Hi all!

I just bought a nice ST-70 intended for full rebuild. It is missing
the original PA060 power tranny, but that's not a big deal since here
in Spain power line is 230v.

Question is, does anyone know of a good source for a power trafo for
this amp with a primary of 220-230V? It can be anyone selling the
original PA521, or a modern rebuild.

I know Sowter makes a nice upgraded copy, but it costs ***more***
($240 shipped) than the rest of the amp itself! So a cheaper option
would greatly be appreciated.

By the way, I am designing for it a board using EF804S and 6SN7
instead of the original 7199. Will post the schematic real soon.

TIA

Ignacio

izozaya wrote:

Question is, does anyone know of a good source for a power trafo for
this amp with a primary of 220-230V? It can be anyone selling the
original PA521, or a modern rebuild.

Can't you just order a custom made transformer in Spain?

Otherwise try looking he
http://fragjanzuerst.de/dindex.htm?/trafo.htm

But European transformers may not fit the chassis, so perhaps buying a
new or used 120V transformer and using a 230/115V auto-transformer would
be easier?

Best regards,

Mikkel C. Simonsen

Hello Ignacio:

I would buy the Sowter replacement for several reasons.

1) The original ST-70 transformer mounts horizontally.
So you don't only have a Primary Voltage issue, you also
have mechanical mounting considerations, the Sowter is a
proven drop-in replacement.

2) Custom wound transformers will cost you about the
same (multiple-pieces) or more (a single piece) money and
you are introducing variables, unless you order from a reputable
source like Hammond, Bartolucci or Doc Hoyer.

a.Will the transformer actually perform well?
b.Will it fit the chassis?
c.How reliable will it be over time?
d.Will all voltages and currents work as expected?

Price paid for cost to restore is not always a good metric, unless
you plan to sell the amp later and maximize profit.

In your case, you are lucky that you were able to buy an ST-70 w/o
trafo for the price you paid. One look around Ebay and you can
see that ST-70 prices have sky rocketed.

Four years ago a mint ST-70 was $180 dollars + shipping. Now they are
selling for around $550 to $650 dollars if you can find one in
good enough shape that has not been 'upgraded' (butchered.)

If lucky Ebay might have a used replacement ST-70 Transformer and
for 240V at that! Or you may be lucky to find a real ST-70 230 V
replacement.

As a last resort you can use the Triode Electronics upgrade model with a
good quality step-up transformer unit with good capacity and low noise.

Buena suerte!

BR/

Rich Sherman


"izozaya" wrote in message
om...
Hi all!

I just bought a nice ST-70 intended for full rebuild. It is missing
the original PA060 power tranny, but that's not a big deal since here
in Spain power line is 230v.

Question is, does anyone know of a good source for a power trafo for
this amp with a primary of 220-230V? It can be anyone selling the
original PA521, or a modern rebuild.

I know Sowter makes a nice upgraded copy, but it costs ***more***
($240 shipped) than the rest of the amp itself! So a cheaper option
would greatly be appreciated.

By the way, I am designing for it a board using EF804S and 6SN7
instead of the original 7199. Will post the schematic real soon.

TIA

Ignacio

Rich Sherman wrote:

2) Custom wound transformers will cost you about the
same (multiple-pieces) or more (a single piece) money

Not in Europe... Here a custom-made transformer is often cheaper than a
standard Hammond transformer.

a.Will the transformer actually perform well?
b.Will it fit the chassis?
c.How reliable will it be over time?
d.Will all voltages and currents work as expected?

Apart from b, none of those concerns are too important. A and C is not
an issue when you buy from a good transformer company. And D is not a
big problem in a tube amp...

Best regards,

Mikkel C. Simonsen

http://cgi.ebay.com/ws/eBayISAPI.dll...m=5738437 856
&rd=1

Here's a good used Dyna ST-70 Transformer for sale on Ebay (they
show up once in a-while.

Good to know that Custom made transformers are cheaper than
standard Hammonds. Please share the contact info
with the rest of us.

I am in need to two custom made transformers and so far the cheapest
has been Bartolucci at approx 115 Euro a piece + shipping from Italy.

Custom Hammonds are a 10 pieces per order minimum and it gets close to $900
dollars
for all 10 pieces + shipping.

On your comments below, I have to say you are an optimist. I tend to
be more of a pessimist myself on custom work. It's probably the poot
quality of things in my county.

I was 6 weeks in Stockholm Oct-Nov this year and everything was
super-expensive
in every aspect, except for some very nice wines in Systembolaget that were
cheaper
and better than in Puerto Rico.

Good CD's start at approx 189 SEK. Some as high as 225 SEK!

BR/
Rich

Mikkel C. Simonsen wrote in article
...
Rich Sherman wrote:

2) Custom wound transformers will cost you about the
same (multiple-pieces) or more (a single piece) money

Not in Europe... Here a custom-made transformer is often cheaper than a
standard Hammond transformer.

a.Will the transformer actually perform well?
b.Will it fit the chassis?
c.How reliable will it be over time?
d.Will all voltages and currents work as expected?

Apart from b, none of those concerns are too important. A and C is not
an issue when you buy from a good transformer company. And D is not a
big problem in a tube amp...

Best regards,

Mikkel C. Simonsen