In my opinion it'll be shame, despite it may be necessary to keep the unit running - wouldn't be better solution to get original  transformer from same unit and keep it crispy original?

Some parts may prove difficult to be find, but there seem to be quiet a few non working or  working units on eBay  decently priced (your solution won't be for free neither 😕) but that's my personal view - I like to use original parts only while restoring unit.

Bob

Once you start altering it, at which point should you stop call it B&O

jamesymurray wrote:

I have an old Beomaster 3000-2 (2402) which I have been trying to get back up and running. Signal path is now nice and clean, but the mains transformer is vibrating/humming.

I have tried to decouple the capacitor from the chassis with rubber grommets but this hasn't improved the hum much.

 

Looking at the schematics, the mains transformer has a 22V tap and a 43V tap.

Would there be any problems with replacing the original transformer with a pair of toroidals for each output voltage? Obviously an original transformer would be like hen's teeth.

I'm not worried about having the mains voltage selector as I have no plans to deviate from UK mains.

I'd replace the transformer only, so rectifiers and everything upstream of those would be untouched.

 

Thanks in advance!

 

James

 

I do understand what you mean, and ideally I would like to replace with another original transformer, but they seem very hard to come by, even units for spares/repair, in the UK.

Hypothetically speaking, if one was to go down the route of a pair of toroidals to provide the 22v and 43v rails what VA would be required?

22v toroidals are common to come by, but 43v not so. Would 44v/42v prove too much/too little?

I think the transformer for the BM 2400 is the same, after rectifiers it has 15/31V.

As the in coming line never is stable at exact 220 or 240, 42/44 V should not give problems.

But I have the same opinion as Bob, get a used unit and use it for spares, you may even be able to sell some of the rest.

There is quiet a few on eBay usually (only now seem be just 2 good ones listed) 

my grandma used to say: patience brings the roses 😕

bob

p.s. not long ago there was few under £20 - I've bought one for parts under £30, which I've restored and sadly have to sell

jamesymurray wrote:

I do understand what you mean, and ideally I would like to replace with another original transformer, but they seem very hard to come by, even units for spares/repair, in the UK.

Hypothetically speaking, if one was to go down the route of a pair of toroidals to provide the 22v and 43v rails what VA would be required?

22v toroidals are common to come by, but 43v not so. Would 44v/42v prove too much/too little?

It got me thinking..... so I've checked service manuals (as I remember working on mine and comparing to BC3500) to see if those two have same transformer - it appears that they do BC3500 Part Nr 8013057 and BM3000-2 Part Nr 8013058 ;)

Make long story short - I have one for you 😕

pm if interested

bob

P.S. I'm braking the unit into parts and selling all for charity see post: /forum/imported-unmapped/looking-to-get-good-home-for-some-of-my-bampo-guys#post-2175910 very bottom :)

jamesymurray wrote:

I have an old Beomaster 3000-2 (2402) which I have been trying to get back up and running. Signal path is now nice and clean, but the mains transformer is vibrating/humming.

I have tried to decouple the capacitor from the chassis with rubber grommets but this hasn't improved the hum much.

Looking at the schematics, the mains transformer has a 22V tap and a 43V tap.

Thanks in advance!

James

Problem is this is a rather common problem with these units so buying an old replacement is no guarantee of this happening again. If you can find a good fitted modern replacement solution then IMO that will be the best option!

I happen to respectfully disagree

Parts I'm offering are coming from fully working unit, question remains if the hamming is caused by the main transformer in first place - modern solution is NO NO for a vintage product in my opinion

b

Step1 wrote:

Problem is this is a rather common problem with these units so buying an old replacement is no guarantee of this happening again. If you can find a good fitted modern replacement solution then IMO that will be the best option!

Being very non technical, I don't wish to weigh into this discussion particularly! However I do believe the 3000 type transformers have a tendency for the core to delaminate and this can be a source of hum. Certainly both mine hummed and the 4400 I had did as well. The 4401 seems immune just at the minute! I think you can rebuild these though it is clearly labour intensive!

If 3000's were rare, or a new transformer somehow effected the performance I would wholeheartedly agree with you Bob, but they are pretty common, and as long as an original transformer could later be put back in there then I don't see a problem!
As Peter has said these transformers are prone to failing, and I am sure they are potted so I don't know where this leaves a rewind?

I believe Martin was looking at having custom made unit built but not sure how far he got with this?