At the risk of posting a mind-numbingly dull thread, thought I’d
briefly report on my faulty Laney VC50.

The problem was basically a non-functioning heater circuit – front
panel lights came on – and that was about it – nothing glowing and
obviously nothing when switching on standby.

It was sensibly suggested by a few helpful people here that it might
be the heater fuse and soupdragon gave me a link to a schematic
(thanks v. much!), but even with this information, I was fully
expecting to have to dump the whole chassis with Tipton Amps, thinking
that the situation was going to be beyond me.

However, I work at home and the amp was sitting there, so every so
often I’d wander over and have a look at it, switch it on in the vain
hope it would suddenly spring back into life – hmm.  Anyway, this had
become a bit of a routine and just a way of postponing the inevitable
call to Trev, and then I switched it on and as I was absently
examining the heaters of the output valves I nudged one and lo and
behold all the valve heaters came on!  I heard the time delay relay
latch and so I switched on the standby – normal service resumed! …
albeit very temporarily.

Naturally I was delighted – new hope, possibility of not having to
drag the whole thing over to the west midlands etc.

Cutting a very long and not very interesting story short; I repeated
the switch on and off process many times – sometimes the valves would
heat up, other times – nothing.  But I could nudge one of the output
valves and that would generally do the trick.

So, I whipped out the valves, cleaned the contacts of them and the
sockets – re-installed them – still not cured the problem.  Then,
remembering a problem I had with my old Carlsbro 50 Top head, I
thought I’d have one last go at trying to fix it myself.

Pulled out the chassis and resoldered the heater connections to the
output valve bases and problem cured!  I’ve switched it on and off
repeatedly, played it at volume, moved it around and waggled the
output valves (gently!) and it’s all good – hurrah!

…that is, until the next fault crops up.  And I suppose this is the
reason for posting; to say that for me, living/gigging with aging
valve amps seems to be a source of both joy (for the most part) and
frustration – and can demand the sort of curiosity/patience/
desperation/devotion I’d previously thought was exclusively reserved
for motor mechanics.

Valve amps – aren’t they great. (well, some of them!)

Thanks again to all who responded with help and words of
encouragement!

Tim

snip[]

  I suppose this is the
reason for posting; to say that for me, living/gigging with aging
valve amps seems to be a source of both joy (for the most part) and
frustration


Keep a POD handy........ just in case

Andrew(lefty)

"Tim Hacker"  wrote

<snipped for brevity>

 just a way of postponing the inevitable
call to Trev, and then I switched it on and as I was absently
examining the heaters of the output valves I nudged one and lo and
behold all the valve heaters came on!  I heard the time delay relay
latch and so I switched on the standby – normal service resumed! …
albeit very temporarily.

Hi Tim,

Well done on sorting your amp. Must admit to being chuffed that I was 'in 
the frame' for your repair, mind :)

The problem with valve heater circuits is that they are designed to run at a 
very modest 6.3V, nominal. Being low voltage, it only takes the merest hint 
of 'dryness' in the solder joints for the resistance to rise to the point 
where little or no voltage will flow, hence no heaters and thus no amp :(

The situation is made worse by the vibration and handling a guitar amp gets. 
Your granny's old bakelite valve radio will work happily for half a century 
without failure, as it sits in a fixed position and doesn't get the 
buffetting your typical road abused Marshall is expected to withstand.

Allowing an amp to properly cool down before it's moved will aid greatly the 
life expectancy of both the solder joints and the valves. Next time the 
roadie attempts to move your amp before it's had a chance to cool down, then 
the  judicious application of a blunt instrument, say a microphone stand to 
the bonce, should prove a great learning tool ;)

On a routine 10 000 chord service, dry joints on the valve heater chain are 
among the things I look for, re-flowing the solder on the socket heater pins 
as a matter of course. That is, unless it's a <insert classic collectable 
and hence spendy amp>, where I will obtain the owner's consent first. 
Collectors are a bit cork-sniffy about original solder joints/components. 
Has a major effect on the value. Daft, I call it, but then, that's just me 
:)

PCB based amps like the Fender Hot Rod Deluxe suffer badly from dry joints 
on the heater chain. The high temperature/high current environment doesn't 
lend itself to long term reliability of the soldered joints on the PCB 
traces and should be the first suspect when the amp doesn't 'light up'

regards,

Trev

Trev,

Great feedback and I now appreciate the dry solder condition a bit
more. Indeed when my 50 Top expired at the Lamp Tavern in Digbeth not
so very long ago - this was the exact problem, not solved by me sadly.
But bearing in mind that the amp was approaching 40 years old, I guess
I shouldn't be too surprised.

My abilities are limited in respect of sorting out such problems and
so I think that it won't be very long before I bowl up to Tipton Amps
with another ailing amp.

So thanks for the useful info - and I'm sure we'll meet before too
long!

Cheers

Tim





On Sep 23, 9:30 pm, "Trevor Ridney" 
wrote:
> "Tim Hacker"  wrote
>
> <snipped for brevity>
>
>  just a way of postponing the inevitable
> call to Trev, and then I switched it on and as I was absently
> examining the heaters of the output valves I nudged one and lo and
> behold all the valve heaters came on!  I heard the time delay relay
> latch and so I switched on the standby – normal service resumed! …
> albeit very temporarily.
>
> Hi Tim,
>
> Well done on sorting your amp. Must admit to being chuffed that I was 'in
> the frame' for your repair, mind :)
>
> The problem with valve heater circuits is that they are designed to run at a
> very modest 6.3V, nominal. Being low voltage, it only takes the merest hint
> of 'dryness' in the solder joints for the resistance to rise to the point
> where little or no voltage will flow, hence no heaters and thus no amp :(
>
> The situation is made worse by the vibration and handling a guitar amp gets.
> Your granny's old bakelite valve radio will work happily for half a century
> without failure, as it sits in a fixed position and doesn't get the
> buffetting your typical road abused Marshall is expected to withstand.
>
> Allowing an amp to properly cool down before it's moved will aid greatly the
> life expectancy of both the solder joints and the valves. Next time the
> roadie attempts to move your amp before it's had a chance to cool down, then
> the  judicious application of a blunt instrument, say a microphone stand to
> the bonce, should prove a great learning tool ;)
>
> On a routine 10 000 chord service, dry joints on the valve heater chain are
> among the things I look for, re-flowing the solder on the socket heater pins
> as a matter of course. That is, unless it's a <insert classic collectable
> and hence spendy amp>, where I will obtain the owner's consent first.
> Collectors are a bit cork-sniffy about original solder joints/components.
> Has a major effect on the value. Daft, I call it, but then, that's just me
> :)
>
> PCB based amps like the Fender Hot Rod Deluxe suffer badly from dry joints
> on the heater chain. The high temperature/high current environment doesn't
> lend itself to long term reliability of the soldered joints on the PCB
> traces and should be the first suspect when the amp doesn't 'light up'
>
> regards,
>
> Trev