Laney Cub 12R fault - intermittent.

ICBM

Voxman said:

Thanks @ICBM - but having looked at the cost of an RFT these seem pretty expensive and hard to find in new condition. I've only found one so far from Langrex Vintage Electronics and at £40 that's not far off the cost of a full set of tubes.

A bit more I'd have been prepared to pay, but 4 x the cost for a single ECC83 just doesn't seem realistic especially as there's no guarantee as to how long any tube will last.  I've read that they are more mellow sounding but darker with lower break up. As I liked the chimey cleans from the JJs I'm not sure how an rft in V2 might impact on that.

Is the Genelax Gold Lion ECC83 the same tube by a different brand name?

No. If you mean the modern ones they're made in Russia so not suitable for V2.

I would just buy a used RFT, they're much less expensive and they're not unreliable. I tested about forty of them recently, all old used ones, and didn't find a single bad one - unlike a similar number of Mullards and Brimars.

I'm actually surprised you find the Shuguangs darker than the JJs - my main dislike of JJs is because they're muddy-sounding. RFTs are 'bright but rich' if that makes sense.

Voxman

ICBM said:

I'm actually surprised you find the Shuguangs darker than the JJs - my main dislike of JJs is because they're muddy-sounding. RFTs are 'bright but rich' if that makes sense.

?? I've never had Shuguangs in the Cub ...in fact, I'd never heard the name before you mentioned them. Unless you mean the original Ruby tubes it came with but were muddy. I'm puzzled you think JJs are dark as they sound nice and chimey with lots of sparkle in the Cub.

ICBM

Voxman said:

?? I've never had Shuguangs in the Cub ...in fact, I'd never heard the name before you mentioned them. Unless you mean the original Ruby tubes it came with but were muddy. I'm puzzled you think JJs are dark as they sound nice and chimey with lots of sparkle in the Cub.

Ruby are not a manufacturer, they’re made by Shuguang - easily identifiable by the double chrome strips on each side of the plate structure.



Most of them are, anyway - they also seem to have used JJ though! Which you can also easily identify by the vertical dimple in each plate.




JJs sound muddy and also oddly harsh, to me. They’re my least favourite modern valves other than the standard Sovteks.

If the Rubys you’ve got are actually JJs then *definitely* try a Shuguang... they're the only modern valves that are reliable in V2.

Voxman

Just did some research and the Rubys my Cub came with are rebranded JJs. These are dark, muddy and lacklustre. If this is the JJ tone you're referring to @ICBM then no wonder you dislike them. The set of JJs I put in to replace them sounded completely different, bright glassy cleans, with a nice harmonic crunch. They are described as HRX premium selected hand tested.

ICBM

Voxman said:

Just did some research and the Rubys my Cub came with are rebranded JJs. These are dark, muddy and lacklustre. If this is the JJ tone you're referring to @ICBM then no wonder you dislike them. The set of JJs I put in to replace them sounded completely different, bright glassy cleans, with a nice harmonic crunch. They are described as HRX premium selected hand tested.

I was beginning to wonder how we could be hearing them so differently...

Try a Shuguang in V2, if you’re interested - they’re cheap and good-sounding, and don’t have the cathode-follower issue.

Voxman

ICBM said:

Voxman said:

Just did some research and the Rubys my Cub came with are rebranded JJs. These are dark, muddy and lacklustre. If this is the JJ tone you're referring to @ICBM then no wonder you dislike them. The set of JJs I put in to replace them sounded completely different, bright glassy cleans, with a nice harmonic crunch. They are described as HRX premium selected hand tested.

I was beginning to wonder how we could be hearing them so differently...

Try a Shuguang in V2, if you’re interested - they’re cheap and good-sounding, and don’t have the cathode-follower issue.

Actually, I'm not sure now - these might be Shuguang ?

ICBM

Voxman said:

Actually, I'm not sure now - these might be Shuguang ?

There can’t possibly be any doubt if you look at them, the chrome strips are very obvious.

Voxman

ICBM said:

Voxman said:

Actually, I'm not sure now - these might be Shuguang ?

There can’t possibly be any doubt if you look at them, the chrome strips are very obvious.

I realise that, but it was the reference to dimples that threw me and also that these tubes sounded significantly darker and muddier than the JJs I put in, which oddly is the opposite of your experience. But I'll try one in V2 as you suggest.

Voxman

I'm still getting some crackling and volume drop, but oddly if I bang the top of the amp lightly, it clears. 

What would this indicate?  A faulty valve, a loose connection, dry solder, dirty contacts somewhere? 

ICBM

Voxman said:

I'm still getting some crackling and volume drop, but oddly if I bang the top of the amp lightly, it clears. 

What would this indicate?  A faulty valve, a loose connection, dry solder, dirty contacts somewhere? 

Probably a bad solder joint or a loose jumper connector, but try contact cleaner in the valve sockets first.

Voxman

ICBM said:

Voxman said:

I'm still getting some crackling and volume drop, but oddly if I bang the top of the amp lightly, it clears. 

What would this indicate?  A faulty valve, a loose connection, dry solder, dirty contacts somewhere? 

Probably a bad solder joint or a loose jumper connector, but try contact cleaner in the valve sockets first.

I'd already done the contact cleaner. I'll have to take the chassis out to see if there's a loose jumper socket. How do I check for a bad solder joint? 

ICBM

Voxman said:

How do I check for a bad solder joint? 

With an insulated poking stick, a good light, and immense amounts of time and perseverance...

Voxman

ICBM said:

Voxman said:

How do I check for a bad solder joint? 

With an insulated poking stick, a good light, and immense amounts of time and perseverance...

Thanks (I think!  ) Doesn't sound terribly scientific though 

ICBM

Voxman said:

Thanks (I think!  ) Doesn't sound terribly scientific though 

It can be, but it's very slow. Often you just get a bit of inspiration and luck...

Voxman

Bugger, saw my tech this morning - he charges £60 an hour and if it's an intermittent fault eg a dry solder (which he thinks it is, as when you bang the top the fault clears) it could take hours to trace and much as I love this little amp it could very quickly become uneconomic.  I'm off work now until the New Year so I'll have a go at taking it out of its chassis just in case it's something I can see, but otherwise (and unless I can find a tech who will sort it for a fixed price) it will be beyond economical repair - which is a real shame. 

77ric

Bugger, presumably it is out of the 5 year extended warranty. Fingers crossed for you, it would be a shame to scrap what is a nice sounding amp. 

ICBM

Voxman said:

Bugger, saw my tech this morning - he charges £60 an hour and if it's an intermittent fault eg a dry solder (which he thinks it is, as when you bang the top the fault clears) it could take hours to trace and much as I love this little amp it could very quickly become uneconomic.  I'm off work now until the New Year so I'll have a go at taking it out of its chassis just in case it's something I can see, but otherwise (and unless I can find a tech who will sort it for a fixed price) it will be beyond economical repair - which is a real shame. 

I understand "time is money" and that other techs may have a different viewpoint, but I find it very hard to charge by the hour for this sort of work - yes, it could possibly take hours to find (although *an* hour is more likely if you approach it logically), but if you're lucky it could be minutes. If you're lucky you can charge for half an hour's work that took five minutes! If you're unlucky you just charge for half an hour and put the rest down to experience, like many other jobs that over-run... but maybe that's just me.

It's a shame I'm not closer to you or I'd be happy to have a look at it.

Voxman

77ric said:

Bugger, presumably it is out of the 5 year extended warranty. Fingers crossed for you, it would be a shame to scrap what is a nice sounding amp. 

Yup, 5yr warranty expired yonks ago sadly...it was bought 2012!

ICBM said:

Voxman said:

Bugger, saw my tech this morning - he charges £60 an hour and if it's an intermittent fault eg a dry solder (which he thinks it is, as when you bang the top the fault clears) it could take hours to trace and much as I love this little amp it could very quickly become uneconomic.  I'm off work now until the New Year so I'll have a go at taking it out of its chassis just in case it's something I can see, but otherwise (and unless I can find a tech who will sort it for a fixed price) it will be beyond economical repair - which is a real shame. 

I understand "time is money" and that other techs may have a different viewpoint, but I find it very hard to charge by the hour for this sort of work - yes, it could possibly take hours to find (although *an* hour is more likely if you approach it logically), but if you're lucky it could be minutes. If you're lucky you can charge for half an hour's work that took five minutes! If you're unlucky you just charge for half an hour and put the rest down to experience, like many other jobs that over-run... but maybe that's just me.

It's a shame I'm not closer to you or I'd be happy to have a look at it.

That's a really kind thought John, thank you. And I would love you to be near enough to be my tech on amps and guitar! You don't fancy moving to North London do you? Lol.

But I have spoken with another tech, Ravi Rajani, that seems a nice helpful guy and he's sure it could all be sorted in an amp service that won't be more than £60 Inc VAT. In fact, he posted on here a while back when promoting a new amp he's built.  

Earlier I decided to change all the tubes with the original Ruby tubes the amp came with, which were hardly used. I still think there's a connection or solder issue but at least I can then be reasonably sure it's not the tubes if the problem recurs with a completely different set.  I've left the amp on for a while so will wait to see what happens. 

Voxman

So far, after the full tube change, an hour of playing on and my Cub seems to be behaving itself....but I thought that last time when it was fine for an hour or so too, then it 'went' again!  Mind you, last time I only swapped the pre-amp tubes out one by one.  Who knows, maybe it was a power tube that was iffy. 



However, the thing about yer actual intermittent fault  - that is, its main distinguishing feature, ..is that it's a fault that's intermittent!  (coz I do have an IQ of 6000, so I'm technical like that!   ). 

Anyway, time will tell.  Fingers crossed.

 

ICBM

The classic intermittent fault is very shy, and likes to hide - especially from rough technical types who poke around inside equipment and drive it deeper into its hiding place where it stays very quiet until it's quite sure the coast is clear.

Then when it is confident enough - ideally about five minutes into a paying gig, or an important recording session that's paid for by the hour - it reappears. It's also a solitary creature, so tends to stay hidden if it thinks a backup amp that might contain another of its kind is around...