Weber Mywatt 200 Leistungstransformator unknown make and specification

jmUK1

New Member
Beiträge
3
Bassix
ß80
Hello, greetings from the UK, I'm new to the forum, which looks very interesting.
I need to replace the power transformer in my Weber Mywatt 200, which is shorted and red coated.
So far, I have not been able to determine the brand and specification of the power transformer. If anyone has experience with this amplifier and can help, that would be greatly appreciated.
 
Hi,

4x KT88


6x EL34

 
I guess @jmUK1 means the power transformer which is a toroidal transformer in the Weber200. I used to own one but sold it about 10 years ago. Unfortunately I don't know supplier and type ID either.
 
You can take the specs from any replacement transformer for the DR201 and either use that or check for a toroidal transformer with usable specs (maybe Max had used custom transformers - i don't know). AFAIK (from Max Weber) the transformer is a 300W type, which is actually a bit low for 200W output. So 350 or even 400 W with suitable outputs is better.

Important: the Mywatt has 670V on the secondary power rail of the KT88.

@cfortner: thanks fpr the hint with Jan Wüstens. I would have given it, too.
 
I would suggest AC these voltages

1x 190V 1,2A
1x 280V 1,2A
1x 6,3V 10A with center tap
1x 15V 3A
1x 50 V 0,2A

Depends to the Mywatt circuit, may be little different to the Hiwatt DR201.
 
Zuletzt bearbeitet:
That means a 800VA transformer 😳 , enough for a 400W amp!

190V and 280V 0,6A may fit better, 350-400VA.

And you have to look at the BIAS DC voltage before installing the KT88, may be it is too low or too high, because we don‘t know the Mywatt AC voltages exactly.
 
Many thanks to everyone who responded so quickly with their answers and suggestions, especially Cfortner and Beate. You now have important insights that there doesn't seem to be a Weber website/contact!
This was a painful episode as the mains/power transformer damaged all four KT88s when it failed. I myself don't have the skills to work on this amp, and it's with a general amp technician who has no experience with the Mywatt. However, it seems that a solution will be easier than I first thought.
I will definitely do some research with Askjanfirst.com and tubetown.net.

Cheers
 
Mywatts are nearly exact clones of the corresponding Hiwatt amps with two differences:

-separate BIAS-regulation
-DC heater for the preamp valves

I recommend a more powerful torioid transformer 500-600VA, not very more expensive and not very more volume and weight.

What are the dimensions of the cracked tranny (in cm, diameter and height)? Perhaps a photo?
 

@jmUK1

@cfortner is a very valuable source of information, as he has restored / rebuilt / enhanced at least two Mywatts in his spare time.

Cheers
claudio
 
Well, seems like I´ve had the same problem here in Munich. The toroidal transfo is shorted. During rehearsal 2 weeks ago 1 of the 5amps fuses blew (the 3 amp of the HV is fine). After some investigations, I've taken out the transfo and when I connect it unloaded to the mains via a lightbulb in series, the bulb fully glows. (which should not happen, and does happen with an JCM800 spare transfo I have here).
I've looked at Dirk's (Tubetown) replacement, but there would be some mods to be done since:
1- There is no 15V winding for the DC heating of the Mywatt
2- I think that for the bias, my watt uses a 100V winding instead of the 50V (When I connect 23VAC to the bias circuit, it gives me about -11VDC for the bias instead of the -47VDC I had measured a while back).
BTW the dimensions on the tranny in mine are: Diameter: 147mm Height:65mm weight 3,9kg
Cheers!
 
1. You may use an independend second transformer with 12,6V AC or 15V AC 2-3 amp for DC heaters

2. Use the 50V AC winding with a bridge rectifier instead of a single diode, you may get about 70V DC

But I espect better results with a transformer with the voltages I told you above.

Your old tranny may be a 400VA type. A Getra toroid transformer 750VA f.e. measures 147x93mm, same diameter, but higher.
 
Zuletzt bearbeitet:
Thanks for that. Yes the mods are definiely possible. As for DC heating, Reeves did without it. I´ve never felt the need to use it on other builds (Even on fire breathing lead channels). The 50 VAC would give enough (-70vdc thereabout).
The R400 might indede be the one I have (It´s potted so I cannot tell), but I think to remember Weber amps was based not too far from there, and the weight and dimensions more or less match.
Question: I can not see the voltages on their spec sheet. Are they made to order (i.e. custom made)?
Thanks again
 
The best source I know ist askjanfirst.com, every custom toroid possible.

I dont believe that Getra delivers custom made toroids in small numbers like one single transformer, ask them and do an internet search for custom toroids, but there will not be too much for private customers.
 
So... I got the big one from Tube Town (https://www.tubetown.net/ttstore/de/tt-dr405-hiwatt-style-netztransformator.html).
It works. I rewired the heating for 6,3VAC. The good thing is that apart from that, there is no need to mod the bias circuit. I needed to cut a bit of the wood support for the back (it does not show with the back in place) and mount the transfo on its long side (as shown on tube town but rotated 90 degrees). The only way to install it so that it fits.
Works fine. I have a slightly lower voltage (625) than before (640) - on 227VAC mains. No big deal, I biased the tubes at 75% of 35W.
And now it weights 27,7 kgs. Lovely.
Cheers!
 

Beliebte Themen



Zurück
Oben Unten