Orange Rocker 30, combo, 2006

"Nutcase Kook"

.... Phil

Definitely PbF, resoldering the usual suspect points. I realised I was using the wrong gauge of cut down sewing needle and 2 of the preamp valve socket pins are highly suspect. Those glossy white ceramic mounts with holes just bigger than the valve pins.

If it continues to cut out, a generator, a 'scope and a meter should tell all. Valve circuits are very simple and very straightforward to trace signals in, and troubleshoot. Even if it is a bad PbF joint, it should be easy enough to pin it down to at least a stage, and possibly to a specific component, based on valve voltages.

Arfa

"Arfa Daily"

The ones that were originally well made are now so old they have strange faults most techs have never seen before - while the ones made more recently have designed in faults never seen before by anyone.

A few examples.

1. Recent Marshall combo amps with fibreglass PCBs that become LEAKY when hot - output valve bias goes crazy and even the phase splitter stage goes way out of DC balance in normal operation because of leakage from anode tracks to grid tracks. There is simply no fix for this problem.

1. Recent Gibson /Trace Elliot amps that develop mysterious crackling noises all over the circuit due to the use of water soluble flux that was never properly washed of the PCB. Removing the main PCB entirely and washing it thoroughly in solvent is the only fix.

2. Same amps as above use 9 pin PCB mount sockets that SHRINK - yep, the plastic material used to make the socket shrinks under the heat from EL84s, reducing the pitch circle diameter so much it is impossible to fit a new tube in the socket. Replacing all the output valve sockets is the only fix.

Then there are all the issues with the valves themselves - all new production now comes from China or the former USSR and most of the valves have designed in faults of kinds that were never seen previously. Eg. nearly all 12AX7s now crackle and pop if tapped with the back of a screwdriver and/or have bad heater cathode hum or are very microphonic - while octal power types often suffer from bad soldering (PbF ?) on the pins causing all manner of weird intermittents when the solder joint lets go.

Yep - fixing valve amps is pure joy.

.... Phil

of

Coincidence or action of high V on springiness of the socket metal? One valve base, pin 1 , the other pin 6 , both anodes so killing throughput if connection fails.

While on valve stuff , has anyone come across any output transformer or mains transformer ,for that matter, in any equipment , where there is failure of PbF joint inside the transformer where tail meets magnet wire?

Er, that would be a yes then ... Probably three or four a week, most every week, and have been doing them for around 40 years ... Whilst some faults are a little obscure, most are very straightforward, and I'm sure that you don't have any more trouble fixing them, than I do Phil. I would pick a fault on a valve amp over a transistor one, every time, as would probably any engineer who has ever worked with valves. Every stage is pretty much independent, and troubleshoot-able as a separate entity. You can't say that about most transistor amps.

Care to give me a model for that behaviour ? I see a lot of Marshall combos, as they are built just a few miles from where I live. I have not seen any similar problems here. I used to visit Jim Marshall in his factory in the early days. He was a very good friend of a friend of mine. As to the problem with a - g leakage, I would have thought that you might have been able to get away with isolating the affected tracks by cutting or even removing them from the board completely, and then hard wiring.

Whilst I would agree that valve quality is not as good as it was when the likes of Mullard and Brimar etc made them, I also don't think that they are quite as bad as you seem to find them, if you buy decent quality ones, or manufacturer's originals, which have been vetted by the amp manufacturer as being of the required quality. The Ruby HG (Hi Grade) 12AX7s that I use, don't crackle and pop, and are no more microphonic than any high gain triodes have ever been. I also don't find the h - k leakage bad either - certainly not enough to identify as being a predominant source of unwanted hum. And as to bad soldering on octal base pins, I honestly can't say that I've ever seen this problem on any amp that's been across my bench, or on any replacement valves that I have fitted, which may have had their bases connected to the leadouts by PbF. Perhaps I've just been lucky ...

Well, I find it so ...

Arfa

"Arfa Daily"

But there is plenty of trouble with most of them.

Easy to find many stories about the same problem on usenet and web forums.

The PCB wound up looking like a piece of Swiss cheese and still the problem was not cured.

The only "treatment" that helped at all was to install a fan to keep the valves and hence PCB cooler.

Colleagues have complained to me about the exact same problem.

There are NO " manufacturers originals" available in Australia AFAIK.

You compare the particular with the general.

How tedious.

.... Phil

Apparently, a very different one from you ...

But then, of course, I was forgetting who I was trying to have a reasoned discussion with. It had completely slipped my mind that anyone who looks at anything from a different point of view to you, must be wrong. I suppose you'll start in on the hysterical abuse hurling next. Well, if that's what you need to do, go right ahead. I really don't care. And I suppose you know Jim all the way from upside down land do you ?

Arfa

If you are such an expert, please tell us how they got that volume control to go to 11, while (whilst?) everyone knows they only go to 10?

:-)

Geoff.

If I told you that Geoff, I'd be destroying my niche market. Suffice to say that they used triodes with more than three electrodes ... d;~}

Arfa

"Arfa Daily"

Maybe Marshall, Gibson, Fender, Peavey and others ship their bad batches to Australia deliberately or maybe you have been leading a charmed existence.

What you have NOT see cannot be dismissed as non existent.

Before Jim accepted any questions, the MC gave a stern warning to the assembled audience that Jim was not involved in the design or manufacture of Marshall amps and that no questions about the notoriously poor design or appalling reliability of the amps would be allowed.

Wise move.

.... Phil

Let me guess... instead of using thorium as a dopant in the filaments to enhance electron emission, they used quadmium, right?

I figure you could get an extra 20 to 30 quid an amp if you offered to upgrade them from a maximum of 10 to 11. :-)

Geoff.

How did you know that, huh ? Well that's just great. Now you've told everyone, and my plans to dominate the music world with one notch upgrades, are in shreds. Cheers pal ...

Arfa :-)

Don't forget to sell them these:

Although they have long since been discontinued (or deleted in English).

Geoff.

Oh, that's soooo unfair. I was just about to put in an order for some of those to use as the controller for my LED pilot bulb replacement upgrade ... Rats. I guess it's back to using the warehouse full of ZX Spectrums that I've got then ... :-|

Arfa

...

What is the state of the vacuum-formed plastic of the Sinclair ZX80s these days?

I'd forgotten that ! Dunno. haven't seen one in years ...

Arfa

Yes, Marshal TSL 100. Sigh. I have had two of these with faulty PCB's. They do indeed leak, and destroy the output tubes, as the bias goes totally crazy. I spent hours on the first one trying to establish what the f*ck was going on, as it made no sense whatsoever.

Eventually I phoned Marshall. They know about this problem and are unable to fix it. You need to replace the PCB with an upgraded design.

Gareth.