Dallas Scala Amplifier circa 1961

This image belongs to Jonathan Lewis

Model 519 with tremolo.

The "improved Scala amplifiers" 515/519 brochure below, lifted form Steve Russel’s Vintage Hofner website (Hope you don’t mind Steve) used a similar chassis to the featured amplifier. Fashion changes and I guess it would be cheaper to produce a plain rectangular box rather than the relatively complicated shape and two tone livery of the featured cabinet.

The amp I really wanted to talk about is the little sloping TV front Dallas Scala pictured below, for which there is next to no reliable information on the web that I could find anywhere, so I have documented it as best I can in this feature compiled for publication in January 2021

I have seen this model referred to as a 519, the chassis looks the same, but I have seen no hard evidence to back it up so is it a 519?

This amp actually is very lucky to have survived as when it came my way many years ago it was in a terrible state, riddled with woodworm and covered in filth as it was stored in an old chicken house. I almost threw it straight in the skip but there was just that something about it I liked and that’s what stopped me! By this time the uninvited guests had long gone to pastures new so I pulled the chassis and speaker out thinking I might make another cabinet for it, but these amps are so rare I cleaned it all up and gave it several good soakings of woodworm killer but I saw no beetles or larvae emerge, but it was 'shall I or shan’t I bin it?'. I left it to dry out, put it all in a box and forgot about it for a further decade or so. When one day having a workshop clear out it showed its ugly head once again and still I was not sure quite what to do with it, but checking the cabinet again there was absolutely no wood dust anywhere to be seen as there would be in the presence of any live worm. But just for good measure I dosed it up with woodworm killer yet again and although the cabinet and back panel looked like it had been blasted with a shotgun, it was still holding together ok and otherwise looked pretty good. I think the "patina" just adds to its age charm and its character, so to restore it I think would be sacrilege.
Before looking at the chassis, here are few horrifying images for you to see below.

There must have been something pretty tasty in here, damn critters!

Good thing they didn’t fancy the speaker cone.
Below is the cabinet with the chassis installed.

Now for a look at the chassis before any restoration work.

The filter capacitor clearly shows its date of manufacture as August 1961, therefore it is reasonable
to assume the amplifier dates from the latter part of '61 to the first quarter of '62.

My intention here was to replace only the components necessary to get it working as it should,
they would be the three black Hunts wax capacitors with the polyester ones you can see in the image below.

One across the left ECC83 valve socket and the two mounted fairly centrally on the tag board.

The next image is the tremolo board mounted at the bottom of the control panel. An EF86 is the valve for this circuit and works as tremolo only. On the control panel above the tremolo board are: Input jacks 1 & 2, and the pots. Top to bottom - 1 is a switched volume pot. 2 volume, 3 tone and 4 tremolo speed. Bottom jack socket tremolo foot switch.*

Looking at this board you can see x 2 Hunts wax capacitors to the left, I replaced both of those. To the right of the valve socket you can just see another Hunts capacitor hiding beneath the 100k & 470K resistors. Further to the right a .05uf Metalmite capacitor. These I replaced regardless of condition. To the left of the valve socket is a 1.5k variable slide resistor pre-set, adjusted to set the tremolo depth* The 50uf 12v Plessey bypass cap, which was unusually in spec was left in place as were the pair on the chassis underside.

EF86 and four new capacitors in place and ready to go

*I don’t have access to an original footswitch for this amplifier so have configured it as a straightforward ON/OFF foot switch but think that I read somewhere it may also have changed the depth setting by switching in or bypassing a resistor. This I’m sorry to say at the time of writing I am not able to confirm.

I would be grateful if anyone can enlighten me on this subject.

You might have noticed the valves look a bit "wonky", this is because the base sockets are rather crudely mounted by their flanges being attached, one to the paxolin of the tag boards, the other to a metal rail/strip attached to the chassis. Not being exactly the same height throws the valves out of line with the chassis.
The valves are EF86 Tremolo, ECC83 Preamp & driver/tone. EL84 Output, EZ80 Rectifier.

Assembled images for you

So there it is in all its splendour

I’m not intending to give this away but for anyone interested in it, with or without a brand new repro cabinet covered in the Dominator Retro Blue and grey material, I’m open to offers. Contact details on the contacts page.

I think this about concludes this article but just for good measure, below is the schematic drawn by yours truly,
nobody is perfect so it might have a few mistakes, but I’m sure if you have such an amp it will help you find your way around it.
Schematic provided for personal use only, not to be published on any other websites or printed publications.

© Copyright Amp-fix 2021 Not for publication without the written consent of John Beer