engl ironball 20w no signal

[vegaluthier]

Hello, technician friends! Long time no see!

I have this engl all tube amp and it turns on, and all valves seems to turn on normally but it doesn't amplifly anything.

I can only hear powering sound from on/off and stand by switches and statics. This last one increase statics when turned on, but only from headphones out. Volume controls and all preamplification stage modifies nothing from this out.

From 8ohm out seems dead. It has a selector which reduces amplifier power from there, to 20w/5w/1w or speaker off. Tried already to remove it and from 16ohm out.

I have checked input and output jacks, bypassed the effect loop by now... I will check if preamp stage is connected and if it gets any power next...

But first, please ... Any hints? Anyone had a similar problem with or there are known issues about this amp?

Thank you in advance!

See you!

[Jon Snell]

A schematic would give us a clue as to where to look.

[vegaluthier]

Hello Jon, thank you, yesterday I looked for schematics at elektrotanya but there isn't any of the model.

Today, I found user manual online only. Maybe some other sites to recommend?

Anyway, there were similar avaliable and I guess that found the reason for the failure.

It has main voltage and an output transformers. Seems that the output transformer melted, or there is something shorting all transformer pins to ground. Fuses are ok. Maybe diodes?

I would apprecciate some hints of what to look first, in cases like this.
I found it because output jacks were shorting but were definitely good.

Thank you guys!

[Jon Snell]

Very sorry but without a schematic there is not at lot anyone can do without it actually being on the bench in front of them.

Don't over think the issue, it probably is a pre amp problem, dodgy connector as you state you have static sounds to the speaker.

It is an Engl after all.

[Chuck H]

I guess that found the reason for the failure.

It has main voltage and an output transformers. Seems that the output transformer melted, or there is something shorting all transformer pins to ground. Fuses are ok. Maybe diodes?

Why do you think this is the reason for the failure? Are there charred or burned components? Electrical fire smell? etc. Otherwise I'm with Jon. It would be strange to see such a catastrophic failure as both power and output transformers having all connections shorted to ground in any amp. Let alone an Engle. I can't even think of how that could happen.

[Enzo]

ALL OT pins shorted to ground? Or just the secondaries? Secondaries have extremely low DC resistance normally.

[Chuck H]

ALL OT pins shorted to ground? Or just the secondaries? Secondaries have extremely low DC resistance normally.

This was my first thought. But vegaluthier said:

"I guess that found the reason for the failure... ...there is something shorting all transformer pins to ground."

[Enzo]

He did say that, but I have seen too many descriptions of things that were faulty. AS in ALL the wires to the output jacks.

[vegaluthier]

Hello guys.

The amplifier also has two fuses for the valves. One was broke (not visibly, but no continuity) and two of the preamp valves didn't turn on.

At first, I thought that was the problem, and the dead valves turned on. As I told, all pins of output transformer gave positive continuity test to chassis ground, as speakers out jacks did. I only get some statics and power sound on from headphones out. Power transformer doesn't behave as that, those has low resistance but not continuity.

I don't see much catastrophic melts, but there are many overheated solder spots in many places, there was a strange red corrosion near the digital reverb module, and maybe someone thrown a liquid on it.
About smells, I don't feel anything remarkable, but the owner told me he did (years ago when the engl died) and told me about smell and smoke too.

That leads me to think that the inner coil of the OT melted. How it happen, I don't know now.

Now I will double check, take pictures and desolder shorting pins to see if that caused the output jacks to short.

[vegaluthier]

Shortly, like Enzo asked: Only OT pins shorting to ground chassis (all of them, main and secondary). Main trasformer doesn't. I don't get statics from speaker, only through headphones.

Later I will send the pictures when I discover if it is the transformer or something else. Power soak selector is also good.

Thank you very much for your attention.

[Delta362]

I fixed an Engl Powerball II recently that had no signal passing, but did have static thru the speakers. There were several things I ended up finding/repairing, but let's work thru your amp's issues.

In your amp's case, did you verify that you have heater voltage (check VAC as well as VDC) at all of the tubes? Are the plate resistors ok? What voltages do you have on the tubes?

[vegaluthier]

Hey folks.
I disconected the transformer and the output plate and seems that short is located on the plate. Readings on the transformer isolated seems odd but not melted, secondary pins have from 1.8 to 2.6 ohms, but different each, main pins do read more like normal.

So, I am sending a picture of the plates and overheated solder points. Next I will try to locate the short cause in the output plate, and later I am assembling all to measure voltage at valves.

If you allow videos, or readings are worthy, I will send as well...

Thank you very much!

[Enzo]

My first suspect then becomes any flyback diode they may have used.