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60ies Klemt Echolette M40


This Klemt Echolette M40 from the early 1960s had spent the last 20 years in an old shed, unnoticed. The new owner asked us: "Do you think you can get this thing flying again?". Of course we can... 


those were the days.


The Klemt Echolette M40 and the matching Echolette LE2 speakers were THE club PA of the 1960s in Germany. Equipped with 4 inputs that could process everything from microphones to guitars to high-level keyboard instruments and a 32W ultra-linear power amplifier with 4xEL84. With this device, the band or club was prepared for anything that might come.


So, the best of the best. Those were the days! History is that the Beatles also used it for their legendary performances in Hamburg's "Star Club".

The starting point

Oh oh!


Our customer rescued exactly such an Echolette Club PA from an old shed after more than 20 years of "resting" there and would like to use it again in the same way as in the 60ies. Namely as an amplifier system for vocals and instruments with lots of vintage charm.

A few first mobile phone photos of the owner did not suggest anything good.

Power supply electrolytic capacitors that had "vomited" their electrolyte. A power switch that was defective and was simply bypassed with twisted-pair cables. A defective fuse that was not replaced but simply bridged with aluminum foil.

Our clear recommendation

Don't turn this thing on! Bring directly to the Tube WorkShop for assessment.

After the Echolette M40 had arrived at the Tube WorkShop, we were reliefed.

Yes, the mains switch broke off internally... someone had bridged the fuse... the power supply electrolytic capacitors were dead... and the device contained the dust of the last 60 years...

But otherwise the amp was in really good condition!

The housing was still OK...

There was an original tube set with 5x Telefunken ECC83, 4x Siemens EL84 and EZ81's from Valvo and Siemens...

When measuring the windings, the transformers showed no short circuits or interruptions...

The circuit was in absolute original condition and had never seen a soldering iron since it left the factory...

The last one in particular is very helpful in a restoration, since defective components can be replaced based from factory condition and there is no need to first sift through and eliminate lengthy, well-intentioned tinkering attempts by soldering iron artists from the past.

First, the innards of the amp were freed from the dust of the decades using compressed air and a brush (tip: better do this outdoors). When the cloud of dust settled in the workshop, things looked very promising.

The plan

we'll get it "back to life".


In consultation with the owner, we have determined that the Echolette should be as "vintage correct" as possible. This means that components such as capacitors and resistors are replaced by structurally identical types wherever possible and avsailable. Safety-critical components are replaced by modern, higher-quality types. We didn't want to let "NOS fever" break out here. Overall, however, the original condition of the amp should be preserved or restored as technically and optically correct as possible. 

Since the amp arrived in an unsafe condition, the first restoration step on the agenda is to overhaul the power supply. Only then can the amp be put back into operation, piece by piece, and the further measures required can be assessed.


Therefor the first steps are:

  • Exchange of the 2-pin mains socket for a modern type with a dedicated ground connector. 

  • Exchange of the power supply capacitors

  • Measurement of the existing tube set for condition and function

  • Replacing the power switch while keeping the original look

  • Firing up the revised power supply

Power supply

Klemt, what were you thinking?


As already written, the Power supply electrolytic capacitors had already started to “vomit” electrolyte and were more than obviously exhausted. This is also normal for 60-year-old electrolytic capacitors. 


However, it should also be mentioned that Klemt used electrolytic capacitors with a voltage strength of 350V in an amp that had a B+ voltage of approx. 380V after the rectifier tubes. Ok, even if you assume that the mains voltage in the 60s was slightly lower than today (and therefore the B+ voltage was also lower), this is still a more than "borderline" design.

In our amp, the power supply electrolytic capacitors were replaced with mechanically identical types from F&T that have a voltage strength of 450V. We are now in the “safe area”.


A little tech tip at this point:

After removing the old electrolytic capacitors, I had the fun of checking one of them for capacity and ESR value.

Interestingly, a capacitance >50uF could be measured and an ESR value <2Ohm.


So was the capacitor still “good” and perhaps even particularly “strong” with a capacity >50uF? Um, nope!

What is crucial about an electrolytic capacitor is that it is not “leaky” (i.e. does not allow DC voltage to pass through) and all of the existing electrolytic capacitors already had a worryingly low DC resistance in the three-digit kiloohm range. So you were well on your way to creating a short circuit in the power supply. Incidentally, an increased capacity value (as in our case) is a quite good indicator, since when measuring capacity, the value is determined via a time constant during the charging process. If the capacitor allows direct voltage to pass through, it charges more slowly and a higher capacitance value is displayed.

High capacitance value = particularly strong capacitor? No... more of a sign that he is "Leaky". 
But enough of the tech babble that no one understands anyway...

Next up was the Power button restoration at. This was quite a time-consuming step.
The original power switch was still there, but was broken off before the connection terminal.

Of course, this switch is no longer available and it had to bea replacement type can be found that can be integrated into the Echolette M40. We actually used this switch [LINK]. The old switch button had to be removed and applied to the new switch using epoxy resin using a device. The Echolette then had to be dismantled on a larger scale in order to make suitable holes for the new switch on the existing bracket. At the end of the day, the Echolette M40's power switch could be restored with its original appearance from the outside.

The originalsrectifier tubesfrom Siemens/Lorenz have in our eTracer tube testing system optimal values are still achieved and can continue to be used.

Finally there was still “Better living” on the program and the tube bases of the rectifier tubes were cleaned with isopropanol and the chassis was cleaned of dirt and rust with isopropanol and then treated with WD40 to protect the surface. An old toothbrush (chassis) and interdental brushes (tube base) are your friends here!

After the 2-pin power socket was replaced with a modern cold device socket with a protective conductor (and the protective conductor was connected to the amp chassis), the Echolette M40 was able to be slowly started up again for the first time using a control transformer brought to life become. Of course, there were no other tubes in the amp apart from the rectifier tubes.


All voltages from the mains transformer (HV, heater, power amplifier bias) are present and stable. Let's move on...