Standel 25L15 reversed engineered schematic request

[kingplank]

I am building a Standel 25L15 like amp using 6L6 from pieced together schematics from the web. There seems to be several errors on these. I dont want to start a house fire or blow tubes as soon as I hit the standby.
I am not attempting to build a clone or for commercial interests , been facinated with the Standel sound for 40 years. Any help will be appreciated
Thanks in advance.

[Enzo]

Hi, glad you got here.

Can you link us to these schematics, and what errors are there on them?

My STandel collection is pretty much solid state, and the collection on their web site is mostly the same. But for all interested, visit Standel support page:
Standel | Schematics

On google I find some clone drawings.

The thing to keep in mind is that tube amps are mostly all the same. Look at the circuit for something basic like a Fender Bassman, then compare any other schematic to it. Sure, your Marshall may have a 0.68uf cathode bypass ap on a stage and the Fender has 25uf there, but the circuit itself is the same. One might add a cathode follower before the tone stack. Details. The push pull output stages will all be similar. SO if you feel some element of your schematic is wrong, see if it was done in similar fashion on the Fender.

Is that absolutely foolproof, no of course not. But for the most part that is good enough. I am not bragging to say I could easily sit down with a paper and pencil and draw a working amp schematic. Most guys who have worked with them for any length of time could do so. Power pentodes will need screen supplied, bias to either their grids or cathodes, and some sort of phase inverter to feed those grids.

[Leo_Gnardo]

Those are terrific amps! You picked a good one to copy. I've had to repair 2 in the last 10 years, but no schematic in sight. I'd post one if I had.

If you see some glaring error that would short-circuit if you built that way try to figure out what they really meant. Also it's a good idea to slowly bring up the line voltage with a variac on any new build, with an undersized fuse in the fuseholder, and monitor current draw as the AC voltage is increased with the variac. You could build a piece at a time, starting with power supply, power amp then preamp & check for proper operation as you complete each section. Good luck & keep us posted.

[dmeek]

A few years ago I went looking for the elusive 25L15 schematic. I felt like
Indiana Jones on a quest, meeting those who claimed to own or have
seen the Sacred Document but had promised not to share it. I did eventually
find a few versions, so at the risk of offending some Secret Society, I'll post
them here. There is an owners manual for what seems to be a re-issue
here: Standel | Manuals.

Doug

http://music-electronics-forum.com/a...1&d=1366937572
http://music-electronics-forum.com/a...1&d=1366937572
http://music-electronics-forum.com/a...1&d=1366937712
http://music-electronics-forum.com/a...1&d=1366937712

[kingplank]

Thanks fellas for your replies.
I also have this "napkin" schematic. It is said to be the reissue 25L15; very similar to the Bob Crooks 1953 schematic, The giveaway are the cap values of which this one is modern.
I've been basing my new built on all these schematics, I know they all have errors

From my past 2 years of research, I concluded that Ted Weber's Pennebaker 25 is genuine; Ted was an honest guy. When Bob Crooks first built th 25L15, he based it on the Williamson; but it did not sound good for guitar so Bob redesigned it for the next verson. The Pennebaker is very close to a Williamson.

Now that leaves us the 3 remaining circuits; which I gathered are very close to the real thing, bare in mind that there are many versons of it and how much variences amongst them I do not know.
I have made my own adjustments to the circuit, mainly to suit my transformers. I am hoping that I have all the info needed to finish it off.
Unfortunately I dont have a varitransformer, and usually start a new built with stages as suggested. And trouble shooting is so stressful.

[Enzo]

Errors, errors, they all have errors... WHAT errors? Can you point some of them out?