Whats the value of a Fender bassman?

[Subthumper]

Hi folks I've just been offered a 77 Fender Bassman 100w head. Although it was initially brought to me for repair-needs a new set of valves and some resistors replacing-about £80+ ish to fix, I have no idea what its value is. Does anyone out there know what the value of these old beasties is? I'm very tempted as I've been hankering after a valve amp for some time.
Cheers Just
Ps Have just seen a completly original mint condition 1960 bassman combo on ebay. They are asking over £9000......

Edited October 16, 2008 by Subthumper

[Mr. Foxen]

As with anything, its value is whatever someone will pay for it. Think one went for around £300 here, but might have been a different rating or something. Think its a good one to have. If you can get it for current sorta rate - repair cost, and play and use it for a few years, you are likely on a winner if you want to move it on then.

[Hamster]

£300 - £350 is about the right money for an original amp with no issues.

[molan]

I think the combos go for silly money to guitarists, not sure they are that great for modern day bass use.

Heads are a different matter of course.

[Thunderhead]

[quote name='Subthumper' post='308229' date='Oct 16 2008, 10:43 PM']Hi folks I've just been offered a 77 Fender Bassman 100w head. Although it was initially brought to me for repair-needs a new set of valves and some resistors replacing-about £80+ ish to fix, I have no idea what its value is. Does anyone out there know what the value of these old beasties is? I'm very tempted as I've been hankering after a valve amp for some time.
Cheers Just
Ps Have just seen a completly original mint condition 1960 bassman combo on ebay. They are asking over £9000......[/quote]
That's a completely different thing - although it was designed as a bass amp and can still be used as one (for a very specific, old-fashioned sound at pretty low volume) it's really a guitar amp nowadays, and is highly desirable for that. Even then it sounds like too much money.

A 70s Bassman 100 head is worth, as Hamster posted, about £300 to £400 - possibly a little more if in fully overhauled and excellent cosmetic condition, but no more than £500 even for the very best example. This makes them among the best value for money valve bass amps.

£80 sounds a little low to replace all the valves - there are four 6L6s and three 12AX7/12AT7s, although you almost certainly don't need to replace them all. In particular, do NOT replace the preamp valves unless they are faulty - the original US-made ones can very well be in perfect working order even now and will sound better than any new-production ones. The same even applies to the power valves if the amp has not been used that much, although they do wear out somewhat faster - but again, original US-made 6L6s outperform and outlast any more recent versions. It's a complete myth that valves need replacing 'regularly' - they don't unless the amp is being used VERY regularly.

But, if the amp is a '77 and has never been overhauled, you should budget for replacing the filter caps since they will be at the end of their life expectancy and could fail without warning. Electrolytic capacitors DO degrade simply with age, and actually worse if the amp has not been used regularly than if it has. Even if they don't fail, you will get better performance from the amp with new ones (especially for bass - some guitarists like the sound of tired caps). You need to replace all the caps in the tray under the chassis, the bias cap on the little board near the power light, and if you're being really thorough, all the preamp cathode caps on the main board. Don't replace any non-electrolytic caps unless they're failing. This job is about £100-worth too.

The resistors that need replacing are most likely the power tube screen resistors, and it's a good idea to at least check the power tube grid stopper resistors while you're at it (these are the smaller ones under the screen resistors and easier to get at when those are out) since these can also crack with the heat from the valve over time and if one fails you will blow the valve. If in any doubt, replace them. Use modern metal-film, metal-oxide or wirewound resistors for the screen resistors and metal-film or carbon-film for the grid stoppers - these are much less prone to heat damage than the original carbon-comp type. Changing them does not affect the tone in this location.

Hope that helps! (I do this sort of work professionally by the way.)

Edited October 17, 2008 by Thunderhead

[Shaggy]

[quote name='Thunderhead' post='308357' date='Oct 17 2008, 09:00 AM']That's a completely different thing - although it was designed as a bass amp and can still be used as one (for a very specific, old-fashioned sound at pretty low volume) it's really a guitar amp nowadays, and is highly desirable for that. Even then it sounds like too much money.

A 70s Bassman 100 head is worth, as Hamster posted, about £300 to £400 - possibly a little more if in fully overhauled and excellent cosmetic condition, but no more than £500 even for the very best example. This makes them among the best value for money valve bass amps.

£80 sounds a little low to replace all the valves - there are four 6L6s and three 12AX7/12AT7s, although you almost certainly don't need to replace them all. In particular, do NOT replace the preamp valves unless they are faulty - the original US-made ones can very well be in perfect working order even now and will sound better than any new-production ones. The same even applies to the power valves if the amp has not been used that much, although they do wear out somewhat faster - but again, original US-made 6L6s outperform and outlast any more recent versions. It's a complete myth that valves need replacing 'regularly' - they don't unless the amp is being used VERY regularly.

But, if the amp is a '77 and has never been overhauled, you should budget for replacing the filter caps since they will be at the end of their life expectancy and could fail without warning. Electrolytic capacitors DO degrade simply with age, and actually worse if the amp has not been used regularly than if it has. Even if they don't fail, you will get better performance from the amp with new ones (especially for bass - some guitarists like the sound of tired caps). You need to replace all the caps in the tray under the chassis, the bias cap on the little board near the power light, and if you're being really thorough, all the preamp cathode caps on the main board. Don't replace any non-electrolytic caps unless they're failing. This job is about £100-worth too.

The resistors that need replacing are most likely the power tube screen resistors, and it's a good idea to at least check the power tube grid stopper resistors while you're at it (these are the smaller ones under the screen resistors and easier to get at when those are out) since these can also crack with the heat from the valve over time and if one fails you will blow the valve. If in any doubt, replace them. Use modern metal-film, metal-oxide or wirewound resistors for the screen resistors and metal-film or carbon-film for the grid stoppers - these are much less prone to heat damage than the original carbon-comp type. Changing them does not affect the tone in this location.

Hope that helps! (I do this sort of work professionally by the way.)[/quote]
Stonkingly good advice which I wish I’d known years ago. Just to confirm your observation on pre-amp valves; one of the three in my late ‘70’s Bassman 135 is “Fender” branded and so probably original, and the other two Mullards which I don’t think have been made for donkeys’ years – still going strong.
So how would you know if the non-valve components were starting to fail (capacitors etc) – how would it affect the sound / operation of the amp?

[Thunderhead]

[quote name='Shaggy' post='308389' date='Oct 17 2008, 09:58 AM']Stonkingly good advice which I wish I’d known years ago. Just to confirm your observation on pre-amp valves; one of the three in my late ‘70’s Bassman 135 is “Fender” branded and so probably original, and the other two Mullards which I don’t think have been made for donkeys’ years – still going strong.
So how would you know if the non-valve components were starting to fail (capacitors etc) – how would it affect the sound / operation of the amp?[/quote]There are often no very definite warning signs for cap failure (unless you can compare the tone to an amp where the caps have already been changed, which you will find makes it sound stronger and more punchy) - but any tech will tell you that old filter caps do often fail, and that it's better to change them before they do rather than afterwards as they can occasionally damage other parts, or leak nasty corrosive gunk everywhere.

You'll hear varying advice on their life expectancy, but in my experience thirty years is a good point to take for when a routine cap job should be done - they can and do fail before that, but not very often. Up to twenty years I normally wouldn't bother unless there's strong evidence that more than one cap is failing. But this means that all Silverface and earlier Fender amps are now very nearly due or overdue.

A lot of people (guitarists mainly!) seem to worry about it affecting the 'vintage tone' of their amps, but I've actually never heard an old amp that didn't sound better after a cap job, even if it already sounded great before! (Although 'better' is a matter of taste, certainly.)

The resistors which are likely to need changing are the screen resistors and grid stopper resistors, because they get cooked by the heat of the valves - in fact, screen resistors often fail when a valve blows, and in a four-valve amp the owner often doesn't notice because although it stops the replacement valve working too (but doesn't damage it or blow the fuse again), that isn't obvious from the sound at least at lower volume - it is in a two-valve amp since then one half of the output waveform is cut off.

Preamp plate resistors often go bad too - they drift in value and get noisy, and if your old amp is randomly hissing and crackling it's fairly likely that these are the cause. You need to use the proper original carbon-comp type for these to keep the 'vintage' tone, although carbon-film and metal-film aren't bad-sounding (don't use metal-oxides in the signal path though, they sound awful). I wouldn't change resistors ONLY because they've drifted a bit, but if they're approaching double the marked value they are definitely on the way out.

If the pots have become 'scratchy' when turned, this is most likely NOT a pot problem! It's all too easy to change the pots to 'cure' this and find it doesn't, and then most techs won't put back the original parts (or at least not to the same standard of workmanship). If cleaning them with contact cleaner/lubricant doesn't work, it's usually caused by DC leakage through the tone stack caps.

Old Fenders also have a nasty problem called 'board conductivity' which is when the waxed fibreboard eyelet board develops very slight (incrediby high resistance, you can't measure it directly) conductive paths through it which are enough to leak small amounts of current when subjected to the high voltages in a valve amp. This problem is difficult to identify - usually you can only be sure once you've eliminated all the resistors and caps, but the usual symptoms are also random crackling and noise, odd tone or in rare cases even instability and self-oscillation. Fixing it isn't always easy without quite a lot of work either.

One other important thing to check in an old amp is the fuse - over the years many get 'fixed' with much too high a value, or at worst some idiot wraps a blown fuse in foil or sticks a piece of guitar string down the fuse holder to 'keep it working'. This just means that the next time something goes wrong, something much more expensive will fry instead. In fact with export-model (with the rotary voltage selector) Fenders in the UK, the labeled fuse value is too high anyway since it's a universal value that will work at 110V too - you're better reducing it to half the marked value for 240V, since it's the only protection the amp has (there's no HT fuse on old Fenders).

[Shaggy]

Thanks for that Thunderhead - an imminent visit to my tech methinks! That info should really be pinned for posterity somewhere
NB; I confess to being the idiot doing the silver paper/fuse thing, just once, just to get me though a gig! :wub:
.

[Thunderhead]

[quote name='Shaggy' post='308671' date='Oct 17 2008, 03:26 PM']I confess to being the idiot doing the silver paper/fuse thing, just once, just to get me though a gig![/quote]Did it?

If so, you're very lucky. It must have been a bad fuse (they do exist, although nowhere near as common as most people think when they say that meaning that it blew) or a momentary surge that didn't damage anything.

What normally happens is that there is a fault with the amp, so the fuse blows. The musician then wraps the fuse in foil to 'get through the gig', and when they turn back on again the fault is still there, but the fuse can't blow this time, so something really expensive (like the mains transformer) acts as the fuse instead.

If the original fault was something fairly trivial like a shorted rectifier diode this is a great way to turn a £20 repair into a £200 repair and STILL not get through the gig.

Regardless of whether you did this once and got away with it - never, EVER do it again. Carry a spare fuse, of the same correct value as the original (never increase fuse values either, for the same reason). If the fuse blows, put in the spare and try the amp again. If it holds, you had a momentary surge or a bad fuse. If it blows, STOP. There is no point in doing anything else because the amp needs to be repaired, and anything you DO do will only make it worse.

Lecture over...