1960 Watkins Westminster Transformer Replacement Help

[ValveBytes]

Hi,

I want to reinstate the full-wave rectifier in this amp and I'm not sure what transformer to get, I have found these two transformers from Douglas Transformers would either of them be suitable:

MT1FT
250-0-250v 80ma
0-6.3v 3a
0-5-6.3v 2a

MT10FT
250-0-250v 120ma
0-6.3v 3.5a
0-5-6.3v 2a

The valves in the amp are 2x ECL82 1x ECC83 and an EZ80 all use 6.3v heaters and I need two heater outs from the transformer if following the original circuit here.

Rectifier EZ80 specification is: (could use EZ81 instead higher rated?)
Vh 6.3
Ah 0.6
Va 350
mAa 90

Background to the story:

I got a broken Westminster some time ago and got it fixed by an expert who was maybe a little too old to do the job properly, anyway the 'new' smoothing capacitors blew up with clouds of white smoke so I opened it up and saw what had been done to this amp, the EZ80 had been replaced by two diodes for rectification and a new MASSIVE transformer had been put it.

So I decided to go about restoring the amp myself, replaced all the capacitors and tested every resistor against the values in the circuit diagram and replaced some of them too.. anyway the end result was an amp that sounded a lot better and had a really bright and vibrant tremolo, only snag is I still have a buzzing sound and a pair of diodes and an over sized transformer, also a 3 part 32+32+32 capacitor doing the smoothing that I made myself from 3 separates inserted in to the old can from the original cap.

I'm not an expert at all I just learned what I could from books and common sense but as this isn't a find and replace job anymore I'm getting a bit stuck.

I want to build a capacitor reformer and figure out valve biasing as my future projects.

any help would be great!

[Bruce / Mission Amps]

Do you have a proper schematic for this amp?
Your buzz is probably from the filament supply not being referenced to a common ground point.
As far as the PT goes.... did the original have a non center tapped power tranny that required the full wave bridge?

Here's a heads up for you for now though:
Using either of the listed PTs with a full wave bridge rectifier will give you a B+ of well over 650vdc to 700vdc!!!

[ValveBytes]

thanks for the reply here are the two schematic diagrams that I used to replace the parts I could:

http://www.xbytes.pwp.blueyonder.co....ges/west1.jpeg
http://www.xbytes.pwp.blueyonder.co.uk/Images/west2.jpg

the buzz may also be caused by the large transformer being too near the speaker?

any other info would be great!

[Bruce / Mission Amps]

One players buzz is another players hum, and to me, it could be noise from a badly seated switch on an input jack.
Note that the filament supply for the preamp tubes is grounded on one side?
I'd consider rewiring the sockets more like the sockets in a blackface Fender amp.
Then use a virtual center tap with a pair of 100 ohm resistors to reference the filament supply to ground.
It might help some of the buzz.
Considering it's age, the historical period in time it was designed and built, anything is possible now that we have all been exposed to some of the finest tube amps ever built for guitar players, but I doubt the buzz is from the proximity of the speaker and transformer.

[ValveBytes]

Hmm interesting I do think the buzz is probably a grounding issue, sounds like AC mains buzz not noticeable during play, but what I really need advice about is a replacement transformer to get that rectifier back and get rid of those two diodes! also I have found the amp is more likely 1957-59 rather than 60 not that it makes much difference.

it does sound great the amp if you play les paul through it distorts very well, also nice with a Tokai telecaster.

thanks for the info been very helpful.

[ValveBytes]

Now you got me thinking about the buzz!

Actually two sounds come from the amp, one is a constant bzzzz not from the speaker sounds like AC mains hum... the other sound(s) come from the speaker, sounds a little bit like a radio being tuned in. I had another look inside and noticed the 50mfd electrolytic that someone attached to the pentode cathode of the ECL82's that goes to ground, anyway took it out and popped in a new 25v 22mfd cap and radio tuning type interference seems to have cleared up!