Philips N4307 problems
 

Hi, I've recently adopted this machine from my late father-in-law. He hadn't used it for forty years so it needed what I now understand is the usual clean up and replacement of belts and clutch rubbers.

Everything now seems to work as it should except the brake on the left spool, which isn't sticky enough to stop it quickly from fast forward. Even after lightly sanding the "pad" (to make sure no belt goo was left) I really can't see how the cardboard/wood material will ever stop the shiny plastic spool mount fast enough when spinning at speed. And there only seems to be a small spring pulling it into place.

I've tried searching the site and can find mention of both rubber and cork pads being used by others. Does this mean the pads should have a rubber lining (perhaps that's why they needed cleaning?) or are they made of cork that seems to have hardened over the decades? Or perhaps I'm missing something else?!!

Any help on this would be very welcome. Thank you.

Re: Philips N4307 problems
 

The cardboard actually should work pretty well . On all the ones I have it does . enough to stop it spooling the tape off anyway . I have a few of these and I have just cleaned them up and made sure the mechanics all work ok and I`ve not had any issues with them . Maybe you could take a pic of what you have and we can advise further .

Re: Philips N4307 problems
 

This is the supply turntable brake arrangement. The brake "pad" is some sort of friction material. There is an adjustment in the service manual, which consists of bending the narrow part (to the right off the brake pad) that slides along the slotted bracket until a certain clearance is achieved. I'd have to find the service manual to give any more detail. It could also be due to hardened grease under these sliding brackets increasing friction and slowing down the movement of the arm/pad when stop is pressed after fast forward winding.

Re: Philips N4307 problems
 

Thank you both for the replies. Here's a photo of mine, but it does look very similar!

The mechanism seems to be moving freely - it snaps back immediately I press stop. I wonder if it should have more than just that thin spring (to the left of the pad) pulling it towards the spool. Perhaps the bracket mechanism, which is also sprung, should be forcing them together, in which case the adjustment you mention could help.

If you do find any instructions on this it'd be very useful :)

Re: Philips N4307 problems
 

Ahh , the problem you are having is all that black stuff on there , its belt goo and gets every where . Acetone will get rid of it . Thats whats making the brake not work though . Damn stuff is a pain .

Re: Philips N4307 problems
 

It certainly was everywhere! But I'm not sure that's causing the brake problem, Dave, as I lightly sanded the friction surface to get it clean. It's not really visible in the photo but there's no goo on the important bit and the mechanism's moving freely. It just doesn't seem to have enough friction against the plastic to stop it quickly.

Re: Philips N4307 problems
 

Here is the adjustment detail for the turntable brake. I agree that you need to clean off any liquefied drive belt/turntable clutch residues from the brake "pad" and the turntable (but be careful, don't use Acetone on plastic parts, as it may well damage them!).

Re: Philips N4307 problems
 

Thanks Dazzlevision. My gap is within the range they specify so no need to adjust that, it seems. The black you see on my brake pad is just a bit of staining on the side. The friction surface is clean, as is the lever mechanism. It all moves very nicely and snaps "shut" when I press stop.

As I said before, I just don't see how there's going to be enough oomph in that small spring on the left to stop a (relatively) heavy tape reel quickly. The right brake operates completely differently and presses very firmly on the turntable. I don't understand why they have different mechanisms on each side, but I know there will be a good reason!

Re: Philips N4307 problems
 

It's due to the direction of rotation. If the feed is on the left and transferring tape to the right hand side then the left spool needs a stronger brake than the right and visa versa. Otherwise the feed may release more tape than the receiving end can spool. That's why the cam shape self tightens.

Re: Philips N4307 problems
 

As coincidence would have it I had to perform this very adjustment last week. From stop mode, first push the LH brake pad in the direction of the arrow. Then bend the indicated tab with pliers until the RH brake is within a millimetre or less(!) of the RH spool table. You'll have to do a bit of tweaking and trial and error.

I had to extend the spring as mentioned above because there was still spillage with 7" reels. I just hooked it around the pivot point just visible on far left of image. It's still not 100% perfect but a whole lot better.

Re: Philips N4307 problems
 

When they are working right they are actually really good.

Re: Philips N4307 problems
 

Well, I've made some progress. I've found that switching the two turntables over (so the one with the brown felt circle underneath is now on the right and with the white circle now on the left) has greatly improved things.

The left spool still overruns a little after fast forward, but nothing like before. The right spool is a little slow to get going on starting to play, so the tape goes a tiny bit slack between it and the roller for a second or two, but these are pretty minor issues. Not sure if there's an easy solution to the latter?

I imagine the two turntables got switched at some time - surprising that it makes a noticeable difference but I suppose they were made differently for a reason!

Thank you everyone for your contributions. And if anyone has a suggestion about the slow take up, I'd love to hear.

Re: Philips N4307 problems
 

There were at least two configurations for take up. One has a separate pulley fed IIRC from the capstan, and this in turn drives TU with a belt from there. The other uses a belt between motor pulley and spool table. If yours is the latter then that belt could be a bit weak.

I have not ever swapped spool tables so cannot comment, but it'd be a fairly safe bet that if the take up started promptly before the swap, then this is likely the cause. Differences in height or contact area of parts may play a role.

Re: Philips N4307 problems
 

Moving on from the spooling issues, which are now reasonably under control, I'm having a problem with playback levels.

Basically, the old recordings I adopted and a new one I've just made myself are both playing back clearly, but far too quiet to be of any use. That's both through the built-in speaker and using an external amp. I understand the DIN socket output should be line level and therefore not need any pre-amplification, but even if it did, that wouldn't explain why the level of the built-in speaker is also low.

It seems the tape player's own amplifier isn't boosting the signal to the extent it should. Is there anything obvious I could look for here to either test it or rectify the problem?

Re: Philips N4307 problems
 

Play a known good tape on it. If the volume through the speaker is low, then you have the problematic germanium transistors with tin-whiskers.

A quick test is to disconnect them one by one form the heat sink and test. There are two o/p and a driver IIRC.

Re: Philips N4307 problems
 

Thanks Ben, that's really helpful.

I wasn't familiar with tin whiskers but, having looked up some of the discussion on it, it's fascinating stuff!

More investigation needed...

Re: Philips N4307 problems
 

You might find this thread helpful: https://www.vintage-radio.net/forum/...d.php?t=114678

Although it is about an N4308, they are very similar. The N4307 audio output stage uses a smaller (lower power output) transistor pair.

Re: Philips N4307 problems
 

Thanks for this - some very useful background info there. Will report back in due course...

Re: Philips N4307 problems
 

I need to ask for more help, please!

I'm now trying to identify the transistors, with a view to replacement to see if I can overcome the low output problem.

Although there seem to be more on the N4307 circuit diagram, the only ones I can find are the three indicated on the photo. The one in the middle is marked AC188/01 but the other two don't seem to have any markings.

Can anyone confirm these are likely to be the ones, and if so, how do I identify the part number?

Re: Philips N4307 problems
 

added info to picture