Parts-box (Tek 465) Transformer - How to figure out ratings?

P

Pete Chrisbacher

Guest
I'd like to build a battery eliminator to run an old Radiola 16 battery set
I just picked up. There are a couple of commercial battery eliminators out
there (e.g. ARBE-III, and a kit from AES) that look real nice, but I'd
prefer to build it myself with stuff from my parts box (i.e. free).

In my parts box I found a Tek 465 transformer which (with its multiple
primaries and secondaries) I figure I can use as the basis for providing the
necessary voltages. (For those not familiar with circa 1926 battery radios,
this thing appears to need six different voltages - I'm still trying to
figure out the specifics here but looks like I need: A: 6V @ 2A B:
135V, 67.5V, 45V @ 60mA C: -9V @ 20mA A, B, and C all need to be
electically isolated from each other)

Figuring out the various secondary voltages is easy. My problem is that I
haven't been able to locate any AMPERAGE specs on this transformer (Tek P/N
is 120-0798-01).

Anyone have specs on this thing? If not, anyone have any suggestions re how
I might be able to roughly determine the secondary amperage ratings without
letting out any magic smoke?

Thanks -

-Pete
 
In article <wAKdb.11114$yU5.6241@nwrdny01.gnilink.net>,
pxbacher@netaxs.com says...
|
| Anyone have specs on this thing? If not, anyone have any suggestions re how
| I might be able to roughly determine the secondary amperage ratings without
| letting out any magic smoke?
|

Gradually increase the load on one of the secondaries, whilst measuring
the voltage and current. When the voltage decreases by about 5% below
the open circuit voltage, note the level of current flowing. That will
be the approximate current it is able to deliver.

Anyone care to comment on the 5% rule of thumb?


--
Regards,
Harry (M1BYT)...

Remove the 'NOSPAM' in my email address to reply.

Free Amateur Radio Courses:-
http://www.ukradioamateur.org
 
030929 0727 - Harry Bloomfield wrote:

In article <wAKdb.11114$yU5.6241@nwrdny01.gnilink.net>,
pxbacher@netaxs.com says...
|
| Anyone have specs on this thing? If not, anyone have any suggestions re how
| I might be able to roughly determine the secondary amperage ratings without
| letting out any magic smoke?
|

Gradually increase the load on one of the secondaries, whilst measuring
the voltage and current. When the voltage decreases by about 5% below
the open circuit voltage, note the level of current flowing. That will
be the approximate current it is able to deliver.

Anyone care to comment on the 5% rule of thumb?
Click to expand...

Also, check the heat generated onto the frame. If you cannot hold your
fingers on the frame because it is too hot, then reduce the load a little
until it is just warm to the touch. A transformer is designed to take a
little heat.
 
Thanks to Harry and Indago for the replies -

I measured the transformer secondaries this evening using a big old Ohmite
rheostat as a load (along with some parts-box resistors). I couldn't get
exact readings on the higher voltage secondary due to excessive wattage load
required, but the approximate values I was able to get are close enough for
my needs.

Before I get to the specs, I should mention that the transformer is set up
with a voltage adjuster for high, normal, and low voltage ranges - I used
the normal setting for my measurements. Vin was set to exactly 120 VAC with
a variac. To figure out current capacity of each of the secondaries, I used
the 5% Vdrop rule suggested by Harry. All values are approximate - your
mileage may vary.

Tektronix 465 Power Transformer Secondary Specs
====================================
Secondary #1 (Orange-White-Violet (center-tapped = White))
O-V: 128VAC @ 300mA (approximate)

Secondary #2 (Yellow-Yellow)
Y-Y: 20VAC @ 2.4 A

Secondary #3 (Brown-Brown)
Brn-Brn: 9.5VAC @ 1.4 A

Secondary #4 (Blue-Blue)
Bl-Bl: 12VAC @ 1.4 A

Note that this transformer has a second set of primary connections - I
believe these are used with the inverter option (8?). I didn't bother with
these.

Turns out this transformer is close enough to suit my needs. I hope to have
my power supply done in a week or two - now waiting on a shipment of 22V
zeners - my parts box should supply everyting else I need.

I hope this info is useful to others as well.

-Pete




"Pete Chrisbacher" <pxbacher@netaxs.com> wrote in message
news:wAKdb.11114$yU5.6241@nwrdny01.gnilink.net...
I'd like to build a battery eliminator to run an old Radiola 16 battery
set
I just picked up. There are a couple of commercial battery eliminators
out
there (e.g. ARBE-III, and a kit from AES) that look real nice, but I'd
prefer to build it myself with stuff from my parts box (i.e. free).

In my parts box I found a Tek 465 transformer which (with its multiple
primaries and secondaries) I figure I can use as the basis for providing
the
necessary voltages. (For those not familiar with circa 1926 battery
radios,
this thing appears to need six different voltages - I'm still trying to
figure out the specifics here but looks like I need: A: 6V @ 2A B:
135V, 67.5V, 45V @ 60mA C: -9V @ 20mA A, B, and C all need to be
electically isolated from each other)

Figuring out the various secondary voltages is easy. My problem is that I
haven't been able to locate any AMPERAGE specs on this transformer (Tek
P/N
is 120-0798-01).

Anyone have specs on this thing? If not, anyone have any suggestions re
how
I might be able to roughly determine the secondary amperage ratings
without
letting out any magic smoke?

Thanks -

-Pete
Click to expand...
 
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