Date   

Re: 7704A - Delayed Sweep Intensity Too Bright

Mark Vincent
 

Barry,

See if having the A/B intensity turned up and the crt bias up (more negative at the grid) helps. If your S/N is <210000, check Q320, Q322, Q420 and Q422. These are in the two heatsinks on the right side top. If these are leaky, use KSP10BU. I do not see any internal intensity control in this model. It may be that the delayed signal is to be brighter to give contrast.

Mark


Re: Idle Question About the 485

Tom Gardner
 

No disrespect taken :)

Looking at the circuit diagrams, the 485 has two separate attenuators, one 1Mohm and one 50ohm. A relay connects the BNC input to the relevant attenuator. Overload causes the relay to switch to the 1Mohm attenuator.

OTOH, the 24x5 has a single 1Mohm attenuator, and a relay simply puts a 50ohm resistor in parallel with that.

Using a NanoVNA to (imperfectly) measure the VSWR of my 485 shows it is between 1.00 and 1.03, rising to 1.04 at 350MHz.

OTOH, my 2465 varies between 1.01 and 1.15, and is 1.12 at 350MHz.

On 21/10/21 15:06, Jeff Dutky wrote:
Tom,

no disrespect intended, but I'm looking directly at my 2465, and it has five input coupling positions for channels 1 and 2, labeled in order: 1MΩ AC, 1MΩ Gnd, 1MΩ DC, 1MΩ Gnd, and 50Ω DC (with a red border around the 50Ω DC label). It also has, according to the manual, overload protection in 50Ω DC mode, and will revert to 1MΩ Gnd position in such a case. The precise mechanism of the overload protection seems to be more direct in the case of the 2465, which appears to have a thermal sensor that triggers the switch back to 1MΩ input, but the effect is the same.

-- Jeff Dutky




Re: 7704A - Delayed Sweep Intensity Too Bright

n4buq
 

Mark,

Intensity settings for normal traces are about right. The main intensity is somewhere near mid-range and the A/B intensity controls are in the 9:00 to 12:00 range (or less).

I'm using a 7B53A and when I pull the time/division knob to its outward position for a delayed sweep, the delayed trace is very bright. I presume the intensity of the delayed sweep is an independent setting from a normal trace in the main frame but not sure.

Thanks,
Barry - N4BUQ

----- Original Message -----
From: "Mark Vincent" <orangeglowaudio@gmail.com>
To: "tekscopes" <TekScopes@groups.io>
Sent: Thursday, October 21, 2021 9:55:27 AM
Subject: Re: [TekScopes] 7704A - Delayed Sweep Intensity Too Bright
Barry,

It sounds like the time base you are using is the source of the delayed sweep.
Some have an intensity control for the delayed sweep. A 7B92A is an example.
The 7704A has two main intensity controls, the one at the top and two above the
plug-ins. One of the two could be turned up. I have the two about 70% up and
adjusted the crt bias so that the main intensity is about at the 11 o'clock
position to get a trace visible. Controls in the Z circuit were adjusted. Those
will alter intensity and focus.

Mark



Re: 7704A - Delayed Sweep Intensity Too Bright

Mark Vincent
 

Barry,

It sounds like the time base you are using is the source of the delayed sweep. Some have an intensity control for the delayed sweep. A 7B92A is an example. The 7704A has two main intensity controls, the one at the top and two above the plug-ins. One of the two could be turned up. I have the two about 70% up and adjusted the crt bias so that the main intensity is about at the 11 o'clock position to get a trace visible. Controls in the Z circuit were adjusted. Those will alter intensity and focus.

Mark


7704A - Delayed Sweep Intensity Too Bright

n4buq
 

The delayed sweep intensity is way too bright in my 7704A. If I understand it correctly, a time-base sends a signal to the mainframe to indicate the delayed sweep is active and the mainframe knows to make that a higher intensity trace.

Is there a separate adjustment for that intensity? I haven't attempted to set the CRT grid bias and that could be part of the problem but it appears a signal standardizer may be required for that and I don't have one of those and am hoping that I can at least reduce that excessive brightness just a bit without having to get one of those first.

I know this might sound like a "golden screwdriver" sort of thing but if I could just reduce that intensity for now, it would be a big help.

Thanks,
Barry - N4BUQ


Re: Idle Question About the 485

 

Jean-Paul,

I have already lucked out on a 2465 in January of this year, which cost slightly less than this 485 ($120 before shipping). I'm not really interested in the 2465A or 2465B, both because the controls move further and further away from direct control of the instrument on the A and B models, and because of a certain fellow in California who sells disfigured 2465As as 2465Bs, so I'm unsure if I can trust any second-hand 2465Bs I would find in the wild.

I did notice the deterioration of the upper trigger slope knob, but the rest of the unit looks to be in fairly good condition, considering its age. Also, this is a scope from exactly the period that I most like (which includes the 475 and the 7000-series). I also noticed that the hinge covers on the handle seem to be quite faded, which makes me worry that they are about to go brittle, and there is some damage to one of the rear feet. The serial number is B010156, which I think means that it is a very early production unit indeed.

For being so old, most of the knobs appear to be in excellent shape, and the CRT looks quite strong (the intensity is set at less than the half way mark and the traces look nice and bright). Still, your warning is heard and heeded.

Actually, on a second examination of the images, it appears that the CH 1 and CH 2 VOLTS/DIV knobs don't match, which means that one (probably CH 2) had to be replaced, and all they could find was a knob from a much later instrument (a knob without the black insert at the top).

teamlarryohio,

That is a very small button for trigger view. Even in the close-up of the CRT section (second picture) I can barely tell that's actually a button.

-- Jeff Dutky


Re: Idle Question About the 485

 

Tom,

no disrespect intended, but I'm looking directly at my 2465, and it has five input coupling positions for channels 1 and 2, labeled in order: 1MΩ AC, 1MΩ Gnd, 1MΩ DC, 1MΩ Gnd, and 50Ω DC (with a red border around the 50Ω DC label). It also has, according to the manual, overload protection in 50Ω DC mode, and will revert to 1MΩ Gnd position in such a case. The precise mechanism of the overload protection seems to be more direct in the case of the 2465, which appears to have a thermal sensor that triggers the switch back to 1MΩ input, but the effect is the same.

-- Jeff Dutky


Re: Idle Question About the 485

Jean-Paul
 

Dear Jeff the trigger difference is the least of the considerations

Beware the 485 are very old, notice the small gray knobs are deteriorated.

The ebay lot has total with shipping $225 minimum, and the seller is a surplus dealer, so I would advise to pass on this, especially if shipping will be international eg to UK or Japan.

With patience a nice 246xB can be found for perhaps $100..200 more.

Bon Chance


Re: Idle Question About the 485

teamlarryohio
 

On 485, A Ext trig view is the little button at left end of vert mode switches.


Re: Idle Question About the 485

Tom Gardner
 

The 485 has two separate inputs: 50ohm and 1Mohm//20pF.

The 24x5 have 1Mohm//15pF inputs, and you can add a 50ohm resistor to make that 50ohm//15pF.

By and large, my preference is for two "proper" inputs, or for >4 inputs - as found in a logic analyser or protocol decoder.

On 21/10/21 12:14, Jeff Dutky wrote:
I'm trying to convince myself not to bid on this 485 (https://www.ebay.com/itm/393631311648) which has no bids, mostly because I don't have the cash, but also because I already have a 2465 that I am quite happy with, and that I perceive as an upgraded version of the 485 (it has almost the same bandwidth, 50 ohm input mode, and ALT horizontal mode, along with on-screen readout, cursors, and in my case, a multimeter and counter/timer).

While perusing the TekWiki page for the 485, however, I noticed that the 485, unlike the 465 and 475, does not appear to have a TRIG VIEW feature (or, at least, it doesn't have an obviously labeled button). Is this true? Does the 485 have no way to display, even momentarily, the external trigger signals?


Re: USPS shipments comments

stevenhorii
 

I’ve been to quite a few warehouses to pick up stuff I had delivered by
freight. It’s a lot cheaper to pick it up compared with home delivery since
they need to dispatch a truck with a lift gate for most home deliveries
(unless you have a truck dock!) I have had to uncrate stuff in the customer
parking area when the crate was too large for my SUV.

I know why they generally do not allow customers to walk around the
warehouse. It’s dangerous. The forklift drivers zoom around and are not
expecting inexperienced folks to be on the floor. I have been allowed on
the floor when they were having trouble finding the crate I was expecting.
They did find it with my help - it turned out that it got moved to a
staging area for a later pickup day than I had told them.

I got talking with one of the foremen about the hazards of the fork lifts.
He told me that they are usually very good and that accidents with
shipments are few (but he would say that). He did tell me about a couple of
incidents with the driver running the forks through a crate. One of them
was a large screen flat-panel TV (in those days it meant a large insurance
payout). Things falling off the forks is another problem, but the drivers
usually know when they start to lift a pallet or crate if it is not far
enough back on the forks. I worried a little when they used a lift to get
my crate into my SUV. I could imagine the forks going through the rear
bumper or something. But the guy got it in and then raised the forks so the
ends of them were at the wood frame around the rear of the crate. He then
very slowly pushed it all the way into the back of the SUV managing to
avoid pushing into the backs of the front seats (I had folded the rear
seats down). These guys can be careful when they need to be.


On Thu, Oct 21, 2021 at 07:03 Michael A. Terrell <
terrell.michael.a@gmail.com> wrote:

That sounds like a Drew Carey show episode where Oswald smashed the scanner
in shipping while playing on a forklift.

On Wed, Oct 20, 2021 at 12:19 PM Jim Ford <james.ford@cox.net> wrote:

Wasn't there a Dilbert strip like that where the company provided beer
for
the employees to loosen things up? They ended up jousting with the
forklifts in the warehouse! Jim Ford Sent from my Verizon, Samsung
Galaxy
smartphone
-------- Original message --------From: Ken Eckert <eckertkp@gmail.com>
Date: 10/20/21 8:51 AM (GMT-08:00) To: TekScopes@groups.io Subject:
Re:
[TekScopes] USPS shipments comments My wife worked for a while in a BC
Liquour control board warehouse, guys would drive the forks into a pallet
just for a giggle............









Re: TEK 475: Dead on Start Up.

Redguuz
 

Dear Tom, Michael and Mark,

Thank you very much for your extensive answers.
I will attempt to diagnose / repair the TEK475 in the next few weeks and will surely report back on the diagnosis/results.

I'm also very grateful for the advise of Mark on the Changing Brightness due to an OFF SPEC R1378.
This scope initially had this problem very much, but somehow it became less ( I bought it 4 years ago).
I will have a look at this circuit as well.

Cheers,

Martin


Idle Question About the 485

 

I'm trying to convince myself not to bid on this 485 (https://www.ebay.com/itm/393631311648) which has no bids, mostly because I don't have the cash, but also because I already have a 2465 that I am quite happy with, and that I perceive as an upgraded version of the 485 (it has almost the same bandwidth, 50 ohm input mode, and ALT horizontal mode, along with on-screen readout, cursors, and in my case, a multimeter and counter/timer).

While perusing the TekWiki page for the 485, however, I noticed that the 485, unlike the 465 and 475, does not appear to have a TRIG VIEW feature (or, at least, it doesn't have an obviously labeled button). Is this true? Does the 485 have no way to display, even momentarily, the external trigger signals?

-- Jeff Dutky


Re: USPS shipments comments

Michael A. Terrell
 

That sounds like a Drew Carey show episode where Oswald smashed the scanner
in shipping while playing on a forklift.

On Wed, Oct 20, 2021 at 12:19 PM Jim Ford <james.ford@cox.net> wrote:

Wasn't there a Dilbert strip like that where the company provided beer for
the employees to loosen things up? They ended up jousting with the
forklifts in the warehouse! Jim Ford Sent from my Verizon, Samsung Galaxy
smartphone
-------- Original message --------From: Ken Eckert <eckertkp@gmail.com>
Date: 10/20/21 8:51 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re:
[TekScopes] USPS shipments comments My wife worked for a while in a BC
Liquour control board warehouse, guys would drive the forks into a pallet
just for a giggle............





Re: USPS shipments comments

Michael A. Terrell
 

My last UPS delivery arrived as an empty, torn box with tire tracks on it.
The Ebay seller won't even reply to me, so I'm going to ask for a refund
from Ebay or Paypal.
A UPS delivery before that was from the VA. It was in one of their plastic
bags, but the corner of the box and the bag were torn, so my Hydrophilic
foam dressings were ruined and full of dirty water.
A delivery from Sam's Club was missing some cans, and that box was ripped
open as well.
They have misdelivered several items that were never located, as well. I'm
sick of poor service!

On Tue, Oct 19, 2021 at 2:57 AM Jean-Paul <jonpaul@ix.netcom.com> wrote:

We used UPS for decades now very poor service and wastes time.

DHL is hopeless as the owner German post has outsourced to a different
entities per country so custom clearance and tracking takes weeks.

Only use Fed Ex now both us and international

All shipping costs have gone up 20-70 % i last year.

The postman was 100% on extra adresse or labels causing misdirection we
have had that.

The $30 for two plug-ins was a great bargain.

Finally we have better results with new double wall boxes than recycled or
two box package

Jon







Re: USPS shipments comments

Dave Seiter
 

I reuse boxes all the time, and have a huge selection, because even though most of what I ship goes in the flat rate boxes, some items don't.  I always either strip off old labels or black them out, and have never had a mis-delivery (except when I shipped the wrong slot car to Japan; that was an expensive mistake, but at least both buyers understood!).  USPS does use FedEx as a currier (or maybe the other way around), so you can't say "I don't need to black it out because I'm not shipping the old box with the same currier.  For really pricey stuff (like a set of jeweler's collets I sold a year ago), I always put the "to and from" info on the inside as well, usually tape to the item. 
-Dave

On Wednesday, October 20, 2021, 04:56:21 PM PDT, Roy Thistle <roy.thistle@mail.utoronto.ca> wrote:

On Mon, Oct 18, 2021 at 11:57 PM, Jean-Paul wrote:


The postman was 100% on extra adresse or labels causing misdirection we have
had that.
I can see, sort of, if there's an old label with a bar code, or a bar code printed on the box. I remove those, or black them out, with a marker. I'm not so sure why it should matter... particularly with printing or writing on the box... since the "post office" uses a particular bar code, which ought to be fairly unique. The sorting machines are supposed to scan for the U.S.P.S. label on the box. If the "postman" sends your plugins back to Kimberly-Clark because you posted them in a Huggies box, with a U.S.P.S. label on it... well... it's just another day at the post office: right?

--
Roy Thistle


Re: Tek VAR Pot Repair Rings

Jim Adney
 

On Wed, Oct 20, 2021 at 01:55 PM, snapdiode wrote:

What's the timeframe for getting back to you with a commitment?
I don't have any timeframe in mind, but the machine shop predicted a lead time of 5-6 weeks. They must be busy. I don't plan to place an order for these until I've got enough commitments to get me close to 150 pieces. I won't ask for prepayment, but I won't object if someone offers to make one. Take your time, but I hope this doesn't get dragged out too long.


Re: Replacement caps for DC 505A

Dave Peterson
 

Blame it on me: I wasn't doing a proper job of searching Mouser. Not even sure what I did to get only two results. Using Mark Vincent's search as a start point I found the variety of Vishay axial capacitors. Looks like the 125 ALS line 6800uF cap is a good fit.

Still good to get thoughts and ideas from others. I'm still a newbie at capacitor selection, so don't completely trust myself.

On Wednesday, October 20, 2021, 05:29:02 PM PDT, Jeff Dutky <jeff.dutky@gmail.com> wrote:

Dave,

How close are the mechanical tolerances? The highest values for each voltage range (e.g. 6800 uF @ 16 V) is only 21mm in diameter. Would that still fit in the space?

Otherwise, my (relatively ignorant) understanding is that 4700 uF is today's equivalent to 5000 uF from the 1970s. Also, you are not designing this to be manufactured in bulk. If you order several more caps than you need you can select for highest capacitance, and not have to worry that the parts might be 20% below spec. You might get lucky and get a couple of parts that are 10% above spec.

-- Jeff Dutky


Re: Tek VAR Pot Repair Rings

 

Jim,

After I committed to only 10 rings, I did a more thorough survey of my letter and 1-series collection, and I would like to increase my order to 20 rings.

Almost every plug-in in my collection has these pots, but I had not noticed because many of them are not showing any symptoms of failure, and I had (obviously) not investigated pots whose knobs were not slipping.

-- Jeff Dutky


Re: Tek VAR Pot Repair Rings

Dave Casey
 

For anyone needing more than just a repair ring, I have a handful of NOS
Tek Made pots in this style. Send your part number requests and I'll see
what I have.

Dave Casey

On Wed, Oct 20, 2021 at 1:55 PM snapdiode via groups.io <snapdiode=
yahoo.com@groups.io> wrote:

That is *very* interesting and timely for my collection. What's the
timeframe for getting back to you with a commitment? I need to examine 20
plugins ...
And do you need a deposit or 100% upfront?





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