Date   

TEK 485 Question

w1ksz <w1ksz@...>
 

I think I found the cause of the trace shifting on my 485. One end
of the Position Pot (R1300) goes to +13v. The voltage drops slowly
to 11.5v as the scope "warms up". Now I just have to locate where
the +13v comes from. The power supply schematic doesn't show it, and
the reference to the A Time Base Generator schematic doesn't help.
Does anyone know where it comes from ?

Thanks, Dick, W1KSZ


Re: 7104 Service Manual wanted

Miroslav Pokorni
 

Hello Bruce,
I got manual for my 7104 from Deane Kidd ( dektyr@teleport.com ). Back in
1998 it cost me $50. Take heart, I got cheap manual but paid close to $800
for scope with only two plug ins (only one was 7A29).

Regards

Miroslav Pokorni

----- Original Message -----
From: "Bruce Lane" <kyrrin@bluefeathertech.com>
To: <tekscopes@yahoogroups.com>
Sent: Friday, January 16, 2004 1:31 PM
Subject: [TekScopes] 7104 Service Manual wanted


Hi, gang,

OK... I've checked my usual sources. Cheapest price I've seen so far for a
service manual (original Tek hardcopy) for the 7104 was $135.00.

That really seems kind of high. I know there's at least a couple of
listmembers who sell manuals -- that being the case, I'd like to hear from
you if you can beat that price.

The serial number involved is B021884.

Thanks much.
-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been equipped with
surreal ports?"


Re: Tek475 strangely in heat

Miroslav Pokorni
 

A possibility to consider is that there were heat sinks on them at one time.
They might have fallen off or someone smart decided that scope works just
fine without those damn things and removed them.

Regards

Miroslav Pokorni

----- Original Message -----
From: "josko_flander" <josko_flander@yahoo.com>
To: <TekScopes@yahoogroups.com>
Sent: Friday, January 16, 2004 9:56 AM
Subject: [TekScopes] Tek475 strangely in heat


Hi!

I have recently acquired an old Tek475 scope and although it works
great I was tempted to poke my nose in it. There I found something
strange. A pair of double transistors (Q914 and Q938) is literarily
steaming. They are too hot to touch. I have made some preemptive
measurments (compared the voltages in the circuit to those in the
schematics) but it all checks fine. I was wandering if it is their
normal working temperature or they are overheating and are about to
die.

Any comment would be sincerely appreciated!

Thanks!

Josko Flander


Re: 5L4N

Miroslav Pokorni
 

The 5L4N appears to be 5000 series equivalent of 7L5, with upper frequency
somewhat reduced: frequency range is 20 Hz to 100 kHz, dynamic range 80 dB.
There is a built in tracking generator and asymetrical and symetrical input.

These data is coming from 1995 Tucker's catalog, could not find it in
Tektronix catalogs that I have as hard copies. To indicate demand for those
units, Tucker's asking for 7L5 was $4900 and a $3800 could get you a 5L4N.

As for 'what do you do with 15 pieces', you parcel them out and if you do
not make money on it, shipping companies will.

Regards

Miroslav Pokorni

----- Original Message -----
From: "Stefan Heinzmann" <stefan_heinzmann@yahoo.com>
To: <TekScopes@yahoogroups.com>
Sent: Friday, January 16, 2004 9:45 AM
Subject: [TekScopes] 5L4N


Hi all,

there's a lot of 15 5L4N spectrum analyzer plugins on ebay at the
moment (item 3071668755). Never heard of those, are they any good?
1000 Euros for 15 of them means less than 70 for each one. How do they
compare to a 7L5? Bargain?

(Now don't ask me what you do with 15 at a time...)

Cheers
Stefan



Re: 7104 Service Manual wanted

nr1dx@...
 

Bruce

I tried to email you direct but your email address bounced??? Contact me , I can help you out.

Dave
NR1DX


From: "Bruce Lane" <kyrrin@bluefeathertech.com>
Date: 2004/01/16 Fri PM 09:31:31 GMT
To: tekscopes@yahoogroups.com
Subject: [TekScopes] 7104 Service Manual wanted

Hi, gang,

OK... I've checked my usual sources. Cheapest price I've seen so far for a service manual (original Tek hardcopy) for the 7104 was $135.00.

That really seems kind of high. I know there's at least a couple of listmembers who sell manuals -- that being the case, I'd like to hear from you if you can beat that price.

The serial number involved is B021884.

Thanks much.
-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been equipped with surreal ports?"




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Re: Replacing CC resistors

Dave Wise
 

They're also less inductive.

Dave Wise

-----Original Message-----
From: Michael Dunn [mailto:mdunn@cantares.on.ca]
Sent: Friday, January 16, 2004 2:26 PM
To: TekScopes@yahoogroups.com
Subject: [TekScopes] Replacing CC resistors


Yes, old carbon comp resistors *can* drift. Just a thought: if
you're replacing CCs with film resistors, keep in mind one of CC's
attributes - their high surge capacity. Analyze or measure the
circuit (most likely during turn-on), and overrate the replacement's
power if necessary.

Michael


TDS700A Field Adjustment Software

DANNN31
 

Does anybody have a copy of the TDS 700A Field Adjustment Software? Got a
TDS744A and a TDS754A that need a little dialing in.

Thanks,
Dan


Replacing CC resistors

Michael Dunn <mdunn@...>
 

Yes, old carbon comp resistors *can* drift. Just a thought: if you're replacing CCs with film resistors, keep in mind one of CC's attributes - their high surge capacity. Analyze or measure the circuit (most likely during turn-on), and overrate the replacement's power if necessary.

Michael


Re: Tek475 strangely in heat

adenton <adenton@...>
 

Hot means too much current at too much voltage -- power = volts x
amps and all that. If the voltages are OK look for excessive
current. High heat is NOT normal. A common cause of excess current
is a leaky capacitor, either supplying excessive base current, or for
example in bypassing an emitter resistor thus greatly increasing
emitter/collector current.

Depending on the circuit configuration, it is possible for this to
happen without apparent malfunction, especially in a differential-
amplifier circuit. Since yours are duals, I strongly suspect that.
Check all those caps for leakage. Strap a current meter in one of
the emitter circuits and measure the juice. This times the CE
voltage gives you the power dissipation which you can compare against
the case type. (Although you already know it's too high.)

Note, caps sometimes check OK at low voltages (VOM ohmmeter) but leak
like fishnet at circuit voltages. Perhaps a current-meter in series
with the cap, with the circuit quiescent. (If it's in the sweep, try
single-sweep mode etc.)

Which suggests a topic, Does anyone know anything about electrolytic
capacitor leakage??? (JUST KIDDING!!!)

--- In TekScopes@yahoogroups.com, "josko_flander"

A pair of double transistors (Q914 and Q938) is literarily
steaming. They are too hot to touch.


Scope humour

Michael Dunn <mdunn@...>
 

Came across this joke as a young lad, and though I knew what a 10:1 probe was, it took a friend and I literally several years before we "got it"! If you don't understand, try saying it out loud a few times.

Q: Why are they called 10:1 probes?

A: Because when left unattended, they 10:1 away.


7104 Service Manual wanted

Bruce Lane
 

Hi, gang,

OK... I've checked my usual sources. Cheapest price I've seen so far for a service manual (original Tek hardcopy) for the 7104 was $135.00.

That really seems kind of high. I know there's at least a couple of listmembers who sell manuals -- that being the case, I'd like to hear from you if you can beat that price.

The serial number involved is B021884.

Thanks much.
-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Owner & Head Hardware Heavy,
Blue Feather Technologies -- http://www.bluefeathertech.com
kyrrin (at) bluefeathertech do/t c=o=m
"If Salvador Dali had owned a computer, would it have been equipped with surreal ports?"


Re: GR, not Tek!

regman10
 

Thanks Craig,
Very interesting site. It made me appreciate my V5 Variac (in almost daily
use for over 30 years) and decade resistor box even more.

"Subject: [TekScopes] GR, not Tek!"


Tek475 strangely in heat

josko_flander
 

Hi!

I have recently acquired an old Tek475 scope and although it works
great I was tempted to poke my nose in it. There I found something
strange. A pair of double transistors (Q914 and Q938) is literarily
steaming. They are too hot to touch. I have made some preemptive
measurments (compared the voltages in the circuit to those in the
schematics) but it all checks fine. I was wandering if it is their
normal working temperature or they are overheating and are about to
die.

Any comment would be sincerely appreciated!

Thanks!

Josko Flander


5L4N

Stefan Heinzmann <stefan_heinzmann@yahoo.com>
 

Hi all,

there's a lot of 15 5L4N spectrum analyzer plugins on ebay at the
moment (item 3071668755). Never heard of those, are they any good?
1000 Euros for 15 of them means less than 70 for each one. How do they
compare to a 7L5? Bargain?

(Now don't ask me what you do with 15 at a time...)

Cheers
Stefan


7104

spectrabei <spatial_electronics@...>
 

Resistors are vary stable, If your looking to a resistor
as the source of your focus voltage problem your on the wrong
track. Check a 200 volt zener diode (VR1784) on the high voltage
(A22)Board.
Enough of this about resistors. High Voltage problems are usually
the result of a breakdown of the dielectric in the high voltage
caps or a breakdown of the PN junction in a high voltage diodes.
The 200 volt Zener sets the collector switching voltage for
transistor Q1784.


Steve


More New Photos

oldtek2003
 

If anyone's interested, I've added some photos of a recent
restoration/repair job of an older 316 scope (in 316).

Tony Denning


7103

Craig Sawyers <c.sawyers@...>
 

Those interested in a 7103 (rack mounting version of 7104, with only three
slots), there is one listed at the moment on eBay number 2589050283 for $139
Buy It Now.

Craig


Carbon resistors, was 7104: Self-blurring focus

Craig Sawyers <c.sawyers@...>
 

I have found the same thing. I always verify the value of caps and
resistors in my spare parts box before using them.
If you check the archives, there was quite a discussion about this around a
year ago.

Craig


Re: Any way to clean...?

Jeff W <vwthingy@...>
 

Bruce wrote:
Does anyone know of a way to clean the (apparently sealed)
pots on the front panel of a 7000 series?

I have found that the cycling them results in a very temporary fix.
I have become pretty good with taking apart these pots, cleaning
them, and putting them back together. In the past, I used to just
collect the excess grease and recycle it, but I recently picked up a
couple tubes of Electrolube contact oil to try out.

Jeff


Re: 7104: Self-blurring focus

regman10
 

I have found the same thing. I always verify the value of caps and
resistors in my spare parts box before using them.


I've been starting to notice a problem with most carbon resistors in general
that they are way off in value.

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