3below

Fretless P neck, anaemic finish, but given more with more yellow aged tint. Quality very good, nice to use, would buy another.

Had Peavey bass combo from 1983 to 2009. Never failed Really like my Tour 700 with Barefaced Big One, only downside is that it does not seem loud enough... pardon

Secondhand Eastern European, just keep looking until you find the one... ebony board, solid front (back if you want) etc.... remember accessories and setup also cost.

Have had the 'only a copy bass' about my G&L, had to smile then said nothing Would only take really good kit out somewhere safe, otherwise it has to be kit that can be replaced easily and cheaply.

Setups are an interesting point, both my basses have been done in the last few years, £40 a time which included fret levelling and profiling. I paid a fair price for the last one, having had it setup it is better than it was (A1 in fact). So if I sell what do I do, just take the hit or try and get the cost back. Can't blame people for asking, though it does depend on quality of setup. I just factor this into my buying price.

I have small hands ( and am vertically challenged - 5'3"), I find my G&L SB1 neck really easy to play. It also stays in tune impeccably and in some 26 years use the neck has had no issues whatsoever. I think it is great bass, plug into almost anything get good sound. My advice, try them all.

An excellent job well done !

[quote name='Musicman20' post='1313137' date='Jul 22 2011, 07:38 PM']What does it look like?![/quote] Pictures please

[quote name='Mr. Foxen' post='1309782' date='Jul 19 2011, 10:49 PM']Current state of play: Ordered bunches of caps, but are from hong kong, will be sorted for the next one, but I picked some up in maplins, and others from the spares box, to replace some on the pre board, along with replacing various resistors (carbon comps can apparently get noisy whilst still measuring fine, so putting all new ones in a few at a time between firing it up to check other stuff, if it cures all the noise, I'll stop, but looking like they'll all go). The only caps of the right value and high enough voltage Maplins had were Polypropylene box ones, so had to get a bit creative, some axials are on order. The pink one on the end of the board fixed the DC on the volume pot issue, no more horrible noise from turning it. Still have oscillation though.[/quote] Good progress, by pink one do you mean the rectangular Wima 0.022 ? Can't see clearly which terminal on volume pot connection made to, where is the cap on the 4.7k potential divider resistors between normal and brilliant volume, one end or in between the pair. Looking through the schematic I am trying to work out a) how the d.c. is getting to volume pot (was it one or both) and where it is coming from, decoupling again. If you look at V1 there is a potential route back to volume pots through either the (upper) 0.02 uF cap or the (lower) 1000pF cap. You could replace the two capacitors or investigate further. Disconnect your 'fix' at one end, and disconnect the wire that emerges from between the two 4.7K resistors. Clip voltmeter to ground and somewhere between cap and volume pot. You now need to work live so take real care !!!!. Switch on, hands well out. Check if any d.c. voltage present. Switch off, repeat same with other capacitor, care as electrolytic smoothing caps will be charged. Finally connect one end of voltmeter to the disconnected wire from 4.7K pair. Check for any d.c. here. These tests should let you know where d.c. is originating from, in theory Very nice 'new' noise free SC120 available soon courtesy of Mr. Foxen ??

[quote name='Mr. Foxen' post='1308465' date='Jul 18 2011, 09:45 PM']Swapped in a new volume pot, seems to be a lot more volume, a little abrupt, but I think it is just lots more headroom, rather than the glitchy jump, there is still crackle, as the new pot turns, so I think that is an issue, dc on the pots or something. Also, if you look at the right angle, through the little slots in the plate, there is a blue glow inside that pulses along with the oscillation. Might be normal, not had that much of my face up against the inside of an amp before. Counting from the left with the amp facing you, including the one on its own, it is the third in, I worked back from the phase splitter, pulling each at a time (much wincing at horrible noise, as it was live when I did it), I pulled two valves previous, phase splitter and the next one in, and the oscillation stopped each time.[/quote] Your description above suggests dc on the pots, its capacitors again (and / or design), I need to go and look in Merlin's book Designing Tube Pre amps for guitar and bass again - have mislaid in house so will not be tonight. He covers these issues. I will have to look at my sc120 to visualise which preamp valve it is, more to follow tomorrow. You are winning, and I must get started on mine.

[quote name='Mr. Foxen' post='1308404' date='Jul 18 2011, 08:47 PM']Opened it up, replaced some more resistors in the preamp bit because they had arrived, sprayed the volume pot with the crackle some more, the spray came out brown, so must be doing something, and stirred the wires round the phase splitter some. Fired it up again, no more moving cones, played a little, still fine, then I turned some knobs and post a crackly bit, it started again. It changed speed whilst I was fiddling with the mid knob, but I can't replicate that. The really loud crackle from the volume pot I know is duff really set it off. Have pulled pre valves till I find which one doesn't stop the oscillation, and it is the middle one.[/quote] Promising progress, when you say the middle one, V3, V4 or V5 phase splitter. Won't hurt to replace the 0.047uf, 400v mustards between the pre and power sections as you mentioned earlier. On the schematic there are several non electrolytics leading into V4, some have values on schematic some do not. If it is V4, replace these. The fact that you have stopped the oscillation and can identify where it originates means you can stop it (theoretically ).

Depending on which method you use, at some stage apply hot soldering iron to screw and get it really warmed up. Take care not to melt pickup if still in place. heat often 'breaks' the binding between screw and wood. Gives the easy out/ pliers/mole grips a better chance.

Had a pair of these circa 1977. Replaced with Acoustic 361 cab. Seemed better at the time.

In my youth a long time ago, Boz Burrell inspired my fretless playing. Not a cliche to me.

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.