[Peter Wieck]

On Sunday, January 12, 2014 5:11:25 PM UTC-5, hugeshows wrote:
Ok, pics coming soon...



First step was to take voltage measurements off the bias and HV+ rails. Here's what I got on my S-5000. By the way, there are two variants of the S-5000 that I will discuss later, basically the older, longer version and the newer, shorter version. The one I am working on here is one of the shorter types.

A few things out in the deep background he

a) Voltages at the wallplate: These days, with average household electrical use being anywhere between 50% and 200% greater than it was when that Sherwood was 'new', Utilities that have not significantly upgraded their final distribution systems (most) have increased the voltage in those systems. It is not uncommon for us to see up to 130V commonly at the wallplate at our house these days. And 5% over the 'nominal' 120V would account for most of your B+ variations.

Do you have access to a variac such that you might reduce the input voltage to 115V or so (much closer to what would have been the case in the 1960s throughout most of the US)?

b) Selenium diodes decay over time (and when they fail it can be quite spectacular and leave you gasping in amazement). As they decay their resistance increases.

My guess is that your selenium diodes are 'out' about 10% - so the higher line voltage overcomes some of that. NOTE and WARNING: if I am correct in that assumption, those diodes are closing in on the failure point. Get that block (or individual units) replaced ASAP.

I am not above installing the occasional dropping resistor in some of my equipment that was designed against a typical wallplate voltage of 110V or so - most 'stuff' made in the 1930s and 1940s. Post WW-II, nominal was about 115V, into the 1980s, mostly around 120V. And from about 2000, commonly well over that voltage. Filaments do not like voltage in excess of their rating. 5% high typically will translate to a 40% drop in life. AND, despite anecdotal and cult beliefs to the contrary, nor do they like low voltage very much either. Look up 'lazy cathode' and other phenomenon along those lines. Generally, there is nothing much wrong with 5% low. Beyond that and the consequences are worse than the benefits. Interesting aside - clearing 'lazy cathode' (AKA 'rejuvenation' in some circles) involves running filaments at a high voltage under controlled conditions. So be aware.

c) Drifted resistors - resistor technology has changed (mostly for the better) since the 1960s. These days, even 'cheap' resistors are typically well within 5% however they are marked. But older compositions often drifted - usually higher. It is always a good idea to check all the resistors.

Best of luck with this - it is a worthwhile endeavor.

Hum in the pre-amp: Given the extra amplification of the phono-stage, it will exaggerate any hum in the system that may not show up at from the line-level inputs. But, as it happens, most sources of hum in the phono section will be related to bad shielding, and/or a shield that is grounded at both ends (or the one end that should be connected is not). Start with the simple stuff such as physical damage or a failed connection. Then, look for the obvious - caps.

Never mind Andre - he is neither of consequence nor any particular use. Note also that the pictures (of himself) he allows are over 30 years old... There is far more ego than substance going on there.

Peter Wieck
Melrose Park, PA