Laney Cub 12R fault - intermittent.

Voxman

Last year I had a problem with the volume dropping and tone getting distorted. Turned out that the multiway plug and socket on the PCB had got oxidised and had to be cleaned.  Same symptoms are occurring so I'd like to check this myself so I can clean it instead of having to get it to my amp tech guy again - could someone kindly guide me how to access this?

There's also a possibility it's just a tube - if it is, would that be more likely to be a pre-amp tube rather than a power tube?

Thanks guys

ecc83

I don't know the amp but m/way plugs can get 'tired' the receptacles loose tension. Look at the plug and you will see a tiny 'tag'. This need pushing gently down to release the part. The 'business end' can now be gently squeezed with pliers and then clicked back in. Work systematically ONE receptacle out at a time! You might even find a wire falls out of the crimp, best soldered back in. Flood the connector with your chosen cleaner (I won't start a cow and suggest one!) leave to dry/drain.

And, check for dry joints etc in the heater circuits.

Dave.

Voxman

Thanks Dave ( @ecc83 ; ), but can you guide me to where it is and how I can access it?

ecc83

No, sorry, as I say I don't know the particular amp but I am sure ICBM will have finished his Wheaty-bangs soon!

Dave.

Voxman

ecc83 said:

No, sorry, as I say I don't know the particular amp but I am sure ICBM will have finished his Wheaty-bangs soon!

Dave.

Thanks Dave, appreciate your response and guidance. Hopefully @ICBM can give me an idiot's step by step guide to access and find it. I'm a real nonce when it comes to amps but I'd like to try fixing this myself if I can. 

ICBM

I can’t remember exactly where it is inside but it should be fairly obvious once you get the chassis out.

... however, as this is a Laney you may have to contend with the chassis snagging on the poorly-glued vinyl - be patient if it doesn’t come out cleanly first go, or you’ll rip it.

If the fault is *exactly* the same as last time it probably is the same fault, but if it’s not quite the same it could be a valve - either a preamp or power valve could give a lower-volume distorted sound. The first thing I would try, before removing the chassis, is to take each one out and spray some contact cleaner into the socket, then put it back and wiggle it a bit, which will clean the pins.

Voxman

ICBM said:

I can’t remember exactly where it is inside but it should be fairly obvious once you get the chassis out.

... however, as this is a Laney you may have to contend with the chassis snagging on the poorly-glued vinyl - be patient if it doesn’t come out cleanly first go, or you’ll rip it.

If the fault is *exactly* the same as last time it probably is the same fault, but if it’s not quite the same it could be a valve - either a preamp or power valve could give a lower-volume distorted sound. The first thing I would try, before removing the chassis, is to take each one out and spray some contact cleaner into the socket, then put it back and wiggle it a bit, which will clean the pins.

Thanks ICBM, seems like a good thing to check first...have to be over the weekend now.

midlifecrisis

i had  an intermittent problem with mine which turned out to be a dry solder joint on the valve socket to the pcb.

77ric

If I remember correctly there are 2 multi plugs in the cub12r one smaller one beside the OT which is related to the negative feedback and the other near the back of the chassis fairly central on the PCB and very obvious, larger than the other one, that’s the one you want.

as icbm said just be patient when removing the chassis is will catch on the vinyl somewhat, but go slowly and give it a little wiggle as you slide it out it will come eventually. 

Top tip:

Do not to do it when it’s plugged in! 

Voxman

77ric said:

If I remember correctly there are 2 multi plugs in the cub12r one smaller one beside the OT which is related to the negative feedback and the other near the back of the chassis fairly central on the PCB and very obvious, larger than the other one, that’s the one you want.

as icbm said just be patient when removing the chassis is will catch on the vinyl somewhat, but go slowly and give it a little wiggle as you slide it out it will come eventually. 

Top tip:

Do not to do it when it’s plugged in! 

Thanks - Laney kindly sent me a pic so I know what I'm looking for now. In fact, Laney said leave it 2 hrs before taking the chassis off to give any stored voltage in the capacitors time to dissipate.

Voxman

midlifecrisis said:

i had  an intermittent problem with mine which turned out to be a dry solder joint on the valve socket to the pcb.

Always possible, so I'm going to first look for a bad tube, then clean all the sockets, & then take the chassis out only if I need to.

Keefy

I’ve had one of these apart and iirc it’s a bit of a pig for access, with components on 3 surfaces in a u-shaped layout. Should be easy enough to spot the connectors, maybe not so easy to reach them!

midlifecrisis

Voxman said:

midlifecrisis said:

i had  an intermittent problem with mine which turned out to be a dry solder joint on the valve socket to the pcb.

Always possible, so I'm going to first look for a bad tube, then clean all the sockets, & then take the chassis out only if I need to.

if it is a dry joint cleaning wont help, it will need to be resoldered i think

Voxman

midlifecrisis said:

Voxman said:

midlifecrisis said:

i had  an intermittent problem with mine which turned out to be a dry solder joint on the valve socket to the pcb.

Always possible, so I'm going to first look for a bad tube, then clean all the sockets, & then take the chassis out only if I need to.

if it is a dry joint cleaning wont help, it will need to be resoldered i think

If it is, then yes of course.  So, the latest is that I (intentionally)  tilted the amp at the front a bit  (it sits on top of my DSL401) and then ‘dropped’ it down slightly whilst it was distorted, and the distortion cleared & the volume came back up immediately.  Been playing it for the last 45 mins and it’s stayed clean. So clearly there’s a connection issue somewhere – perhaps just a dirty or loose contact.  I’ve not taken the chassis out yet to have a look (I’ll see how it goes). The valve sockets are clean, speaker connections are tight & clean (did that whilst the back was off) so possibly it’s that push fit plug on the pcb but could be anything inc a dry solder somewhere.  I’ll see how it goes but if it comes back & persists and I can’t see anything amiss if I take the chassis out, then it’s an amp tech job.  

Voxman

So this evening one at a time I changed each of the 12AX7 pre-amp valves with one of the spare good valves I have, and even though it looked healthy with the same glow as the others, it appears to have been the valve in V2 that was the problem.  I've been running it and playing through it for the last half an hour with the replacement valve and so far, touch wood, it seems fine now.  I'll run it for longer over the weekend but if it's still playing well and not farting out then I'm going to treat my Cub to a new set of pre-amp valves.   

The previous set were JJ hand-tested which were much nicer than the Chinese Ruby valves it came with when new.  It's only a single channel amp so it's about getting a good balance between nice cleans and a good classic rock crunchy distortion.  In this regard I believe the circuit might even share some characteristics with a Marshall amp, but I'm not 100% sure.

I'd like to get a bit more crunchy distortion from the Cub but that might well lower headroom and not give me as nice a clean.  @ICBM if you're looking in, any thoughts as to what pre-amp valves might suit or should I stick with JJ's?  If memory serves, I seem to recall you quite like JJ's for power tubes but are not a great fan of them for pre-amp tubes.  

ICBM

Voxman said:

So this evening one at a time I changed each of the 12AX7 pre-amp valves with one of the spare good valves I have, and even though it looked healthy with the same glow as the others, it appears to have been the valve in V2 that was the problem.  I've been running it and playing through it for the last half an hour with the replacement valve and so far, touch wood, it seems fine now.  I'll run it for longer over the weekend but if it's still playing well and not farting out then I'm going to treat my Cub to a new set of pre-amp valves.   

The previous set were JJ hand-tested which were much nicer than the Chinese Ruby valves it came with when new.  It's only a single channel amp so it's about getting a good balance between nice cleans and a good classic rock crunchy distortion.  In this regard I believe the circuit might even share some characteristics with a Marshall amp, but I'm not 100% sure.

I'd like to get a bit more crunchy distortion from the Cub but that might well lower headroom and not give me as nice a clean.  @ICBM if you're looking in, any thoughts as to what pre-amp valves might suit or should I stick with JJ's?  If memory serves, I seem to recall you quite like JJ's for power tubes but are not a great fan of them for pre-amp tubes.  

The problem here is that V2 is a cathode-follower in this amp, so it's not surprising it's failed - JJs are a bit prone to this, although not as badly as Russian ones. The only modern 12AX7s which are definitely safe are Shuguangs, which the Rubys will be. It may be worth putting just one back in V2 even if you prefer JJs in the other two. I'm really not a fan of the sound of them, but this is a personal taste thing so if you like the JJs I would stick with them for V1 and V3.

If it was me I would probably spend a bit more and get an old-production RFT for V2 at least, if not all three - they're just the best in Marshall MV-type circuits (which this is, basically) in my opinion, but if you like the JJs that may not apply as much for you... try a Ruby back in V2 first and if it doesn't ruin the sound you're probably better to leave it like that.

Voxman

Thanks @ICBM ' so I did recall correctly that the Cub has a Marshall type circuit.

ICBM

Voxman said:

Thanks @ICBM ' so I did recall correctly that the Cub has a Marshall type circuit.

Yes - the preamp is reasonably similar to a 2203, although there are some detail differences.

Voxman

ICBM said:

Voxman said:

So this evening one at a time I changed each of the 12AX7 pre-amp valves with one of the spare good valves I have, and even though it looked healthy with the same glow as the others, it appears to have been the valve in V2 that was the problem.  I've been running it and playing through it for the last half an hour with the replacement valve and so far, touch wood, it seems fine now.  I'll run it for longer over the weekend but if it's still playing well and not farting out then I'm going to treat my Cub to a new set of pre-amp valves.   

The previous set were JJ hand-tested which were much nicer than the Chinese Ruby valves it came with when new.  It's only a single channel amp so it's about getting a good balance between nice cleans and a good classic rock crunchy distortion.  In this regard I believe the circuit might even share some characteristics with a Marshall amp, but I'm not 100% sure.

I'd like to get a bit more crunchy distortion from the Cub but that might well lower headroom and not give me as nice a clean.  @ICBM if you're looking in, any thoughts as to what pre-amp valves might suit or should I stick with JJ's?  If memory serves, I seem to recall you quite like JJ's for power tubes but are not a great fan of them for pre-amp tubes.  

The problem here is that V2 is a cathode-follower in this amp, so it's not surprising it's failed - JJs are a bit prone to this, although not as badly as Russian ones. The only modern 12AX7s which are definitely safe are Shuguangs, which the Rubys will be. It may be worth putting just one back in V2 even if you prefer JJs in the other two. I'm really not a fan of the sound of them, but this is a personal taste thing so if you like the JJs I would stick with them for V1 and V3.

If it was me I would probably spend a bit more and get an old-production RFT for V2 at least, if not all three - they're just the best in Marshall MV-type circuits (which this is, basically) in my opinion, but if you like the JJs that may not apply as much for you... try a Ruby back in V2 first and if it doesn't ruin the sound you're probably better to leave it like that.

As I'd kept the originals, that were only 2 months old when I replaced them with JJ's, I tried a Ruby (2 in fact) in V2 and it made the amp noticeably duller killing the top end sparkle and making the distortion muddier...which is exactly why I put JJ's in. 

So, having looked at a replacement set, I'm a little confused by the descriptions and price differences on what appear to be the same valves. For example:

Ampvalves.co.uk  £71.40
https://www.ampvalves.co.uk/product/replacement-valve-kit-for-laney-cub12/

Guitarlodge.co.uk £61.40
https://www.guitarlodge.co.uk/product/laney-cub12r-valve-kit/

Interestingly, guitarlodge refer to a balanced ECC83S for the phase inverter in position V3. 

HotRox £51.85
https://www.hotroxuk.com/laney-cub12r-valve-set.html

Karltone £56.25
https://www.karltone.co.uk/jj-el84-x-2-ecc83s-x-3-valve-amp-set-185-p

Karltone refer to platinum matching and premium tested, with a test sheet.

@ICBM I know you like Karltone and they seem competitive. But what's all this about a balanced phase inverter (I've seen this from some other tube suppliers too). Is this just sales talk or is this bona fide and needed?  And are there any differences between these JJ tubes?

Please help unconfuse me! 

ICBM

Sales talk. The phase inverter circuit itself is not balanced, so there’s no point in balancing the valve. It is possibly true that you might have a better chance of more consistent *mis*matching if you change the valve a lot, but that’s all.

I would not use a JJ or any Russian valve in V2. You’d be better to spend your money on a RFT and just keep ordinary JJs in V1 and V3.

Voxman

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?