sure. Color blind). The black wire is coming off of the removable back of the m70. The green wire is connected to the inside of the front of the unit - to plastic, right above the right speaker. The lower tab does not seem to be connected to any other wires underneath the PCB. The upper tab has a wire connected to it underneath the PCB. Again, not sure of the color of the wire underneath. Could be either green or orange. Anyway, I was thinking black wire = lower tab, green wire = upper tab. But then, they both seem to be ground wires, even the green wire, which doesnt really seem to go anywhere - its just fastened to the plastic chassis above the speaker. Or maybe I need to hook the wires up somewhere totally different? I just want to check & make sure so that I don't damage anything.

Thank you!

Of course I'm right!

As for the 2 grounding tabs. You are correct in that both tabs are grounded. But the official designated routing of the wires is that the top tab is destined for the rear cabinet shield and the lower tab is for the front shield. They ground the shields to reduce interference and to prevent the large panels from acting like antennas.