Date   

Re: 1L10 crystal

Carl Hallberg
 

It is an oscillator, not a filter.  It is a quartz xtal, not ceramic.  I have 1L5, 1L10, 1L20 that I don't use anymore.  I may even have 900KHz xtal, but so much junk to look through.  
W9CJH

On Saturday, September 25, 2021, 02:46:09 PM CDT, snapdiode via groups.io <snapdiode=yahoo.com@groups.io> wrote:





If it's used only in an oscillator you have options but if it's used as a narrowband filter, it's bad luck, No one even makes ceramic resonators near those frequencies anymore either.


Re: 1L10 crystal

snapdiode <snapdiode@...>
 

If it's used only in an oscillator you have options but if it's used as a narrowband filter, it's bad luck, No one even makes ceramic resonators near those frequencies anymore either.


Re: 7704A Vertical Amplifier Issues

Albert Otten
 

(continued) After a temporary replacement of the open R4420 I measured the following:
Q4420 Vb = 14.98 V, Ve = 15.64, Veb = 0.66 V and across R4419 again 50 mV (of coarse).
This means about 6.2 mA via Q4420, 1.5 mA via R4419 and 4.7 mA emitter current via Q4420. Altogether very reasonable values for that transistor.
Albert


Re: 7704A Vertical Amplifier Issues

Albert Otten
 

I still wasn't very confident about my results and now did measurements in another 7704A. The A44 board is the later version and R4419 is 33R as should be. But guess what ... the voltages were as if Q20 etc. did not exists (Ve < Vb) and as if CR4419 just conducted.
50 mV across R4419 (in stead of earlier 125 mV across 39R) which is closer to what Barry found.
I appeared that R4420 (5k6 to +50V) was open, but without any sign of overheating. Luckily this does no harm and explains the results.

Albert


1L10 crystal

Joel B Walker
 

Hello all, I am in need of a 900 kHz crystal Tek number 158-0021-00. It is Y450 on the schematic. I tried Walter Shawlee and every other conceivable place to no avail. I have been looking for this for nearly 10 years. Surely there's one out there somewhere. Thanks for looking.


TEK R568

ChuckA
 

I recently picked up an R568 with 3S6 and 3T6 plugins. I'd like to find a Model 230 Digital Unit for it. Would prefer a rack mount unit but not going to be particular.

Anyone have one for sale or trade?

Chuck A

--
See Early TV at:

www.myvintagetv.com


8393 Nuvistor to 2N4416A FET conversion

Mark Vincent
 

I wanted to see if the nuvistors could be replaced with FETs in a 454 to be like the A version. It worked. The FET was chosen to be the same number in the A version. I added two 27V zeners from the 75V supply and a 24V and 27V zener from the 65V supply in channel 1. The other channel was original. Testing between the two proved either worked fine. The B+ to the drains was about 15V. The zeners were ones I have in stock. A 30V zener could be used with a 27V to further lower the B+. I did not see any problem with the B+ for the FETs being 15V instead if the 12V used in the 454A. The load resistors were left in, only opened to add the zeners. If I decide to make this permanent, 1,3W 2% tolerance zeners will be used. The wattage is needed. The FET pins fit the sockets easily. I found it interesting and happy to see the experiment work. If any owners of a 454 want to do this conversion, go ahead. The A version of the FET is 35V while the non-A is 30V.

Mark


Re: 7704A Vertical Amplifier Issues

n4buq
 

I checked the voltage across R4419 and that measured 32mV. I'm pretty sure either something shorted or Q4420 acted badly before losing one of its junctions.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Roger Evans via groups.io" <very_fuzzy_logic=yahoo.com@groups.io>
To: TekScopes@groups.io
Sent: Saturday, September 25, 2021 11:08:01 AM
Subject: Re: [TekScopes] 7704A Vertical Amplifier Issues

Mark,

I agree completely with Albert, if you look at the nominal voltages on the
schematic the output transistors of U4413 should have a collector current of
36mA ( (50-37)/360R ) so with any reasonable current gain they should not
draw more than a couple of mA of base current. Albert measures 4mA for the
total base current into both output transistors which is eminently
resonable.

Neglecting the base current into Q4420, its base should sit at 14.88V ( (5k /
16.8k) * 50V) and its emitter should be around 0.6V-0.7V more positive so
15.5V - 15.6V and Albert measures 15.45V. The function of Q20 is to provide
a low source impedance to bias the output transistors of U4413 at 15.45V
rather than the 15V whichTek could have obtained by connecting R33 directly
to +15V. This also implies that R4419 should be a low inductance type to
maintain the frequency response of the amplifier.

I think it is safe to say that any junction transistor which measures a
forward Vbe of 2.6V is no longer a transistor! If you take Q4420 to be open
circuit from base to emitter then R4420 and R4419 supply the base current to
the output transistors without any voltage regulation which is why the bias
voltage shoots up to 17V.

Regards,

Roger






Re: 7704A Vertical Amplifier Issues

Roger Evans
 

Mark,

I agree completely with Albert, if you look at the nominal voltages on the schematic the output transistors of U4413 should have a collector current of 36mA ( (50-37)/360R ) so with any reasonable current gain they should not draw more than a couple of mA of base current. Albert measures 4mA for the total base current into both output transistors which is eminently resonable.

Neglecting the base current into Q4420, its base should sit at 14.88V ( (5k / 16.8k) * 50V) and its emitter should be around 0.6V-0.7V more positive so 15.5V - 15.6V and Albert measures 15.45V. The function of Q20 is to provide a low source impedance to bias the output transistors of U4413 at 15.45V rather than the 15V whichTek could have obtained by connecting R33 directly to +15V. This also implies that R4419 should be a low inductance type to maintain the frequency response of the amplifier.

I think it is safe to say that any junction transistor which measures a forward Vbe of 2.6V is no longer a transistor! If you take Q4420 to be open circuit from base to emitter then R4420 and R4419 supply the base current to the output transistors without any voltage regulation which is why the bias voltage shoots up to 17V.

Regards,

Roger


Re: Type M Cracked Channel Position Pots

c n
 

JB Weld Plastic Bonder (NOT their Plastic Welder) is a two part urethane that I have found will stick well to polyethylene, polypropylene, abs, phenolic, and vinyl. I have not tried it on Delrin, but would if need be. Its original use is structural bonding of torn car bumper covers. The same brand plastic welder is an epoxy that I do not recommend. Sorry if this sounds like an infomercial but it has worked very well for me.

--
Chuck N.
547 453 475


Re: 7704A Vertical Amplifier Issues

Albert Otten
 

On Sat, Sep 25, 2021 at 05:15 AM, Mark Vincent wrote:
The reason I specified 1W for the 33 ohm resistor is because I measured 3,13V
across the 33 ohm resistor. The base voltage is 14,4 and the emitter voltage
is 17V. I measured this in mine that is working fine at the time of this post.
I know the EB voltage is not standard ,6-,7V.
Hi Mark,
Something must be wrong here. For comparison, in one of my 7704As, at Q20 I measured Ve = 15.45V, Vb = 14.86 V, Veb = 0.59 V.
Across R4419 I found merely 0.125 V. (BTW this resistor was 39R 1/8W, clearly a replacement soldered in later. Original 33R also burned??).
Is your A44 board an early version at which Q20 etc. have been added later on? With possible mistakes? All my boards are later versions.
Albert


Looking for WaveStar WSTR31 Version 1.3

Andrew
 

Hey all --

I've spent more hours that I'd like to admit trying to locate WaveStar WSTR31 Version 1.3 online, but all I've turned up are 1.0.3, 1.1.1b and 1.1.2. Was really hopping to find 1.3 (and maybe even 1.2) to run on some older period correct hardware.

I'm surprised 1.3 seems to have completely vanished from the face of the internet. Tek used to have it up on their site to freely download and run as either an upgrade version or full 30 day demo version for years (file name for it was wvstrup.zip) but it sadly didn't make it to the Internet Archive as it was a hot link off their page to their FTP.

Does anyone happen to have or know where I might find a copy?

Thanks!


Re: Tek 6R1 used in the real world

Tim Phillips
 

Or a PDP-11 for your 7704A / P7001 combo :-)

Tim


On Fri, 24 Sept 2021 at 18:59, snapdiode via groups.io <snapdiode=
yahoo.com@groups.io> wrote:

Anyone know where I can buy a PDP-4 to complement my 567?






Re: 2215 front cover

Ananda
 

Mike,
Thanks for the reply. Yes, I saw those. There is one that I am following. Some are way beyond the value of a full, working scope!
BTW, I am in the US-east bay.
Regards,
Ananda


Re: 7704A Vertical Amplifier Issues

Mark Vincent
 

Albert and Barry,

The reason I specified 1W for the 33 ohm resistor is because I measured 3,13V across the 33 ohm resistor. The base voltage is 14,4 and the emitter voltage is 17V. I measured this in mine that is working fine at the time of this post. I know the EB voltage is not standard ,6-,7V. The reason for the two longer leads on the out is to the load side of the distributed plates. That is what it is supposed to be. Having them go to pads would increase the C of the circuit.

The nonlinearity in the horizontal circuit may be due to bad parts. I can give you a list of parts that should be changed. If necessary, I do have a spare horizontal board that is known good if you need one. Check to see if the inputs are linear with another oscilloscope. I do know some resistors should be increased in wattage. I did add heatsinks with compound to the outputs to keep them cooler.

If Barry needs 33 ohm 1W and 5600 1% I can send them to him. The 33 ohm does not need to be 1%, 1W yes.

The output IC is operating normally at warm. I so happy you got the vertical problem fixed easily. I did add a 12V fan to cool the two circuits. It is running less than 12V. I like my items to be cooler than original to give longer life of parts.

Mark


Re: Relabelling push buttons on Tek 7603

Dave Seiter
 

I've used print-on waterslide paper for quite a few projects, and the only drawback I've come across is the thick edge.  All (or most of) the decals in model kits are tapered so that the edges are almost invisible, but you can't get that from a sheet of water slide paper.  A small decal on the end of a small push button will only accentuate the problem.  Lots of lacquer, I guess!
-Dave

On Friday, September 24, 2021, 07:54:18 AM PDT, Paul Amaranth <paul@auroragrp.com> wrote:

I once used a toner transfer method to relable a button on a 468.

Use your favorite graphics program to get an image of what the
label should be like.  If you end up using 6pt fonts, you will
probably be able to find a font that's close enough.

Reverse the image and print it on toner transfer media.  I used
PnP blue, but you could also use the slick side of some label
backing paper.

Heat transfer it onto the button (after it's been cleaned and
the old label removed).

If it's good (or good enough), spray it with a protective
fixative, then a couple of coats of lacquer.

If not, clean it off and repeat until good.

The details are in the technique, but you can get pretty good
results.

Using actual decal paper might be easier but I always worried about
the edge of the decal coming up, toner transfer makes it look like
it was printed right on the button.

  Paul

On Fri, Sep 24, 2021 at 01:51:57AM -0700, Roy Kalawsky wrote:
Hi Dave

Further details would be appreciated. Did you use laser or ink jet water slide paper.

I’m not sure how thick the decal is at the edges having never used this stuff. Alternatively I could use dymo labels.

Cheers Roy







!DSPAM:614d91b412151954911623!
--
Paul Amaranth, GCIH            | Manchester MI, USA             
Aurora Group of Michigan, LLC  |  Security, Systems & Software
paul@AuroraGrp.Com              |  Unix/Linux - We don't do windows


Re: 2215 front cover

Mike Dinolfo
 

Ananda:

An Ebay search (in the US) for "tektronix cover" comes up with several
options, including model # 200-2520-00, which should fit.  I don't know
where you are located, but the seller ships to many countries.

Mike N4MWP

On 9/24/21 7:12 PM, Ananda via groups.io wrote:
Hi all,
I am looking for a 2215 front cover. The 2213 also has the same cover P/N. Is there any member willing to part with a front cover for a 2215 (or 2213) that they are not using?

Thanks in advance.
Ananda




2215 front cover

Ananda
 

Hi all,
I am looking for a 2215 front cover. The 2213 also has the same cover P/N. Is there any member willing to part with a front cover for a 2215 (or 2213) that they are not using?

Thanks in advance.
Ananda


7704A - Sweep speed changes near center of trace

n4buq
 

So, after getting a trace from the function generator, I'm noticing that the sweep speed changes somewhere near the mid-point and the trace from the mid-point to the right edge is slightly faster than the first half. For example, if I display two cycles from the left side to the center, there are only 1-3/4 cycles on the right side of the screen (I hope that's a clear explanation of what I'm seeing).

This is occurring with three different time bases so I presume the problem is in the display unit. Anyone know where I might find the problem? Horizontal amplifier?

Also I presume this is not normal and isn't an operator error.

Thanks,
Barry - N4BUQ


Re: Type M Cracked Channel Position Pots

 

Jim,

I'm in for a batch of ten. I've got other 500-series plug-ins with the same kind of pots. They're not currently showing any signs of cracking, but best to have and not need than to need and not have.

Just to be clear, a batch of ten Adney rings (shipping included) would be $58?

-- Jeff Dutky

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