7704A Repair and modules.


Bob H. <fisher_c_body@...>
 

Good Evening

I have a 7704A mainframe that is in need of repair. I turned it on
this morning after not having been powered up for about 2 years. The
trace was moving around erratically. Then I heard a sizzling sound
(never a good sound) and immediately turned it off but not before a
whisp of smoke emerged from the bottom of the scope.

I live in the Atlanta metro area and would like to find a company or
individual who is able to repair it.

Also I am in need of a horizontal sweep module. I'm not sure what
model I am looking for. This scope will be primarily used for audio
frequency applications. Any hints or suggestions would be very
helpful.

The modules I have are 2 7A26 and 1 7A16P that is also in need of
repair.

Any help would be greatly appreciated.

Thanks

Bob


 

--- In TekScopes@y..., "Bob H." <fisher_c_body@y...> wrote:
Good Evening

I have a 7704A mainframe that is in need of repair. I turned it on
this morning after not having been powered up for about 2 years.
The
trace was moving around erratically. Then I heard a sizzling sound
(never a good sound) and immediately turned it off but not before a
whisp of smoke emerged from the bottom of the scope.

I live in the Atlanta metro area and would like to find a company or
individual who is able to repair it.

Also I am in need of a horizontal sweep module. I'm not sure what
model I am looking for. This scope will be primarily used for audio
frequency applications. Any hints or suggestions would be very
helpful.

The modules I have are 2 7A26 and 1 7A16P that is also in need of
repair.

Any help would be greatly appreciated.
Often the Tantals for Supply Decoupling having a short.
The Chokes which are located before them then usualy smoke.
(at least in the last week i have repaired a 7A26 with such a failure)

For mostly audio frequencies a 7B53(A) would be the right choice for
the time base plug in.

Jorgen
dj0ud


dd@...
 

I have a 7704A mainframe that is in need of repair...

Also I am in need of a horizontal sweep module.
For mostly audio frequencies a 7B53(A) would be the right choice for
the time base plug in.
The 7B53/7B53A is not recommended for use in the 7704/7704A. I don't
remember why, but I think it was a good reason. The original poster needs
to find a 7B70+7B71, 7B80+7B85, or 7B92/7B92A.


dhuster@...
 

There's not a darned thing wrong with using a 7B53A in a 7704 or
7704A. It's the 7B92/A that you can't easily use on lower bandwidth
scopes only because they can't handle the faster sweeps. And 7B53A's
are so plentiful that they should be cheap. Having to come up with
and pay for a pair of 7B7x or 7B8x is a lot more difficult and
expensive -- and you'll need two service manuals instead of one. And
the 7B53A leaves a horizontal compartment free for a counter or DMM.


Stan or Patricia Griffiths <w7ni@...>
 

As I recall, the reason Tek would not recommend a 7B53 as a timebase for a
7704 is that it will not sweep fast enough to take full advantage of the
7704's 200 MHz bandpass. Other than that, I believe it will work just fine.
An even simpler, and probably cheaper, timebase would be a 7B50 or 7B50A with
does not have the delayed sweep feature. You could even use a 7B51 that is
normally used with a 7B50 to provide delayed sweep but can be used as a simple
timebase without a 7B50. I only suggest the 7B50, 7B50A, and 7B51 because
they might be more available and cheaper than the 7B53/A alternatives. There
was also an earlier version of the 7B53 called the 7B52 which would work as
well . . .

I really need to get on with finishing my second book . . .

Stan
w7ni@easystreet.com

dd@adobe.com wrote:

I have a 7704A mainframe that is in need of repair...

Also I am in need of a horizontal sweep module.
For mostly audio frequencies a 7B53(A) would be the right choice for
the time base plug in.
The 7B53/7B53A is not recommended for use in the 7704/7704A. I don't
remember why, but I think it was a good reason. The original poster needs
to find a 7B70+7B71, 7B80+7B85, or 7B92/7B92A.

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Stan or Patricia Griffiths <w7ni@...>
 

Hi Bob,

There is some possible incompatibility using the 7A16P in a normal 7K
mainframe such as the 7704A. The 7A16P was specifically made to be used with
the 7912AD digitizer and is programmable (that's what the "P" on 7A16P
means). Anyway, I have read a note that says the additional circuitry for
implementing programmability in the 7A16P may overload one or more of the
7704A's power supplies causing some unpredictable results in all the other
circuits powered by them. You might try it with caution. You might get
lucky and not cause any permanent damage and it might even work for you.

There is probably a way to disable some of that extra circuitry in the 7A16P
without damaging it as a nonprogrammable amplifier and reducing the power
supply load to an acceptable level. I have not looked into that yet. Future
project . . .

Stan
w7ni@easystreet.com

Bob H. wrote:

Good Evening

I have a 7704A mainframe that is in need of repair. I turned it on
this morning after not having been powered up for about 2 years. The
trace was moving around erratically. Then I heard a sizzling sound
(never a good sound) and immediately turned it off but not before a
whisp of smoke emerged from the bottom of the scope.

I live in the Atlanta metro area and would like to find a company or
individual who is able to repair it.

Also I am in need of a horizontal sweep module. I'm not sure what
model I am looking for. This scope will be primarily used for audio
frequency applications. Any hints or suggestions would be very
helpful.

The modules I have are 2 7A26 and 1 7A16P that is also in need of
repair.

Any help would be greatly appreciated.

Thanks

Bob

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