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--- In TekScopes@y..., "Phil (VA3UX)" <phil@v...> wrote:

Can anyone find the current rating of the 6.3V winding on

transformer T402

(#120027) from a type 517 power supply ? T402 may actually be a

dedicated

6.3V filament transformer since there were something like 106 six

volt

tubes in the 517.

If all else fails, why don't you just add up the heater currents of
all the tubes fed by it?

Morris



l

My opinion is that a working and calibrated 7S14 that meets all of its
original specifications should be worth $150. The problem is that almost
nobody has the ability to determine if one is really working properly or
not. You have to have a very fast rise and clean pulse generator, an
amplitude calibrated 50 ohm voltage source, and a fast time mark generator at
a very minimum in order to get any idea if it really works correctly.

If it does not work correctly, it may be impossible to find the parts you
need to fix it. The most vulnerable parts are the sampling diodes and I
suspect they are impossible to find, but I have to admit I have not searched
for any. I am sure there are other critical, hard to find parts in the 7S14.

Does this unit come with a "money-back guarantee" . . . ?

Stan
w7ni@...

JOSE V. GAVILA (EB5AGV/EC5AAU) wrote:

Hi Phil,

Yes, that is a challenge. First, there were several 6.5 volt filament
windings on T402. Here is some of the info you need:

pins 17 & 18, 6.5 VAC, 12 A
pins 21 & 22, 6.5 VAC, 12 A
pins 5 & 6, 6.5 VAC, 4 A
pins 15 & 16, 6.5 VAC, 2 A

pins 19 & 20, 5.2 VAC, 2 A

The usual reason that there were so many separate filament windings on Tek
transformers that seemed to supply the same voltage is that these filament
windings were often elevated to different DC voltages to reduce the
heater-to-cathode potential difference in an effort to prevent internal tube
arc-overs. One winding may be elevated to +100 V DC and another to +225 V DC.

In researching this, I found out that I don't own a 517 or 517A manual. I do
have at least two sets of microfiche on the 517/517A but both sets are very
nearly unreadable (too small, too dark, and out of focus). But even if you
had perfect microfiche or a good manual, you would not find the current
ratings in either place since Tek never published transformer current ratings
in those places. There was an internal Tek document describing each Tek-made
transformer, including the pin-outs and current ratings. You have to know
someone who has a set of these very rare documents . . . Maybe this is
something we should add to our Tek web page, huh?

Stan
w7ni@...

PS I would be happy to accept a 517/517A manual as the prize ! !

Phil (VA3UX) wrote:

Hi Dean

Sorry I confused you. I thought I read a message about
replacing a number of capacitors in a 475 that was
posted by you. Sorry for the confusion.

Richard



--- dhuster@... wrote:

Is there any plan for replacing capacitors? I have

seen reference

to this a few times.

I'm not sure I'm on the same page here. What kind
of plan? Which
caps?

Dean

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> I am in need of some info about the 7S14 plug-in... is it worth $150
> in operating condition?. How does it performs?

I have one, though I haven't really used it. It seems to work ok, except for a slight "ghost" signal on one trace. Think mine was closer to U$100! If you get a manual too, I will gladly pay a bit for some photocopies.

Keep in mind that these samplers typically have more finicky triggering circuits than a normal module. Also, all the buttons on mine are quite sluggish -- almost binding. I'm sure that'll improve with a bit of maintenance...

Michael

I am in need of some info about the 7S14 plug-in... is it worth $150
in operating condition?. How does it performs?

I used one of these plugins for a couple of years back in the 1980's.
It worked just dandy for me (measuring risetimes of pulsed electron
guns), under some fairly demanding conditions.

I'd happily pay $150 for one in operating condition.

-- John Rehwinkel
spam@...

Hello!

I am in need of some info about the 7S14 plug-in... is it worth $150 in
operating condition?. How does it performs?

Please, any information will be welcomed.

Thanks!

JOSE
----------------------------------------------------------------------
73 EB5AGV / EC5AAU - JOSE V. GAVILA
La Canyada - Valencia (SPAIN)

EB5AGV Vintage Radio Site:

European Boatanchors List:

Can anyone find the current rating of the 6.3V winding on transformer T402 (#120027) from a type 517 power supply ? T402 may actually be a dedicated 6.3V filament transformer since there were something like 106 six volt tubes in the 517. I don't have the thing in hand so I'm not sure.

There should be a prize if someone can answer this.

Thanks in advance.

Phil

I'd be careful of using a Radio Shack resistor in that spot.
Depending on where it's being used, a 1/8-watt CARBON COMPOSITION
resistor might be required as the 1/4-watt (or an 1/8-watt) CARBON
FILM resistor may have too much inductance for the application. You
can still get carbon comp resistors at Mouser Electronics
( ), but they have only the 1/4-watt size, not
1/8-watt. I looked through my parts and did find a 1/4-watt 3.9K
carbon comp resistor. Measure the hole spacing in the PCB and see it
it'll fit. You'll need about 5/16" (7mm-8mm) between centers. My
part (used) has remaining lead length of about 5/16", so check to
make sure your holes aren't TOO far apart or you'll have to add a
little lead to the part.

I checked through the 50-ohm thin film parts that I have (all new)
and didn't find what you needed, which surprised me. 7A24 attenuator
parts must be different than those for the 7A19. I have 307-1018,
1034, 1035, 1036, 1037, 1038 and 1040-00 plus the mounting studs/pins
(they're staked onto the board 214-1797-00) and the hold-down leaf
springs (344-0248-00). E-mail me if you need some pieces or the 1/4-
watt resistor (I can mail the resistor for $0.34 or you can have a
nasty minimum order and shipping charges from Mouser).

Dean

Hello!

Well, after some time working with radio gear, now I am back to test
equipment... Last time I powered my Tek 475, I found that the chopper
circuit no longer worked. CH1 and CH2 work fine sepparately and also in ALT
mode. But no in CHOP mode. So I guess it could be related with the
oscillator in the chopper. Any hint?. I plan to work on it soon. Now I use
the 485 or the 7603 to work. It is nice to have backup gear :-)!

Regards,

JOSE
----------------------------------------------------------------------
73 EB5AGV / EC5AAU - JOSE V. GAVILA
La Canyada - Valencia (SPAIN)

EB5AGV Vintage Radio Site:

European Boatanchors List:

Hi All,

I am looking for the following Tektronix parts:

317-0392-00 RES.,FXD,CMPSN:3.9K OHM,5%,0.125W

This is simply a 3900 ohm, 1/8 watt, 5% tolerance resistor.
I expect a quarter watt unit would do fine. You can find
these at Radio Shack. Or I can send you some. I have
plenty (I bought out a Radio Shack when it was going out of
business).

307-1020-00 ATTENUATOR,FXD:50 OHM,2X
307-1023-00 ATTENUATOR,FXD:50 OHM,5X
307-1024-00 ATTENUATOR,FXD:50 OHM,10X

1 of each would be great at this stage and if anyone has 2 of each I
would like to know.

You can actually make these -- though for compensated high
frequency use, you generally have to parallel the resistors
with small capacitors.

There are two basic arrangements for resistive matched-impedance
attenuators, "tee" style with two series resistors and one shunt,
and "pi" style with one series resistor and two shunts. Here is
an attempt at ASCII diagrams:

tee attenuator:

in o--/&#92;/&#92;/&#92;---+---/&#92;/&#92;/&#92;--o out
series | series
>
< shunt
>
|
= (gnd)

pi attenuator

in o--+---/&#92;/&#92;/&#92;---+--o out
| series |
> >
< shunt < shunt
> >
| |
= (gnd) = (gnd)

Note that these are unbalanced (signal referenced to ground)
attenuators -- there are also balanced varieties. When I'm
building these myself, I tend to use the tee variety, as it
seems a little easier to wire up.

Here are the resistor values for the listed attenuators (since
the input and output impedances are the same (50 ohms), the
attenuators are symmetrical, that is both the series resistors
in the tee attenuator are the same and both the shunt resistors
in the pi attenuator are also the same.

tee attenuator:

series (2) shunt

2X 8.58 141.
5X 19.1 55.9
10X 26.0 35.1

pi attenuator:

shunt (2) series

2X 291. 17.7
5X 131. 44.7
10X 96.2 71.1

Resistor values are in ohms, and I've rounded them to
3 places. Note that most of these aren't standard
values, so you'll have to obtain precision resistors
(a good idea any to maintain calibration) or build
them up out of combinations of standard values (this
doesn't work well for high-frequency use).

Good luck,
John Rehwinkel
spam@...

(currently repairing a 7844 and a 570)

Is there any plan for replacing capacitors? I have seen reference
to this a few times.

I'm not sure I'm on the same page here. What kind of plan? Which
caps?

Dean

Hi, Andrew,

The 317- resistors are standard stock items in many catalogs. I may
have one here, though in case you're having a nasty time trying to
find one.

Regarding the 307- attenuators, are these the thick-film-on-ceramic
resistors that slide over two metal pegs and get a spring clip on top
to hold them in place? I think the 7A19 uses them. If so, I may
have some. I gathered up several of them with the idea of using them
to make a really hot 50 ohm switchable attenuator one day. Never got
around to it and ended up finding a pair of hp 355 attenuators
instead. Let me know and I'll look up the parts.

Dean

Hi All,

I am looking for the following Tektronix parts:

317-0392-00 RES.,FXD,CMPSN:3.9K OHM,5%,0.125W
307-1020-00 ATTENUATOR,FXD:50 OHM,2X
307-1023-00 ATTENUATOR,FXD:50 OHM,5X
307-1024-00 ATTENUATOR,FXD:50 OHM,10X

1 of each would be great at this stage and if anyone has 2 of each I would
like to know.

Best Regards,

Andrew

--- In TekScopes@y..., mongteen@e... wrote:

Hello

My email is mongteen@e... Anyway the motor module is on it's
way. Hopefully customs won't hold it up too long. If bits of white
foam show out of the corners they might suspect something :)


Windsor

Hi windsor

In case your mail is not working, the fan module arrived today. That
is what I call prompt service. My payment should be there soon.

Richard

Hello

My email is mongteen@... Anyway the motor module is on it's
way. Hopefully customs won't hold it up too long. If bits of white
foam show out of the corners they might suspect something :)


Windsor

Hi Dean

Thank you. I have been looking over the fan installation. I have a
good solder removal tool, plus solder wick. Actually I think I did ok
for $225 for the scope. The jitter is minimal, though I want to clean
it up.

Is there any plan for replacing capacitors? I have seen reference to
this a few times.

I am still waiting for my manual from Fair Radio Sales in Ohio. The
manual is a photo copy and I think they copy an original when an order
is sent in. I ordered the manual via their web page but there response
is not as fast as Radio Shack or Newark Electronics.

What is happening to Windsor's Email? When I try to respond to his
message I get an answer back that the address does not exists.

Richard

Windsor, you discovered the fundamental truth we were always taught
in Navy "A" school. Always check the power supplies first.

And Don, bless his generous Aussie heart, is correct also: you're
not fixing the problem -- you're getting rid of the symptom. Always
assume the original circuit worked great at one time and fix the
problem so that the orignal circuit works great again.

We had a tech in the Dallas Service Center who "re-engineered" the
front end of a sampling system to get it to work. I couldn't believe
the supervisor didn't rain fire and brimstone on him, but I don't
think the supervisor knew about it. Maybe he got the sampler to
work, but I pity the technician who had to work on that thing the
next time!

Dean (and you're welcome for the CRT)

Rich,

You'll find that the fan motor is a circuit unto itself. The motor
itself is brushless and has several Hall-effect sensors inside for
input to the drive circuitry. I've replaced motors before, and it
isn't too bad. Step 1: Clip the motor leads close to the board
before desoldering so that they don't get in the way of your
desoldering tool. Step 2: Make sure your solder sucker has LOTS of
hard suction. Relube the o-ring inside with silicone grease if
necessary.

Dean

Hi All,

I am looking for a Vertical Amplifier IC for a Tektronix 2235A Oscilloscope.

Tektronix Part Number is 234-0133-20

Can anybody help?

Regards,

Andrew