replacement cpacitors

a lot of ceramic caps suffer severe loss of capacity once a few volts are applied. If it works fine, great. If the limited amount of original bass has vanished, that might be why. If rf drifts all over the place as mains voltage varies...

It depends on the type of ceramic, some don't suffer this but most do.

NT

Mylar and polyester film caps are better than ceramic disk type for most pu rposes. Ceramic disk types are better than foil and paper if the foil and p aper caps are more than a few hours old.

This also applies to Russian PIO caps - the latest fad in boutique audio. T hey are no better than they should be, and, for the record, less safe and l ess reliable than their Mylar/polyester equivalents. What they 'sound' like is irrelevant as unless the initial quality is truly wretched, capacitors of any given class sound no different than other capacitors of that class, whatever the price-tag.

Correct value is the key, and then the environment and requirement for prec ision. Modern Silver Mica caps are very precise, very stable and resist he at and accept harsh environments. Then down the line to mylar, ceramic disc , polyester. But the reality is that a consumer-grade receiver is a very ge ntle environment overall.

Peter Wieck Melrose Park, PA

it also can cause nonlinear distortion if C is changing as signal voltage changes.

The other cap type to be a bit cautious of in valve kit is polystyrene, the dielectric has low melting point.

The issues with electrolytics & paper are relatively well known.

Oh, also beware of reduced voltage rails that go very high during warm-up. Caps there might need 400v+ rating despite running at 20v.

NT

Thanks, I may replace the 'replaced' capacitors with some of the 'Orange Drop' ones I have if I ever pull the receiver back out of the case.

I am using it a boat anchor station from around the time I was born along with a Johnson Viking ll transmitter. By the time I was old enough to get into electronics much had switched to solid state, but I did learn enough to do repair work but replace like parts with like parts except the paper capacitors with the newer tublar type. As mentioned electrolytics do tend to dry out after 50 years.

NB: the bar on Orange Drops is the side _away_ from the outside foil!

CHeers

Phil Hobbs

The author use a 5 digit "Gen Rad" LCR meter to demonstrate differences in various types tempcos.

.... Phil

WAAT! Why would they want to be different?

Dunno. I discovered this on Paul Carlson's YouTube channel--he made an outside-foil detector gizmo and tried it out.

Cheers

Phil Hobbs

It would have been a lot cheaper and more convincing to have sacrificed a c apacitor and open it up. If it were important, I would pay this price befo re I put my faith in a claim of a non-standard marking on the part, based o n the old adage that extraordinary claims require extraordinary proof.

Suit yerself, or watch the video. You probably don't believe that tantalums are marked on the positive side either. ;)

Carlson wanted a test gizmo for many caps used in his antique radio and test equipment restorations. Some of them are fun, though a bit slow-paced for experts, of course.

Cheers

Phil Hobbs