New Amp Day - Schaller KV 10

[Pepe]

I bought a vintage German amp, a Schaller KV 10. It cost next to nothing, the shipping costs were almost the same as the price for the amp.

Technically, it is in pitiful shape. It has loud ground hum and lots of problems with the built-in tremolo, which apparently has the same circuit as the Schaller TR68 Tremolo pedal that I purchased quite recently. And the latter is the main reason why I bought this amp. You can see that most of the knobs have their aluminium cover plate missing*, just as one knob of my Schaller Tremolo pedal. I am going to switch those knobs so that my pedal looks as it should - I can live with an amp that has pure black knobs.

I am going to give this amp a thorough overhaul. So far it sounds promising, much louder than one would expect from a 10W RMS solid-state amp. In perfect working condition, this should be great amp for small gigs.



*one has fallen off from the two bigger knobs today, but it is still existent, also the one knob that is completely missing in the picture

[Pepe]

I disassembled the amp today, and the main fault was immediately visable. One wire from the can-type electrolytic capacitor had a bad solder spot and was hanging around without any connection. I'm certain that a proper recapping and overall maintenance will be sufficient to get it back to full working state.

The speaker was made in a town nearby, by DEW Magnetfabrik in Dortmund, which is still existent under another name, but they don't produce speakers anymore.



The solder side of the circuit board looks pretty good for its age. I am going to give all those solder spots a reflow maintenance to ensure solid connections for the next decades.



The other side is really dirty and full of dust. I am going to replace the tantalum and the electrolytic capacitors.



Here you can see the wire that has come off from its solder spot, leading to a massive amount of humming sound.

[laurie]

That's a really solid looking amp! Nice score.

[Pepe]

I think so, too! I'm looking forward to trying it out after the maintenance.

Some of these amps - and there are bigger ones from the KV ("Koffermischverstärker" = "suitcase mixing amplifier") series, some have tubes, some even have a built-in Binson-style disc echo - can be had for really good prices, but they do often need a lot of service, and most of these units are commonly found in the South of Germany, as Schaller has always been located there, in the near of Nuremberg. I was lucky that the seller was willing to ship this amp to me.

[Pepe]

Those coloured tantalum capacitors look so great. It's almost a shame that I have to replace them. Another interesting looking component is the Siemens (B 32215) 0.047µF MKT film capacitor in the middle (above the Roederstein 100µF/35V electrolytic capacitor). Vintage stuff can be fascinating!

[Pepe]

I ordered the replacement parts today:

• a new power cord

• instrument jacks

• fuses

• cable grommets

• several washers and screws that are missing

• 13 axial electrolytic capacitors (IC Illinois)

• 10 low-ESR electrolytic capacitors to replace the tantalums (Panasonic FC)

• test cables with crocodile clips on both ends (for the calibration of the power amplifier)

And - bam! - that's over 50 EUR without shipping, more than what I spent for the amp.
But in the end it will hopefully work for another few decades.

[Gasgano]

Beautiful.