3below

Serious answer now, depending on the plastic, several years under tensile stress may cause compressive creep. The plastic will deform and flow even though the forces (hence stress) are well below the yield stress. So lowering of nut slot is quite possible irrespective of any frictional wear.

[quote]Do Nuts Wear Down?, Looser and Lower[/quote] Just a male thing with age I am afraid. Learn to live with it, or get a young thing.

[quote name='Mr. Foxen' post='1298890' date='Jul 10 2011, 11:58 AM']Would out of spec resistors in the pre cause the oscillation? That's the problem rather than noise, the noise is ok currently.[/quote] The theory suggests so, courtesy of Merlin, [url="http://www.freewebs.com/valvewizard1/smoothing.html"]Valve Amp Power Supplies[/url], it is a good book, highly informative and readable. The RC network is a [url="http://en.wikipedia.org/wiki/Low-pass_filter"]low pass filter[/url] since you want to pass d.c. (0 hz) or nearly d.c. only. From a pragmatic angle, you have replaced all electrolytics and still get the motorboating / LFO. This really only leaves three options- either faulty resistor(s), decoupling capacitors need to be larger or amp has inherent design flaw. Once you know that the power supply resistors are OK, then you might be able to find the 'faulty' pre amp stage by measuring the plate voltages (HT) on each pre amp stage and looking for a significant discrepancy - the soundcity site LB120 schematic has the reference voltages for these points. I do remember that using a choke instead of the 100R resistor between plate- and screen supplies has been suggested [url="http://audiopaja.ws/gpage3.html#Sound%20City"]here[/url].

[quote name='Mr. Foxen' post='1298684' date='Jul 10 2011, 12:40 AM']All of the electrolytic capacitors were replaced at the start.[/quote] I remember that you mentioned that earlier, a good decision. Satamax's advice on Vintageamps about lead dress is well worth exploring. To minimise coupling you want wires crossing at right angles or if they must run (semi) parallel get as much distance between them as possible. Oscillsocope and looking at the B+ waveforms from the power supply filtering is where I would start, then looking for any 'ripple' on the signal chain. If you lived nearer I would borrow a 'scope from school and help out on this one. The 'brute force' method would be to unsolder one end of each resistor in the power supply section (one at a time). check that the resistor is in spec, then resolder. Check the 100R and 6K8 resistors that connect through standby to output transformer centre tap. If these check out OK you will have to plough through the pre amp sections for resistors out of spec (or poor joint). This is where the 'scope will speed matters up no end by helping locate the stage where the problem starts at. Keep posting the progress.

In order of cost effectiveness [list] [*]Unplug instrument cable [*]Place cabinet speaker side down to floor [*]Send Mrs out shopping [*]Buy larger house [*]Divorce [/list]

The symptoms are described here [url="http://www.scribd.com/doc/55820085/73/Stability"]Valve Amps[/url] page 410. The problem is not new [url="http://vacuumtubebrasil.profusehost.net/Hi%20Fi%20amplifier%20instability.pdf"]Radio and Television News 1955[/url] The encouraging answer is found here [url="http://www.geofex.com/ampdbug/mtrboat.htm"]Ampdbug on Geofex[/url]. Whether we consider that a Sound City 120 "has ever worked correctly once" is another matter Hope this helps.

[quote name='Mr. Foxen' post='1298304' date='Jul 9 2011, 04:13 PM']Having a little play with this now the switch is replaced, an some resistors replaced to clean up some hiss. Noticed a new problem: the speakers are moving in and out really slow, too slow to make noise, like 5hz or something. Any clues?[/quote] My first guess would be some ac ripple 'artefact' due to poor filtering that is getting into signal circuit. I use the phrase artefact since you would expect ripple at 100 Hz or mains hum at 50 Hz. This sounds like 'motorboating', possible cures are changing plate resistors, screen resistors, and decoupling capacitors. however before diving in you can try and isolate the input stage it happens at by removing preamp tubes in turn. At this point it is time for the oscilloscope and start looking at the waveforms at various points in the circuit. It might just be a poor solder joint on a resistor or capacitor rather than a failed component. Your noise reduction reports encourage me to get started on mine, and the summer hols are only 4 days away.

Later thought - lessons in our part of the world, no idea, self taught electric bass player 40 years, DB player (beginner) 17 years. Someone on the forum suggested this [url="http://www.amazon.co.uk/Rufus-Reid-Evolving-Bassist-DVD-Reid/dp/B0000X02OQ"]Rufus Reid - the evolving bass player[/url] . I found it is a really good buy, I had been doing it wrong for many years, it has improved my physical technique beyond belief (sounds like an email scam).

The plywood base (9mm?) could have some angled wood wedges glued/screwed on to support the PB pickups at the correct angle. Cable tie and ply base idea came about because I do not want to put screw holes in my pristine ebony fingerboard. (if you want a possible diagram, pm me) If you had an electric bass, guitar, mandolin etc I would highly recommend Tony Revell, Montgomery, in Mid Wales. If anyone can suggest / recommend a luthier for DB setups in Mid / West Wales or West Mids I would like to know.

[quote name='oldslapper' post='1297555' date='Jul 8 2011, 07:26 PM']Not sure about that, others here may know. I think one of the advantages is that you can angle the pups to follow the curve of the board....roughly.[/quote] Absolutely correct. Make up a rectangular plywood board, same width as fingerboard and about 6" long. Screw PB pickup on one end. Cable tie to fingerboard with two ties - non damaging attachment. Adjust PB pickup heights, solder jack socket somewhere and enjoy. Cheap bar magnet types (so no pole alignment problems) are available on the bay. Alternatively wait until a Schaller appears here. Many thanks to oldslapper for mine

Both routers and chisels are nice. Try out what you want to do on scrap wood of the same type as body (guitar) with both methods. Try several times. Then make your decision and go for it. Practice four times, measure twice, cut once (in an ideal world). Router is a great tool but I am so very aware of the damage one can do, think clamps, bit snatching and SAFETY at all times.

And of course [url="http://www.weber-amps.de/en/index.html"]Mywatt[/url] [url="http://www.reevesamps.com/"]Reeves[/url] But why buy new, there are still good deals out there, just wait long enough, search hard enough. My greatest regeret, Hiwatt 100, Hiwatt 200, Marshall Plexi, all sold at silly (cheap) money in my youth (70s,80s) because they were widely available and you could not give them away at the time. Hindsight - the most exact and useless science.

Find a good woodwork shop, ask them to cut the 'cutlist' parts. Get glue, clamps etc and get sticking. If not confident ask woodshop to glue cabinet, chamfer sides etc. Blue Aran - 3015LF, 18 sound 6", T nuts etc. and Tuffcab. Speakerhardware.com for crossover, either loose components (if good with soldering iron) or pre made - easier than sourcing in UK. Paint cab with Tuffcab - I used a sponge pad, looks just like tolex, easy to do. Seal edges of plywood with PVA first, otherwise you get sinkage Get metal grille made, fit all parts, staple polyester wadding inside and way to go. You will be impressed with tone and power handling. make sure you have sufficient Watts available. Total cost £375 to £475 there is a Barefaced Big One on the forum at the moment (or there was yesterday) - might be worth looking at, it is essentially the same thing.

Looking at the DIY can capacitor, I wonder if you could fit them inside 35mm plastic piping. If so you could glue a pipe end cap on and have a low cost tidy can capacitor. Might work, might not.

Keep the details coming, I need to do some work on my (unmolested, bedroom condition, bargain of a lifetime,) SC 120. Will be interested to see how the noise level pan out, mine is noisy when not playing. Tip 1: get a temp controlled soldering iron and damp sponge pad Tip 2: Solder suckers are good, de-solder braid is also excellent for final clean up of tricky parts Tip 3: Flux paste of the correct type

Pricing / costs are going to be a serious factor, particularly in these times I thought about building a fEARful, however was able to purchase a used Barefaced Big One for less than parts cost. When I started to build BFM Omni 15 a rather nice example came up on BC for less than parts cost. Look long and hard at which models you offer and make sure you can make a profit. Business is tough at the moment as my other half ois noticing. Alex has succeeded, so can you. Good luck if you go ahead.

Hard case every time, unless it is a £30 type bass (yes I am increasingly enjoying the Peavey Milestone Jazz clone). Having seen a car go over a Les Paul in a puny case it is a no brainer.

[quote name='daz' post='1264138' date='Jun 10 2011, 04:56 PM']answering my own question. this site may be of interest (i've not looked yet. but its the cab designers site) [url="http://greenboy.us/fEARful/"]http://greenboy.us/fEARful/[/url][/quote] You got there before me, it has all the essentials. There is also a [url="http://greenboy.us/forum/"]forum[/url] and at present it has a vastly better signal:noise ratio than the other talking bass site. I can not rate my Barefaced Big One highly enough - the best cabinet I have had in 37 years of bass playing. Great sound, loud, light and small (relatively). From what I read the fEARful 15/6 etc. have the same broad design goals, I look forward to finishing and trying my fEARful (stacked with Barefaced = fill venue with bass).

[quote name='solo4652' post='1263408' date='Jun 9 2011, 10:53 PM']*Convulses with laughter* Build your own?!! For me, DIY = Destroy It Yourself.[/quote] Unlucky or A lucky break? Plan B, find a good woodworking type, give plans,exchange cash - still way cheaper than purchasing. YMMV. Like the definition of DIY, will have to get this one in circulation at work

Not that I am a great bass player but having had one I now find I can get a near enough Ric sound with my G&L. The G&L also does other stuff. It is also better built, has not started to fall apart and suffer vast amounts of paint sinkage unlike the 79 (approx) Ric I had from 1980 to 1990 or so. When they have : A better bridge for comfort and adjustment A better bridge pickup surround for comfort I might consider another one. It played very well, stayed in tune impeccably, and I really liked the tone. I just keep listening to Deep Purple, showing my age. Why do players leave them? like bicycles, guitars and amps you can not have enough.

Barefaced Big One does all my stuff, and it's lightweight. Alternatively build your own 15/6 fEARful - plans etc on the web. The Big One does like a lot of Watts if you want a lot of volume (filling hall with 900+ people - loudly).