Boiling power transformer

skunkwerx

I'm not familiar with the amps, but If I bought a Katana in Jan and its faulty by April, I'd be pushing for a brand new replacement. 

Repair is within the sellers rights to insist on, but its fucking July now.

Then again I really get arsey with brand new products needing a repair within months.. 

Modulus_Amps

ecc83 said:

Modulus_Amps said:

ecc83 said:

It is not the OP's fault that the design was so poor that the transformer was not protected but it IS the retailer's responsibility to effect a proper repair or a full refund in a timely manner.

Dave.

I would think a "proper" repair was fairly oviously a new transformer and a return of the amplifier to as new specification?

Dave.

I was wondering if you would consider a Hammond replacement a proper repair.

From reading other comments there has been a few PT failures with the LE amps, maybe they are not made for 50Hz or our near 250v wall voltages

ecc83

Well I am "old school" you see Mods. I come from a time when manufacturers had a dialogue with retailers and if a component showed an abnormal rate of failure a change/upgrade would be forthcoming in short order.  I will also add that mains transformer failure was ulmost unheard of in radios, hi fi and PA amps (100V line "Wimbledons") . OPTs would fail but very rarely.

Having spent a very concentrated period of time testing both mains and OPTs for voltage, correct ratios and doing a resistance heat rise test it beggars my belief that a competent manufacturer could fit an usuitable part? THEY obviously are not that fussy!

Dave.

edenfield99

And to finish up on this...I got it back on Thursday. It works, it sounds great and all’s well that ends well :-) 

edenfield99

Only it didn’t end well...I’ve not played it that much as I only use it for bigger gigs and I’ve not played one recently so it’s had about 6 hours of play in the spare room. I fired it up tonight to try some new delay pedals and after about 15 minutes it started hissing and popping! I looked at the back and the rectifier valve, you know the one that was replaced along with the transformer as that was what caused the problem, was arcing blue lights. Looks like it’s a bigger issue than they thought so it’s going back and I don’t want to see it again!!! Asking for money back or replacement goods to the same value. Annoyingly, since having it back I’ve bought a reverb/tremolo switch and a Roqsolid cover both of which will now be surplus to requirements and I’ve thrown the box out so will have to sort something for shipping as well! 

ICBM

edenfield99 said:

Only it didn’t end well...I’ve not played it that much as I only use it for bigger gigs and I’ve not played one recently so it’s had about 6 hours of play in the spare room. I fired it up tonight to try some new delay pedals and after about 15 minutes it started hissing and popping! I looked at the back and the rectifier valve, you know the one that was replaced along with the transformer as that was what caused the problem, was arcing blue lights. Looks like it’s a bigger issue than they thought so it’s going back and I don’t want to see it again!!! Asking for money back or replacement goods to the same value. Annoyingly, since having it back I’ve bought a reverb/tremolo switch and a Roqsolid cover both of which will now be surplus to requirements and I’ve thrown the box out so will have to sort something for shipping as well! 

Unless there's something very wrong with the circuit or the choice of rectifier valve type (eg not sufficient current rating for the draw), that sounds like simply a faulty rectifier valve. However, I totally understand your frustration and why you want a refund - which I think you should be entitled to.

Keep the footswitch if it's a universal type (dual latching switch with a stereo-type plug) - you never know when it might be useful again; or sell it and the cover here or elsewhere. If you measure the amp before you send it back you can list the dimensions the cover will fit.

edenfield99

ICBM said:

edenfield99 said:

Only it didn’t end well...I’ve not played it that much as I only use it for bigger gigs and I’ve not played one recently so it’s had about 6 hours of play in the spare room. I fired it up tonight to try some new delay pedals and after about 15 minutes it started hissing and popping! I looked at the back and the rectifier valve, you know the one that was replaced along with the transformer as that was what caused the problem, was arcing blue lights. Looks like it’s a bigger issue than they thought so it’s going back and I don’t want to see it again!!! Asking for money back or replacement goods to the same value. Annoyingly, since having it back I’ve bought a reverb/tremolo switch and a Roqsolid cover both of which will now be surplus to requirements and I’ve thrown the box out so will have to sort something for shipping as well! 

Unless there's something very wrong with the circuit or the choice of rectifier valve type (eg not sufficient current rating for the draw), that sounds like simply a faulty rectifier valve. However, I totally understand your frustration and why you want a refund - which I think you should be entitled to.

Keep the footswitch if it's a universal type (dual latching switch with a stereo-type plug) - you never know when it might be useful again; or sell it and the cover here or elsewhere. If you measure the amp before you send it back you can list the dimensions the cover will fit.

But two faulty rectifier valves in a row...am I really that unlucky?
Yeah, the switch has gone in the box of “stuff I might need one day” and I’ll try and sell the cover but it’s no real loss if I don’t, it’s just the inconvenience.

ICBM

edenfield99 said:

But two faulty rectifier valves in a row...am I really that unlucky?

Possibly, but I’m suspicious too. Modern rectifier valves do seem to have a bit of a problem with reliability, but equally a lot of modern amps are poorly designed and put extra stress on them.

edenfield99

Cheers ICBM, wise words as ever!

Modulus_Amps

yes return it, but the engineering side of me would love to have a look and see why it has had so many issues, there will be a reason as ICBM says.

jpfamps

My experience with quite a few US mains transformers is that the voltages come out on the high side when used at UK mains, so maybe these are wound with 230 VAC mains in mind rather than UK 240 VAC.

I tend to use Hammond transformers as my go to replacements in most amps as the voltages always seem to come in in spec.

I'd be interested to know where the standby switch is located in this amp, as if you are hot switching the rectifier this can cause rectifier failure.

Standby switches and not really needed on most valve amps, particulary those with valve rectifiers as they inherently have a soft start as the rectifier warms up.

My experience with modern GZ34s is that they are not that reliable and I see plenty of failures, with no brand in particular being any better than any other.

The 2 issues with rectifiers are maximum peak inverse voltage (PIV) and maximum ripple current.

The rectifier can be protected from excessive peak inverse voltage by wiring silicon rectifier diodes in series with the rectifier plates. This is very cheap and the unused pins on the rectifier socket can by used to mount the diodes.

Maximum ripple current needs careful consideration, and depends on a few variables, including current draw, filter capacitance and series resistance.

It is NOT simply a matter of not exceeding the maximum filter capacitance stated in the GZ34 datasheet.

For example, the ripple current on an AC30 is right at the limit of the GZ34s maximum ripple current even though the main filter cap is only 16 uF, cf a maximum of 60 uF.

I reckon in the past this was less of an issue as there was a certain degree of over engineering, so GZ34s would survive in more challenging circuits, but modern GZ34s don't seem to be as robust hence the relatively high rate of failure.

jpfamps

Fenderish said:

shorted rectifier tube is common with GZ34. What's less common is that the mains fuse didn't blow before the PT

It's either bad design or bad luck (if the rectifier tube shorted "strangely" enough to make the PT really hot but not enough to blow the fuse...)

If you saw smoke from the PT it's likely the PT is dead or soon to be, I wouldn't use it anymore...

oh and filter caps have a good chance to be dead too, sorry

Shorted rectifier / transformer will have no effect on the filter caps.

It could be that a filter cap has shorted and taken out the rectifier and / or the transformer, bit I would say it is unlikely.

professorben

Modulus_Amps said:

ecc83 said:

Modulus_Amps said:

ecc83 said:

It is not the OP's fault that the design was so poor that the transformer was not protected but it IS the retailer's responsibility to effect a proper repair or a full refund in a timely manner.

Dave.

I would think a "proper" repair was fairly oviously a new transformer and a return of the amplifier to as new specification?

Dave.

I was wondering if you would consider a Hammond replacement a proper repair.

From reading other comments there has been a few PT failures with the LE amps, maybe they are not made for 50Hz or our near 250v wall voltages

Where are you getting near 250v’s???
im a sparky and measure voltage every single day and I’ve never come across anything over 235v....

ICBM

professorben said:

Where are you getting near 250v’s???

im a sparky and measure voltage every single day and I’ve never come across anything over 235v....

Come and try it at King Street in Glasgow!

Modulus_Amps

@professorben said:

Modulus_Amps said:

ecc83 said:

Modulus_Amps said:

ecc83 said:

It is not the OP's fault that the design was so poor that the transformer was not protected but it IS the retailer's responsibility to effect a proper repair or a full refund in a timely manner.

Dave.

I would think a "proper" repair was fairly oviously a new transformer and a return of the amplifier to as new specification?

Dave.

I was wondering if you would consider a Hammond replacement a proper repair.

From reading other comments there has been a few PT failures with the LE amps, maybe they are not made for 50Hz or our near 250v wall voltages

Where are you getting near 250v’s???
im a sparky and measure voltage every single day and I’ve never come across anything over 235v....

Thats low for the UK, where are you based?

London is often just under 250v, I am in NE Scotland and my wall voltage never goes below 246v

jpfamps

professorben said:

Modulus_Amps said:

ecc83 said:

Modulus_Amps said:

ecc83 said:

It is not the OP's fault that the design was so poor that the transformer was not protected but it IS the retailer's responsibility to effect a proper repair or a full refund in a timely manner.

Dave.

I would think a "proper" repair was fairly oviously a new transformer and a return of the amplifier to as new specification?

Dave.

I was wondering if you would consider a Hammond replacement a proper repair.

From reading other comments there has been a few PT failures with the LE amps, maybe they are not made for 50Hz or our near 250v wall voltages

Where are you getting near 250v’s???
im a sparky and measure voltage every single day and I’ve never come across anything over 235v....

In my workshop in Denmark St, London.

And I am using a true RMS meter.

Usually around 247 Vrms, but a little higher in the evening.

jpfamps

I should also point out the American amp makers (including Fender) seem to have an allergy to fuses and many transformer failures in my opinion could be avoided with proper fusing of the transformer secondaries.

professorben

Modulus_Amps said:

@professorben said:

Modulus_Amps said:

ecc83 said:

Modulus_Amps said:

ecc83 said:

It is not the OP's fault that the design was so poor that the transformer was not protected but it IS the retailer's responsibility to effect a proper repair or a full refund in a timely manner.

Dave.

I would think a "proper" repair was fairly oviously a new transformer and a return of the amplifier to as new specification?

Dave.

I was wondering if you would consider a Hammond replacement a proper repair.

From reading other comments there has been a few PT failures with the LE amps, maybe they are not made for 50Hz or our near 250v wall voltages

Where are you getting near 250v’s???
im a sparky and measure voltage every single day and I’ve never come across anything over 235v....

Thats low for the UK, where are you based?

London is often just under 250v, I am in NE Scotland and my wall voltage never goes below 246v

Interesting. 

I work across East Anglia,Norfolk, Northamptonshire, into North London and Oxfordshire. 

gringopig

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