Transformer ma rating?

[beasleybodyshop]

So i called up Heyboer to order a replacement transformer, and they asked me what the Milliamp rating is on the B+.

In my particular case, 200ma would be fine - but would it be an improvement to have them wind it to say, 240ma? what advantages does having a high current rating give me, if any?

[Littlewyan]

Less heat from the transformer itself, longer life (they last years anyway), possibly less sag when there is a large current draw. However be careful that you don't overdo it too much with the current rating as the specified voltage on that secondary will be voltage under load. So if you have too high a current rating then the transformer may never be under load and you will end up with a higher secondary voltage than required (been there done that). You also have to bear in mind that the transformer will get physically larger as you up the VA.

I'm sure there are other benefits that others will chime in with.

Edit: Sorry, should have said 'they last years if used within their ratings'

[Phil_S]

I imagine they'd be willing to look at a schematic and tell you what they think is right. These guys are pros. Give them the bolt pattern, too. From there, they should know.

[beasleybodyshop]

I imagine they'd be willing to look at a schematic and tell you what they think is right. These guys are pros. Give them the bolt pattern, too. From there, they should know.

Yeah I did send them what I had - They were very easy to work with and very accommodating. Aside from the three week lead time I might be custom ordering transformers from now on instead of getting off the shelf units. Its nice to be able to get custom B+ windings, getting a heater tap that will have plenty of current for as many tubes as I want, etc. And the price is comparable to off the shelf units. I wish I had called them sooner!

[ToneMerc]

Yeah I did send them what I had - They were very easy to work with and very accommodating. Aside from the three week lead time I might be custom ordering transformers from now on instead of getting off the shelf units. Its nice to be able to get custom B+ windings, getting a heater tap that will have plenty of current for as many tubes as I want, etc. And the price is comparable to off the shelf units. I wish I had called them sooner!

Exactly the reasons why I use them.

TM

[matt h]

(deleted)

[tubeswell]

Depends on what sort of amp you want too. You can run 3 x 12AX7 and 2 x 5881 with 150mA on the HT and it will sag a bit on power chords and heat up more. A 5F6A typically has a 200mA rated HT winding and was designed initially to run as clean as possible (as a bass amp). 200-240mA is much of a muchness.

[ToneMerc]

A 5F6A typically has a 200mA rated HT winding and was designed initially to run as clean as possible (as a bass amp). 200-240mA is much of a muchness.

The aftermarket ones yes, the original Triad 8087 Tweed Bassman PT was much lower in HT rating and it's part of the charm.

TM

[matt h]

(deleted)

[tubeswell]

200-240mA is much of a muchness.

Vote for a Best-of-the-Week on TAG.

I suppose.

[beasleybodyshop]

I went with the 200ma rating. Its for a Sovtek Mig 50 - so its sorta supposed to be in tweed bassman territory. Anyways, i will give a report on the tranny when it comes in!