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Hi all,

I have a 2465A scope here which fails to boot.

It briefly flashes some LED's before going to sleep. No beam finder, no scale illumination etc.
The PSU had the Rifa's replaced and the voltage test points are all fine and within spec.

Obviously I'll be going through the manual, however thought I would post here first, on the off-chance that someone might already know what might cause these symptoms?


Thanks in advance,

James

On Fri, Feb 21, 2025 at 6:10?AM James55 via groups.io <james_55=
[email protected]> wrote:

It briefly flashes some LED's before going to sleep. No beam finder, no
scale illumination etc.

If the scope is dropping into the diagnostic monitor due to a power on self
test (POST) failure, the 2465A should leave a front panel LED lit. The LEDs
flashing on the front panel (FP) are indicating POST progress, so you can
tell what's happening and where it's getting stuck. There is a table
somewhere in section 6 of the service manual that correlates FP LEDs to
tests *one I always fail to find when I look for it).
If the scope is failing a POST, then you should be able to drop out of the
diagnostic monitor by pressing the A/B TRIG button, at which point you
should be able to mess with the CH1/2 V/DIV controls, hear relays clicking
and such.
If you report which test is failing (I'm going to bet on the 05 tests), we
can probably point you in a profitable direction.
The scope can also fail earlier tests, the "Kernel tests" (IIRC), which
would also leave breadcrumbs on the FP LEDs, but those indicate more
serious A5 failures.

My 2467 suffered a problem on the A5 board that collapsed the -1.25 and
1.36 reference voltages, which led to no trace, no on-screen-display (OSD)
and 05 POST failure. If you have another A5 board to drop in, my bet is
that'd resurrect traces and OSD.

Good luck,
Siggi

Wow. That A/B Button trick is one worth remembering!...

The scope now has Scale Illumination and no longer goes to sleep.

..Still no trace, nor on-screen read-outs, but the relays can be heard clicking as I select different options.

Gonna look up where to find those -1.25 and 1.36 reference voltages

So..

The reference voltages are both present. Perhaps 2 or 3 mV on the high side but very much present.

Mmm!?

Ok, so taking a closer look at the A5 board there are at least 4 IC's which have either been removed or 'attempted' to be removed.

Gonna have to pull these over the weekend, check or replace them and install sockets.

I'll be back...

On Fri, Feb 21, 2025 at 3:40?PM James55 via groups.io <james_55=
[email protected]> wrote:

Wow. That A/B Button trick is one worth remembering!...

Sure, but which FP LED is lit before you exit the diagnostic monitor?
This tells you which POST is failing, which may help pick a direction for
diagnosis.

It's not really clear which LED's are lit as lots of them light up, before all switching off.

Wondering which tests can be done by a process of elimination in order to rule out the faults?

Considering that the LV test points all appear to be good, testing the HV section might not be a bad idea, 'if' my testers can handle it?
Checking the A5 board waveforms and voltages must surely be worth a go too...

My main issue is time. Hence my writing here instead of reading every page of the 323 page Service Manual several times

Just a quick update..

After walking away from this 2465 and working on other scopes, following a hunch, I checked the HV board and discovered that the 120-1418-00 high voltage transformer had failed short, hence the lack of display.
Fortunately I have a 2445B waiting to be repaired, with an almost identical HV board, so I popped that into the 2465 and the unit came to life, although the screen is incredibly out of focus.

/g/TekScopes/album?id=301087&p=Taken,,,50,1,0,0

I'll have a read-up of the manual when I get a moment and check out the focus circuit.


James

Came across someone with the same problem which he located to the HV board.

That could well be the case, as the 245B this A9 board came out of has no display either. It's only a small board so if the fault is there it shouldn't take long to identify.

Nothing shorted nor open on the A9 board

And before the RIFA's were replaced, what was its condition?

Menahem

Hi Menahem.

Before, it wouldn't turn on. The two 0.068?F's had exploded.

James.

The PSU hasn't been fully recapped although it the ESR was checked

Last night I swapped the entire supply over and the problem remains. Surely the chances of two PSU's having identical and 'uncommon' faults, rules out that possibility.

Considering that we have both vertical and horizontal deflection, Sweep, and intensity control, then it seems to me that I need to deep dive into the focus section.

James,

The focus problem may be due to resistors in and around the focus circuit. They should be raised to 1W types due to the voltage drop across them. These resistors are from B+ to the collectors and from C to B of a few transistors on the h-v board. The part numbers are from Mouser. The 150,000 ohm: 71-CCF60-150K-E3, 180,000 ohm: 279-H4P180KFDA, 332,000 ohm: 71-CCF60-332K-E3, 442,000 ohm: 71-CMF60442K00FEWF (12 week delay) or (2) 660-MF1/2CC2213F (in series), 430,000 ohm: 279-H4P430KFZA, 100meg: 708-HVA12FA100M or (measure in mm the hole spacing of the original carbon then select the on that will drop in which will be larger in wattage than original). If yours has the two 39meg 1/4w carbons on the bottom board, use two 594-MBE04140C2005FC1 in series. These will be R710 and R910.

When you finish recapping the unit, use high temp, low ESR and long life types. Make sure to get the polarity and look to see if yours has the incorrect voltage and values of two condensers in the supply. Replace them as you find them. There are resistors in the supply that should be increased in wattage. The two 4,7mfd tantalums likely will test bad. I used 50V film types to replace them. M. Yachad has a kit for these to recap and some resistors that should be replaced.

Mark

Hi

NO NO NO Standard 1W resistors only have a working voltage of 350V and some of rare ones of 500V, use resistors from the Vishay VR range or equivalent. R4434 must be suspected.

G Edmonds On Thursday 6 March 2025 at 16:34:03 GMT, Mark Vincent via groups.io <orangeglowaudio@...> wrote:

James,

The focus problem may be due to resistors in and around the focus circuit. They should be raised to 1W types due to the voltage drop across them. These resistors are from B+ to the collectors and from C to B of a few transistors on the h-v board. The part numbers are from Mouser. The 150,000 ohm: 71-CCF60-150K-E3, 180,000 ohm: 279-H4P180KFDA, 332,000 ohm: 71-CCF60-332K-E3, 442,000 ohm: 71-CMF60442K00FEWF (12 week delay) or (2) 660-MF1/2CC2213F (in series), 430,000 ohm: 279-H4P430KFZA, 100meg: 708-HVA12FA100M or (measure in mm the hole spacing of the original carbon then select the on that will drop in which will be larger in wattage than original). If yours has the two 39meg 1/4w carbons on the bottom board, use two 594-MBE04140C2005FC1 in series. These will be R710 and R910.

When you finish recapping the unit, use high temp, low ESR and long life types. Make sure to get the polarity and look to see if yours has the incorrect voltage and values of two condensers in the supply. Replace them as you find them. There are resistors in the supply that should be increased in wattage. The two 4,7mfd tantalums likely will test bad. I used 50V film types to replace them. M. Yachad has a kit for these to recap and some resistors that should be replaced.

Mark

George,

Where is it on the spec sheet that is says 350 V NOT 500V? ,

Mark