Stereo2Go Forum Reader

seb968 - 2013-11-12 15:36

Hi all

I' beggining to see the light at the end of the tunnel as far as my M-70 repair but the left hand channel volume slider is faulty. It won't turn all the way down. The right one was the same but a dose of servisol cured it. Replacemet sliders seem to be difficult to come by. It appears that JVC sell them but they are out of stock! I understand that a number of you have fixed these. I just wonderd which method of repair worked best long term.

Thanks

Seb

michiel - 2013-11-12 23:53

You can open them up and clean them from the inside. It's possible to repair the carbon track, but you need a little luck for good results.

northerner - 2013-11-13 00:33

The track can be repaired with silver conductive paint if there's a minor break on it but you have to be very sparing otherwise the resistance goes out of whack and the volume levels will be uneven like mine was until I got a replacement. Very minor cracks can allegedly be filled with soft pencil...this comes from a tech who confirms it works but I've not tried it myself.

How are the resistance readings on it if you take it out...should be a 50k pot as far as I remember

I ended up getting a new (old) one from the states from someone who was parting out an M70...works perfectly now but took a long time to find the part

northerner - 2013-11-13 00:36

Not uncommon to have tiny hairline cracks at either end of the carbon strip...need to take the slider out and check resistance levels as your next step I reckon to see where the fault is

docs - 2013-11-13 01:11

Correct, you need to check resistence on the slider which should be 50k end to end.

You can check it from end to end (50k), from end to middle (25k) and from middle to end (25k) to identify precisely where the issue is. if those check out resistence wise then it is likely to be dirty and in need of a clean internally. They are relatively easy to work on once you have it removed.

michiel - 2013-11-13 01:36

Will ad that you not try to open them twice, because the little aluminum feet from the housing most likely will break the second time you open the slider

deliverance - 2013-11-13 02:04

do any of the other jvc models share the same slider i wonder ? might be worth looking into

michiel - 2013-11-13 02:30

I don't know about other jvc's. The M70 slider has a take of pin in the middle for the loudness function and that is what makes it special. None of the current slider they sell have this pin.

The M70 slider is made by ALPS. So you could use the sliding contacts from other vintage alps slider if they are broken.

northerner - 2013-11-13 03:00

I've got a few M70 rec level sliders...not sure whether any parts within them are interchangeable but you're welcome to one if it helps...they don't have the middle peg tho so not sure whether any bits can be used

seb968 - 2013-11-13 05:21

Hi all.

Thanks very much for all the info, very helpful. One pot is measuring 28K so the carbon track has gone just below half way. The middle connection does indeed make the part unusual. I don't want to loose any functionality least of all the loudness feature. There is a website called 4 our home who specialise in JVC spares. A very nice lady promised me that they could get these sliders (£9.75p each) within four weeks. However I am sceptical and will only believe it when they turn up! If they do; happy days. If not, I will have to go down the repair route. Thanks for the offer of the record level slider Si. I would like to take you up on that if the record level side of things is iffy. I don't think they will be interchangeable though unfortunately. Anyway I'll concentrate on cleaning the M-70 now and then shelve it until these parts (hopefully) turn up! I will also post what I have done to this machine so far along with the service manual. Then I've got repairs on a CS-600 and a Sharp GF-4343 to occupy me in the meantime!

Thanks again for all your advice, I very much appreciate it!

northerner - 2013-11-13 14:33

Hey Seb, doesn't take much to repair the track...clean it then dab as small an amount of silver conductive paint on the fault as possible and you're good to go. Might not be perfect but will be improved. On mine the two sliders had to be positioned slightly differently to get the balance right but it was waaaay better than the mono box it once was. Balanced now tho :-)

An alternative is that Norm (superduper on boomboxery) rebuilds the whole sound board on these and those who've had it done really rate it. Norm is the electronic wizard of that forum, he knows his stuff. Not sure of the cost tho.

seb968 - 2013-11-13 15:52

Originally Posted by Northerner:

Hi Si. I like the idea of silver conductive paint. I'm going to get some as a matter of course. Don't know if JVC will come up with the goods but even if they do I'm going to have a crack at repairing the existing sliders anyway. I'll hopefully have some spares then. (May as well, could come in handy for someone ellse!)
May have a word with Norm too, but see how it goes.

Thanks again for the advice