Panny NV-J35

[HamishBoxer]

I did always use Duraglit for the cleaning of the lower drum but Brasso should be ok I guess.

[welbeck5]

Thanks mate.
I used the Brasso, but it hasn't made much difference so far.
What I have noticed, is a tiny imperfection on the lower drum.
Looks like it's been damaged in the past, maybe by a slipped screwdriver.
It's a tiny small dent (maybe less than 1mm wide) and running my finger across it's raised and is postioned on the right side where the tape runs across.
Obviously it might still not be the culprit, but do you think there's anyway to smooth this out?
If not, I'll put the machine away and keep a look out for a VEH0386 drum.
I've tried to capture the damage in this photo.

[HamishBoxer]

I will stick my neck out and say possibly, very fine wet and dry emery cloth, see if anyone else has a better idea.

[welbeck5]

Originally Posted by HamishBoxer

I will stick my neck out and say possibly, very fine wet and dry emery cloth, see if anyone else has a better idea.

Cheers, didn't know you could get an emery cloth.
The other possibility I was toying with, is to swap out a lower drum from one of the donar G decks I have, but uncertain of the fittings, they may be different and if they're not, how easy is it to prise apart the upper and lower drums?

[Maarten]

The upper drum is removed by sucking away the tin on the 4 pins that stick through the PCB from the head posts. Make sure the pins can move freely so they will not snag when removing the head. I always used desoldering wick for that. Then, unscrew the 2 phillips head screws and pull up on the upper drum.

There's also a special pulley-puller for that, with two M3 screws that screw into the upper drum.

[Nickthedentist]

Yes, I would have thought if you were thinking of polishing the lower drum, removal of the upper drum and heads would be mandatory, to save wrecking the head chips!

[TIMTAPE]

I would be reticent to polish the lower drum unless that was the problem. I was just looking at one of my VHS VCR's which has had low use. It's hard to photograph it but under magnification there can be seen many fine parallel lines milled into the lower drum surface where the tape runs over it. This would have been machined in the factory. I wouldnt even think of polishing them out.

[TIMTAPE]

Just following on from this, the normal action of playing tapes actually polishes the heads, guides, drum etc to a fine mirror like finish. But normally surfaces meant to be polished came ex factory in that polished state. Normally there shouldnt be a need to polish such surfaces unless they have become corroded, scratched or roughened in some way.

Some Sony Betamax machines developed problems when after many tapes were played the lower drum became more polished than designed. The solution was to either replace the drum with a new drum, or failing that to actually roughen the drum surface to about the same degree as the new part.

[welbeck5]

Just been changing the 400v1uf cap in another j35 I have and the cap the previous repairer put in was a 100v2.2uf .

[HamishBoxer]

This just a start up cap for the power supply and well worth changing anytime on Nat Pans.

[welbeck5]

Originally Posted by HamishBoxer

This just a start up cap for the power supply and well worth changing anytime on Nat Pans.

Yes, I was just amazed the primary cap had a completely different rating to what the spec says, yet didn't cause any noticeable probs sort of makes a mockery of the design, guy obviously knew it would be ok.

[Maarten]

I think the original value might have been 1u 100V or 160V in early models, so it probably doesn't see 400V normally, but will last longer if the right value is used.

2u2 versus 1u might not have too much effect on the circuit, just that a 1u was a bit cheaper and a higher value wasn't needed.

[welbeck5]

Has anyone tried these digital handheld oscilloscopes?
For my purposes, just wandering if it would be best to shell out £40 - £50 on one,
rather than buying a 30-40 year old analogue behemoth for twice the price (judging by prices I see).
I'll just need it for adjusting the p2 and p3 guides and the ACE using the technical manual.

[HamishBoxer]

Yes, I have on here and not really used it too much yet, sig gen, scope and multimeter 3 in 1.

It was on Ebay at the time at £53 but now back at around £90. Aliexpress has varying prices on it but I was unable to buy as said account closed, most odd as I did not have an account. Previous comments under Modern Technology on it, worth a read.

[welbeck5]

Originally Posted by HamishBoxer

Yes, I have on here and not really used it too much yet, sig gen, scope and multimeter 3 in 1.

It was on Ebay at the time at £53 but now back at around £90. Aliexpress has varying prices on it but I was unable to buy as said account closed, most odd as I did not have an account. Previous comments under Modern Technology on it, worth a read.

Thanks, I'll go over to Modern Technology and see what they're saying.