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@dc_rawding,
I've been looking for Dennis Tillman's boards with no luck, but the effort led me to this thread. At only ~15 months old, I have some hope that it's still relevant... I did check out the album you linked to. Looks promising. Do you have boards for sale?

Thanks!

Ryan

I have repaired and adjusted a 2756P and a 494P.

Apart from replacing all old capacitors as recommended by KE5FX
document I also checked all RF boards for "suspicuous" components.

One thing to look out for is that there are several resistors with very
high resistance. Old Allen-Bradley, 4.7, 10 MOhm, etc. that has aged far beyond
their rated tolerance. In my case > 50% (!). One is located on the span attenuator:
R1046 and that one was some 16 MOhms.

There are also low resistance Allen-Bradley types used in the decoupling networks.
They too had drifted and was replaced even though I cannot say that they were
faulty.

Before replacing these resistors, I was able to execute the internal calibration
procedure without any problem only to discover that the analyzer did not
lock the next time it was used in narrow band modes.

The batteries were dead on both analyzers and I replaced them with modern
types. On the 2756 with a larger capacity battery that was placed outside
the PCB (plenty of space in that instrument).

There are also electrolytic capacitors that should be checked and replaced
in the phase lock assembly modules.

After having replaced most axial and radial type electrolythic capacitors, a number of
A-B resistors and having re-run the calibration routine, the analyzers
became stable, not needing any further adjustments.

And a bit OT. I mentioned, before in another thread: The Air inlet holes
for the 2756P are IMO way to few/small. The small Buhler fan ran at full
speed and the air that came out from the PSU was very very hot.

After having drilled a lot more holes on the bottom side close to the
front, the fan now runs at lower speed. I have not noticed any drift or other
instabilities on the analyzer after that modification.

Ulf
SM6GXV

On Sun, Mar 16, 2025 at 11:39?AM Giuseppe Marullo[iw2jww] via groups.io
<giuseppe@...> wrote:

2) would it be possible to use the FRAM+DIP adapter solution and get rid
of the battery altogether?

I have not done this, but IMHO if any of the 24X5|7A|B scopes allow this,
all of them do, as they all have the same processor and the same bus
timings. IIRC the one concern is what happens when the power is dying,
which is where the original NVRAM module has well defined behavior. I've
never heard of NVRAM corruption with the FRAM conversion, though that
doesn't mean a lot :).

3) is there any way to know for sure which are the options installed? I

see these options (BU EXER F1, CT EXER 01, TV EXER something, maybe
CCT/WR OPTION 9?), but is there an official method to confirm?
this is the back panel:

Is that the connector for the P6407?

From the back panel it looks like you have option 09 (CTT) at least. I know
there is an options service manual, maybe it has the details?
You could pull the case and have a look-see, though it's a bit of a pickle
to pull out the options (I only have the CTT in my 2467).

4) Is there any way to retrofit a 2465B with a GPIB board? Is it worth it?

I have a 2467, where in my opinion this isn't worth it because it only
really gives you the ability to set up and read back measurement
settings. I guess with the -Bs you also have auto measurements, and so the
ability to read back measurement. Unless you have a whole lot of batch
measurements to do, that's not going to be worth it either.

Thank you for that information. That means that we can add the 666 to
Dennis' list of tube testers that will work with his VCTC.

DaveD
KC0WJN


On Sun, Mar 16, 2025 at 13:09 Kurt Swanson via groups.io <kurt2135=
[email protected]> wrote:

Dave,

The difference between the Eico 666 and 667 was purely to update the types
of tubes tested: the 667 added support for 9 pin Novar and 12 pin
Compactron tubes, and dropped the sockets for large pin pre-war tubes.
The test methodology remained the same - the 666 should work just fine as
long as it has the sockets you need.

Good luck - Kurt

Dave,

The difference between the Eico 666 and 667 was purely to update the types of tubes tested: the 667 added support for 9 pin Novar and 12 pin Compactron tubes, and dropped the sockets for large pin pre-war tubes.
The test methodology remained the same - the 666 should work just fine as long as it has the sockets you need.

Good luck - Kurt

Finally I decided to take care of the baby, before is too late:

TEK2465B
S/N: B017389
Hours: 10045
Pwer On/Off: 1783
AFAIK never recalibrated, no sticker applied

Apparently I have at leasr OPTION 5 installed, I have the same panel:


I dumped the CAL values using a video (actually two, I discovered I made some errors, with light "0", "B" and "8" seems similar, so I took another one (still to be triple checked).

Now I would like to know which are my options:

1) could I apply the solution that writes the values after burning a special eprom/eeprom with cal data in it? Keep the same/replace SRAM after replacing the battery? I see there is a utility (24xxAB-writecal-1.1) that would allow me to put CAL data and have it be written in the SRAM. Is this one fit for the purpose:

GQ PRG113 GQ4X4 + ADP054 + EPROM ERASER



2) would it be possible to use the FRAM+DIP adapter solution and get rid of the battery altogether? It is not clear to me if this could be used on the low serial scopes also. Same goes for the programmer mentioned before.

In addition:
3) is there any way to know for sure which are the options installed? I see these options (BU EXER F1, CT EXER 01, TV EXER something, maybe CCT/WR OPTION 9?), but is there an official method to confirm?
this is the back panel:

Is that the connector for the P6407?

4) Is there any way to retrofit a 2465B with a GPIB board? Is it worth it?

Thanks in advance.

--
Giuseppe Marullo
IW2JWW - JN45RQ

Jon,

I have 2 SC504. Both of these units have this exact mod. I found some documentation that stated that a later crt required a circuit mod.

Thanks, still putting the pieces together.

Barry

The power supply on a 2465 has 2 four pin connectors to power optional Lemo jacks on the rear panel of the 2465. No new power supply needed, just a jack, board connector, hole and some wire.

Hi, I have VmtWin-release032201.zip and some more. Try this:

My VM700T backup battery did run out, and I don't have security key to activate unit anymore. I tried to ask key from Tektronix, but they can't generate those anymore. I'm looking working serial number + activation code (not sure if it's possible to change serial on unit and then activate it again).



Ramppa / OH2LIY

Thanks, I'll look at that. Andy.

Hello Jose,

the one you are mentioning is not right schematic for TDS784A power supply.

Here you can find proper diagram: (PS).pdf

Power supply in TDS784A is the same as in TDS544A (above link) and several other TDS models.


Vladimir



Dne 16.03.2025 v 6:16 Jose Luu via groups.io napsal(a):

OK, found one good enough: page 5-141

I'm assuming a similar setup like the later 492 for the following comments...
The issue seems to be one of accuracy. It won't lock in time when high accuracy is demanded by the cpu.
If like the 492 scheme, there are 4 oscillators used in 2nd if, a 2200 fixed from 100 MHz ref, a 16 to 20MHz, a 2182 and 719Mz which is used only for the middle bands.

It's like noise is getting into one of the oscillators, likely the 2182, or 18 hz or the error amp. After the cal, if no joy, check the 2182 error signal is clean. The later 27xx units may have the surface mount caps that fail and or leak. Checking inside rf shields is a good idea as some circuits have a dedicated 5v regulator under shields. I bet it's similar to the older design 492b etc.

Good Morning All:
Got a 784A where the PSU is bad (this model: )
one of the capacitors has leaked and may be exploded to the point where the fiber glass weaving of the PCB is swollen and exposed.
It may be the +5V @22A supply.
Since these are large PCB traces, not to many are destroyed, I may attempt to repair the area, having the schematic would help.

Thanks
闯辞蝉é

I think you should probably review what was done with the EHT transformer replacement. My guess is its running unregulated and the output is way too high. That would cause reduced horizontal and vertical deflection and probably the lack of intensity control.

The bus,wire is,perhaps an indicator of a mod,perhaps b y previous repair attempt.

Suggest you Remove the Trim pot see the,original PCB.

Jon

GM all -

Someone from the list has responded to my plea for assistance and I have a couple of the required connectors on the way.

Cheers,
Bill

GM Clark -

Buying a 1101A would definitely be more practical but building stuff is fun. It is, after all, why i have all this gear in the first place. If I fail, the 1101A is the fallback option (and, yes, probably cheaper in the long run).

Cheers,
Bill

Does anyone have a copy of the “REV B” manual? If so, does the HV board show a trimmer?

Many thanks!

Anybody know how close the 2755 is to the earlier 492b ... 494a series design?