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?ann fim., 25. nóv. 2021 kl. 15:15 skrifa?i k6whp <k6whp@...>:

On Thu, Nov 25, 2021 at 01:06 AM, Albert Otten wrote:
Thanks. Saw the eBay listing. My motor and fan work fine. Was looking for
explanation/documentation of the whole board and why such a seemingly
simple concept of a cooling fan had all the added circuitry.

While I’ve never seen a 7704A, my guess would be that the circuitry is the
same as in the 485, 2465 and other scopes that use the Siemens motor. The
circuitry does two things; commutates the brushless motor on signals from
the Hall effect sensors in the motor, and temperature-regulates the fan
speed.
The impeller fan design in the 2465 is IMHO vastly better than the PC fan
used in my 2467. The former is virtually silent, while the latter is
annoyingly loud and whiny. I imagine by that time, it would have made for a
fair cost saving to design in a by-then commodity PC fan, which is
presumably why Tek went backwards in this respect.

Hello Phil, thanks for reply.

Removing the caps was not so hard at all. All came out quite easily after removing a board for acces to caps. No pads broken or lifted from board..
When I test then out one by one they all show good readings, both in capacity and esr.
Tested all the tantylum ones, but havent found any shorted yet.
Will fiddle around with the socketed IC's and transistoor checking on the horizontal board.

So while waiting for new caps to arrive, I did get 2 ea 2335 scopes to work. They are quite good looking for their age (arent we all :-). Shorted caps and burned resistors on both of them....the rest is like new.
Received also a Tek 491 Spectrum analyser, but the CRT is blown....shame. And a 184 Time Mark Generator with dead tubes......not easily sourced in Norway.

Hugo / LA4WKA

Does the AA5001 have a DIP switch for the address and terminator options?
These very often fail open and is the first thing I would check on any Tek
gear with gpib issues. Even though you think you've ruled it out by trying
multiple addresses, ohm out the DIP switch.

Dave Casey

On Thu, Nov 25, 2021, 1:54 PM Brian Nordlund <brian.nordlund@...>
wrote:

I thought my AA5001 was fully working, but have discovered that the GPIB
board is not responding to commands. I have over a dozen working GPIB
devices, including four other TM modules. Since the AA5001 does not work
in any (otherwise working) slots, I have no reason to suspect my controller
or chassis.

When my controller writes a command string to the device (or tries to
read) it times-out, so the GPIB board appears to not be responding. I have
tried several different device addresses, to rule out a bad bit on the
address switch / decoder on the GPIB board.

Since the freely available service manual is missing all the service /
maintenance sections, I bought the Artek manual, which I am very happy
with. However, I am wondering if it might be missing the larger pull-out
pages that are mentioned on page 6-11 under the (short) discussion on
Signature Analysis. The pdf does include Figure 9-8 which is called
“Signature Analysis Table”. However, it is not much help. It shows some
parts-outlines, with some codes alongside selected pins. The codes are not
hex, since they include characters like ‘P’, ‘H’, and ‘U’. It provides no
detail as to how to capture or interpret them.

When signature analysis is supported, I normally will find more detail as
to how to capture the data. More importantly, I would expect to find a
table that provides some diagnostic commentary on where the problem may be
when you don’t see the expected codes.

Does anyone have the printed manual or otherwise have any details to get
me started with Signature analysis on this unit?

Thanks,
Brian.

Was looking for explanation/documentation of the whole board and why such a
seemingly simple concept of a cooling fan had all the added circuitry.

Hi William,
A circuit diagram is shown in the 7904A manual (Tekwiki, 3rd manual) at page 333. Short Theory at page 109.
I hope this helps you a little further.
Albert

OK, signature analysis:

Put the processor in a no-op loop that effectively reads all locations in memory and wraps.? (the processor sees no-ops on the bus regardless of what's out there.

The signature analyzer generally has a start, stop, clock, and ground leads.

Instructions on how to connect them are in the manual, as are the settings on how to capture data (clock, active levels, etc).

Once connected, you can read the pattern.? It's a hex pattern, with the H, P, U and so on replacing the hex characters.? You can, once connected, take the data lead and connect it to ground and to VCC and get an idea of what the pattern is for a node that is stuck at 1 or zero.

All you're looking for is "is the pattern as stated".? You can't really go from a pattern (132H rather than 132P) and say oh, this chip I'm not connected to is bad...

What it does tell you is that connection (node) is not performing as desired.

You then look at the inputs of the gate/element with the bad output, and look for bad inputs.? Tracing that bad input back to a bad output from something, says that the something is bad.? If all the inputs to the chip you're testing are good, and you have a bad output pattern, suspect the chip.

If you haven't used it before, you'd think it did more, but you're really looking at "functional/non-functional" for each circuit node they give you.

Hopefully, this fills in the blanks.? If you already knew this, my apologies.

Harvey

On Thu, Nov 25, 2021 at 01:06 AM, Albert Otten wrote:
Thanks. Saw the eBay listing. My motor and fan work fine. Was looking for explanation/documentation of the whole board and why such a seemingly simple concept of a cooling fan had all the added circuitry.

I have a printed manual, a copy of the BAMA manual, and the Artek manual and none of those contain a schematic or description of the fan board. Not essential; just curious.

147-0035-00

--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"

I thought my AA5001 was fully working, but have discovered that the GPIB board is not responding to commands. I have over a dozen working GPIB devices, including four other TM modules. Since the AA5001 does not work in any (otherwise working) slots, I have no reason to suspect my controller or chassis.

When my controller writes a command string to the device (or tries to read) it times-out, so the GPIB board appears to not be responding. I have tried several different device addresses, to rule out a bad bit on the address switch / decoder on the GPIB board.

Since the freely available service manual is missing all the service / maintenance sections, I bought the Artek manual, which I am very happy with. However, I am wondering if it might be missing the larger pull-out pages that are mentioned on page 6-11 under the (short) discussion on Signature Analysis. The pdf does include Figure 9-8 which is called “Signature Analysis Table”. However, it is not much help. It shows some parts-outlines, with some codes alongside selected pins. The codes are not hex, since they include characters like ‘P’, ‘H’, and ‘U’. It provides no detail as to how to capture or interpret them.

When signature analysis is supported, I normally will find more detail as to how to capture the data. More importantly, I would expect to find a table that provides some diagnostic commentary on where the problem may be when you don’t see the expected codes.

Does anyone have the printed manual or otherwise have any details to get me started with Signature analysis on this unit?

Thanks,
Brian.

CL postings give one pause when the description begins, "My father..." or "My grandfather..."

Actually, when doing a previous repair I had bought these parts but not put them in. It makes sense that this might be an issue since they are in the feedback path. Thanks for the reminder, I'll try that.

board with a semi-circular array of solder points

Probably the old style "Siemens" fan motor 147-0035-00. At present there is one at Ebay. Board for instance pictured in (my) 7104 manual, Fig. 8-22, <14>, page 328.
Albert

I used a 117 Volt to 6.3 Volt in my 502, but that was
over 50 years ago.
I think it was a Stancor to the best of my memory.

Whichever? way you go check the placement and orientation
make sure that the magnetic field doesn't distort the CRT trace.

Leon Robinson ?? K5JLR
Political Correctness is a Political Disease.

Politicians and Diapers should be changed
often and for the same reasons.

,as does mine. But, on that subject, I wonder if anyone who DOES have a 7704A with a fan has the one that is mounted laterally to the upper chassis above the horizontal bays and can explain the nature of the rather complex PCB with one IC and a number of discreet components.

The fan seems to blow air OUT of the case in the vicinity of the CRT rear end. It is powered by a two-wire lead from the illuminated graticule pot. Why the elaborate circuitry and why the fan mounted on the board with a semi-circular array of solder points.

Apologize for the crappy description. I have a 7704A service manual but it contains no mention of the board/fan setup. Appreciate an explanation.
--
William, k6whp
"A friend told me to cheer up, things could be worse.
So I cheered up and, sure enough, things got worse!"

Michael,

See if your board has two 620,000 1/2W carbons. If your has these, replace them with 2W types. Using a 1% will make sure better accuracy and low thermal drift. These are available on ebay. These two resistors are known to go bad. This site will explain more if you need it: . The board photo is on page 9 of the pdf. I replaced these in my 494AP. I replaced the two 300,000 ohms on the same board with 2W 1% types. These resistors I mounted off the board to allow better air flow around them. I would like a schematic of the one I have.

Mark

I'm also in Sunnyvale, and sent the guy a note, but I haven't heard back yet.? Good items on CL tend to vanish here pretty quickly.
-Dave

I hope someone saves this package from being plundered
by some tube merchant.

73, Dick, W1KSZ
________________________________
From: [email protected] <[email protected]> on behalf of Stefan <Sscandizzo@...>
Sent: Wednesday, November 24, 2021 5:05 PM
To: [email protected] <[email protected]>
Subject: [TekScopes] Free 545A posted in Northern California CL



I live in the area but no way I could handle this project.

-Stefan

I live in the area but no way I could handle this project.

-Stefan

quadzilla,

if you look carefully at the tunnel diode pages on the TekWiki you will find that the 1N3717 is the same as Tek part# 152-0125. There are 1N3717s available on eBay for half the price of the 125-0125.

-- Jeff Dutky

I am trying to correct a scan non-linearity in the 492 spectrum analyzer.
This is a picture of the display using the calibration procedure for the horizontal sweep.
/g/TekScopes/photo/270207/3340785
The 10ms pulses are expanded on the left of center, OK to the right up to the last two which are compressed.
The calibration has a single gain setting (R1055) but my problem is a linearity issue.
The deflection amplifiers (schematic 26) have a couple of trim capacitors (C5021 & C4057). Would these be the adjustments or is it likely that another component is failing?

The 'horzizontal out' sawtooth (generated before the deflection amplifier) appears to be a linear ramp but that is just by eyeballing.

Help appreciated!

Michael

quadzilla,

the tunnel diodes in the 453 are TD3A 4.7 mA parts, I assume that Roger Evans is correct and that they are Germanium diodes. If you were to follow the link provided by Roger you would find a list of Russian made tunnel diodes in a large table. All you need to do is find a part whose material is "Ge", whose use is "Switching", and whose Ip exceeds 4.7 mA (preferably something close to 4.7 mA). Several diodes early in the list seem to match these criteria:

1I304A (1И304А) / GI304A (ГИ304А) Ge Switching 4.5-5.1 mA
1I304B (1И304Б) / GI304B (ГИ304Б) Ge Switching 4.8-5.4 mA
1I308A (1И308А) / GI308A (ГИ308А) Ge Switching 4.5-5.5 mA
1I308B (1И308Б) / GI308B (ГИ308Б) Ge Switching 4.5-5.5 mA

I would go with the 1I304B/GI304B (1И304Б/ГИ304Б) since it's minimum Ip exceeds the spec for the TD3A. The 1I308A/B (1И308А/Б) parts have no leads (you would see this as soon as you searched for these parts on eBay), so I would avoid them. Adapting a leadless part into a circuit using a leaded part is not impossible, but it is extra work.

The 1I304B parts are available on eBay at reasonable prices (quantity four for $12.75 including shipping). I'm not sure how much work it will be to adapt the ribbon-style case to the circuit in the 453.

I also see that the exact part you are looking for (Tektronix 152-0125-01 tunnel diode 4.7 mA, 15 pF) is on offer on eBay. It's the first hit I get using the search string "tektronix 152-0125 tunnel diode". This part is much more expensive than the Russian TDs, but has the advantage of being a drop-in replacement.

-- Jeff Dutky

On Wed, Nov 24, 2021 at 1:38 PM Sigur?ur ?sgeirsson <siggi@...> wrote:

I've always been curious to peep at the firmware in my Tek scopes, so for
giggles I installed Ghidra and pointed it at the ROMs from my 2467.

Incidentally there are some handy tricks in there.
As a case in point, the DAC_MSB_CLK and DAC_LSB_CLK address ranges are
defined in that order, each 0x40 bytes in length. When writing the DAC,
however, they write a 16 bit value to the last byte in the former, which
results in writing the full 16 bits with a single instruction,