561A early s/n HV supply


Ondrej Pavelka
 

Hi folks,

I have acquired 561A which looks in decent condition visually but the HV transformer and associated valves and caps are all missing. I can see somebody attempted to make replacement HV supply and failed in doing so and put the scope to side. When his kids were doing a cleanup I bought it without checking as it was cheap enough and I don't have any valve Tek scope.
Rest of the HV supply is easy to make using diodes and fresh new caps but the transformer is a show stopper. I couldn't find many floating about for sale but by an off chance aren't the original transformer specs available? I can have one made but it will be much easier if I know the exact spec.


Mark Vincent
 

Ondrej,

https://vintagetek.org/transformer-drawings/ Look for 120-275. Let us know if the transformer you have wound works. Ask your source if he will rewind other Tek. HV transformers.

Mark


Ondrej Pavelka
 

Thank you!

I don't think it's about rewinding rather then making a new transformer
0-200-300 primary and 2370 and 2440 specified for 35kHz

Today's materials designed for 40kHz or even 300kHz switchers should make
it easier to wind compared to the original construction.

I will explore the options and get back to you.

On Tue, 4 May 2021, 04:30 Mark Vincent, <orangeglowaudio@gmail.com> wrote:

Ondrej,

https://vintagetek.org/transformer-drawings/ Look for 120-275. Let us
know if the transformer you have wound works. Ask your source if he will
rewind other Tek. HV transformers.

Mark






Roy Morgan
 

Ondrej,

I knew a fellow who taught college electronics classes (at Cornel).

Their lab had a number of 561's that were idle all summer. They followed a regular necessary procedure to get them running each year. The HV transformers would gather moisture and had to be dried out.

They ran an incandescent lamp to heat the transformer moderately for a day or two and the scopes would operate normally.

I suggest you try that.

Roy

Roy Morgan
K1LKY Western Mass

On May 4, 2021, at 2:31 AM, Ondrej Pavelka <info@vintageaudiorepairs.eu> wrote:

Thank you!

I don't think it's about rewinding rather then making a new transformer
0-200-300 primary and 2370 and 2440 specified for 35kHz

Today's materials designed for 40kHz or even 300kHz switchers should make
it easier to wind compared to the original construction.

I will explore the options and get back to you.


 

Roy:

This sounds like a viable plan for certain items of equipment, but I
don't completely follow the part about "ran an incandescent lamp to heat
the transformer..."   Was the lamp connected in-line with the 561 power
cord as a "dim bulb" power limiter, or was the energized incandescent
lamp physically placed near a  non-energized 561's transformer to
increase the transformer's temperature by means of thermal radiation?

Could you clarify?  Thanks!

Mike Dinolfo N4MWP

On 5/4/21 10:44 AM, Roy Morgan wrote:
Ondrej,

I knew a fellow who taught college electronics classes (at Cornel).

Their lab had a number of 561's that were idle all summer. They followed a regular necessary procedure to get them running each year. The HV transformers would gather moisture and had to be dried out.

They ran an incandescent lamp to heat the transformer moderately for a day or two and the scopes would operate normally.

I suggest you try that.

Roy

Roy Morgan
K1LKY Western Mass

On May 4, 2021, at 2:31 AM, Ondrej Pavelka <info@vintageaudiorepairs.eu> wrote:

Thank you!

I don't think it's about rewinding rather then making a new transformer
0-200-300 primary and 2370 and 2440 specified for 35kHz

Today's materials designed for 40kHz or even 300kHz switchers should make
it easier to wind compared to the original construction.

I will explore the options and get back to you.


Ondrej Pavelka
 

Hi Roy,
It's not really an option for me because in my unit the transformer as well
as valves and associated caps in the HV section are physically missing.
There are empty ceramic strips and two holes where transformer used to be
mounted

On Tue, 4 May 2021, 16:45 Roy Morgan, <k1lky68@gmail.com> wrote:

Ondrej,

I knew a fellow who taught college electronics classes (at Cornel).

Their lab had a number of 561's that were idle all summer. They followed a
regular necessary procedure to get them running each year. The HV
transformers would gather moisture and had to be dried out.

They ran an incandescent lamp to heat the transformer moderately for a day
or two and the scopes would operate normally.

I suggest you try that.

Roy

Roy Morgan
K1LKY Western Mass

On May 4, 2021, at 2:31 AM, Ondrej Pavelka <info@vintageaudiorepairs.eu>
wrote:

Thank you!

I don't think it's about rewinding rather then making a new transformer
0-200-300 primary and 2370 and 2440 specified for 35kHz

Today's materials designed for 40kHz or even 300kHz switchers should make
it easier to wind compared to the original construction.

I will explore the options and get back to you.





Ondrej Pavelka
 

I found two companies locally. One old school company which is willing to
make one exactly like the old one but they would need the old transformer
which I don't have.

Other company specializes in transformers for high frequency converters and
they can too make one but on modern special core. I have ordered one piece
to test it. It will comply with input voltage output voltage and current at
specified 35kHz frequency.


If anybody (probably better in Europe) have one broken transformer I can
get the old school company to rewind it so we can test both routes.


O.

On Wed, 5 May 2021, 06:00 Ondrej Pavelka, <info@vintageaudiorepairs.eu>
wrote:

Hi Roy,
It's not really an option for me because in my unit the transformer as
well as valves and associated caps in the HV section are physically
missing. There are empty ceramic strips and two holes where transformer
used to be mounted


On Tue, 4 May 2021, 16:45 Roy Morgan, <k1lky68@gmail.com> wrote:

Ondrej,

I knew a fellow who taught college electronics classes (at Cornel).

Their lab had a number of 561's that were idle all summer. They followed
a regular necessary procedure to get them running each year. The HV
transformers would gather moisture and had to be dried out.

They ran an incandescent lamp to heat the transformer moderately for a
day or two and the scopes would operate normally.

I suggest you try that.

Roy

Roy Morgan
K1LKY Western Mass

On May 4, 2021, at 2:31 AM, Ondrej Pavelka <info@vintageaudiorepairs.eu>
wrote:

Thank you!

I don't think it's about rewinding rather then making a new transformer
0-200-300 primary and 2370 and 2440 specified for 35kHz

Today's materials designed for 40kHz or even 300kHz switchers should
make
it easier to wind compared to the original construction.

I will explore the options and get back to you.