Tubeman Transformer problem

[Michael Weidenauer]

A friend gave me an old Hughes & Kettner Tubeman 1 that stopped working after it fell down. If found out that the secondary winding of the internal trafo is broken so I need a replacement for it. The original Trafo is an Engel EV3770.
I couldn't find this part anywhere - the only thing I could find was a post in a forum (in French, so I didn't understand everything) where someone said it transforms the 12V to 400V,
but another guy there said it were just 220V.  So what is true?
Anybody got the schematic or the specs of the trafo ?
Or maybe someone got a Tubeman 1 and can measure the secondary voltage?

Thanks!
Michael

[brett]

Hi
if all else fails, these people will sell you a schemo
http://www.candisc.com/ranger/stock28.htm
but I'll search some more...
cheers

[brett]

Hi
on the Tubeman II schematic, it's marked as a 12:240V step-up, for a B+ of 280V.
http://www.tubeguitaramp.de/hughes/tubeman.pdf
To be really sure that this transformer is correct, check that your external AC adapter gives an output of 12 to 15V AC. 
Also, stick with at least the 2VA rating of the transformer.
Looks like a very cool pre-amp.
cheers

[Michael Weidenauer]

I've got this schematic too but:
The Tubeman 1 is not a 3 channel pre-amp like the newer version -
Its only single channel with a 4-way Mode selector switch and can also be used as stompbox in front of the amp.

So, maybe the TM2 uses the same voltages like The TM1,   but maybe not! 

If I don't find any further information I think I'll try to start with a 12V/230V 1VA transformer.
Anybody knows how much mA a 12AX7 needs in such application

Michael

[Michael Weidenauer]

Thanks Brett! I just read your last post again and I noticed I didn't see that you recomend 2VA for start.
I Wanted to use the 1VA 12V/230V trafo because it's a cheap standard part for about 3,50Euro and it fits in.
The 2VA I've found yet were to big for the enclosure.

Michael!

[brett]

Hi
A 12AX7 typically uses 1/4 of a VA (unless it's faulty, and then your fuse should save you).  The only other components that I think will draw serious current would be LEDs and small "grain" bulbs (allow 1/4 VA each), and any relays (hard to say how much they draw).

Why not try the small transformer?  Almost all transformers have thermal fuses that turn them off if they get too hot.  If you idle it for 3 hours and the transformer is no more than warm to touch, it will be ok.  But don't stick your finger on a live transformer. 
cheers 

[Michael Weidenauer]

Yes i think 1VA should be enough cause the 280V are only needed to supply the B+ for the anodes of the tube.
But anyway - last night a found a cheap trafo with 2,3VA (EI 30 12V/230V) that should also fit in well.  - just for savety (the original trafos seem to die quite often)

I hope that the 230V will be enough (the trafo in the TM2 schem reads 12V/250V) to get close to 280V.
Anyone knows what happens to the sound if you lower the voltage for the anodes? (more distortion? - less dynamics?...)

I didn't know that most transformers have a built in heat fuse. Nice!

Michael

[brett]

Hi again
a bit lower B+ will lower the headroom just a bit.  You'll get a bit more distortion and compression.  But don't expect it to change too much.  Line voltages in many countries vary by +/- 10% from area to area or even building to building, so B+ voltages vary by +/- 20V due to that alone. (My area is supposed to be 240 V, but is often 255 V. My Marshall therefore has a B+ of 510 V instead of 480 V but it's still a dirty beast.)
cheers

[Michael Weidenauer]

Last night I put in a 2,3VA trafo (230V/12V) and it works very well.
Sounds very good in front of my Twin Reverb and provides many different sounds (although the drive modes sound a bit to british for my taste).
The speaker sim from the mixer out didn't convince me so much- it needs lots of tweaking on the mixer-eq to sound right.

The strange thing is that i only get 175V-AC on the secondary of the trafo (or 200V when i unplug the tube) and about 200V-DC B+ (or 230V with no tube).
The primary AC is about 13V so there should be at least 230V-AC on the other side. Am I wrong?
So, is it a normal thing or could it be a leaky Elko in the B+ supply?

But anyway - it works and the trafo doesn't get hot at all. 

I also tried different tubes (EH, Sovtek, Svetlana, EI) but only the EI and the original H&K tubes sounded right.

Thanks for your help Brett!

Michael

[Bruce Bennett02]

 Hi Guys !
  Though I'm not actually new to this forum, it has been well over a decade since I last posted.
I picked up a Used H&K Tubeman of the same model and vintage as the OP of this thread.
and it has the exact same issue. dead tranny. and they don't seem to be available anywhere.


  Wonder if anyone could tell me what transformer the OP end up using.
a model or part number and supplier name would be greatly appreciated.

  Thank you!

[Rob Strand]

If someone knows the answer please post because I don't.

Wonder if anyone could tell me what transformer the OP end up using.
a model or part number and supplier name would be greatly appreciated.

Given that's a PCB mount transformer the options are narrowed down somewhat.
If possible measure the spacings of the  transformer pins on the PCB.  Then look at some 2VA PCB mount transformers.  You can search on-line.  The ones I saw were encapsulated/potted.    See if the footprint matches (and overall height is OK).

From what I can see TubeMan (I) and TubeMan II both use a 12VAC adaptor.    It's still not clear to me if the on-board transformer is 15V or 12V as the labelling on the schematic is ambiguous.   Both the TubeMan I and Tubeman II schematics show voltages.  The voltages *after the PSU filter* were Tubeman (I) 300V and Tubeman II 280V.    However, I'd have to do a lot of guessing to work out if that implies a 12V or 15V transformer.   To me it looks like a 15V transformer would struggle to get to those voltages but it all depends on how close to 12VAC  the plug pack is producing under load.

[freefuzz]

look for an EI30 230V to 12V transformer around 2VA (W)
https://www.reichelt.de/printtrafo-2-3-va-12-v-192-ma-rm-20-mm-ei-30-18-112-p27471.html?&trstct=pol_32
something like this.

[MikeA]

Sorry I'm late to the party, but I just received a Tubeman Mark 1 for repair and wanted to share the transformer info and schematic.  This is the 4-channel version of the Tubeman, released in 1991, in the black plastic case.  The transformer is rated for 15V/250V, and the schematic calls for nominal 12VAC input with output voltages of +300, +/- 12, +/- 15 and 12.5.  If you need measurements of actual voltages once I get it working, let me know.  Best regards,  Mike

[Rob Strand]

Good info thanks.

The transformer could very well be 12V.

The part number is VN30.15/10474, but from this page
https://www.buerklin.com/de/search?text=vn30.15

it looks like the "30.15" part doesn't mean 15V, it's the 10474 part of the part number which defines the voltage(s)

Another snippet is the HK Tubefactor also uses that transformer,
https://www.mikrocontroller.net/topic/136867
http://www.sonicurbs.com/tubefactor/board2.jpg

I didn't spend any more time hunting down the exact transformer and specs.