Bare Knuckle Pickups Forum
Forum Ringside => Guitars, Amps and Effects => Topic started by: tomjackson on September 20, 2009, 08:35:22 PM
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Just won a WEM Dominator MK3 on ebay for £100. It works and has the original Mullard Valves (which will probably be changed to JJ for reliability).
Looks in okay condition for the age. Are these amps okay and is that a decent price?
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great amps and even greater price.
Mullard are great valves, I wouldn't change them out thinking that JJs will be more reliable, I'd say doing that would give you the opposite effect - a LESS reliable amp.
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Oooh great, I'm getting excited now :D
Loud enough for use with a loudish drummer? Not too fussed about the clean headroom if the overdrive is nice.
I got it for a bit of fun anyway so it does nat matter if it's not powerful enough.
Well yeah if the valves are okay there's no point in changing them, I'm just half expecting them to be a bit knackered considering their age. Apparently the amp hums a bit on switch on but it settles down after a while so I guess that would be the power valves?
35 years of power up / power down with no standby and SS rectification must take its toll....
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One of my friends has one( I am not sure of the model designation) but it has Mullards in it too.He gigs it regularly though in conjunction with a Fender amp.He loves his-I played bass in his band for a gig a few weeks back and his set up is great sounding though he plays clean. He bought his from a dealer but didn't pay a huge amount but he is a fussy sod and tried all sorts of old amps but loved the WEM the best.
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Oooh great, I'm getting excited now :D
Loud enough for use with a loudish drummer? Not too fussed about the clean headroom if the overdrive is nice.
I got it for a bit of fun anyway so it does nat matter if it's not powerful enough.
Well yeah if the valves are okay there's no point in changing them, I'm just half expecting them to be a bit knackered considering their age. Apparently the amp hums a bit on switch on but it settles down after a while so I guess that would be the power valves?
35 years of power up / power down with no standby and SS rectification must take its toll....
I'm willing to bet that the Mullards will stay sound great, even after 35 years. I've taken Mullards from 40 year old amps that look to have seen it all during their life and the valves still sounded great.
The hum will be the smoothing caps in the HT line - they should really be replaced if they're original to the amp.
As for gigging the amp, from my experience it won't be enough. However, if you run it with another amp you'll be fine. How about watching out for another Wem Dominator and running a pair of them :D
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Well yeah if the valves are okay there's no point in changing them, I'm just half expecting them to be a bit knackered considering their age. Apparently the amp hums a bit on switch on but it settles down after a while so I guess that would be the power valves?
Most likely cause is the power valves heating up at different rates.
I would be tempted to change the filter caps though if I wanted to gig the amp.
One point with the old WEM Dominators. Mullard EL84s have pin 1 and 2 connected internally, so wiring the drive lines from the PI to either pin or pin 2 will work fine. However most modern EL84s have the control grid only wired to pin 2.
I've seen 2 WEMs with the drive lines connected to pin 1, which isn't used in most (all?) new EL84s, so if you do change valves I would check how the sockets are wired up.
The consequences of having nothing connected to the control grid is that there will effectively no bias voltage and very high current draw. The consequences of this are not good.......
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Smoothing caps and filter caps is this different terminology for the same part? I'm presuming they filter / smooth the ripple out of the DC supply coming out of the rectifier and that if they are that old they may be not doing their job hence contributing to ripple / hum leaking through to the audio path?
Where is a good place to get these from and will turning the amp on while not plugged in drain them for safe removal?
2 amps is a good Idea HTH, I could have a stereo set up, I've always wanted to try that!
I'll check the Pin layout then prior to revalving but hopefully the valves will prove to be okay.
Are these amps early PCB?
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Smoothing caps and filter caps is this different terminology for the same part? I'm presuming they filter / smooth the ripple out of the DC supply coming out of the rectifier and that if they are that old they may be not doing their job hence contributing to ripple / hum leaking through to the audio path?
Correct.
Smoothing/filter caps are electrolytic and have a finite lifespan; old amps really benefit from changing them. By the way they are actually in the audio path.
Where is a good place to get these from and will turning the amp on while not plugged in drain them for safe removal?
You will need a can cap and a couple of axial electrolytics (worth changing all these once you are in the amp). There are several vendours that sell these including:
http://www.audiocap.co.uk/
In my opinion F&T make the best can caps.
The on/off switch switches the mains on/off and will not effect the filter cap draining. You may need to drain the filter caps through a resistor. You should check the filter caps with a multimeter before working on them.
Are these amps early PCB?
Yes. WEM started using PCBs in the mid/late 60's.
Removing the chassis and PCB is a bit of a pain due to the huge number of screws but is more time consuming than difficult. Also the loudspeaker is hard wired in and will need unsoldering.
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Thanks for the info, that's great :D
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Smoothing caps and filter caps is this different terminology for the same part? I'm presuming they filter / smooth the ripple out of the DC supply coming out of the rectifier and that if they are that old they may be not doing their job hence contributing to ripple / hum leaking through to the audio path?
Correct.
Smoothing/filter caps are electrolytic and have a finite lifespan; old amps really benefit from changing them. By the way they are actually in the audio path.
Where is a good place to get these from and will turning the amp on while not plugged in drain them for safe removal?
You will need a can cap and a couple of axial electrolytics (worth changing all these once you are in the amp). There are several vendours that sell these including:
http://www.audiocap.co.uk/
In my opinion F&T make the best can caps.
The on/off switch switches the mains on/off and will not effect the filter cap draining. You may need to drain the filter caps through a resistor. You should check the filter caps with a multimeter before working on them.
Are these amps early PCB?
Yes. WEM started using PCBs in the mid/late 60's.
Removing the chassis and PCB is a bit of a pain due to the huge number of screws but is more time consuming than difficult. Also the loudspeaker is hard wired in and will need unsoldering.
I suggest getting a tech to check the amp for AC leakage from the electrolytics before replacing them if they're still testing fine and have no signs of bulging or leaking electrolyte i'd keep them in and reform them, aslong as they're not putting a ripple onto the filtering they're usually good to go, Im not for re-capping an amp because it surely changes the tone the old RS/Erie and LCR caps are much better than the stuff on the market now, I do agree with JPF, F&T make a fine cap and I use these in my own builds.
There are mixed opinions on this subject though, so I if your want 100% reliability simply just replace them all as a cap blowing in the HT line can cause all sorts of problems that weren't there before, you need to be sure these caps will last if you keep them in and a visual inspection alone isn't really enough.
The Original Mullards will most likely be ok as most here have said. They're good for hundreds of thousands of hours and they regularly exceed this, I've got a set of Mullard XF2 Dual Getter EL34s in one of my amp builds and they've been around 40+ years and seen extensive use and they're still testing fine so are the Brimar & Mullard 12AX7 tubes I'm using too!
If you're not sure about draining the smoothing caps i'd get a tech to do the work for you.
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Well I had a little play last night and it turned out pretty quiet, it was side by side with a Laney Lionheart.
If it was noisy I certainly could hear it above the hum and hiss of the Laney!
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I suggest getting a tech to check the amp for AC leakage from the electrolytics before replacing them if they're still testing fine and have no signs of bulging or leaking electrolyte i'd keep them in and reform them, aslong as they're not putting a ripple onto the filtering they're usually good to go, Im not for re-capping an amp because it surely changes the tone the old RS/Erie and LCR caps are much better than the stuff on the market now, I do agree with JPF, F&T make a fine cap and I use these in my own builds.
There are mixed opinions on this subject though, so I if your want 100% reliability simply just replace them all as a cap blowing in the HT line can cause all sorts of problems that weren't there before, you need to be sure these caps will last if you keep them in and a visual inspection alone isn't really enough.
If you're not sure about draining the smoothing caps i'd get a tech to do the work for you.
re changing electrolytic caps. I can see the attraction of the "if it ain't broke don't fix it" approach, which is also the cheaper option.
However, I've also seen plenty of amps from that era where an electrolytic cap failure has caused damage to other components (ie an expensive repair), so I'm not convinced that leaving components with a limited lifespan until they fail is a sound approach either.
I've seen no evidence to suggest that old Erie/LCR caps are better than good quality modern electrolytics.
Notwithstanding the fact that it is impossible to compare like with like here (ie you are comparing a 20-30 years old part which ages with a new component), the only aspect of older caps which I have measured that is better than new caps is that old caps are more tolerate of over voltage (measured by destructive testing). This isn't because old caps are better, but simply that tolerances on old electrolytic caps was so bad, often +100%, -50%, that a significant margin for error had to be used to ensure correct voltage compliance.
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The consequences of having nothing connected to the control grid is that there will effectively no bias voltage and very high current draw. The consequences of this are not good.......
Unless you're a bit nippy and want something to keep you warm :lol:
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Nice amp. I've had one since 1981!
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I know there are techs, mainly American, that support the school of thought that you should keep using old filter caps if the amp still sounds good.
I saw an old JTM45 in otherwise pristine condition on the Metroamps forum where a can cap inside the amp had literelly exploded. Luckily it just caused a mess and didn't take anything else out. For my money, I think there are no downsides to putting new caps in an amp. F&Ts are really nice and I've had excellent results from Rifa axial caps too.
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One of my very first amps back in 1977... played a lot of cr@p punk rock on that little guy. Happy days :lol:
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Apologies for the threadnomancy but I thought the Dominator-o-philes here (sounds like something Max Mosely would be interested in) might like to know that in the current issue (May 2010) of Vintage Guitar Magazine there is an article about WEM Dominators and their history. A good and informative, if short, read.
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Congrats on a cool amp! I just got one a couple of weeks ago - pretty neat 8)
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I'm actually selling mine, it's in the Seconds Out section in this very forum!
Will be sorry to see it go actually, it's a great little amp. I Just need some more headroom and some more gain as it has been my only amp for the last 6 months. I can only really justify one amp (I don't include my VOX DA5 in that)
Price has gone up a little though since I bought it :oops:
But it has had a new speaker / service / preamp valve / filter caps and some cobwebs blown out of it!
I guess it fits in well with the Pink Floyd stuff then Dashface, they were partial to the odd WEM weren't they?
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I guess it fits in well with the Pink Floyd stuff then Dashface, they were partial to the odd WEM weren't they?
The name is certainly what attracted me to it, though it's far too teeny for actual use with the Floyd act. I'm glad I got it; it has a great sound and makes a fine practice amp at home. I would, of course, kill for a WEM cab or three (such as the real Floyd used), but over here in Canada WEM cabs are rarer than a hen's wisdom teeth.
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I'm actually selling mine, it's in the Seconds Out section in this very forum!
Saw it yesterday and had hard time resisting the GAS attack - specially for the price... :?